Ahesive for Solar Panels to Motorhome

A waterproof silicone adhesive should work, but more importantly, you should think about adding a wind deflector in front of them. It would eliminate the need to withstand 150 MPH winds.

Although you will get many here who swear their glop is the "ONLY" thing to use, my suggestion is to use a silicone adhesive sealant.

The weak link may be the paint-to-fiberglass bond. I'd do some peel tests with some various brands of silicone. Wet some small strips of nylon fabric with some different brands/types of silicone and see which one is best.

Cyanoacrylates degrade if exposed to moisture.

You've got plenty of surface area so bond strength isn't critical.

Don't use anything rigid, like epoxies.

Clean, clean clean!!!!

Remember things will be under zero stress at the cure temperature, and will be stressed as the temperarure goes above or below that.

Lyn, I would be concerned about the acetic acid in many silicone products and the potential to cause havoc with fine trace lines in PV panels. If it smells like vinegar, best keep it away from any electronic products. We have several RTV products we use here for staking on electronic assemblies that are non-corrosive per MIL-A-46146. (RTV 167 GE, RTV 3145 Dow Corning)

Cheers !!

A good answer. I have already ruled out normal silicone sealers. Some RTV labled products might be suitable, but it must not be air cured. Many manufacturers have warned against their products for that. The middle of the panel will never cure. There used to be some 2 part RTV that didn't require air. It also didn't have the acetic acid. I haven't seen it lately except in chinese manufacturers and used for molds, not adhesives.

Air cure technique?? Could you put a glob of the stuff in the center, but not the edges; then, after that cures, go around and do the edges? Might be a bit awkward getting the adhesive between the edges, but might open up more adhesives to choose from.

I would use this stuff around the edges....

http://www.campingworld.com/shopping/item/dicor-self-leveling-lap-sealant-white/32125

I would not use that particular sealant since it tries to level itself right off the roof. But the vendor is the place to buy ProFlex Flexible Sealant.

They say: "Developed specifically for RV use, ProFlex Flexible RV Sealant is more elastic than silicone sealants, and has superior adhesion as well. Tripolymer formula displaces water that might be hiding in seams and joints, and ensures a watertight seal. Bonds to virtually every RV material, even when damp, oily or frozen. Long lasting, durable and paintable. USA. Not recommended for use with rubber roofs."

I've used this on my RV over the past 7 years and it appears to be everything they say. It is NOT silicon seal which will eventually give up and it attracts dirt. This is a hydrocarbon-based sealant as far as I can tell.

I no longer use silicon seal since I discovered this product.

http://www.campingworld.com/shopping/item/proflex-rv-flexible-sealant-clear/20440

Thanks,

I will check that out

501-LSW is not that thin. Yes it is self leveling, but it also has a fair amount of surface tension such that between two surfaces to bond together, it does not just run all over the place. It is almost thixotropic. I just used tubes of the stuff to redo the joints on the the galvy steel roof panels on my Haulmark trailer. I just laid down a wide bead (3/4 to 1 inch)of the stuff about 1/8" to 3/16" thick on the raised joint sections and I was originally concerned that all the 'bumpiness' was not going to 'fill-in'. The stuff sets up pretty well in less than two hours in reasonably dry conditions, temps in the 50s-60s. It does not just go running off. It pretty much just sits exactly where you put it unless you pour it on really thick. (On more or less horizontal surfaces).

It bonds well to surfaces that have been cleaned. I would have no problem recommending it as it creates a nice medium strength bond with good flexibility. Do watch your CT mismatch as with any adhesive. The Dicor stuff is also hydrocarbon based so you don't have to worry about corrosive effects of silicone sealants with acetic acid in them.

If you want a firmer product from Dicor, their 551LSW is designed for vertical surfaces. In subjective terms, the 501LSW is about 'half' the viscosity of the typical cheap latex caulk you buy at a local home improvement store.

Good luck with your quest.

The one concern that many manufacturers have raised is that with the thin panel applied the way I will, is the center area will not cure if the product air cures. As far as I can tell, this is an air cured product and therefore will not work. I have not heard back from Dicor yet.

Then, it sounds like a contact adhesive is a suitable product. In my reading yesterday, I learned that contact adhesives are designed to evaporate the solvent before bonding. That is why you apply the stuff to both parts and let it sit until the solvent is gone (surface no longer comes away on your finger when touched). Some require several hours to evaporate before you can bond the two materials but most are ready in just a few minutes.

Drew K

Dicor makes a fiberglass roof coating you might consider first....

http://rvdailyreport.com/products/dicor-introduces-coating-and-primer-system-for-fiberglass-rv-roofs/

what quantity of power are you looking to generate? and what will you do with this power?

Something devious no doubt.

I currently have 400 watts of conventional panels and plan to increase that to 800 watts of flexible, removing the 400 watts. I will use mppt controller as before but must increase rating. I am charging 360 amp hour lithium cells. The reason for the change is to increase loading capability when dry camping. This motorhome has no generator so if I dry camp I have to rely on the panels. The motorhome was designed for 32 mpg. Some of the owners actually get that, but I like to drive what ever those little signs allow. Before I put the 400 watt units on I got 27mpg towing a car, but most of the time I get 24-25 with the wind drag on the roof. The reason for the increase is that sometimes we let someone else plug into the external outlet. (my daughter) I also will divert the solar panels to a grid inverter when at home and recover a tiny amount of the investment.

Hmmm. So is it a Vixen?

Yep

There have been some complaints about the performance of flexiblre panels degrading more quickly than conventional solar panels.

.

Have you considered using traditional glass covered solar panels (at least for the top plane) to create a boxy boat tail of the kind you are beginning to see on some semi trailers? It could provide some modest aerodynamic benefits, and could be hinged to be angled for better sun reception when camping.

.

My motorhome is much more aerodynamic than that. Glass is breakable. Most of the fast deterioration of flexible panels was before the use of Tedlar for the top coating. Some of these have been on Boats close to 20 years now but were extremely pricy and the manufacturer is giving the same warranty as a glass covered panel, 80 percent at 20 years. They are now dropping quickly in price.

How about posting a photo of the motor home. I can't imagine what it looks like after the height you mentioned and saying how aerodynamic it is.

You could always google Vixen RV for images.

I sent you a PM with some info

What plans do you have for keeping the solar panels clean? I understand the output degrades rapidly when they get just a little dirty.

There is a website for recommending glues to use for various surfaces. It is called www.thistothat.com. Have you checked that one?

To keep the panels clean, I intend to rely on rain and my occasional washin. That has kept the existing panels within 95% of their best recorded output.

Interesting site you suggested but no help on painted surfaces and no differentiation on different plastics. Also no inputs for environmental conditions. It would be great if all the manufacturers got together on a site like that with some real technical inputs and the chance to link to data sheets, etc. I think it would bring business and make it easier for consumers to identify the correct product. Many people purchase poorer quality items because they are readily available and it takes too much time to look. I would rather buy the correct product and not have to worry.

A bit of dust etc. On a PV panel doesn't affect performance very much.

The problem arises when only one or two cells on the panel are covered by a leaf , bird excrement etc.

The reason for this is that the panel consists of groups of individual cells connected in series, and these are connected in parallel with other identical series strings .

The current in a series circuit is the same through all components, but the covered cell can't pass current due to the lack of excitation of its substrate.

Therefore the current in that entire string drops to near zero. The other parallel strings now also have a higher voltage, and they force the shaded cell into reverse bias as they attempt to push current through it.

This causes that cell to overheat with almost all of the panel wattage being dissipated across that one cell. This is commonly called "hot spot heating" and can result in the destruction of the panel.

That seems like a serious design flaw. Could it be corrected with a thermal bypass switch that shorts the current past the un-excited cell?

Drew K

Very well described.

I have been planning to acquire a motorhome and do this, so this is very timely. My concern is the heat that solar panels are supposed to produce, causing expansion or disbond due to thermal degradation of the adhesive ?

Why don't you use the same mounting for the 800 as the 400 ?

I also would be concerned about the oxidizing, crazing/cracking due to UV of the 25 year old paint.

Why can't the solar panels be mounted in a U-channel with a gasket like a window allowing for thermal size change, as the solar panels are typicly silica base like window glass ?

One of the biggest efficiency losses with solar is dirt accumulating on the surface, do you plan to address that somehow ?

Yes, don't stick them on!

While you have done all the research, i guess by your question you're still not 100% convinced it is the right thing to do, and you are correct.

What happens if you need to replace one? What happens if there is a problem with the motor home?

You say you don't want to use mechanical fasteners.. (Why not?). but really they are the best option. You could make a slide rail type of securing, have on each side of the roof a metal slide/slot that the PV sheets side into, so if need be they can be removed quite easily, and they would still follow the curve of the roof.

With the windage and flexibility of these panels, they would pop right out if secured by a rail at the edge. It won't work. On boats, they secure them with gromets, but that fails on motorhomes due to windage and they get ripped off. They get ripped off boats secured that way, but only in gale-force winds when the insurance will cover the loss. Adhesive is the only way to go, unless I decide to stop everytime I have a head wind, which I choose not to do. If a panel fails, I will deal with that problem when it happens.

I would be looking to devise a rack mounting system for the panels for several reasons. Obviously it would be easier to replace one should it fail. You would also be able to transfer the panels to another vehicle at some point. And if you got a little more ingenious you could mount the rack on some arms that could be tilted and rotated to allow for best orientation/maximum exposure to the sunlight.

Just a thought.

One way or another, I will adhere the panels using adhesive. I just want to be sure to use the best adhesive. I do not want the appearance of the conventional panels and the semi-flexible panels are only 1/16 inch thick. One of the reasons I am getting rid of the 400 watt panels is for appearance and wind turbulence problems. This motorhome attracts a crowd whenever I stop and as soon as I get the panels in place I plan on a new paint job and some body work. The interior has just been redone. The existing paint is very secure and high quality. I don't worry about it coming loose and am confident that I can bond to it and then paint around the panels. One of the problems with many silicone products is that they cannot be painted if a small amount gets on the old paint surface. I am going to contact 3M since they have a tape product that many commercial installers are using. The problem with that is a small edge that attracts dirt and looks unsightly. By the way, mechanical fasteners will always fail, it just a question of when. I have bonded some items that are approaching 50 years service. Better products are available today. Both the top and the panels can flex, expand, and contract so the adhesive will have to be able to do the same.

Have you considered using clear self adhesive film (clear contact) over the top of the flexi panels and lapping onto the roof of the RV?

You can reinforce the edges of the film with duct tape to mitigate peeling at the edges.....also gives you a visual indication if things are getting unstuck.

I will bond the entire panel, not just the edges, no matter what I use. Thanks for the silkaflex information. I think I have another of their products on my list already. I tend to check the manufacturer's tech people to find their recomendation and I will see what they say. Good point to others about the need to bond the entire panel. I used Silicone on top of my pickup camper to bond a small set (4-20 watt units) and have not had problems. It was a test for that type off unit (thin semi flexible collectors) and has shown to be a good application. The silicone, however has that problem of collecting dirt where exposed and is hard to clean. I used masking tape around it and only have about 1/8 inch at most exposure. Doesn't bother me much on that vehicle, since it is above head height, but on the motorhome, it will be at eye level for many people and I want it to look good. Plus the silicone is impossible to paint over.

but on the motorhome, it will be at eye level for many people and I want it to look good.

Something is not adding up here! You want to put these panels on top of a motor home, but the motor homes I have seen are tall, at least as tall as a pickup camper. So how can it be at eye level on the motorhome? Even basketball players aren't that tall.

It will fit into an 8 foot garage with an overall height of 78 inches yet a 6 foot 8 inch person can stand up easily inside. You just thought you were good at math. Figure it out.

4WSilver, the adhesives info provided so far is all excellent and chose your favorite poison accordingly. My one piece of advice is the red flag that pops up when you say "painted fiberglass roof that is 25 years old". I would suggest removing the paint and do a thorough evaluation of the stability of the surface as all fiberglass is not the same. Some poorly laid glass will laminate and flake off in layers over time. This is very hard to stabilize once it starts. Others have too much hardener and can "dry out" become powdery and make adhesives useless if you don't first refinish and glaze the fiberglass. So just be sure of you substrate before you put those expensive panels up there.

Otherwise have fun.

I have evaluated the surface and determined that it is solid. I used to live in an area that had an incredibly large boating community and am familiar with the failures and life of fiberglass. While the body of these motorhomes have some problems, the roof seems to be well made and I have seen no problems with paint adhesion unless the original surface has been violated. I have seen many boats that are more than 50 years old, still in good condition, but have seen many failures that occur within 5 years, with most problems showing withing 10-15 years. The problems on these units show up where the two halves of the body was fastened together but the roof is in one piece and has not shown problems. The paint is a quality application of Dupont Imron.

personally I think this is a dumb Idea for a few reasons. 150MPH??? are you kidding me? since all you stated you want is to charge a small lithium battery for camping purposes you really don't need to be charging during transit. flex panels have their place.....on your roof isn't really one of them. as noted already, any panel including thin film, poly, etc works best when placed in direct sun. having a flat panel glued to roof will only get maximum exposure when the sun is directly overhead. this also becomes a problem once you park, your choice of parking spots becomes a slave to exposure of the flat roof.a more portable set-up that can be oriented to the sun will have far more output. gluing anything to your roof is just dumb.

GA! that's what I like about you.. not afraid to say what you mean! PV panels need to be angled at the sun for max effect.. on a moving roof?? Flat? Please!!

I don't know, maybe his motor home goes 100MPH into a 50 MPH wind

Good reasoning Fredski; I would suggest he buy a generator and eliminate the problem. Some portable generators, like mine!, are horribly noisy, but I have seen, not heard, some that are pretty quiet. Might have been Honda.

Yes, Honda. (Usual disclaimer)

Honda engines are nice, but their generators are not. Too many odd harmonics and weird waveshapes. Best is a Honda powered generator with the generator built by someone else. They are still not quiet enough for my wife and myself, though. The only reason I have thought of having a gun while camping is to shoot the idiots with generators. It is really good I don't carry one.

I don't know the situation where you guys live, but here in Australia, using a generator in an otherwise nice quiet bush camp is a good way to gain enemies fast.

I'd rather have the modules stationary, mounted flat and secure on the roof of the RV rather than be a slave to setting up and moving a portable array. If I wanted the output of a 800 watt dual axis tracking array, I would rather add 400 watts of modules mounted flat. Maximum performance is a great thing, unless it involves parts that add weight, cost, complexity and additional maintenance.

Example: N 36 degree latitude:

Simple: 800 Wp flat - 4.42 kWh/m2/day 894 kWh/yr

Complex: 800 Wp dual axis tracking - 6.35 kWh/m2/day 1,330 kWh/yr

Simple: 1200 Wp flat - 4.42 kWh/m2/day 1,341 kWh/yr

For comparison - not practical for a vehicle.

Best: 800 Wp fixed 30 degree tilt - 4.95 kWh/m2/day 1,009 kWh/yr

(The above information is a compilation of data from PVWatts and the opinion of someone who does not want anything else to work on or maintain. If someone has the time and energy for a project, tracking is great, but not really cost effective.)

Actually, when camping, my roof is normally at a tilt of about 18 degree to horizontal by the construction of the motor home. When it is parked or traveling it is horizontal. I have taken readings in both positions, summer and winter at various latitudes in the US and there is only a slight variation in the summer and in the winter, while very noticible, not enough to ever consider the ability to change the angle. I do try to orient the vehicle to the optimum direction when the batteries need more charge. This sometimes involves turning the vehicle around in the morning when microwave usage is high after a hard night on the computers. If we are spending only a couple nights, the batteries are large enough not to really need the solar. Unless we run the AC. We rarely do that, preferring to head to the mountains instead.

If you think you might be heading somewhere other than the mountains you might consider finding a way of making a false roof with an air gap. The flexible panels I have seen were all dark colored and would transfer a lot f heat into your cabin. It would cost more to make a false roof and modifications to keep it from flying off while driving would require some good engineering but it would keep the new black roof from heating the cabin.

Drew K

Although not as large a square footage as I intend, but another owner put 2 on top of his unit and I did not feel any heat gain on a hot day in Las Vegas, NV. I put my hand directly underneath the panels on the ceiling and then at the other end of the roof. The panel was hot outside, but the ceiling didn't change temperature. He used RTV but, as with any silicone product, the edge was unsightly. Also, it couldn't be painted.

It is possible to experience 150 mph windage on the roof of a vehicle traveling at legal speeds with a head wind of less than 50mph. Remember the physics courses where you studied airplane wings and other shapes? This motorhome is quite aerodynamic not like a normal one. The wind over the top of the vehicle is the sum of the forward speed and the added wind created by the compressive forces on the front of the vehicle forcing air over the top of the vehicle added to the headwind. The 150 is not a conservative value, it is a real life probability.

balony

Did you even bother to read what I wrote, or are you simply not capable of understanding it?

Not sure where you're located, but here in the US I've found an excellent product for RV use at Lowes called 'poly seam seal', in the caulking department, about the same price as quality silicone. I've used it for setting ceramic tile, marble, etc., sealing joints, it makes a flexible grout and sealer for fittings on my '87 EMC motorhome and after 10 years exposure to uv is still tight.

I will check that out, along with other suggestions. Thanks.

I check out the polyseam seal and the manufacturer says no. It is air cured and the middle of the panel will have no strength.

I can't figure why so many folk here are trying to talk you out of using these flexi panels.

If it was my RV I'd go the same way. It's 2013 already!!

Have you stuck 'em onto your roof yet?

No, I haven't even received the panels, they sent them UPS which is very unreliable in my area, even worse than normal. At least they are insured for full price. They have totally lost track of shipment right now. They haven't the slightest idea of where it is. I will probably have to tent the top to bring heat up enough to use an adhesive due to winter chill. Right now we are having a winter storm so I will have to wait that out anyway. I40 is closed off and on due to wrecks.

Wow, lots of good discussion on this thread. Not much mention on how different adheisives actually fasten to the surfaces. I am not a chemist and can't talk too much about it.

From my experience and thinking about it when you use a silicon on smooth surfaces the goo remains tacky and there is some bonding between the materials but I feel that it is the removal of air and the air pressure on the outside that actually holds the brunt of the binding force. This can be very effective, I saw a demonstration with two very smooth pieces of glass that are bonded without any chemical at all. They are placed one on top of the other and gently pressed from the center, you can watch a ring of refraction move as the air escapes. Once all the air is out even if the glass overlaps you cannot separate them, even if broken the small pieces hold together. It is due to the static friction (temporary association of electrons between the two materials) and the air pressure holding it together.

Some adhesives bite into the surface so you have to roughen (key) both surfaces for a permanent bond then the glue hardens and physically holds them together. But this is not best for your fiberglass and plastic bonds.

From experience, my favorite is a contact adhesive. You apply it to both surfaces and wait till tacky then press them together. I made a belt for my sander out of 1 inch wide roll of sanding cloth and it has sat for 3 years with tension on it without separating any (I only needed it for a quick job and have not used it since). Your job is on smoother materials but I feel that it would work just as good. As for what brand to use, you get what you pay for as you seem to already be aware of.

When it comes to removal time you might consider just putting another panel over top of the damaged one instead of removal!

Drew K

I have never used contact cement in the outside weather. I have heard from some companies that they are worried about their product curing with two flat surfaces together. I wonder if I could use contact cement in the center and a sealer/bonder around the edges to keep weather out. I would have to try an experiment and think a lot about it Also I would need to look at the temperature range of the contact cement bond. If the temperature is OK, then maybe I could just lift the edge slightly to apply the sealer if the panel will flex enough. Thoughts.

No matter what you use, if it does start pulling, I would repair it with contact adhesive. It will likely leave an unsightly bulge but it will hold. I have used it after watching people try to use silicone caulk to repair a counter-top edge that was pulling away. I did key the surface a bit to get through the silicone but it held after that (but it was not as smooth as it was originally).

If you were to use it as the primary sealant and not for repair you could get it to sit quite smoothly without bulges.

I have seen it used in kitchens and baths for linoleum, vinyl and tile flooring / counter tops. With the vinyl flooring they usually use a 'toothed' trowel to texture the contact adhesive. I am not positive if this is to allow air to move for curing or for another purpose. I have always applied it smoothly.

Here is a website with some frequently asked questions. It only mentions that you want to avoid high heat for 3 days after application and it takes longer to cure in cold weather.

Contact cements , like 3M 77 super are useful, and are used by upholsterers and automotive people, as well as aircraft and boating types. One problem is the surfaces have to be perfect for the adhesion, and the chance of failure is not known until FAIL (It will not give you an idea at application. It seems stuck, but temperatures and humidities sometimes cause failures.) 3M also produces 4200 and 5200 sealant/adhesives, with the 5200 being considered permanent. These are similar to the SikaFlex 291 mentioned, which is also great. With the 5200, You need to chisel the cleats off my boat. Look at a company called Master Bond, which advertises on Global Spec. Call em up, and they will give you a lot of ideas. Good luck!

4wsilver-

Due to my extensive experience in the adhesives I will not provide you with an answer. There too many important parameters that have been left out to give you any sort of even close adhesive to your question. For example-

You have a painted fiberglass roof- What kind of paint, coats, any repairs to it, etc.

What condition is the roof in?

Are there any seams in the roof, protruding objects such as rivets?

Do the panels ever need to be removed?

Etc.

I would seriously advise not doing anything with the answers you receive with this forum. How do you know which answers are good or those that aren't worth sh$t? How do you know what the knowledge of the posters is relative to adhesives and their properties? How do you know what the intent of the poster is? It could be someone who has extensive knowledge and could recite "Skeist's Handbook of Adhesives" forward and backwards? Likewise it could be some jerk only interested in leading you astray. Unfortunately there are a very small percentage of them here. My old boss was a "glue guru" like you need but he is long retired.

Start with Adhesive Manufactures, they are the ones who know their products and their competitors products. Try with Henkel, Locktite, 3M Adhesives systems div of 3M Specialties Div., Franklin Int'l., and many others. Ask their tech service depts. and describe your application to them. If they have one they will tell you. If they don't, ask them who would. They are honest with you because they want to make a good impression for later sales.

Besides all this, how can you tell I'm really versed in adhesives or just a jerk? No replies to that part please.

Good Luck, Old Salt

Wow...not sure if I should give you a good answer or vote off topic. You seem to have a very harsh negative view of CR4 contributors and have displayed a perspective that the OP is in imbecile also!

Ok, despite the good advice I am going to give this an off topic vote because disrespect should be challenged not rewarded. Your advice on contacting a vendor for expertise is good but proposing that the forum is ill advising or outright sabotaging people is reprehensible!

Drew K

Drew K-

Sorry to see you have misunderstood what was said and it's purpose. Having used it several time when specific but vague questions are asked, I have never, that I recall, received the comments you have given. Most times other contributors have acknowledged the problem and have verified they do exist on this forum. Fortunately they are a very small percentage as most of us, yourself and myself I'm sure are, are honest and try to assist in the best way possible.

No, the OP is not an imbecile but someone who has posted a reasonably smart question and should be given a smart answer. Having worked as a Plant Manager and District Operation Manager for a large adhesives division of a large chemical corp. during the early part of my career I am somewhat familiar with so relevant things. Due to this I am somewhat familiar with adhesives. I am familiar enough to know that there is a whole lot that I don't know and would have to know about this specific application to give a good answer. If the OP wants a good answer he must provide additional information, he needs to specify much more about the situation. That is why I asked those questions. Since I know that many other items must be given I knew that I couldn't recommend an adhesive without them. My intention was to do the OP a favor by not recommending something that I wasn't positively sure of and get him in trouble later on. There is a saying of concerning smart people, of which many of the contributors are: "The more you know, the more you know you have to learn" or sometimes expressed as: "The more you know, the more you know the more you don't know."

As for disrespect, there was none! I stated what is true and acknowledged by many who give good answers and know what they are speaking of. There are some people, a few as I stated, that get some deviant pleasure by giving information that they know is wrong. I have never done that but many others have seen it besides myself. I would be doing the OP and CR4 an injustice if I did not warn him of those few. Would you want to post a question, see what seems to be a good answer and then find out after you have spent your good money and time that it was an intentionally bad answer? Also if you know much about adhesives you would recognize that many of the answers are incorrect and unworkable, especially since more information is needed.

As for the adhesion to the roof, it is mandatory to know much more about the two substrates. Elmer's Carpenter Glue is great for adhesion to wood or OSB but won't hold onto paint for example. That is called adhesion failure or substrate failure. Why do I know, I made it.

Your statement about my conduct in being truthful about the few ill-intentioned contributors "but proposing that the forum is ill advising or outright sabotaging people is reprehensible!" is a great exaggeration of the truth, what was stated and the obvious intention of its use. I did not state that and did not ill advise anyone. As for "outright sabotaging people is reprehensible" That was never done and was clearly not stated as such. Since when did warning an OP about the fact that some of the contributors were probably guessing at answers when all is considered become a reprehensible thing? If you go through some of my previous answers, some other contributors have though they stunk and have told me so. If they are correct I thank them, I they are wrong I politely state the reasons for my conclusion to the answer.

Also, as stated, adhesive manufacturer's tech service people are far superior to any other resource for getting a correct answer about adhesives. Analogy- "I go to a dentist for my teeth. I have a dremel and could do it myself but he does a much better job."

Finally, I don't post any answers to any OP unless I am truly positive, and have other resources that agree with me, that I have a correct answer. There are many more that I don't answer than I do answer. Perhaps other contributors should follow suite. If you desire to, I do accept gentlemanly apologies.

Good Luck, Old Salt

Drew K-

Your latest correspondence definitely shows that you have taken it upon yourself to be the CR4 police. Don't do that, I won't but someone could burn you for that, figuratively speaking. As for the eloquent language that your perceive I was derogatory about, eloquent talk if not talk but babbling it doesn't have substance. There is a very popular book which mentions that. paragraph #2

If you don't want the cookie why are you persisting on forcing your personal policies on others? You won't win and I perceive you as being regretful when you realize it. paragraph #1

If you think something is insulting to the forum, why do you force your opinion upon everyone else. You're only one person so as I said before, "Who went on vacation and made you the CR4 police" forcing you views on others and making me write all this rubbish because you apparently don't like me. Maybe I don't like you but I never acted the way you have and I don't gloat on it. NO, paragraph #3 is not insulting in my view and many others I'm sure. paragraph #3.

If you are unwilling to go through other posts you are going off half cocked and with out substantiation. I'm responsible for my comments and am willing to discuss them with anyone, except you. Paragraph #4

I find it hard to believe that you would honestly apologize. That's my opinion about that. Remember that great philosopher, Dirty Harry "Opinions are like a$s holes, everyone has one". Also in my opinion you are wasting much time on your behalf, my behalf and many others time. Paragraph #5

I'm done with your CR4 policeman aberration. Trying to discuss something with you is like p$ssing into the wind, you only get wet feet.

If you think you are not being offensive and using eloquent language to attempt to demean me, forget about that. Not only do I have the vocabulary of my grandfather the coal miner but also that of my mother. Many times growing up I couldn't understand her sophisticated language to me. paragraph #2

This is my last correspondence with you, I hope. Get with engineering and not grammar, composition, philosophy, and Emily Post. Come down to reality. Very few other people on this forum take it upon themselves to force their viewpoint onto others. Why should you? Put away the badge, who knows, I may have one too!

Yes, this is one of the most terse correspondences I have written in a long time. I don't like to but your actions were very impolite and condescending.

As a good friend of mine says: Hasta luego , Hasta manana, Good Bye, and other phrases that I won't mention in public correspondence.

Get a life.

Old Salt

You're both top blokes as far as I can tell through CR4.

Stop being so sensitive about what really and rationally doesn't matter.

We can all be a bit snarky at times...human engineer's nature.

At least your both not hiding behind an "Anonymous Poster" handle.

Peace, and be excellent to each other.

Wal-

Thank you for your comment. That is the message I was attempting to get across. I haven't been told that I am too sensitive in quite a long time so I'll disregard that, with humor of course. I Just try to be a good guy and good enough that I make it to the place where things are nice.

Haven't seen snarky used in that term before but if you say so that's good enough for me. Hey, I love life! That has gotten me this far, a long long far! It's worked this long, so I'll stick with it that way.

Good Luck, Old Salt

Old Salt:

I have given the information that you noted in your post. It wasn't in the original question but is covered. I have been in touch with Loctite and Henkel and they do not have an appropriate product but introduced some ideas. 3M has sent me a note but have not given a final answer. They are my best hope. A few other manufacturers I have contacted maybe longshots. I posted to get ideas, but I will check all possibilities and problems. Repeating previous information, the paint and fiberglass is in good shape and the paint is Dupont Imron. I have already done a few random tests for adherance of the paint.

Thank you for your post.

Perhaps you should consider doing this as if you were repairing the fiberglass, i.e. remove the paint and then using an appropriate resin that will work with your existing roof, and possibly minor amounts of glass reinforcement, build the panels into the roof.

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Sure you don't want to reconsider adding a boat tail with a hinged soar panel as the upper portion? The curved panels could be shaped to work with the curves at the back of your Vixen....

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This topic really has become artificially inflated, just get the job done.

1.Clean the roof thoroughly.

2. Use a good quality silicone or Urethane adhesive, acetic or not won't damage the PV substrate as it is isolated from the backing where the glue will be.

3. Even if there is some defective surface on the roof, the amount of coverage will overcome that.

4. The panels will be quite adequately secured and will not come off.

5. After the glue sets, the panels will be so secure that you will have to cut it to get them off.

6. Don't use contact adhesive as it is not a good gap filler and doesn't cure well when thickly applied.

According to the manufacturers tech people, all of them say that with a thin film like that the silicone or urethane adhesive will never cure in the center, for at least years and will provide no adhesive qualities, as in the panels will come off in the wind. None of the manufacturers recommend them.

Why put the adhesive down as a thin film? That's inviting trouble.

Normal practice would be to apply it in beads around 1/4" thick, about 4" apart, get the panel on when the adhesive is still quite wet and don't press it down too far.

A continuous bead around the outer edge will prevent later moisture and dirt ingress and the trapped air in the gaps will promote curing of the inner beads.

Maybe when you have discussed this with the reps, they have confused your mention of thin film panels with an intention to use a thin film of adhesive.

A silicone or other similiar item will become quite thin when the panel is fastened down as you suggest. Perhaps my nomenclature is incorrect but I think the manumfacturers reps and I are communicating and I can see their point. Basically the outside edge cures so fast and so well that the inside never does or takes a long time to do so. Basically they warn against large flat surfaces like this being held at the edges and not at the interior and the flexibility allowing windage to pick the panel up at the center. I believe 3M is working on it, at least they say they are. I will report back what solution I finally use. I basically used the method you propose on the small panels on top of my pickup camper and it worked but I can tell that they are stuck only at the edges. What saves them is that they are so narrow, they only need to be stuck at the edges. Also they probably will cure eventually.

More application technique stuff: Put some adhesive in the center. On the edges, use skip application, maybe 4" on, then 1 or 2" gap, then another 4" on, etc. This will allow air to get to the center for curing. BUT: Continuous across the front (and maybe part of the sides?) to keep air from getting under the panel when you are driving.

Sergeant,

I think that is the way to go. And allow some air channels between these.

When dry, the edges can be sealed separately. G.A.

4wsilver-

I'm not surprised about your problems finding vendors or adhesives. There are at least a thousand adhesive manufacturers in the USA. Each one has, at a conservative estimate, at least 100 different formulations. Some are identical in formulations, mostly household types or large quantity uses. There still is what you want out there, it may take a lot of hunting. My concern with the paint is that gluing onto paint usually causes separation of the paint from the surface it is on. The adhesive has much more holding power to your panel than the paint has to the roof. This is most often caused by the chemicals in the glue softening the paint and causing it to fail in the worst possible situation. Your test for the paint should be gluing the back of the panel to the paint with the adhesive. This is the best sort of test. It will clearly show if there is substrate failure.

I would like to suggest you go to a larger library and look in "Skeist's Handbook of Adhesives". It is the bible of the adhesives industry. Not only will it discuss something that might work but also give you the names of many manufacturers. A google search of "Adhesive manufactures" might help. Also try Glue-fast in lower Manhattan of New York City. They are a distributor of many manufactures products so they might be able to recommend something they handle of direct you to a manufacturer.

Good Luck, Old Salt

Thank you. The tech desk at the manufacturers is not like it was a few years ago, but several have gotten back to me. 3M still hasn't. Our public library does not have Skeist's but I suspect that LANL does in their library. I know there is a way to check out book there, but since it is "behind the gate" I never have. I guess I need to find out how.

4wsilver-

If you are having little success with the "Tech Desks" try going to the "Tech Labs, Development Lab, Technical Services, etc. In working in the industry I found that they are much more helpful, and smarter, than the "Tech Desks". You will also find more "Glue Gurus" there usually. (No offense intended towards Tech Desk personnel).

It will probably take more effort to get to the lab personnel but it should be well worth the effort.

Good Luck, Old Salt

All industries have layered their technical assistance. The first level are either foreign or new people who can only look up information and sometimes have no idea where to look it up. By working through the layers, it is usually possible to eventually get to the right knowledge. Sometimes I have simply had to use my employed identity before I retired. I really hate to do that on personal items, but sometimes that is the only way in.

Your panel strips are probably not very small. Means, they take some glue. Do not use thixotropic glues, they could pose a long term temperature failure problem.

The best glue to use is the 3M 4000 or 5000 series. I would only glue the borders with this glue (3/4 to 1 inch under the strips) and provide a soft (cheap) non- acidic silicone glue (caulk gun type) in between. The silicone is cheap, but will have peeling edges.

The e.g 3M 5200 is bonding like no other and is elastic enough to deal with the silicone and your base.

Here a caulk gun size tube 3M is $25,00 roughly and the silicone $8,00 per tube. If you ever want to release the panel, a razor knife will be needed.

Success to you.

I will check the 4000 and 5000 specs. Again the manufactuers are concerned that the center of the area with silicone will take years to cure and might never develop any strength. I will only pattern bond the centers.

No need to remove ALL the air between. Keep a small distance. That is enough to cure. Ever tried to store a opened silicone caulk for long time? You need tiny ridges of glue. You will see that the panel is stiff enough.

Have you communicated your requirements to this glue peddler (Master Bond) ?

So what do you think of the idea of doing this as if you were repairing the fiberglass roof, i.e. with resin and (limited) glass fabric?

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....or did I get that idea disqualified by posting a picture related to constructing a boat tail with solar panels?

I'm thinking along those lines too.

The flexible PV arrays would be held most securely and look real slick if they were potted into the fibreglass roof's surface gel coat. Something like these boats.

Here is another website to look at with multiple DOW articles, there may also be other manufacturers articles on the website.

http://www.globalspec.com/supplier/TechArticles/DowAutomotive

Have you contacted solar panel manufacturers for there recomendation for this application ?

I tried your link, but even though I am registered it won't go further for more details. Yes, I have tried the manufacturer of my panels and similiar ones and they won't commit to an adhesive. I have gotten to 2 products by contacting application engineers, one by 3M and one by Dow Corning and although they will work they are pricey and have considerations to deal with. The biggest problem I have now is to hold a temperature 50F above high ambient for 24 hours. I can do it, but may wait a few months. I think this thread has about run out and no magic solutions appeared, but I will still keep following it just in case. It appears the Tedlar only has a few adhesives rated for it. Anything that will stick to it will also stick to the paint surface. At least everything I have found. Some of the 2 part are great, but the minimum quantity and special equipment are more than the value of my motorhome.

'....hold a temperature 50F above high ambient for 24 hours....'

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Vixen is low enough to fit in a garage, right? Even if a garage is not available, getting the inside of the Vixen nice and toasty then covering the outside of the area being cured with an electric blanket followed by a sleeping bag should easily meet the requirements in most places.

Again, other methods have been proposed. Friends have just finished a 3 panel Solar array on their sailboat and now are in Mexico--They used a frame system, as mentioned by others, using metal furring strips that are mechanically fastened to the surface, so no worries, then the panels are fastened to those strips. If the panels have no grommet sites, then using a cap-strip over the edges works well. If thin sheet and not able to support itself, then a thin reinforcing sheet under the solar panels and then "clamped" using the perimeter system. This system was recommended by the Marine Solar installer, as he seen just about every type of failure , over the years, on sail and power boats around the world, in both very hot and humid areas, and North and South in subfreezing conditions. He will not use adhesives, only mechanical means of fastening, that allow for repair and replacements down the line. What happens if a tree limb breaks off and damages a panel from above? What about going across the Arizona or another sandy type desert, and having your panels nicely "frosted" by a few hours of Chinook type winds, mixed with a fine sand? Ever been in a REALLY BAD hailstorm? We were in one that blew out tempered glass windshields. You never know, so maybe prepare your self for the potential.

Not a worry if you regard the flexible PV array and the surface it's adhered to as consumables and just accept the risks.

Boats are different. You have to go for robust and maintainable for the sake of possible personal survival at sea, having to withstand the forces of water flow and not just air flow and then there's the higher capital worth of the vehicle itself.

This RV will look "nice" with a flush mount. There has to be a glue that will do it reliably.