Mylar and Mouldless Layup

Mylar works fine with polyester resin,don't forget to apply some mould release or other lubrication on mylar surface.

Thanks,

Mylar is not styrene-based. What you need is polyester film or sheet;it is quite resistant to acetone, MEK, toluene and the like. I don't know if it is resistant to styrene, but if I had to guess, I would say it is.

Mike

Normally, I would let this fly, upside down until it crashed. But in the interest of other hobbyists, I shall comment.

Boats, and ther appeal, partially resides in the fact that they are a curved entity. Graceful transitions in at least 2 directions, unless you are building the most primitive Garvey and it looks like a cement barge. Mylar and sheet metal only bend in one direction at a time, unless you are an adept metalworker who can 'torture' sheet metal. Some boats take advantage if this by designing a transition from one plane to another, and then back again. If this is your type of design, your in luck.

In that case, sheet metal will help with fairing to the extent that your frames have proven fair to begin with. Check this with a full length batten first. Use a plane or belt sander to adjust until the batten touches each frame without wobbling or recurve. A longboard is used to final fair the hull surface after Bondo-ing your plug or female mold.

Polishing the mold to receive a mold release agent requires mucho elbow grease. Long boarding with finer and finer grits. Hand sanding to about 120 grit minimum, 400 grit preferred, and finally 'waxing' the mold. This can be up to 5 coats of mold release agent. Carnuba wax is preferred. Butchers wax will do for a one off. For compound convex curves I have used Saran Wrap® in small areas. Any wrinkles or imperfections will be translated to the final product.

That said; Wood is good, wood/composite is better, cold molded wood/composite is best. See 'The Gougeon Brothers on Boat Construction". You might have saved yourself a lot of work.

Carl P. Boatbuilder

thanks - but the 'fair' curve that we are discussing here is over 60 feet long - and 'fair' IS relative. It is a 'recover' of an aging fishing boat. I'm sure that what you do with longboards and so on is much of what I am doing too.

I will not bore you with my technique for achieving a smooth and fair bottom (successfully - and no - it is neither primitive, nor is it a cement barge...)

the "one direction at a time" (AKA compound curving) issue is mine to deal with .. so you should not get so 'worked-up'. I simply wanted a confirmation that my layup products would not eat what was an offhand recommendation from a passer-by.

:)

thanks and - have a nice day!

My experience with polyester film is that it is very durable.

I think you might want to wax it anyway, to aid release.

Seems to me a simple test of the materials would give you peace of mind. Two samples, one waxed, one not. Perform a water break test of bare polyester, then again after waxing. Does it look different? Beading is good. Sheeting is bad. If they both look the same, maybe release agent isn't needed.

Good luck.

Ah HA! Sorry if I sounded huffy. Saran Wrap® works well for what you want to do. Which is compress the fiber to drive out air and fill the voids. But I have only used it with epoxy, or with the polyester gel coat I get from the original manufacturer.

More importantly is to raise the moisture content in the whole boat to about 14-16%. This is the moisture content, plus or minus, of what your boat will settle to when on the water.

Good luck! (and get lots of helpers)

apology accepted - but huffy isn't the word that came to mind :)

nope - saran wrap will NOT work! not rigid enough! 4 and 6 mil polyethylene have been working well enough on the bottom, at the keel and the chines. I am looking for an even smoother finish at the shear band (she has a "raised-deck" cabin) and between that area and the waterline

oh - thanks for all of the tidbits about moisture... and getting helpers... and whatever other stuff.

At this stage we have 3 barrels of resin installed and 3 barrels yet to be installed - and moisture and labour are only 2 of a number of obstacles encountered thus far.

the boat splashes in 3 weeks

on time and inside the budget. I am looking for tricks to reduce final finish work.

hence the TOPIC OF THIS THREAD - to whit: "Does mylar (intended use - to help smooth the surface) interact with the resins that I am using?"

I hope this helps clear up any misunderstanding about the nature of the question

D

OK, Different terminology, but now that I know what you want, here's a couple more tips: I use a hard rubber roller (photo roller) on a plastic overlay like the poly you're using. The area between the chine and the shear is called the 'topsides' and for that, I can only suggest another coat and wet sanding. A Porter-Cable 6" Swirlaway with a foam pad makes for the fastest smooth finish. Get the vacuum adapter with it, resperators, etc. A gel coat may be sprayed on, but requires equipment you may not be able to rent for your intended purpose. Alternative application is roll on the gel coat (yellow foam roller covers) and tip off with a 4" foam brush, lightly at perpendicular to the hull. Get a box or 3 of them. That method works for paint as well.

This may seem unrelated. Before any finish coat, I hook up an air nozzle and blow off the cieling, walls and work benches, with an industrial fan exhaust. Vacuum everything. Just prior to the finish coat, spray a fine mist of water on the floor, and keep it damp if possible. This attracts the fine positively charged particles in the air to the negativly charged water on the floor.

If I still sound like an a..hole, sorry that's just me. Good luck.

SAND FIBERGLASS,SPRAY GELCOAT,SPRAY MOLDRELEASE,GELCOAT WILL SET-UP,WET SAND.

I have seen finished Masonite used to provide a glass like finish on concrete counter tops. Would that have any use in your application> It is cheap, and easy to work with, and glass smooth. Good luck.

Good suggestion - I may pursue this since I am having trouble picking up big sheets of Mylar locally.

Thanks

Derek