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Threaded Inserts for Small Sailboat Restoration

05/28/2009 9:14 AM

In restoring a Mistral 404, I need to remove and inspect all fasteners to ensure their holding force is sufficient.

Epoxy manufacturers, such as West System recommend gluing the wood screws in, making the fasteners permanent, or semi permanent if using mold release.

Since I need to make the fasteners sturdy for now, and proceed to more in depth restoration after the summer, I am contemplating glueing threaded inserts and using machine screws.

Inserts such as Self-Locking, Blind Threaded, Type IBLC from Penn Engineering would be good in my sense.

Thank you for any advices and warnings.

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#1

Re: Threaded inserts for small sailboat restoration

05/28/2009 9:47 AM

Don't use any of those split inserts that rely on the screw speading them to make them grip...they are awful....the screws always squeak and bind as you put 'em in and the inserts never grip decently.
This is based on small dia' inserts into plastic mouldings, so I'm willing to be gainsaid (assuming there is such a word)

Del

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#2
In reply to #1

Re: Threaded inserts for small sailboat restoration

05/28/2009 10:20 AM

Thanks Dell, the inserts I want to use are knurled, blind, stainless steel, self locking type.

Assuming I can get them in an sufficiently small quantity...

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#3

Re: Threaded inserts for small sailboat restoration

05/28/2009 10:28 AM

Thank you, I would rather go with stainless steel for durability, knowing it is greatly over designed.

Not many inserts can be found blind, witch I prefer in order to seal out moisture from the wood structure under the fiberglass hull, to prevent epoxy contamination of the threads and prevent pull-out if excessive length screws are used.

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#4

Re: Threaded inserts for small sailboat restoration

05/28/2009 11:18 AM

Use the West System guidelines unless you are replacing frames and need the boat to hold it's original shape. In which case decking screws will hold it together until your re-framing is done. Whatever inserts you may use must match the screw material, and be epoxied in place anyway (bad idea).

'Iron sick' holes need to be bored out and epoxy filled, in planking and frames. There us no way to rush a restoration. Repairs are quicker but less satisfactory. Doing this work, you will find all the other areas that need attention, and I would suggest you start by removing the garboard, 1st, 2nd, and 3rd planks. The keel, floors and frame ends will be exposed for evaluation. Then remove the covering board, sheer strake, and devil plank for the topside frame ends, and sheer clamp inspection. Follow that with a few planks at the turn of the bilge, and now you know how much additional work you will need to do, from the stem heel, gripe, all the way aft to the transom.

The Gougeon Brosthers 'On Boat Construction', and 'Boatbuilding Manual' by Robert M. Steward are required reading and reference books, as well as any good restoration books specific to your project. Read first, hire a restorer for a week, and work on your patience skills. You will be tested on this.

Done well, this is the most satisfactory work you can do. Enjoy.

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#5
In reply to #3

Re: Threaded inserts for small sailboat restoration

05/28/2009 11:37 AM

glad 2b of help

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#6
In reply to #4

Re: Threaded inserts for small sailboat restoration

05/28/2009 6:58 PM

There is a product that will work in blind holes, and designed for marine work, and are removable. It might not be right for your application, but I am sure someone here will know the answer to that. The product is called Wellnut. They are manufactured by Hanson. Try http://www.hansonrivet.com/w71.htm . Good luck. Send pictures.

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#7

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 5:33 AM

We are manufacturing many kind of threaded componenst for more detail please visit http://www.nutsboltswashersindia.com

Thanks & Regards,
Harish Doshi

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#8

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 6:07 AM

There seems to be a misunderstanding about the strength and qualities of stainless steel generally. It is (mostly) impervious to rust and corrosion - true. BUT it is not as strong as most good steels.....but of course good steels generally rust......."you pays your money and you makes your choice!"

This is why some really good fittings are high quality steel, but coated in zinc to try and improve it against rusting.......regular /cleaning/greasing may also be needed especially in salt water regions.........

I agree with you that what you are doing needs stainless for longevity, but do not think that it is the best in everything else......

Stainless has some other bad working qualities that I have recently been trying to combat as well, but we need not to go into that here......

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#9
In reply to #8

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 7:23 AM

A very good point.

I am replacing wood screws with metal inserts, so brass would also be sufficient.

I will be sailing in fresh water for the foreseeable future.

SST is used on almost every hardware part on the boat.

Since I need to epoxy the inserts, I want to maximize the bond strength. Over tine nickel or brass may be weaker.

The West System can be used to bond fasteners directly, but my restoration steps are to first ensure all hardware is secure for this season, and then remove all later to complete the hull restoration and gel-coat finish.

For this inserts would be best.

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#10
In reply to #7

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 7:29 AM

Thank you, but not much information can be gathered from your site.

Since this is a one of project, the required quantity is low, below 50 fasteners.

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#11

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 10:19 AM

Brass is not a good alternative, after a few seasons the metals seperate and it just falls to bits.....bronze or gunmetal or stainless would still be better....

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#12
In reply to #6

Re: Threaded inserts for small sailboat restoration

05/29/2009 10:29 AM

Guaranteed to split the frame, after it has already been weakened by drilling a bigger hole in it.

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#13
In reply to #4

Re: Threaded inserts for small sailboat restoration

05/29/2009 10:35 AM

As this is a single hull fiberglass boat, there is no way to disassemble it.

The boat frame must be wood/plywood and after 20+ years, most screws do not have much holding power.

Not good at sea!

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#14

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 11:02 AM

Almost none of you are "getting it". I am a boatbuilder/restorer. Each component in a boat is made to minimum allowable dimensions, with the maximum obtainable strength per material. Even the 'Constitution', or "Old Ironsides', with 3 foot thick planking was made to be as light as possible for its intended purpose.

Drilling into the frames weakens an already minimal section, and unless the doohickey you insert adds to the strength (which in this case does not), you've weakened the section, added weight, and increased the cost of a repair that is just asking for another way to split the frames and allow water into the hull. Compound that with cyclic loading and the lack of frictional and shear advantage from wood to wood contact, and you'll have a flexible flyer in no time.

This is the first reply to CR4 that I am adamant about. Doing this with inserts is not part of a restoration, it is a cobb job! DO F≤^&#ING NOT DO THIS!!. You will ruin the boat, and negate any re-sale value it might have had. One look from a marine surveyor and he'll say "burn it".

Do what you want. Youv'e been warned.

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#15
In reply to #13

Re: Threaded inserts for small sailboat restoration

05/29/2009 12:07 PM

Sorry about the rants. I thought you were doing an old wooden boat. I just looked up the Mistral 40.4 and it's Tupperware. There is a 'repair' for wooden boats that is reversible for a complete restoration. The inserts are still not a good choice, but you can try this: Remove the fasteners one at a time per frame, bulkhead, whatever. Drill out the hole maybe 1/8" dia., and just short of the original depth. Syringe raw epoxy into the holes just enough to thoroughly wet them. Wait until the epoxy 'kicks' and stuff the hole with thickened (wood flour, microballons). Run a cheap drywall screw and a washer that have been lightly greased with Vaseline into the hole. Remove these when the epoxy has 'kicked', wait untill set and drill and countersink for your new fasteners, and fill the screw heads just proud of flush of the hull with low density filler (use microballoons if the screw heads won't get onto the original fiberglass). Wet sand when cured (#320 or 400 wetordry), paint, or order a gelcoat kit from Mistral.

Hope this helps. And again sorry about the Rant.

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#16
In reply to #15

Re: Threaded inserts for small sailboat restoration

05/29/2009 1:24 PM

The rants are a small price to pay for good advice...

Since the screws were siliconed, epoxy without drilling is not a choice.

There is a limit to using larger screws.

Since I want to be able to remove the hardware, to epoxy the screws did not seem a good idea.

Modern boats use aluminium back plates instead of wood, so the insert idea comes from this.

West System people tell me that this has been done before.

This type of insert seems to be a good solution for a permanent restoration, once epoxied no water would get thru.

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#17
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Re: Threaded inserts for small sailboat restoration

05/29/2009 1:28 PM

Boat shops sell sleeping stuffed cats for great boating enjoyment!?!?!

Dead relatives?

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#18
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Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 4:04 PM

My apologies for the rant. I was misinformed in my assumption (= ass out of you and me). Enjoy your dinghy, get in a race, have fun! See #16

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#19
In reply to #8

Re: Threaded Inserts for Small Sailboat Restoration

05/29/2009 7:51 PM

"Stainless has some other bad working qualities that I have recently been trying to combat as well, but we need not to go into that here......"

Galling?

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#20
In reply to #15

Re: Threaded inserts for small sailboat restoration

05/29/2009 8:04 PM

I liked your technique for filling the hole. But as always I have a question. I wonder if the epoxy plug might be stronger if the hole was angle drilled so that some of the epoxy would be under the remaining wood and resist pulling the epoxy plug out better.

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#21
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Re: Threaded inserts for small sailboat restoration

05/29/2009 9:37 PM

This a good idea, there is a technique I saw to do this using a bent nail.

I will try to make a conical shape, or at least to roughen the wood quite a bit.

I may very well be able to get sample inserts, the purchase minimum from Penn is 1000. It is after all a small project for my engineering company...

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#22

Re: Threaded Inserts for Small Sailboat Restoration

05/30/2009 1:56 AM

Whatever you do don't use vaseline...Use KY jelly.

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#23
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Re: Threaded Inserts for Small Sailboat Restoration

05/30/2009 6:10 AM

Ok, but I use neither.

Cooking spay works too, but my Wife does not appreciate.

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#24
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Re: Threaded Inserts for Small Sailboat Restoration

05/30/2009 9:07 AM

We're talking about screwing inserts here, ..........

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#25
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Re: Threaded Inserts for Small Sailboat Restoration

05/30/2009 1:49 PM

It's got to taste good nonetheless!

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