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Best way to add bolt threads in the board for the mast when building board?

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BWD
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Re: Best way to add bolt threads in the board for the mast when building board?

Postby BWD » Mon Oct 15, 2018 4:19 pm

Tee nut on top is stronger. Keeps full board in compression and spreads loads to deck and bottom.
Also easy to inspect and repair.
Nut hidden in middle of core relies on core strength, so needs much more core reinforcement.
And if it starts to break, you won’t know, until it fails completely. Also, every time you tighten the bolts, you will risk over tightening and damaging hidden parts.

If the nut is on deck, you can see if it is corroded, cracked, tightened too much and starts to crack the deck, etc. You have a chance to see the problem and fix it fairly easily before snapping the board or losing a foil.

It is not a problem if the insert doesn’t reach the bottom of the board.

junebug
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Re: Best way to add bolt threads in the board for the mast when building board?

Postby junebug » Wed Oct 17, 2018 12:01 pm

BWD wrote:
Mon Oct 15, 2018 4:19 pm
Tee nut on top is stronger. Keeps full board in compression and spreads loads to deck and bottom.
Also easy to inspect and repair.
Nut hidden in middle of core relies on core strength, so needs much more core reinforcement.
And if it starts to break, you won’t know, until it fails completely. Also, every time you tighten the bolts, you will risk over tightening and damaging hidden parts.

If the nut is on deck, you can see if it is corroded, cracked, tightened too much and starts to crack the deck, etc. You have a chance to see the problem and fix it fairly easily before snapping the board or losing a foil.

It is not a problem if the insert doesn’t reach the bottom of the board.
Thank you.

Another noob question: when I drill out the columns in the board and fill it with epoxy for the t nuts, should I drill the column wider than the head of the t nut (so the prongs of the t nut grab epoxy when I insert them) or narrower than the head (but wider than the barrel) so the prongs grab wood? I would assume the former, so there is less potential for water entry into the board but I’m not sure.

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downunder
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Re: Best way to add bolt threads in the board for the mast when building board?

Postby downunder » Wed Oct 17, 2018 1:16 pm

This is difficult question simply because you can't see what's going on inside. A tiny imperfection in unsealed wood and you got yourself a potential problem.

To be fair, for your first build this is way to complicated. Yes, it is a steep learning curve, but worth only if you'll continue building many boards.
My suggestion would be to build a TT style board, glass it, and than if you wish, slap a foam on top of it. Providing it's shaped nicely. Than glass it again on top only.

That way your SS inserts will be fully visible and as a plus, there will be no long bolts which can pop the insert out if you drill the wide column. Ie, you hit the mast, this makes a huge leverage on insert and pops it out, b/c the bolts are long.

On TT as I see it, there is no leverage, b/c bolts are short and in level. All the time.

D.

BWD
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Re: Best way to add bolt threads in the board for the mast when building board?

Postby BWD » Wed Oct 17, 2018 7:32 pm

when I drill out the columns in the board and fill it with epoxy for the t nuts, should I drill the column wider than the head of the t nut (so the prongs of the t nut grab epoxy when I insert them) or narrower than the head (but wider than the barrel) so the prongs grab wood? I would assume the former, so there is less potential for water entry into the board but I’m not sure.
Suppose the widest part or "head" of the T nut base is 20mm.
I would drill 25mm holes all the way through the board before glassing.
Next fill them with a strong epoxy/fibers putty (microfibers, wood flour, milled glass, etc.).
Drill out so you can fit the barrel of the Tee nut in the holes, maybe 1mm oversize so it slides in easily.
If the Tee nuts have prongs, flatten then with a hammer or pliers. They aren't needed (if possible, just get flat weld-on type tee nuts).
Get some long screws to fit the tee nuts, and wrap them in masking tape or similar leaving only enough threads bare at the tips to engage the depth of the tee nut.
Don't get petroleum jelly on the barrel or head of the tee nuts.
Insert tee nuts into holes from deck side. Secure to deck with tape, being careful to get a good seal.
Turn board upside down making sure the tee nuts are supported from below.
Coat the screws with petroleum jelly, and screw them into the tee nuts.
Pour epoxy into the holes around the screws from the bottom of the board.
When cured, unscrew the screws.
You now have tee nuts secured into strong epoxy holes, with enough clearance to insert screws easily.
Plug holes with surf wax, plasticine or whatever to protect from resin, and glass the board.
After glassing, open the holes with a drill -carefully.
If you feel confident, you could try potting the tee nuts and screws directly into the 25mm holes in one go.
If you feel too cocky to get a good result, you could try doing any of this stuff without using the foil plate or an accurate template to place the screws in the holes.

junebug
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Re: Best way to add bolt threads in the board for the mast when building board?

Postby junebug » Wed Oct 17, 2018 8:32 pm

Thanks BWD. I really appreciate you taking the time to spell all that out for me.


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