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U2U2U2



Joined: 06 Jul 2001
Posts: 5071
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Jul 21, 2019 5:44 pm    Post subject: Reply with quote







This was a Naish 2001era, Titan 109liters. Now about 92l.The nose and tail were both shortened and reshaped, mast track, footstraps, moved, powerbox removed, quads installed. The material for the nose is divinycell foam sheet.Thickest available, carbon overlay to existing top, then various glass and carbon.
Using West Systems 105 Epoxy. The nose rocker could be more. The tail was an experiment , works great with the quads, the tunnels also were, with option to refill, if it exhibited weird handling.This is a really dynamite conversion.
You should under or overlap the layers into existing. Pour foam 8lb would be heavier and much harder to apply. I use it for boxes.
A smaller cut off nose might work, it adheres to the PVC nicely, then carbon, glass on top.

I use a vacuum bag, but itís not necessary, you can weigh the pieces till they cure.

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boardsurfr



Joined: 23 Aug 2001
Posts: 1213

PostPosted: Mon Jul 22, 2019 9:08 am    Post subject: Reply with quote

Trebor_HI wrote:
Going through all the replies to this thread I find that I'm still confused by the options for filling the void. That is should I use a mixture of epoxy & filler - or - some sort of pour foam (?) - or - purchase a piece of EPS or XPS foam and shape as required to fill the void.

U2s approach is neat, and probably the best way to do it. For a larger repair, you'd really want to do it with a vacuum setup. That's costly if you need to buy it (but may be worth it in the long run - I'm glad I got mine).

The hole is too large to use epoxy & filler. Even with slow hardener and lots of filler, it would bubble and probably melt the styrofoam. The most pragmatic solution would be to use PU pour foam (like this 4 lb foam). Then a few layers of glass and epoxy. The PU foam tends to form some bubbles, which you'd need to fill with epoxy + fairing filler before glassing.

I recently did a similar repair, except that the board had a pointier nose. I just cut of the first couple of inches, then rebuild a bit with PU foam, and glassed it. The PU foam is mainly there to prevent water from reaching the core next time the nose gets dinged. The overall result is a bit less robust than a full sandwich reconstruction, but even that will get dinged with a hard enough catapult. Small nose repairs are easy, and you can do them many times on the same board without any issues. It's a bit expensive the first time if you need to buy all the supplies, but additional repairs are basically free, except for your time.
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U2U2U2



Joined: 06 Jul 2001
Posts: 5071
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Jul 22, 2019 9:24 am    Post subject: Reply with quote

Pour foam, is not designed nor intended as a filler for our use. It is water proof, and fairly light weight. I use 8 lb, on occasion 10. The holes , usually when sanded usually most disappeared , you of course can skim a coat of epoxy and let dry. The pour foam will dry in a very irregular surface, so shaping is required.
Any repair route taken, should have several top layers, carbon, s- glass, glass then
Sanded, 3M Marine putty, sanded, primer, paint.

More than 1 way to bake a cake

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Trebor_HI



Joined: 17 Aug 2008
Posts: 19

PostPosted: Mon Jul 22, 2019 10:29 am    Post subject: Reply with quote

Rereading the thread, I believe pour foam was brdsurfr's original plan but the pour foam failed to react. Thus, he went the epoxy and filler route instead. And, I do see that he had some problems with the epoxy fill mix melting the Styrofoam. Thought he addressed that by applying a small quantity at a time.

Been considering the pour foam route...but, there is a pretty good chance we'll be moving overseas. Should this happen the leftovers will be discarded. Is it available in smaller quantities?

Any thought on these expanding foams in a can products?
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U2U2U2



Joined: 06 Jul 2001
Posts: 5071
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Jul 22, 2019 12:13 pm    Post subject: Reply with quote

The PF that comes in cans is to cover areas around windows, cracks, I tried this just to see how crap it would be, itís really crap so far as hardness goes.
2lb is non structural.Absolute min 4 lb. about 1 qt is normal size, they get measured in pounds mostly.
This is a 50/50 mixture, itís sets very quickly, if anything too quick, temp effects things greatly.
To pour into a area, itís easy, like a fin box surround, it foams up like a loaf of bread, you cut the top off with a hack saw blade, then continue the project.
If it didnít set, something was wrong with a.mixture b. It was past its sell by.
Fiberglass Supply, WA state.
I can tell the difference from 8 lb to 10lb. Minimum for me is 8

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DanWeiss



Joined: 24 Jun 2008
Posts: 2276
Location: Connecticut, USA

PostPosted: Mon Jul 22, 2019 2:34 pm    Post subject: Reply with quote

Trebor, you can spec the exact polystyrene for a match, or buy a $4.00 styrofoam cooler and use that to fill the gap. Mix epoxy with microballoons to form a paste the consistency of runny peanut butter. Glue the new piece in place. Laminate divinicell to that, then go with whatever cloth you select.
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U2U2U2



Joined: 06 Jul 2001
Posts: 5071
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Jul 22, 2019 8:02 pm    Post subject: Reply with quote

According to the WWW a styrofoam cooler density is 1.00kg/m3.
This converts to .062428 PCF. Pounds per square foot.
The EPS used on a sturdy board is 28kg/ m3 which is 1.74 PCF.
The highest grade used is 32kg/ m3 which is 2PCF.
Most common used are 1PSF to 1.25.

A 1lb EPS blank vs the coolers density is 290 times more weight/ dense.

Real question is what adhesive to glue the kooler part that wonít melt it

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boardsurfr



Joined: 23 Aug 2001
Posts: 1213

PostPosted: Wed Jul 24, 2019 8:55 am    Post subject: Reply with quote

U2U2U2 wrote:
According to the WWW a styrofoam cooler density is 1.00kg/m3.
...
A 1lb EPS blank vs the coolers density is 290 times more weight/ dense.

Wrong and wrong. Even the math inside your post is wrong - 28 kg/m3 is 28 times 1 kg/m3, not 290 times.

A simple reality check shows even the 28x factor is wrong. Cooler styrofoam is pretty similar to the stuff in cores. Perhaps there's a 2x difference, but that should not matter for nose jobs.

A bit of googling gives cooler foam densities of 1.2 pounds per cubic foot. One cubic meter is 35.3 cubic feet, so this comes to 19.2 kg/m3, or about 1/3 less than EPS core. Not a problem for nose repairs. Epoxy with microballons will glue that just fine.
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boardsurfr



Joined: 23 Aug 2001
Posts: 1213

PostPosted: Wed Jul 24, 2019 9:12 am    Post subject: Reply with quote

Trebor_HI wrote:
Any thought on these expanding foams in a can products?

I checked that last time when I thought my old pour foam had gone bad. The can stuff did not get hard enough, it stayed flexible. I think the chemistry is different. I would not use it for any board repairs.

It later turned out my old pour foam was still good, I just had not mixed it well enough.

If you have divinicell, then the EPS/cooler approach Dan suggests will be fine. I've always used vacuum with dcell, but the Boardlady explains how to do small jobs without. I'd advise against using only EPS without divinicell, since any future damage would let water straight to the core.

The smallest pour foam quantities I have found were 2 pints. With 8 lb foam, that's about 0.27 cubic feet of foam. If you move overseas and don't have someone who you can give your leftovers to, you could just polymerize the remainder before discarding it. Not great, but much better than discarding the raw chemicals.
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U2U2U2



Joined: 06 Jul 2001
Posts: 5071
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Wed Jul 24, 2019 9:55 am    Post subject: Reply with quote

I donít know what I did on that calculation . You are correct mine is wrong. Way wrong !

Since the density values of EPS core used on Windsurf boards are 1 to 1.5, rare 2, because of addition weight, a difference is huge, in even .5.
I see that you show the value of a styrofoam cooler as 1.2 vs my 1.
Adding micro balloons , West Systems 407, has no effect on curing time for its 105 Systems. Any void in the existing EPS core , a hole or gap, would need epoxy that may melt, both pieces, the heat from when the epoxy cures.
Under an ideal repair, the cooler foam might work, I see no circumstance that a nose repair would benefit form using it, as the more robust EPS already broke.

To both who have mentioned it, my view remains unchanged , but I see now itís feasible, but itís not in my recipe book. If worth doing , itís worth doing right. YMMV.
apologize for mis- information

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