fiberglassing & resin question, yo!

[Dustin Crops Boy]

OK... so i'm going to be laying up a semi-large thing in fiberglass soon (about 2.5' x 2')... The item fairly easy and smooth but it has a couple areas that protrude out sort of far...

my question is, can/should I pour regular ol' eurocast resin into these deeper holes before gel-coating and laying up the rest of the glass/resin?

And if so will the resin that I use for the glassing grab onto the eurocast resin "plug" and blend smoothly into one? Or will the eurocast resin "plug" skrink and pull away? Or should I just pour my regular glassing resin into the hole w/o any glass (I don't think i'd be able to get glass down into the hole)

Does that make sense? Here is my crappy diagram trying to show what I mean:

 

[Sidewinder]

Can you not just gelcoat the inside of the plug? I don't mean fill with GC, but just treat it like the rest of the surface. I too would be concerned about material compatibility.

SAS

 

[Harry Harris]

I would have thought gelcoat too.

Is there a reason that you feel you wouldn't be able to use it for those detail sections?

Harry

 

[combatbaby]

depending on how you cut the weave/cloth you may not need to do the protruding detail in solid resin. You should be able to gelcoat that area too and push patches of fiberglass weave into it.

It also depends on how big this mold is. If the protruding detail is say the size of a screwdriver handle, then it should be fine, but if its smaller than a finger than it might be too hard to push material down into the mold. Solid resin though could easily crack off if any force was applied (accidental or otherwise)

allowing weave or cloth in the hole to be connected to the rest of the cloth would really improve the structure, so if it's possible i'd recommend it, even if it means filling the hole with mostly resin and just having a few pieces of weave pushed into it. (then at least it's blended with the rest of the piece)

 

[clonesix]

Gelcoat as ususal, mix up some paste for the hole and any other sharp edges, and lay in the glass. If you can stuff some glass into the hole, it will be stronger than without, but if you can't, the paste has glass fibers in it and will be strong enough.

 

[exoray]

I have seen several fiberglass parts that use a brush grade urethane resin as a solid thick gelcoat and the results are good...

Venkman71 describes it in his GB pack layup tutorial, on page 8

http://www.gbproject.com/plans/mctut/index.html

 

[Dustin Crops Boy]

thanks guys - I guess I was just a bit worried that the gelcote would be a bit too brittle if out too far w/o any glass... but I'll give it a try

 

[hook]

I am not sure if I am seeing your situation the correct way. But to give the fiberglass something to grab onto, you may consider making it all fiberglass. To strengthen the part extending out you can jam glass down in the hole and fill on top of that.

 

[Dustin Crops Boy]

<div class='quotetop'>QUOTE(exoray @ Feb 1 2007, 06:41 PM) [snapback]1409561[/snapback]</div>

I have seen several fiberglass parts that use a brush grade urethane resin as a solid thick gelcoat and the results are good...

Venkman71 describes it in his GB pack layup tutorial, on page 8

http://www.gbproject.com/plans/mctut/index.html
[/b]

Page 9 - he actually DOES pour regular ol' casting resin into the extruding detail pieces (after he does a brush up layer )... so I guess I can do the method I described above, I just should do it 2nd AFTER the 1st layer of gelcote (or "brushable resin" as he describes)... makes sense to me I just feared the fiberglass resin would be too brittle and I'd not be able to get ANY glass into the deep holes.

 

[Kerr Avon]

Gelcoat, or fill with mud, a mixture of the fiberglass resin and some fiberglass 'confetti'

 

[Chris Martin]

Polyester laminating resin has a habit of shrinking. You could try mixing metal powders in the resin for just these deep details which will reduce the shrinkage. You can laminate on top pretty much straight away. It all depends how big the depression is as has been stated. If it's too small to get a gel coat layer in, just fill it with gel coat and press on. If it is big enough, gel coat it and then fill it with a mix of resin and finely chopped fibre strands or the reinforced paste.

 

[dipmaster]

An old fiberglass expert that laid up some monster flares for my Cobra replica mentioned a trick he used for fiberglassing in tight areas. He took scissors and chopped up fiberglass mat, and then put it into a cup of resin and let it sit for awhile, as soon as the binder in the matt dissolves, it gives you a syrupy mix of resin and glass that flowed into intricate details well, and provided strength, albeit not as strong as the longer fibers in the rest of the piece. Last time I talked with him, he was laying up molds off a real GT 40 body.

Gary