To Gel or Not to Gel - That Is the Question

[Fishman_Tx]

We've done a tap test and sounds solid around the spot. But like you said, we're no experts. I'll need to grind the outer patch away as there is no cloth or mat under it anyway. Guess we'll relook after that and bring some more pix.

[Fishman_Tx]

Originally Posted by Solitude

I'm a bit late in this and saw that you were asking about barrier coats..

I Just wanted to add that when your ready to do that I used Interlux Interprotect 2000. It is the greystuff. It is very good. As stated don't use gelcoat on the bottom. I used west system and colloidal silica to fill the blisters. Don't thicken with micro ballons or talc. Water will penetrate it.

I have seen some very and I mean very good results with one and two part poly painted hulls (above the waterline) ... by using the tip and roll methode of painting.



Now I'll shut up and let you deal with the patch problem. (While your dealing with that make sure all your blisters are open and drying out....)

So 'kay Boss, I got TONS of questions! Actually, we're rebuiling the blisters with poly and cloth using the "bowl" method; large piece working to smaller. Then fill and fair with West system & colloidal. And we got LOTS to fill and fair. We also had planned on Interlux, rather than Awlgrip. I just haven't had time to read up all I need yet. (Step 35; I'm still on #6 )

One of the issues I'm definitely need an answer on is about removing ALL the gel, above as well as below. I have stress cracks, gouges and so forth and I don't want any covered cracks migrating thru the overcoatings or paint. Right now we've removed it below the line, but not above.

[SkiprJohn]

Hey Fishman,
Do you think the damage that the patch covers is to interior layers of glass mat/roving/cloth? If it is just pushed in and filled then grind away any exposed damaged edges of glass and lay up success patches of mat then roving then mat, roving and last a layer of 10oz cloth using epoxy resin. If you get a copy of "This Old Boat" by Don Casey it is pretty well outlined what you need to do. The "Fiberglass Boat Repair Manual" by Allan H. Vaitses although old is still good. Use epoxy resins with your mat, roving and cloth. It adheres better and is more water resistant.
regards,

[Christian Van H]

Originally Posted by Solitude

I used west system and colloidal silica to fill the blisters. Don't thicken with micro ballons or talc. Water will penetrate it.

Solitude, where did you come across the info stating that microballoons would let water penetrate? I cant quite figure this one out..they are encapsulated in epoxy, with 3 - 5 coats of epoxy over top (if you do it right). Where is water gonna get in?

[s/v Jedi]

After you barrier-coat it, no water should get in. But it's too soft for repairing big blisters anyway and I agree with using colloidal silica.

cheers,
Nick.

[Solitude]

Originally Posted by Christian Van H

Solitude, where did you come across the info stating that microballoons would let water penetrate? I cant quite figure this one out..they are encapsulated in epoxy, with 3 - 5 coats of epoxy over top (if you do it right). Where is water gonna get in?

I pulled out of a Don Casey book I bought when I did mine. The microballons are encapsulated in epoxy as is the talc. I agree, but talc and microballons allow water to penetrate. The silica does not.

The barrier coat should cover everything and is watertight but if water permeates it the microballons will allow the patch to get wet. I would choose the silica and don’t take the chance. The cost is nominal.

[Solitude]

I used West System. No I have nothing to do with them.

http://www.westsystem.com/ss/assets/...aintenance.pdf

Fiberglass Boat Repair and Restoration

http://www.boatus.com/boattech/casey/03.htm

[Christian Van H]

Originally Posted by Solitude

I pulled out of a Don Casey book I bought when I did mine.

Thats funny, I thought that might be your source! I read that too, and I believe it might be BS. It's in "This old boat". Microballoons are not water soluble, and it's my understanding that most of them are cracked or damaged by the act of simply mixing them in epoxy. They are hollow spheres and both they and the epoxy around them should block water. They ARE too soft to fill large deep areas though, and should be used for final fairing only. Nick on Jedi knows quite a bit about how fillers are used and made. Nick, have you heard this rumor about balloons making epoxy permeable?

[Solitude]

Originally Posted by Christian Van H

Thats funny, I thought that might be your source! I read that too, and I believe it might be BS. It's in "This old boat". Microballoons are not water soluble, and it's my understanding that most of them are cracked or damaged by the act of simply mixing them in epoxy. They are hollow spheres and both they and the epoxy around them should block water. They ARE too soft to fill large deep areas though, and should be used for final fairing only. Nick on Jedi knows quite a bit about how fillers are used and made. Nick, have you heard this rumor about balloons making epoxy permeable?

West System states use 404 or 406 high densityvsilica as well. 407 filler has microballons and is easier to sand.


Should he use microballons just to prove a point? I would still say go with the silica...I would never want to go back to do that repair again..

[Christian Van H]

Originally Posted by Solitude

Should he use microballons just to prove a point?

No, he should use microballoons to fair with afterwards, without worrying about water getting into them. They are MUCH easier to sand, and I was pointing out that your info might be wrong, and be spread even farther. I was trying to start a discussion on this without offending anyone...

[Fishman_Tx]

Hang on there folks

Here's the details:
We have about 35-40 large blisters about half the size of a cd each. Only a few are adjoined to a neighboring blister making a double size patch.

Now the big patch we where thinking of going back to poly, (best fit chemically?) it IS patched inside and out, AND it's still depressed at least a half inch inboard. I suspect it was at least cracked, but i don't think it was holed. A tap test sounds solid but...well you know. Then again there's that 16" wide epoxy "hockey puck" with no cloth in it!

The ENTIRE hull will need a fill and fair as we took off the gel the hard way. 7" of 36 and 50 grit at 20k rpms. And most of the chop is still there.
I'll get better pics this weekend of the inside and out.

Thanks all!

[Solitude]

Well thats quite a job. Are the blisters themselves 2-3 inches in diameter? Did you sand them out to this size?

[s/v Jedi]

Fish: you really need to use epoxy to get a decent bond. Polyester doesn't bond to cured polyester very well.

I have a problem with microballoons for many reasons. The alternatives like that ultra-light from West can't handle heat very well but they say it'll be okay under white paint or gelcoat (not under dark colors). I use it and like the way it works: easy mixing, easy fairing and easy sanding.

Fish: try to fair in between barrier coats to get the rough part done. You can even try the really bad parts with colloidal silica and machine sand it with 80 grit after cure. It will help a lot for the final fairing and reduces the volume of "weak" fillers used.

About that patch area: Try to see if they beveled it. If not (and it sounds like a bad job done), you need to grind that plug out until you get to fibers again. Grind the 12:1 bevel. Use epoxy and no mat: just cloth and woven roving. First cloth, next woven roving 1 or 2 layers depending on how deep it is, and finish with cloth again. Fill the weave of the top layer with epoxy thickened a bit with colloidal silica (syrup consistency). If you end up too low, use the trick with the notched spreader: the West spreader is best and use the side with the biggest notches. Mix a stiff batch with colloidal silica and put the "ridges" on with the spreader. Let cure and sand the tops of the ridges fair with the rest of the hull using a long board. Now it's really easy to fill the rest with a regular spreader and use a fairing filler if it isn't too deep.

I wrote not to use mat but I believe they sell special mat for use with epoxy now. If you can find that, you can use it of course but I have no experience with it. If it's under the anti-fouling I wouldn't bother and use cloth instead (you can get some print-through with cloth when painted on the top-sides).

I just re-read your post and it almost sounds like that patch has no cloth at all?? I can't believe that. Anyway, you have to grind until there's either solid glass (not cracked, that has to go too) or a hole. Don't be afraid of a hole, it's probably even easier to fix than building up on old stuff. If it is indeed a hole, I'll follow up with how to do that. You will need 2 pieces of formica big enough to cover the hole and plastic drop-cloth.

cheers,
Nick.

[Fishman_Tx]

Originally Posted by Solitude

Well thats quite a job. Are the blisters themselves 2-3 inches in diameter? Did you sand them out to this size?

Blisters avg 4"-5" a couple larger, but no popcorn.
Yessir, they are dished out 12-1 or as close as we could get.

Jedi:
Fair "between" barrier coats after initial fairing? Do I assume we should put down a barrier coat prior to initial fairing or are we talking about wetting out? After cure or while tacky? When I ask about barrier coats, I think of epoxy with the 422 barrier additive...
Re patch: Yep, NO CLOTH in or under the puck on the exterior and they applied it on top of the gel. Just just threw it on. God only knows how it lasted this long. had 3-4 coats of bottom pait over it. 1-2 green(soft) and 2 red (1 soft 1 hard). Sould we treat it as a large blister and "bowl" method the cloth/roving large-to-small? It is a very circular patch...
Re Hole: This "ding" is "split" by a bulkhead right...down..the middle. Fun.

Re:sanding
Would a belt sander do a better job of maintaining contour of the hull for fairing work? Currently we have the grinder/sander(NOT good), the DA orbital (ssslllloooowwww), drill attachment sanders, and various palm and 1/3 sheet vibro sanders.

Thx Guys!

[Solitude]

Hi Fish

The links I sent have some good info from the Gougeon Brothers West system.
They are one of the leaders in the area. I went to epoxy on my blisters because I was told (as Nick said it bonds well )and is stronger. I belive that you can’t use polyester over epoxy after. It’s a one way street.

That patch sounds nasty. How is the bulkhead. Is it glassed in to the hull?

As for tools... I used a DA sander 60 grit on the blisters. Sanded the epoxy with 80. All my fixing was below the waterline and I was less concerned about beauty and more about never doing it again.

If you do decide to go epoxy. Play with it first. Mix small pots as it generates a lot of heat. Make sure that when you fill the blisters it is thick enough not to sag.

Yes send pictures. I’m sure we will all learn things along the way.

Take your time