Gel Coat resin + cavisil ??

[Theo]

Hi Guys,

Just a quick question, do any of you drill meisters out there know if it is OK to mix plain old fiberglass cavisil with gel coat resin?

I removed some old hardware from my transom (mind outa the gutter) and need to fill in about 7 srew holes (see what I mean about the gutter) and some gel coat the 5200 pulled off. So I went off to my trusty surfboard repair kit only to find that my fiberglass resin had dried out. I must have been a good boy. Haven't run over any Kooks recently!

So, can I mix some cavisil with gel coat resin (which I have plenty of) to make a paste to fill in the screw holes? I need to patch some of the area with gel coat anyway. Or is it off to the surf store to pick up another repair kit?

Thanks

[Divecoz]

So we are on the same page.. Cavisil to me is just "chopped" fiberglass...( I buy it in a bag ) Its commonly used with epoxy -( 2 parts) for a filler / making it more "workable "and stronger than just epoxy alone.. Turns epoxy into a putty of a sort..
As for the use of Resin alone??? / a gooey mess that never hardens.....What will "make it " harden" ? Gel Coat and resin when mixed, needs to be covered or it wont harden..
I never really thought about it , but, is the Gel Coat Material "The Hardener" in this case??? Personally without more knowledge , I wouldn't..But maybe a call to your surf shop would answer the question..
I am very surprised you peeled off.... 5200 Humm if in fact it was, 5200 ? It tells me that surface , was nowhere near , properly prepared for the repair..

[Harry van der Meer]

BWY sells a gel coate paste with excellent color match. Very easy to work with. Cures without the need to cover it.

[Crikey]

Close to the same problem mentioned here, I've got to open up the sloppy pivot bolt holes in my rudders to take stainless steel tubes sized to sleeve the 3/8" original bolts. Not too concerned about color match gel coat in this location - though it would be nice - I'm more worried about a good strong bond between the SS and the existing rudder material.

Does the chopped fibre with a resin and catalyst mix give proper adhesion to the two different substances? Would one of the air curing putties packed into the gap be sufficient? I think a thorough acetone cleaning of all surfaces prior to starting anything, should be a prerequisite!

Ross

[Trouts Dream]

I have used automotive fiberglass repair compound for my boat repairs. it comes in both long and short fiberglass strands and sticks to most anything and hardens with a catalyst. Usually very short working times, 5-6 minutes tops, but can be sanded after wards. I then top it off with gell coat which is also a 2 part mix. Most gel coats don't require covering anymore and can be wet sanded if you want a really nice finish.

I've used this on my rudders, major damage when I left then down on when pulling out, on a couple of large nicks on the backend of the boat and a couple of deep scratches on the sides.

Google videos on how to repair cars for the fiberglass fill and gel coat videos for the finishing work.

[gyroplanes]

Not wanting to sound like a know it all, just helping clarify things.

Cabosil (also called cab-o-sil) is Colloidal Silica, little hollow glass beads, users refer to as Microballoons. It is mixed with gel coat and other composite resins to thicken it. I see RR freight cars full of it at a crossing near me. It is heavily used in baby powder and other powders to keep them from clumping and to flow easier.

The fiberglass strands or hairs are referred to as "Flox". Flox isn't meant to thicken so much as to add strength to the resin.
I used to be an aircraft mechanics instructor.
Amateur built Aircraft suppliers are a good source for these materials

[Judy B]

Hi Guys,

Just a quick question, do any of you drill meisters out there know if it is OK to mix plain old fiberglass cavisil with gel coat resin?

I removed some old hardware from my transom (mind outa the gutter) and need to fill in about 7 srew holes (see what I mean about the gutter) and some gel coat the 5200 pulled off. So I went off to my trusty surfboard repair kit only to find that my fiberglass resin had dried out. I must have been a good boy. Haven't run over any Kooks recently!

So, can I mix some cavisil with gel coat resin (which I have plenty of) to make a paste to fill in the screw holes? I need to patch some of the area with gel coat anyway. Or is it off to the surf store to pick up another repair kit?

Thanks

Yes, it's okay to mix Cabosil ( aka fumed silica or colliodal silica) with Gel coat resin (which is usually a polyester resin, but sometimes a vinylester). Cabosil is a high density filler, and has excellent strutctural and bonding strength strength. Unfortunatey, for your intended use, it is relatively hard to sand after hardening. It's also not easy to feather the uncured "putty" to a fine edge. If your boat is white, cAbolsil has the advantage of being an offwhite color.

I personally have used it for filling a drill hole below the surface, but I'd leave a slight depression below the surface and finish it with gelcoat. Then do the top 1/4 mm with evaporated gelocoat resin without any filler.

You could also use microballoons, a low density filler designed for fairing and sanding. Resin thickened with low density fillers sands easily, and can be feathered to a fine edge when you are applying them. Unfortunately, microballoons are usually a maroon or light brown color, which isn't ideal if you're color-matching a gelcoated finish coat by applying a thin coat of gelocat over the repaired area.

Polyester gelcoat requires sealing from the air to cure properly. So, just like polyester laminating resin, you need to add a surfacing wax or spray pva mold release or cover with actate film or other air barrier - -or my favorite Duratec High Gloss additive. . And you'll need to catalyse the polyester gelcoat resin of course, using MEKP.

heres a link to a YouTube video on matching color. I'd bet there are many more good ones on youtube. It's a great resource!
http://youtu.be/VZxyrxIC2Ts

And here's a link to an article I wrote 10-12 years ago about repairing small holes in gelcoat. (I'm not a pro at gelcoat, but I've done a lot of gelcoat work for an amateur.)

http://www.blumhorst.com/potterpages/gelcoat.htm

Fair winds,
Judy B

[Theo]

Hi guys,

Many thanks for the input, especially Judy B and Gyroplanes. I went ahead and mixed a batch of gel coat and Cabo-Sil and it seems to have worked just fine. I have not sanded it all down yet, partially since I had a batch of brew mixed up, I buzzed around the entire boat filling in every random crack and ding I could find. But the little I did seems to sand down just fine.

Thanks,

Theo