mike the snake

I recently bought a set of molds for a gas cat.

I am experienced with composites.

I am new to boats however.

I pulled a part, but encountered problems.

3 layers of 9oz cloth seemed light, what, and how much glass do others use? Is the mold laid up with large, single sheets of glass, or smaller pieces cut to fit?

The glass formed air pockets around all sharp corners and edges. How can I prevent this? I'm thinking of doing a Pre-layup with really light glass in all the trouble areas, and then moving on to the actual layup?

Should I use a thickened mix of resin poured into all the trouble areas (edges and corners)

The gelcoat was really thick, and didn't spray on evenly, and there were areas that looked as if they never kicked off (these areas WERE along the air pockets in the glass as well).

This is my first experience with polyester resin and gelcoat. I have only used epoxy resins to this point.

Thanks for any help.

glennb2006

Stick with epoxy resin if you are used to it, should make for a stronger hull anyway. And can be lighter.

Glenn

martno1fan

Hi if i remember right the guy whp made my hull used thinner glass cloth for the first layer then layed another 4 layers of heavier glass matt on top.Theres nothing wrong with polyester resins and they're a dam site cheaper than epoxy for sure.heres a handy how to that might be of interest.
[link]http://www.ecfibreglasssupplies.co.uk/store/laminating.php[/link]

mike the snake

I might go return the extra quart of poly resin and just work with West Systems Epoxy. Sure will stink a lot less if anything.

How long do I need to let gelcoat cure for before I can do my layup over it?

I'm going to get some glass veil, I was told this takes the curves well.

I'm going for a useable part this next try.

thevirginian

Hey, mike;
If you are glassing a rather small project use epoxy, not polyester. With epoxy you can work in a slower pace and you are not pushed by the fast curing polyester resin. Your neighbors will also appreciate an odor free environment . If you want to dye the first layer use ywo part epoxy paint and spray it in the mold prior to the actual lay up. Let teh paint start to get tacky befor you continue with the glassing. Use 0.75 -1.5 oz cloth for the first two layers and wet those two layers thoroughly, especially in all the corners. Make sure you tap the cloth down with a not too stiff brush. Continue with a cloth not heavier than say 4oz. Lay up as many layers as desired. Let lay up cure in mold for at least 48 hours (at room temperature that is). After pulling it out of the mold you can add more cloth if you think you are not strong enough. The actual strength of your fiber galss work is mainly depending on the type of resin you are using and the saturation of the cloth. If the curing temperature is not a minimum of 70° then it takes much longer for the resin to cure properly. So be patient and don't pull it the next day. Raka.com has great resins for different applications. I hope I was of some help to you.

mike the snake

Thanks!

I used 9 ounce cloth, I thought for the boats heavier cloth was used.

Using lighter cloth is much easier to work with. I do as you've suggested with glider molds.

I thought that since I was using the gelcoat that the finish cloth and lighter cloths could be deleted.

glennb2006

Hi there Mike,

not having done a full mould in epoxy, I am not an expert, but I have made a hatch, I did not use any gel coat. The resin that wetted through the first tissue layer gave a good surface finish that is paintable on.

The virginian's idea sounds great for painting into the mould, I presume on top of release agent? just think, if you get it right you can have a fancy paint job that's part of the boat! Just be careful if you put any letters in there to make sure they don't comeout back to front!!

Glenn

stoddy

looks like the resin as reacted with the gel coat . you must let the gelcoat cure for a min of 4 hours before you start to lay up with the resin

showtime808

The wrippling in the gelcoat is caused by the acetone used as thinner to spray the 2nd,3rd or 4th coats of gelcoat. Basiclly the coat prior to the wrippling was not dry. Usually once the gelcoat is tacky (no gelcoat on finger) you can apply the next coat. Same goes for the first layer of cloth over the gelcoat. You dont get wrippling if the gelcoat is brushed on becuase it has not been thinned. Everyboat will have some airpockets unless its vacummed formed. Some companies make the gelcoat thicker so those pockets are not as likely to comethough. As for the tight spots many builders will mix resin with tiny particles of chopped glass to prevent bubbling in those areas.

stoddy

extract taken from cfs fiberglass website gelcoat section (To avoid styrene attack allow 2-3 hours before applying any more resin ).
gelcoat should also be thinned with styrene not acetone. father in law been building yachts for 30 years he says no to thinning with acetone.

as for those hard to reach areas mix fillite or milled glass into resin as a filler very strong and light used for filling strake rails etc before glassing
or you could use fiberglass tow and glass that into the awarkward parts before laying up with matting.

thevirginian

The reason why you don't want to us gel coat is you need to brush it on too heavy to cover evenly.Ans doing so you are not gaining any strength but weight to the lay up. Spraying the gel coat requires a heavy duty air spray sytem. You don't wnat to thin the gel coat too much. If you use epoxy paint it goes on thin and it covers nicely. Of course the mold needs to be prepped with a good parting agent before commencing any lay-up work inside a mold. Wax the mold, buff it to a mirrow shine and then spray a good releasing agent inside the mold. Let that try thoroughly and don't touch it with your fingers.

Paul M

If he uses West, what will he use as gel coat? West will not be compatible with gelcoat (polyester) unless gelcoat is completely cured.

mike the snake

I've been working all day.

I prepped the mold again.

This time I'm going slow, in stages. I used matt around all the trouble areas, carefully working any bubbles out. I have one layer of glass matt on the top, and bottom of the sponsons, next will be a couple layers of glass.

Tomorrow I'll finish the layup. If all goes well, this hull will be heavier and stronger, and hopefully perfect.

Scott Schneider

I will add that for a cost between that of POLYESTER resin and EPOXY is ...... VINYLESTER resin.

It is far stronger than Poly, ages a lot better and shrinks less when curing too !

Still stinks like hel* tho [:'(]

nvs motorsports

Your gelcoat will tripe which is the term for what is happenning to you because your epoxy cure time is very slow an gelcoat will resoften from the epoxy
The trick is to gelcoat mold then tissue glass with a polyester resin or vinylester resin then lay up in epoxy matting
I would personally lay whole lot in vinylester resin it has higher flex strength than epoxy i lay my boats in that way far better product

If you go the epoxy way you will have to add core material to your lay up to get your stiffness back in lamination

Hope this helps any problems PM me im a shipwright composite technician by trade

mike the snake

Spent all day laying up another boat. This one's a lot heavier, with attention to detail around all the corners, and to trimming the edges. I THINK this will be a nice raceable cat.

Layup is with vinyl ester resin, glass mat and cloth.

Scott Schneider

Quote : Layup is with vinyl ester resin, glass mat and cloth.

Good choice

martno1fan

Hi guys good to hear you got it sorted out Mike,this new vinylester resin who sells it ive seen a cat made from this stuff and although its light it seems very rigid and strong.The cat is the Mercury from Dave Marles although i believe its also sold over there as the Falcon.Seems like a great product,id like to know more about it and maybe a few links as to where to find it would help me a lot thanks.Good luck with the build Mike .
Mart

stoddy

try here mart: http://www.polyfibre.co.uk/product.asp
it's under expoxy resins £36.50 for 5kg

martno1fan

nice one cheers for that.
mart

mike the snake

Well, the second try came out much better!

It is usable, although I still found a couple small bubbles where the gelcoat cracked easily, but there's only 1 or 2 and they are very small. I brushed the Gelcoat on instead of spraying it on, it's light, but came out better than spraying it-no runs or drips that form bubbles.

I am wondering just how the layups go. Is it done all in one shot? I have glass veil, and cloth, and matting. I'm having trouble with bubbles forming at all the 90 degree edges.

I suppose if I do an initial layup of veil or light cloth, make sure there's no bubbles, let that kick off, and then lay up the rest would work?

I'm going to use a couple layers of really light cloth first on my next layup

I now have an idea of how much material to use, but still having trouble making perfect layups.

I'm also in the market for a race engine and pipe

patriktegelberg

I find it hard to get a nice thin layer of gelcoat with a brush so I prefer to spray. Difficult areas as sharp inside corners can be addressed first by filler or tow/thin matt. Sharp outside corners should not be there at all and if they are will be a biadg.

For the first layer I use 300 g/m2 (I leave the metric to SAE conversion to u) and carefully work all the bubbles out. Let that set a little if needed so the next layer do not destroy it. Next a 450 g/m2 matt, small air bubbles in this layer is of no consequence. Thats it plus the rails that will stiffen it up plenty. Two 300 layers is thin, 300 + two 450 is thick in my opinion.

Do the conversion and let me know how your layups have been in comparison.

mike the snake

Thanks very much! I'll do the conversions and compare.

I Just ordered a CC full mod racing engine and pipe, and all the hardware to finish this puppy. Should arrive in about 2 weeks.

I HOPE I can get this boat finished in time for the Gold Rush race March 12th, if all goes smoothly I'll have a week to get the boat finished.

Thanks again for all your help everyone.

showtime808

good luck I have been waiting 7 weeks for mine

martno1fan

Sorry to break this to you but you allready missed it its now march 24th