what weight glass should i use for a 35 inch monohull skiff? this will be the first time i make a boat from a mold. also i need to smooth out some stuff in the plaster on the bottom would west systes epoxy work for that? thanks i appreciate it.

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

You can use wests if you want but I would suggest get some flowcoat and Q-cell(microballoons). Mix it to the consistancy of peanut paste and use that. This is very easy to sand and covers well. I used 80 gram cloth with tissue paper on each side the last time I made a glass multihull. Maybe with different loads that you will get try using a double layer of 80 gram cloth with maybe some carbon around the keel area.

Hope this helps.

When you say plaster, do you mean a plaster mold? If so, I would use automotive “Bondo” to fair your mold.

As far as the weight of glass that you want, I would go fairly light. The heavier glass is harder to wet out andleaves a much rougher surface finish that you will need to fair out later. Go with the lightest glass you can find. If you think it is too light, you can add a second layer. But with the smaller tows and finer weave, you are going to have a much easier time getting a good surface finish. This is especially true if you are using a male mold.

If you use a female mold, then the mold will set the surface finish on the outside of the hull and the inside can be left fairly rough. In that case, the heavier cloth would not be as big of a problem. But it will still be good to use a lighter cloth as it is easier to wet out and you won’t get as many voids on your finished surface.

If you want the boat to be light, then you should plan on just one layer of really light cloth and then add ribs to the inside of the hull to add the stiffness you need. This can require a lot of detail work which can be really annoying, so if weight is not as big of a concern, then you should just add more layers of glass to get the hull stiffness and strength you want…

  • Will

Will Gorgen

If you use microballoons or bondo as a finished surface for a mold be sure to use PVA as a barrier coat or your part will stick. Don’t use a silicone based wax before the PVA-it is recommended to use Partall #2 wax then PVA. If you pour the PVA over the mold with the mold vertical you can get a perfect mirror surface since with PVA many times spraying can leave a small roughness. If you pour it be sure to leave the mold vertical until the stuff dry’s…

Doug Lord
–High Technology Sailing/Racing

i have used the west sytem epoxy and find it very usefriendly. but i have gotten my hands on a super product. but you need a scale to use it. digital. the brand is called mgs. and it is super light wieght and hardens like a rock. i was playing with some left over stuff and put some stuff on a niegbhors kid basball bat, that had a chack in it. after 24 hour. it was so hard , he uses the bat for batting practise. now this is the only firbeglass i use. it is slow to cure. but you can mix the harded to play with the harding time. go from 1/2 up to 6. and it is super strong. you might want to look at it. i am still new to the product
but i would try it. maybe other people can give you info on it

MGS is a German system of various coatings. They offer Laminating resin, Polyester resin and Epoxy resins.

It should say on the container which one you have. Visit a local home building site and grab a piece of throw-away foam and put a dab on it. If it melts into the foam, it “probably” is the polyester resin. If it doesn’t melt but stays “tacky” it could be laminating resin, and if it cures without melting foam it most likely is epoxy resin. Regardless - for safety reasons it should be stated on the outside of the container what kind you have.

Pretty spendy stuff. More bent for aircraft building or wind turbines.

Didn’t know they were distributing here. Do you remember where you got it?

i have the 335. and it does not affect the faom in any way. i love the stuff. i just hate the fact you have to get 100/38 grams of the stuff. and it takes so long to cure. but damm when it cures it realy cures hard.
if you want the place where i got it . i wil send you the website. they sell to anybody. and they are helpfull

west is a very rubbery epoxy and has its uses(glassing in bulkheads so that they can have a minimal amount of flex and do not become a a hard point in the hull also putting ribs/stringers in an rc yacht creates a hard point if you want a super strong hull with the corect resin to glass ratio you miht want to think about vacumebagging your hull it normialy means you need a strong ish mould and it is a lot harder to get voids in you lay up

When the Apprentice knows more than the Mentor its time to quit!

Post cure heating of a layup is also an alternative to get good, hard cures using epoxy. Again - a pain to do, and the wife won’t appreciate the oven being used for several hours, (if your hull even fits inside it) but when you consider that epoxy continues to cure for 14 days or more after initial “kick off” - there is a good argument for the post-cure practice.

A good recent article - will see if I can find it - that came out recently suggests using light to white colors for a boat that is going to sit in the sun, since most do not post cure, there is a tendency for the heated hull/deck to possibly soften and twist/rack out of alignment. Using heat to soften epoxy is a normal process if you must remove something (deck fitting, etc.) and it needs to be considered. Next time out - touch the deck of a dark painted boat and one with a light deck and you will see the difference.

The above is a paraphrase of the article’s contents, but I can’t recall where I read it - technical magazine, web, trade journal … ???

Michaelb, your boss may like to find out about a product here in Queensland called Bote Cote(pronounced boat coat), it is an epoxy made locally.

People I have spoken to that use it say that it is easier and better to work with than West’s and it is cheaper.

Be very carefull if you use microballoons or bondo as a final mold surface: you’ll have to use PVA or you have a HIGH risk of sticking. See my previous post in this thread and under “Making a Mold”…

Doug Lord
–High Technology Sailing/Racing