Fiberglassing question

[bfisher33]

Hello. I'm a senior in high school interested in yacht design. at the moment I have 'designed' a couple sailing yachts and I am now in the process of building models of them from scratch, which brings me to my question. What would be the best way to fiberglass over a plaster negative mold of the hull? And what would the best release agent be?

Thanks

B.

Probably your best bet would be to use 2 coats of Partall #2 Paste Wax covered with PVA. PVA can be sprayed but doesn't have to be-you can pour it over a vertical plug if you have a container to catch the excess; the plug and air must be very clean to use this method. If you spray usea high pressure and mist on two to three coats. The PVA is water soluble and can be washed off the plug and or the inside of the hull; it won't allow wax to transfer to the part.
I'd suggest two layers of 6 oz. glass for an inexpensive part or for a bit lighter one layer of 5.7oz. carbon and one layer of 1.5 oz kevlar. Put the kevlar down first if you use it.You don't ever want to sand thru and hit kevlar....Put the material down so that the fibers run diagonally across the hull. Use epoxy resin and if you don't cure it at an elevated temperature(per the manuf. directions) then let it sit for three days before pulling it.
This should give you time to do your finish work on the hull before pulling it.
If there is not a composite's supplier near you you can buy from a number of mail order places; Jamestown Distibutors is probably not too far away and I think they do mail orders though I'm not 100% sure.
Good Luck!

[fiberglass jack]

what type of plaster r u using, wax and pva will work as doug lordsais. i would use johnsons floor wax with carnabua wax its cheap and will seal the plaster good, then pva , when we say wax a mould we are talking about 5 or 6 coats that must be wiped and buffed between coats u can never wax too much

[bfisher33]

hey thanks guys. Fiberglass Jack, I am using the kind of plaster that comes in a roll that you wet, and that you find at A.C. Moore. Also, I have a very low budget and neither really know about nor can probably afford anything you guys mentioned. How much is it? Also, I was going to use a couple fiberglass repair mats that are found at an autobody shop to fiberglass it. Again, I don't have a lot of money. I was working on a 16' Comet sailboat the other day and we were using fiberglass cloth mats from that type of repair packet, and it would have been big enough to cover the entire hull of my model. I was wondering If i should just cut one big peice and cover thehull, cut another one and do a second layer, and then a third, or to do it in small sections. i also only have the tools available to a high school art teacher because I am doing most of this work at school. So, sorry about not being more clear earlier, and, again, thank you for your advice.

[bfisher33]

oh. I forgot. I may have gotten 'negative' and 'positive' confused when it comes to molds. what I have is a solid hull that I am fberglassing over the outside, then removing from the inside.

thanks

[fiberglass jack]

ok then, wax the plaster with the floor wax its cheap and the school janitors room might have some, the type of cloth that the repair packs often have is a weave which is hard to lay down over curves, you should get some chop strand mat its the hairy stuff , and will work better for you , after all your only making a model, some of the experts on this form will be shaking there heads at me, use polyester resin its the cheapest, pva is polyvinyalachohol which wont break down with resin its a sure bet for a mould release, tell u what look in the phone book for boat repairs or a fiberglass manufature tell them its for a school prodject and you should be able to buy some resin from them, also they throw more glass matt into the trash then u would belive, the tools that you need is a brush to wet the glass out, also take a brush and cut the bristels half way this will give you a good tool for daping out air bubbles, go to www.fibreglass.com they mail order

[bfisher33]

Thank you very much. That is exactly what I needed to know. Aslo, I was wondering how to go about fiberglassing it. Do I do the whole thing with one big sheet, Or do I do it in sections one layer at a time?

[bfisher33]

Oh, and to complicate things further (sorry) I want the boat to actually sail. Do I need to change anything You told me to do that?

[fiberglass jack]

what is the size of the model

[bfisher33]

It is 25" long with a scale of 1"= 2'. Representative of a fifty foot sailboat.

[fiberglass jack]

do one full peice its a small model dont put in to much hardner and make sure the room is not to hot the heat will cause the resin to cure take your time and get rid of those air bubbles, one othe thing the matt has a binder that keeps it all together the resin will disolve this in a couple of minutes, so wet the glass on the mould and allow the binder to desolve dont over wet it after you have the first layer on it might start to go hard, do not try and put more matt on as the heat from the first layer will cause the second to go hard in a very quick time, two layers is plenty for your model, give the frist layer (skin) A sand with some 80 or rougher sand paper and go again ,and remember if the resin starts to kick on you before you mave smothed it out just rip it off and try again with a little less hardner once you get skilled with fibreglass you will bang lots of them in a day , enjoy the sweet smell resin,

[bfisher33]

Thanks again for the help. I am hoping to get started soon, but with schoolwork and the end of the marking period coming up it will be hard. Thanks!