plug made.. mold made.. now what

[mungral]

Hi everyone.

I'm building a 14 ft skiff type sailing boat. which is to be of foam sandwich type construction. http://www.ns14.org/

if what i'm about to state correct?

the next step is to wax the mold.
spary gel coat on.
lay fiberglass
lay foam
lay more fiberglass
cross fingers that i have put enough wax on
pull it from the mold.

if this is correct

how do you lay the fiberglass in without having over lapping joint bumps show through to the out side off the boat? (or will vacumm baging fix this?)

and how do you lay the foam in so you dont get gaps between the foam that need filling.(or do you just fill gaps before layng up the inside layer of fiberglass)

any comments would be great

Regards

[John ilett]

It's a good idea to also use a liquid release (PVA) after the wax at least on the first boat from the mould, for the sake of a succesfull first boat and a mould that survived too.

Lay the glass fabrics in as nice as you can and wet through with your resin, the overlaps will not show on the outside of the boat. Once cured fit the foam and vacuum bag into place with a resin coat to bond. Some gaps are ok as you can fill these before finishing the inner skin. Better to have gaps than foam which fits too tight as this could create air pockets under the foam.

[rxcomposite]

Jonh Ilet is correct. A new mold (if it was not allowed to cure properly) always stick to the part no matter how many coat of release wax you put in it. The PVA is an "insurance". Better overdo it than be sorry.

Seasoned moldmakers will tell you that improperly cured resin in a mold will traverse thru layers of wax release and "weld" the part and the mold. PVA will block it.

[mungral]

many thanks for you responce.
your comments well help heaps

regards.

[michael-compwes]

....after the initial mold waxing,you can 'season' the mold by spraying well catalysed gelcoat onto the surface.Once cured,use a air blower to blow-off this layer.The mold is now nicely 'seasoned' with the 1st waxlayer now nicely in the pores of the mold.

[zerogara]

I assume you are doing everything in polyester resin. The PVA, unlike what most sources of "how to do it" will tell you will dull your nicely waxed mirror like mold. If you don't use it and you don't have tons of experience from spraying gel coat, the thin first layer of gel coat will fisheye (pull away in circular fashion and leave uncovered spots). My understanding is that the PVA film adds drag that keeps the gel coat in place till it gels and cures. Very annoying!
The dullness it creates can be polished off the final part.
Catalyst! There is a formula for mixing catalyst in polyester resin in various temperatures for various resins. Since gel coat is less viscous than resin it is next to impossible to mix such a small amount of catalyst throughout in uniform fashion. So the easy way out is to use a little more catalyst and mix instantly preferrably with a mixing tool. The more catalyst you use though the more brittle your gel coat might become, so do not over do it.
If you have minor repaired areas on the mold with filler and primer/paint on it, there is a good chance the surface is more porous than the rest of the mold. This is where it will most likely encounter sticking. So if in doubt over was and over pva the spots that are suspect.
No matter where you keep your mold it will attract dust and particles, flies (I've had some show through the gel coat) because of static building up as you clean, polish, wax etc. Make sure you have everything you need and many many hours ahead of you till the first coat of gelcoat is gelled.
Do not take your molding off the mold until everything else deck included is ready to be bonded to it. The longer it stays in the mold to cure the better it is and more protected both the molding and mold are.
The best way to maintain molds is to leave them covered with a new molding and not pop them.
The overlap of cloth and mat unless it builds up too thick will not show (print through) but stringers and anything else that you will solidly bond might (in long term). Using a sandwich will minimize to eliminate this.
Find out as much as you can on the best way to bond the core to your outer surface so it does not delaminate and loose all of its properties as a sandwich.
Good luck and be carefull and ready. Do not panic, once you start it is a joy to finish.

[Jeff Therrell]

If you use a liquid release agent like Extend 802 you can put 8 coats on and gel your mold and it will not stick.This is a wipe on leave on release you just wipe a coat on and wait 20 min and wipe another coat on,when you are finished the mold will have a dull haze on it DON'T polish it off.After your first pull put 1 more coat on it and then polish off the haze,you can make about 25 pulls before putting another touch-up coat.I can wax a 17' hull mold in half a day.
Thanks,Jeff

[War Whoop]

TR Multi pull system is a good choice also I have had 0 prerelease problems with it.

[rxcomposite]

The best instrument to find out if the mold is fully cured is your nose. If you can smell styrene in the mold, then the polymerization isnt completete yet. Since polymer cure by crosslinking, any molecule that has not fully crosslinked with each other will actively seek any new layer of resin that will be laid over it.

As a general rule, full curing takes about a month indoor, one to two days in a hot sun, or two hours in a paint booth with infrared lamp. Blow drying as suggested by michael is also practised. Use a hot air blower or home heater with a fan. Just get the mold hot enough to touch. dont overdo or you might have a bonfire instead.

[buckknekkid]

fyi the boat comes out when its ready

[buckknekkid]

full open with casting platform forward, single yanmar

[buckknekkid]

www.yachtsurvey.com/core_materials.htm ~read it slowly and often

[zerogara]

I've seen the article in the past and do believe that most of what this surveyor says is correct. But he fails to propose solutions to the problem/s.
Solid fiberglass boats with excessive resin use seem to have lasted for ever and that is not an economically viable trade, proven by all those boat manufacturers that went out of business while their boats are still cruising.
I refuse to accept the impression this guy passes that cores were utilized for economic reasons alone, although he does mention both the weight and flex of flat panels.
I believe the solution lies in fabricating fiber cores in 3 dimentional honeycombs simulating the I beam in finite structure. The cost is probably still enormous for something like this but the future may change all this.
Pearson did use Balsa in boats that are now more than 25 years old, and with the exception of owner alteration that caused failure they are all sound and dry.
To dismiss the use of cores in general is wrong. For the public to be educated and be able to make educated decisions about which boat to buy and why is a different issue.
The Searay article is even more interesting. In the used market SeaRays seem like alot of boat for the money.
http://www.yachtsurvey.com/searay_ba...re_bottoms.htm

[zerogara]

The easiest way to show your customer how proficient you are in your trade (surveyor) is to criticize all problems of a boat as the manufacturers' faults and lack of understanding. That makes you an engineer.
Many of those "scientists" that run around boatyards with pens and rulers in their shirt pocket don't know from which side the fish farts!

[buckknekkid]

I took from a point of view I've seen many times. If your glass crew isnt fastidious in their lay up your hull can be junk. regardless of the lamination schedule it comes back to the experience of the crew and their attention to detail that counts.