Lamination schedule

I’ve purchased an eight foot dinghy mould. The broadest question would be what should the lamination schedule be and that would lead to, “how will the boat be used”. Simplest answer would be, “used as a tender”, light enough to be pulled up on deck or a wharf, strong enough for kids to whack it about.
Furthermore, I may vacuum bag and infuse the lamination.

 

When you say dinghy mould,is there any tooling for a gunwhale reinforcing ring?It may be the biggest addition to a basic hull in terms of work.A picture of the mould would be useful as a simulated clinker hull has the plank land shape to add stiffness and might permit a lighter laminate.If it were so,I might try a double gel and then 2 X 600 gsm overall and an additional ply of the same throughout the bottom.
As for infusion,have you ever vacuum bagged anything previously?It can be really exasperating to have resin curing while you chase vacuum leaks and an old mould is unlikely to have a helpful flange for the tape,which leaves you sealing on the rough side of the mould.If you don't already possess the equipment or have the experience,I'd recommend the bucket and brush approach.

 

From experience, I'd say it's better to have an 84 pound dink that you like and lasts for 10 years as opposed to a 90 pound version that you hate for 15 years. Do you intend to hang a kicker on it? That takes a bit of figuring out as far a weight, strength, and rigidity is concerned.

 

Good advice above ⬆️
Ive. found I can create very lightweight parts by hand laying if I squeegee off excess resin after wet out.

 

I dunno, I'd be inclined to consider using a core if you want to use vac. Make an outside skin and bag it and then add a core and bag it again for the inside. Probably turn out pretty great.

The thing can be made pretty light with a core.

I'm going to build a foam core dinghy no mould. Want to vac bag the inside skins on a table.

 

Thanks for your reply. No reinforcement ring. GSM…Hmmm. I’m familiar with CSM, chopped strand mat. Is GSM nomenclature for the same thing?
I have vacuum bagged and infused. I’d like to do it in this case because I find it is faster and cleaner.
Ordinary I would gel and lay a layer of 450 CSM to block print through before completing a lamination which would include woven or stitched fabrics. I can see that 2-3 layers of CSM could be bagged directly on the gel.

 

What are you thinking of as a core? Foam core or something like core cell?

 

The kicker is the muscle behind the oars. I aim to produce an eight foot dinghy which would be as affordable as can be.
Whadayathink about a lamination schedule?

 

Get your plans for a ply dinghy , then do the math to convert ply to foam core . CM = cold mold (ply) , SFGS = single fiberglass skin , A . ratio 1 cm to .66 sfgs , B . sfgs x 2 = core thickness, C. . 7 of sfgs = total fiberglass laminate . So using 1/4 " ply and say 1/16" glass we get .25 +.062 = .312 , A. .312 x .66 = .207792 , B. .207792 x 2 = .445584 or about 1/2" core thickness . C. .7 x .207792 = .14544544 , D .1454544 divided into 2 surfaces = . 0727272 thickness of fiberglass laminate per side . Triaxial is about .05 in thickness . I would go 1 layer triaxial outside with a layer of light S2 glass and 1 layer of triaxial inside and call it good if my math is good , might check it .

 

An acquaintance in the Keys, retired from Avon Boats, used to build four per day in two molds. In the morning, he drove his car out of his garage and rolled two molds into place. He built 2 in the morning before he went to work at the dolphin rescue center, and two more in the evening when he came home. Then he cleaned the garage and pulled his car in for the night. He had 45 minutes into a boat by the time he had it loaded onto a rack in his yard. Everything was made out of prepreg offcuts from Boeing. Boeing was kind enough to cut them to shape and kit everything for him. He got a couple of freezers worth of prepreg each week and a truck came to haul away the boats once or twice a week. The laminate schedule is the one that lets you compete with this guy. It took him about 45 minutes to prep, gelcoat, laminate and bag two molds. The rest was painting and rigging. This was his idea of retirement.

 

Couple of questions, since it sounds now like you intend to produce more than one. Has the USCG certified boats from that mold? Can you post a picture of the certification label you will be using? You can't deviate from the weight of the as-tested (or as calculated) specimen, and you can't build an uncertified vessel for sale to the public. So the laminate schedule is the one that the approval has been based on or will be based on. Using the certification algorithm, you can back into the max construction weight based on what you want on the data plate.

see section 181. in particular 181.7 - https://www.uscgboating.org/images/514.PDF

Okay, you're in Canada, but the rules there are similar, but I don't have those references at my fingertips.

 

Woah Doggies! I'll never compete with this guy, though I'd love to be his understudy..

 

Good to know. I'll check with Canadian Coast Guard and The Department of Transportation. Thanks

 

This looks like a good, mathematical, scientific approach. Using this method I'd probably start by assuming that a similar dingy could be built out of quarter inch plywood. I'm wondering about triaxial cloth though. I'm sure that it comes in different weights. What did you have in mind?

 

Triaxial 34.5 oz is .050 thickness , 17.3 oz 45/45 bias is .029 thickness . You will have to look at strength , weight , and puncture resistance when deciding on your cloth .