Foam Plug?

[Ron Skelly]

I am planning on making a prototype of small sailboat approximately 5.5 feet wide by 11 feet long and I would like to do it in fiberglass. Someone here had mentioned doing in on a "foam plug". Does anyone know where you would get such a large peice of foam? When I google foam plug I get mostly ear plugs - a bit too small. If not a foam plug is a wood frame a good option?

[Chris Ostlind]

Ron,

Folks who use foam plugs for the creation of a tool to build boats typically stack several layers of foam with a glue of the same type of material (urethane)... OR, they spray sufficient foam onto a wooden armature so that the CNC machine can tool just the foam and not break into the wooden structure.

That CNC process if fairly spendy for small time boat making. You can build your boat hull in stacked foam, (if you also build a structure to keep it rigid enough for shaping) and then hand, or machine shape the hull to the final form. You would do the hand work, in lieu of going to the CNC tooling shop.

This technique is done all the time in the kayak business, especially in the ever-changing whitewater end of the spectrum. Once shaped, these guys will then build a two part mold (tool) in high temp epoxy and glass. The tool is then used to spin (rotomold) a few examples of the just shaped boat in plastic and they are taken to the river for testing.

The method is fast, it yields a boat that can be rigorously tested and if it isn't what they thought it would be, they can quickly build another. Nicely enough, the right kind of tooling epoxy can be used to spin lots of boats and they can be taken directly to market with the standard finishing procedures. The techniques expressed are fast, fairly inexpensive and nearly immediate as responses to a very volatile segment of the boat industry.

[Ron Skelly]

Thank you for your feedback. Is there any websites or books that I can look at / purchase to research this technique in order to get this roto-mold stage? Detailed step by step instruction?

[Itchy&Scratchy]

Roto moulding is a massively expensie route to go for a few items, I dont think hes talking mass production.

Normal old hand layup is surely the way to go.

Do your searches for rigid urethane foam blanks (more expensive than styrofoam)- which would require working in polyesters
or
altenatively styrofoam which would require the use of epoxy resins(more expensive than polyesters)- you cant use polyesters with styrofoam as it eats it.

So basically you have the choice of Polyesters and urethane foams which is more expensive than styrofoams but then if you go the cheaper styrofoam route the epoxy resin is more expensive, so you make the choice.
I personally would go the polyester route.

Hope I havent confused you.

Failing that of course you could just use MDF to make your 'plug' and surface it with a polyester high build primer, which you could flat down and polish and apply your release wax or whatever system you decide to use and take a mould off that.

Have fun
J

[Chris Ostlind]

Ron,


I don't know of any books on the topic. You can start your investigation process, by Googling the multi-axis CNC trade for the shops that do cut foam for boat hull plugs. Janicki just north of Seattle does, for sure. A couple shops in Florida, as well. Right now, it's kinda hard to say just who is still in business and who has been chased by the recession.

The typical CNC router that does this work is of the five axis variety, so that might narrow your search. These shops might have some nice photos and descriptions of the process on their site.

An email to the big industrial epoxy companies, such as West Systems, will get you info on high temp epoxies for tooling. Up in Ontario, you might check with the guys at CCI http://www.fastcomposites.ca/home.php They do CNC work of all types and are really great guys. Ask them for some other links/references, as they know tons of people in the business.

[Chris Ostlind]

Originally Posted by Itchy&Scratchy

Roto moulding is a massively expensive route to go for a few items, I dont think he's talking mass production.

Actually, it can be relatively inexpensive to do a rotomold with high temp epoxy. It will not hold up for more than several dozen hulls like a production aluminum tool would. It's also not going to cost $2500 a running foot to build it.

The guys in the whitewater kayak industry are banging out a fresh epoxy tool every few days, at certain times of the year, in order to stay on top of who has the hottest, most innovative, rodeo/play boat around.

If the design is suitable... and I have no way of knowing if this would apply since I have not seen the design... the boat can also be built as a set of thermoformed plastic pieces that will be glued together as a completed boat. A good portion of the composite kayak industry has gone to that method and the products are very nice.

[Itchy&Scratchy]

Thanks Chris

I wasnt aware that it is possible to do limited pre production runs- have to admit this is one area (rotomoulding)that I am completely out of my depth.
I have to admit I know less than f....all about it
Saying that I now feel I need to have a look around and see if I can learn more about the process.......

by ....... offf to 'youtube'

see ya later
J