Hull forming

[Boaterguy]

I didn't really know where to post this but I thought it would be fine here.
I found a place right outside town that does CNC milling and vacuum forming. I want to make a twin cat for my next project and I would like it to be made professionally.
I was thinking that if people were willing to help put in ideas I could get a big batch made and sell them with minimal profit, people who helped would get the boat for shipping +fab price.
In order to do this I would need to get a few people interested in buying.
I want something around 30-36" to take two T600's, most likely a 6S setup.
I have yet to contact them but i will tomorrow if I can't get ahold of them on a sunday.
So just to be clear the hull mold would be milled out of most likely wood and then vac-u-formed out of plastic. I could also get the bulkheads laser cut if they do that.

[kookie_guy]

It's going to cost you well over $1000 by the time you have just the mold cut. Keep in mind that your design will require A LOT of programming time on the CNC. Shops make all their money on the programming. The cost difference between 1 part and 100 parts is minimal, as the first part is really what you pay for, because that's where they hit you for the programming time.

You are much better off (and it will be much cheaper) to collect your input from others, and build a plug out of balsa/ply. Then make a mold yourself, and do them out of fiberglass. Stay away from plastic.

I know you want a project to work on, but in my opinion, you are biting off a lot. There's already hulls out there that are well designed and thought out, for much less money.

Again, just my opinion.

[Boaterguy]

What about if the plug was formed and I got it just vacuformed, then there would be no CNC programming.
I could try buildigng fiberglass hulls but I don't feel comfortable selling people hulls I made, Unless I made a couple first.
Thanks for the input, I will reconsider

[kookie_guy]

The problem with getting the plug vacuformed is that it's a 'positive' shape. How do you remove the plug from the form without destroying it? That's why with vaccuforming you suck the plastic into a 'negative' mold. Like I said, I know you are looking for a project, I do it all the time. lol

[Boaterguy]

You could just drill into the plug and put a screw in to pull it out, although I do know what you mean.
How would you take the F/G hull out of a Pos. mould?
CF is an option too.

[kookie_guy]

That's the thing, you have to have a negative mold. You can't really work with a plug. You use the plug to make the mold, then use the mold to lay your fiberglass/cf. The whole point is that the mold is to have a flawless finish, so when you lay fiberglass/cf in it, the exterior of the hull will have the flawless finish transferred over. If you were to do a layup on a plug, the nice finish would be transferred to the inside of the hull, and the outside would take considerable work to make it pretty.

[Boaterguy]

I see, but what is the negative made out of? or is it made first?

[kookie_guy]

First you would make a plug. The plug is basically what the finished boat will look like. You can make it out of wood, just like you would if you were building an actual boat to run. You need to make sure the finish on it is FLAWLESS, as it would all transfer to the mold, and all the boats you pull from that mold will show those imperfections. You don't really need any strength to a plug, or you can carve it from a solid piece of wood. As long as it's perfect.

Second, you create a parting line around your plug so you will mold the bottom, and upper deck separately. You have to do it at a point where your angles transition, so that it's possible to pull the molded boat part from the mold. You use mylar wood panels to create a flat lip all around your parting line.

Third, wax the snot out of your plug and you apply tooling gel coat, followed by several layers of fiberglass, to one side of your parting line. When it all hardens, you pull off the mylar wood panel, wax the snot out of the uncovered side, and do the same (gel coat and fiberglass). Once that hardens, you pry the 2 halves apart. You will now have a perfect negative mold of what your finished boat will look like. Any imperfections in the gel coat MUST be fixed, or they will transfer to the finished product.

Fourth, you wax the snot out of the mold, apply gel coat, and lay your fiberglass/cf. This is essentially building your boat. You do this to both halves. Then once they cure, you join the upper and the lower, and do your finish work.

So like I said, it's A LOT of work to do from scratch. You are better off purchasing a ready made cat. There are plenty within the size you are looking for.

[Boaterguy]

alright, I guess I'll go with the genesis or another similar cat, will it be too small for twin T600's? also what prop will it take?
This is the motor i'm talking about
http://www.hobbyking.com/hobbyking/s...i_1400kv_.html

[mickieb49]

Hi, just to pitch in here, here is a build thread of a 72" cat i'm doing at the moment

http://www.rcuniverse.com/forum/m_10539341/tm.htm

, just to give you a bit of an idea on whats involved. So far it owes me about 500-750hours and about $800 in materials ( and i havent done a hull yet).
just my 2 cents.
Mick