Help choosing building method

[fede]

Hi , I need help choosing an amateur building method that's suited to this kind of lines (sections attached).
I have been thinking about C Flex,the only thing I'm concerned with is the chine (the spray strake at the chine) and the sharp corner at the middle of the topside (I don't know the name in english).
How about Cold Molded wood? still...how woud I approach those two spots on the hull?

[CDBarry]

If the hull is developable, you might conside direct female mold construction.

The problem with most one-off FRP construction techniques is that getting a smooth surface involves sanding. Direct female molding avoids this almost entirely, and you can deal with the chines in a standard femal mold method.

[fede]

Thanks for helping CDBErry!
Yes I gave a thought about building a wood mold and that woud be perfect for the chines.
My question now is : how about spray strakes (lifting strakes however you call them) ? The ones under the hull...shoud I make mold that also have the form for rails? or do I have an option that will let me add rails after the hull is pulled from the mould.
ALso: Should I build the mold in one single piece? or 2 halfes? (isn't it difficoult to work in a female mold ? )
How do I know if the surfaces I'm working on are developable? I designed the boat without worring about the "developability" is there a way in Rhino or Maxsurf to check if a surface is developable? Should I rebuild them making them developable?

Sorry for the 1000 questions but I'm in really big trouble choosing which method is the best and not too difficult for an amateur!

[jfblouin]

I have the sames questions!!!
Since 6 months, one week, I choice female mold and the next week after it is the male one-off.

So the boat will be build next year!!! I have the chance to change many times.

The strakes are also one of my problem and lay up inside a mold.

This week the female mold is my choice

[fede]

Jfblouin...it looks like we are in the very same conditions...this week is my female mold week too!! I've been reading 1000 books evaluated 100 diferent techniques...no one of the books deals with the kind of (very common today) hull I want to build!I've spent hours and hours looking at round sailing hulls that nothing have to do with the kind of shape I need to build...

I think that female mold would be the best way to go....I'm not shure on the HOW...
Still considering C FLex though.

Well..I feel better now that I know that another human being with the very same problem exists on this planet!!

Please let's get in touch, exchange ideas thoughts and knowledge so that we could start building before 2010....please...

[jfblouin]

I'v been reading 1000 books too and draw plans and plans. You can see one (but not the latest) in my old post. Me too, I want to design my boat because I dont find any boat like I want. A Rigid inflatable Boat look but hard collar. Low weight and traillerable. Good for soft ride with my 4 childs and good seaworthy for me.

I try male One-off for a 1:6 scale test boat and I found that with this technic, I will have a lot of sanding for a flat surface. Particuliary where the number of layer will be differents.

For the female mold, I'm affraid about all the resin that will be drop in the bottom of the mold. And working inside of a 6,7m x 1,7m will be a tuff job. Working outside a mold is easier.

For the exterior of the boat, I will dont use gelcoat because and prefer Polyurethane painting system so I can make minor work for smootese finish outside te boat. I try differents easy accessible and cheap product to make the mold and I find that Masonite, Hardboard, Coroplast make good support and release easily GRP. Transparent tape make good union between sheets and GRP dont stick on that. I dont find the best methode for stake (I continue me researsh). For the bow shape, I find 13 30"x60" flat shower inside plactic very thin so I try to developpe a cylindrical form.

I think that we are in the same processus, hard and long for a make a good boat but I think that is possible.

Sorry for my not so good english

[fede]

One off: The options here are C Flex,but still I'm not shure how to work (and if it's possible) the material in the sharp coners area.

If you make a male mold of wood and than laminate over it you could do this: do the basic lamination (the number of layers of the thinnest part of the boat...probably the upper topside) ,make reinforcment on the outside turn the boat pull the wood mold and go on laminating in the inside for the lower topside,bottom,chine etc.

This way you will not have differences in layers on the outside.

The problem here is that PRF on a male mold will not behave well on sharp corners...

Female mold: working in the inside of a female mold is difficult....

Let's make 2 half !! And after the two parts are done in wood you put them toghether.
Attached apicture that a person I know posted on another website.

[fede]

As far as strakes are concerned, if you look at the picture, the forms of the sections tells you that they are already in the mold...this is the best way,believe me...if you try to attach wood strakes to a fiberglass hull the risk is to loose them while you navigate.

My Idea is to use no more than 10 mm plywood and then cover it with hardboard glue and staples...then remove staples and fill the gaps and the staples holes.

Some finishing will be needed on the outside but way less than with male mold methods.

[Raggi_Thor]

Why don't you build the boat in plywood instead of building first a mould in wood and plywood and then the boat. The mould+boat is about twice as much work and cost of a plywood boat. Epoxy costs more than polyester but you use less of it. Okume Marine plywood costs much less than most combinations of foam/core/c-flex + glass.

[Danielsan]

Upon the shape of hull and deck structure, you could make the wooden stations, as you would do for plywood construction. Instead of using plywood, use a sort of core foam to create a sandwich construction, then lay up the glass. When this is done you could go and remove the wooden stations, and begin laminationg the internal structure.

This is a guess, but I think this is the way I am going to do it unless someone tells me that this is wrong.

You will have some major work for fairing and outfiiling the outer hull and deck then putting up topcoat and everything.

This is the more economical solution I think th only (waste) you get are the wooden stations. By the way you could reuse them for a next one if you design them well.

On the other hand Making female mold would be more complicated I guess. because the need of working inside the structure. Will have a bit more material then my first idea. could reuse it afterwards. Space taking

Making a male mold wil be more space taking afterwards when job is finished material will cost more in (labour and) money. If good you could sell the mold?

!once again correct me if I am wrong, I am (also) an amateur(builder).

Remark: As I am designing the boat myself, I can design the hull with the exact thickness for every spot. this makes it possible create the stations to take into count the differences of the foam core. so giving a smoot outer foam hull, that i can lay up with the glass.

I am doing my 5th design to try to handle with the fact, that I as an amateur will have to build that thing on an (easy) way.

Greetings,

Daniel

[Raggi_Thor]

One simple way to accomplish a smooth outer surface in sandwich one off costruction: Make a flat horisontal "mold" (smooth and with release agent or simmilar). Then lay up (or down :-) the outer skin + core as you would in a female mold, starting with the gelcoat. Move this panel to the hull, bending it around the stations, then put on the inner skin.

[Danielsan]

I am not shure that this can be done for every hull shape, what about bounding the different surfaces togheter?

[jfblouin]

A two parts female mold is a interresting idea for my small project. I'm only affraid with the solidity of the secondary bond between the two parts of the hull. Especially at the keel. Maybe use polyester for the firts step and epoxy in secondary bond?

[fede]

Well, you do the 2 parts mold then you put it toghether and laminate into it in a traditional way...
The hull will be one piece.

About Plywood construction.

It requires a knowledge of permanent wood structures that I do not have, while I know what to put in a fiberglass boat as far as stringers, bulkheads,etc. are concerned it woul be very difficult for me to know where and how to put reinforcments in a plywood hull.

My woodworking skills are poor and this is ok if I have to make a mold ...not so ok if I have to make permanent structures.

[Danielsan]

Maybe use polyester for the firts step and epoxy in secondary bond?

If got this right you can not bond Polyester with epoxy?