Commercialy Made Stich and Glue

A lot of plywood designs can be built in alloy plate, it's easy for an NA to provide the same plans for building in both type materials.

Have a look at sea angling/fishing Cat designs from OZ and NZ for alloy construction, the home of literally hundreds of good designs; get a NA to convert to plywood stitch and glue: I was interested in a Delvin 32' plywood design, the NA quoted $2000 to convert the plan to alloy.........so alloy and ply are nearly interchangable.

.....when you are getting the plans redrawn get the detachable sections designed as well...........

 

This guy has some very nice alloy designs that could be converted to plywood.
http://www.noahthompsondesign.com/powercats.html

 

Some designs, not all, can be converted from aluminum to plywood but keep in mind that both the weight of the hull and its center of gravity will not be the same so the equilibrium waterplane, which will certainly be different, can give rise to the "look" is also different.
In general, a project designed to be built with a certain material can vary widely if the construction material is changed. It will change not only the look but the constructive solutions, as well as the performance of the boat.
Just an opinion: if the price to change drawings from aluminum to plywood, or vice versa, is only $ 2000 US, you take the opportunity and ask for the conversion of all the ships that are possible. Given that the structure must be changed, you have to recalculate the scantlings and new construction details to be applied (and therefore the construction plans will be almost entirely new), the price seems a gift.

 

This was the ply design I was interested in:http://store.devlinboat.com/topknot-10_meter.aspx

Sam Devlin quoted about $2200 for the work to convert to alloy construction.
I also asked for an estimate for a professionally built plywood hull/superstructure from his yard: $178k for it in stitch and glue, it's only a 10mtr boat!

No, that's not a typo......yes, just for the hull/superstructure with no windows or deck fittings.

I would expect a Commercial GRP hull moulding to cost about $50k for a similar size.

 

Many, many hours of search and still no plans. Also there are no books specific to catamarans. I have bought four books that from their descriptions looked promising but are of no use on catamarans.

 

Just do the maths, aluminium, steel, and wood are all pretty much the same weight for strength. I exclude the truly more specialist ends of some of these materials. So you still need to convert the design correctly, according to loads on the structure. The key point as a generalisation is that wood is far better in tension than compression than the metals, hence alloy masts as an example. But for beam stiffness the above rule of thumb holds pretty true.

Hence TANSL's premise that the design needs recalculating to see where loads are more in compression etc, completely valid. It does not negate re-engineering the structure from one material to another, just change certain parameters.

I'm not surprised that a 'one off' would be more expensive. A very different proposition from tooling a mould that amortises over 5 or 6 hulls.

 

SukiSolo, I have no design to convert. That is the problem. I can not find one that is close enough to my needs. I was never interested in boats when I was young and all my education is in other things so I don't know how to design my own. The work I could have done as I have been a Toolmaker most of my life and have a lot of experience in composite tooling (molds) I also built custom cars and can fair a surface as well as anyone can. I am just too old to do it ( 69 ) and need to just hand a complete design to someone and try for a partnership of some kind. I am just not ready to be my age and set around until I die.

 

Its not expensive to design a mold for a long sysmetrical sponson that could be used to make shorter and shorter versions, and the same mold could also be used for port and starboard.

These fibeglassed sponsons could then be produced in a day and could be fastened together to beams of different widths in the same way that a Macgregor 36 uses 3 aluminum pipes to make up the cross beams so that this wide-large catamaran can be broken down for travel on trailers that are 8' wide or less.

Fuel placement could be centered close to mid ships and be carried by th cross beams instead of inside the sponsons attain the right balance at different lengths with less construction headaches.

But unless you want something that moves at 20 knots and under, the cost of interchanging motors might be cost prohibitive unless they are small outboards.

 

Just re-reading your posts, the thought occurred to me that for, quick build modular designer could be Derek Kelsall.

His stuff is usually foam under glass, but I know he has had some really great innovations in plywood cats in years past.

I have always found him to be easy to contact, and discuss special projects.


http://www.kelsall.com/UniqueKSS/KSSModularAssembly.htm

 

Sukisolo, this is not entirely correct : "wood is far better in tension than compression than the metals" (if I have understood correctly). Wood is worse than metals, in almost everything, from the point of view of structural strength. What happens is that the wood works in compression, much better than bending.

ElGringo, I have 70 years and I have the knowledge, time and resources available to help. I think you have a great age and sufficient skills to start with your project. You only need plans that, maybe, I can help you to get. As, I suppose, you do not want to get a degree in naval architecture, no need to buy many books.

 

TANSL, I have sent you an e-mail

rwatson, Thanks for the link to Kelsall. I am going to try to work with TANSL and see if we can come up with something.

Bullshipper, Wouldn't the weight of a fiberglass hulls and deck be a lot more than plywood? I'm hoping to power this with a pair of 20HP motors.

 

just found this thread... theres plenty of example of commercial stich and glue building in australia, using flat composite panels that is, not plywood. same deal, but higher performance. Theres also kit plans available for quite a few catamran designs, everything precut via CNC router. heres a few examples;

a 9 meter with high deck clearance;


Same hull but with a day boat type of layout;



a 7 meter, planing style;


Theres a few to choose from... usually powered by 40-60hp outboards and speeds above 20kts possible.

 

groper, do you have a link for the website? I tried the redbook.com.au and came up with a car sales website. Using the composite panels in place of the plywood sounds interesting.

 

Schionning designs , also spirited designs, but Schionning doesn't show the prowler 7000 or prowler 9000 on his website anymore. You'd have to contact them and ask about it.

 

To do so, without more, is not possible. There are many other changes that provide