Steel frames & ply cladding anyone

[sandpiper]

Morning folks.
A company I have seen advertising , in one of this web sites many pages, details themselves as builders of steel framed wooden yatch's. This prompted me to sign up to this forum & try to get some feedback on this subject, so here goes. I have often mulled over the thought, of building a small sailing skiff or dory, using ply & a steel frame. The reasons are as follows :- I have20 +yrs as a designer & fabricator of various steel products, & ply is cheap, strong, & able to be glassed. I have however dismissed this idea as out of hand, due to the incompatibility of materials. Having seen this advertisment however, I begin to wonder. What with modern sealants, bonding agents etc, maybe it is possible. Has anybody had anything to do with this area of design, or does this area of design not exist, for good reason. I would welcome any comments. Cheers.

[MarkC]

I think you have a great idea for a composite boat. There is no reason why it couldnt work. Here are my thoughts (ramblings!)

Ply fastend to the steel with small bolts or srews (perhaps without some epoxy used as a glue because you may need to take off the ply and repair it some day. Then epoxy coat every surface - then use a UV resistant paint.

Here is a free dory plan you can use for experiment:
http://www.svensons.com/boat/?p=Mech...trated/rs_dory

and another:
http://www.svensons.com/boat/?p=MechanixIllustrated/Pod

With the curve the sides of the dorys have, your frame made need to be angled (beveled) to match for a flush-fit against the wood. If you are using angle-iron, how are you going to bend it to match the angle of the wood? For example - not 90degrees. You could use a shim but that is complex. With a wooden-frame the builder just uses their saw or block-plane to make the correct angle. You will need metal working equip or a machine-shop. Or you could chose a flat-sided punt-design with no curve.

Also, I don't think that a long-lived-marine ply would be so cheap.

Your dory 'may' be heavier due to the steel-frame but then that can be factored in with the design. A bit heavier wouldnt bother me but it would some.

Was it the company 'Legendary Yachts' that you read about? If you do a search in www.woodenboat.com under 'legendary yachts' there is a discussion about the steel-framed wooden-planked or stip-planked composite building technique. I am a big fan.

On this site and www.metalboatsociety.org a number of folks are experimenting with building older wooden-designs in metal (see Kevin Morin's aluminium dory posts in www.metalboatsociety.org). Not many, however, replace the traditional frame with steel - instead use a monocote construction with the skin as the structural element. But for doin' it yourself, at home, a steel frame is a good idea. I would do it myself....

[SeaSpark]

I am in a bit of a sarcastical mood today, someone please post a sensible reply to all of this. Couse of my mood i feel not up to this serious job.

[sandpiper]

Thanks for your reply MarkC. Well I suppose if I went ahead with a design, the idea would be to try & produce something that would be light, strong, & disposable. Lightweight square, hollow section tubing, I had in mind, this would be lighter than wood & with a few basic formers can be cold formed to shape. The idea of ply, is to use an exterior grade, not marine, as it would be epoxied or glassed. If it became damaged in some way, replace the whole panel or replace all the panels. Should the frame become damaged, weld a new bit in, or build a new one. I know a vessel built like this would not go onto the classics list, but it's not about that, the question is, is it possible to build a safe, strong, little sailing/ rowing boat, that could take a small OBM, but is so quick & cheap to build, it wouldn't break you, if you had to build another. Many thanks for the links.

[SeaSpark]

-A combination of wood and steel guarantees rust and rot.
-The use of hollow steel frames guarantees more rust.
-The use of exterior ply guarantees more rot.
-Steel frames do not make a craft light, especially small ones.


Search the forum for exterior ply, the rest of your suggestions are so far from practical i hope there is no information available on the forum.

Really, my mood is to bad to explain these points further.

To anyone reading this and still thinking there are some good points in this metheod of construction:

-Replacing ply panels underwater is a hazardous affair!

[MarkC]

Complete ********.

Quote:

I have often mulled over the thought, of building a small sailing skiff or dory, using ply & a steel frame.

End quote.

Experimenting with a small-craft using this construction is no problem - clearly steel and ply need to be protected from the elements and from each other.

Wood and steel together do not guarantee rust and rot.

No idiot is suggestion replacing panel under water.

Like I said - your vessel might be a bit heavier than a fully-wooden-one but that doesn't matter except to some (as you have seen).

[SeaSpark]

Modern rust&rot prevention materials will only delay the process and are very expensive.

If you want to experiment with boat design and building on a small scale use only exterior ply and cheap paint and glue. Don't expect it to last for to long but you will be better of than with the wood/steel option.

Your growing experience will make you want to build another craft shortly anyway or otherwise convince you boatbuilding is not something for you.

[sandpiper]

All valid points,thank you. As my previous exp is larger steel craft, with plywood interior, it was just a notion to maybe have a go at a wooden craft with a steel interior. But then again maybe with the dory it's as quick to do the timber work.

[SeaSpark]

Complete ********.

Glad you head your post with a discription of it's content.

[SeaSpark]

Sandpiper, sorry your words got stuck in between ours, in general people are very polite in this forum. Your "thank you" has done wonders for my mood.

[MarkC]

Well Sandpiper you asked for comments!

SeaSpark is correct when he means that salt-water murders everything. Uv from the sun tops it off. Tough environment. If you don't want an aluminium dingy (and there are sometimes problems there too) then the safety of your boat-of-choice will require careful construction and maintenance.

All boats cost money. Your choice. Experiment away!

[duluthboats]

Corrosion and rot are a problem all boat owners have to deal with.

Building with a metal frame and a wooden skin can be done but is it practical for small boats? If you are good at working with metal and can construct the frame I would continue the process and cover it with metal. There are many great designs for small metal boats which only require a skilled fabricator. We may someday see such composite boats but I suspect they will be highly engineered and require expensive manufacturing equipment.

Gary

[MarkC]

in general people are very polite in this forum

SeaSpark - Glad your mood is better.

[Joe6]

Framing a small boat in steel would be an increibly tedious undertaking with little benefit in strength (on a small boat). Add to this all the pitfalls mentioned by SeaSpark. Legendary Yachts uses galvanized Cor10 steel if I remember correctly but they build rather large yachts and their smaller boats are not framed in steel due to weight concerns. After you welded up all frames you would want to have them galvanized. Too much Hassle, expense and weight for a small boat in my opinion.

[sandpiper]

Of course, rot would not be such a problem if alloy or stainless could be used, sorry to put the oar in !