building soon and have ???

[timbecht]

i am looking into start a boat build soon but have a few ??
my build will be a 16' jon boat flat bottom but ?1 i want to use 18 gauge sheet metal and 1 inch square steel tubing for framing on inside can i use this material .

after hull is built it will be covered with fiberglass for other reasons beside sealing hull

the boat will be 16' bye 4' with 20inch transom and sides

will this work and or float reason for using this material is have easy access to

please give me any and all info u guys can give and thanks for a great site have found a lot of info on here for other projects

[hoytedow]

Are you going to weld it or just rivet it onto the frame and glass over it? I would weld it(or have it done as I'm not a welder) and leave the glass off to save weight. Steel really isn't the medium I work in but there are many experienced welders on this forum so read their stuff.

[messabout]

Is your boat to be a planing hull or displacement type? What do you plan to use for power. Why will you use fiberglass over steel? If it is to be four foot beam will that dimension be at the bottom or at the sheer line or both? More information will enable better responses to your post.

The steel boat will be heavy and unless you use a lot of framing it will be limber. You will need to cover the steel very carefully with high grade paint at the intersections of the sheet metal and framing. Otherwise rust will destroy the boat before you are finished using it. You will have a much stiffer boat and probably lighter if you use plywood. I'll go out on a limb here and predict that a jon boat of good quality ply will last as long or longer than a steel one. Meanwhile the ply boat will be easier to launch and retrieve, will perform better with moderate power, but the ply boat will not be as immune to high speed encounters with rocks, fence poles, or collissions with jet skiers.

[Poida]

Steel tubing will rust from the inside to the outside and you won't know about it until the boat falls apart.

[rwatson]

Fibreglass over steel is a bad idea for the same reason - rust betwen the two surfaces.

[gonzo]

There are lots of jonboats like that built as workboats. You'll see them around bridges and seawalls. The fiberglass won't stick to steel for long. They are not compatible.

[hoytedow]

All in all, from what I gather from these well respected responses, I think steel on steel tubing would be a bad idea for this project.

[PAR]

Tim, this is a request of designers on a regular frequency: "can I have this wooden boat design in steel?" "foam core", "glass", "ferro cement", etc., etc., etc.

Let me guess, you have a design for a plywood jon boat and you want to do it in sheet steel and frames? The simple answer is yes, you can. The unfortunate truth is you can toss the wooden boat plans out the window as they're useless.

Sheet steel has completely different structural requirements compared to plywood (or other building materials for that matter), so it requires a different engineering approach. For example, if using sheet steel for your jon boat there are a few different ways you could go about the structural considerations, but all will have very different framing arrangements then the wooden boat and unless you have access to a really big brake, one big ass bead roller or press and you'll be forced to use considerably heavier gauge steel then 18.

18 gauge could be employed, but the stringer spacing on the bottom would be very tight, which makes for an ungodly heavy beast. 16 would be a better choice, though much thicker steel would be wise to offer some penetration resistance.

As mentioned above, using box or rectangular tubing isn't wise in a boat, angle stock and flat bar are the common choices, because they don't capture moisture.

Also, as mentioned above, the idea of 'glass over the steel just doesn't work for several reasons.

At this point it might be best if you just got specific about what you'd like to do, so that we can offer something constructive, rather then tell you what you shouldn't do.