My one sheet steel boat project

[hobo_hut]

Some time ago I was curious about building a steel boat. I saw that a number of other people were also interested in the idea. As steel prices were relatively low and because I feel a little more comfortable working with steel than with wood and fiberglass, I thought, why not just try building a boat and see what happens. The boat is made from one 5x10 sheet of 16 ga steel.

So anyway more about the boat. This would be my first ever designed and built boat. So any criticism on the design and what I did right/wrong are welcomed, you wont hurt my feelings.

The boat is meant for rowing down the local rivers around me which can be very rocky. I do have plans for attaching a sunflower sail that I have laying around, but I am reluctant to make a centerboard trunk. As you can tell it is a multi chine boat assembled in much the same way as a stitch and glue boat but a little different. Ive decided to call this process Tape n' Tack. I don't have any updated pictures but right now but I have all the seems welded and one of the thwarts ready.

Some basic dimensions
LOA: 11'
Beam: 42"

Cost of materials so far:
5x10 16ga steel sheet: $90.00
20' 1/2" square tube: $16.00
Pine boards for seats: $20.00
Pine for rub rails: $10.00

[hobo_hut]

Sorry..I realize this post should probably be moved to the steel boat building/construction area. How can I move it?

[messabout]

Your boat is lookng good. The design smacks of something that might have sprung from the drawing board of Bolger or Welsford. The pix do not make it entirely clear but I suspect that you could use some additional deadrise in the lower strake.

The only criticism is that it will be bitchin heavy for such a small boat. 16 gage steel is about 2.5 pounds per square foot. If you use perhaps 90% of the 5x10 sheet the skin weight will be more than 110 pounds. If you had used used , say.....6mm okumee the skin weight would be less than 30 pounds. I reckon that the steel boat and a single oarsman of 175 pounds will make an all up weight of 325 pounds more or less. You will need 9000 cubic inches of immersed volume to support that weight. Looks like the boat will be able to operate in 6 inches of water.

Nice thing about welding is that you do not need to wait for glue to harden or put up with a mess smelly of sticky stuff.

Keep us posted, you are doing a good looking job.

[hobo_hut]

You are right the boat is heavy. Weights just about 90 lbs as is. Will this add stability in the sailing department? According to the software I designed the boat in she should have a 5 inch waterline with a 350 lb disp. One thing is for sure though that this boat will be able to take a beating going down the rivers. Which leads me to two questions.

1. What kind of paint? I want something that looks nice, but it must be either very durable or inexpensive so that i can touch it up from time to time. I was looking rubberized paints that are like on tool handles as well as epoxy based paints.

2. Flotation or not? Do you think it will be necessary. If so where to put it and how much will I need. I dont want to take up the whole boat with foam. Also any other options for flotation besides foam and making airtight areas?

[Jeremy Harris]

If you can tolerate the weight increase, it might be worth looking at getting the finished boat hot dip galvanised. It'd probably last for many years, with no need to worry about paint or touch ups. Might look a bit agricultural, but maybe you could live with that.

Nice job though, I don't think I've seen anyone use thin steel like that.

Jeremy

[globaldude]

brother its a thing of beauty !!! . well done ! . I don't think it would take the heat of the galv tanks if you tryed to hot dip it ! . Epoxy paint is the way to go as its hard as .
Strong yes , heavy , well relative to light - easy to punch a rock through ply boat -yes, soooo boyancy [ given its open topped ] a must in my humble opinion.Id build in forward and aft [ with inspection hatches so as to be able to utilise the space ] and perhaps under the seat/s.

I'd love a copy of the patern files if possible as I'd often thought to build such a boat and you have done such a nice job .
Is she fully welded yet ? . you'd have had to keep moving around a lot to avoid distortion yes !? .

[Ike]

A thing of beauty is a joy forever. That is really cool.

[Manie B]

Your lines look ok

but

the steel becomes very wobbly and requires a lot of stiffening that increases weight

[hobo_hut]

The boat is fully welded now, and you are correct, you have to move around a lot to avoid warping, so it does take some time. But now that the seems are done it is very stiff a will probably not need any more framing once the gunnels are put on. And if it does need extra stiffening I think it will only need one other rib put in it. Honestly though I am almost positive the gunnels will be plenty adequate.

Do you all think think the epoxy paint will hold up to rock scrapes and hits? The paint alone will almost cost as much as the steel did, but I guess I'm ok with that since the boat turned out to be a successful experiment, at least in my mind.

As far as buoyancy is concerned I would like to make sure she doesn't sink. I will probably make foreword and aft compartments. How much volume will those compartments need to keep the boat from sinking? The thing about the aft compartments is that it interferes with where I want to put my feet when rowing, any suggestions?

One last comment. The boat is very tough, I can hit the hull as hard as I can with a carpenters hammer and it doesn't even make a dent, this thing will take the rocks easily. It is however very loud. So far I have about 12 hours of time in the boat so this technique is pretty fast I pretty much spent one evening cutting, another taping and tacking, and then one more welding the seems. I think the grinding of the welds and finishing will take awhile. Overall this will end up being a very fast way to build a small boat.

[lewisboats]

couple of ?s How is it with twisting? I find that is the hardest to firm up. Also...as far as buoyancy goes... I would go with foam...unencased. Simply shape it, paint it and strap it in. Making chambers filled with only air will cost you more in weight than using foam at 4 lbs/cuft. If you tuck it up under the gunnels along the insides then it is out of the way and at the optimal position for level flotation. You will need 1 cuft of foam for every 58 or so lbs using 4 lb foam.

[Stumble]

Hobo,

A two part epoxy paint is about as durable as paint can be. That being said high speed crashes into rocks will scrape I am sure.

I would recommend enough foam to float twice the weight of the empty boat. That way you have some margin for gear people and equipment. As for its location... I would probably pour expandable foam into the ends taking as much volume as needed to get the boyance I wanted. Then encapsalate the foam with light plywood or really light metal. just to provide some protection from crushing and UV. Just be warned if there is any way the foam can get wet inside the encapsalation, over time it will rot away and turn to mush. Using lewisboats numbers then I am recommending using about four cubic foot of foam total.

If you are really concerned about trying to minimize the amount of space lost in the aft of the boat you could also use a smaller amount of foam in the aft and bow and make a midship seat or box to carry the bulk of the flotation (say 25% in each end and 50% in the middle). But I wouldn't want to have a steel boat with just one end floating... It would sit in the water pointing straid down after all.

[Jeremy Harris]

You could look at gluing sheet foam inside the sides of the hull. Choose something durable and closed cell, not PU. Not only will this give you buoyancy where you need it, but if you choose a fairly rigid foam, then bonding it inside the sheet steel will also stiffen the hull up a fair bit.

Take a look at some of the rigid sheet foams used as composite core material and pick one that is thick enough for the buoyancy you need and affordable (some of them are mighty expensive).

Jeremy

[hobo_hut]

Thanks for the responses. I like all the foam ideas but I'm afraid of how it will look. I might just make a forward and aft compartments, at least that will give me a place for dry storage.

On the other hand I like the idea of having a completely open boat so maybe some type of foam along gunnels might work.

I need some inspiration. Do you all have any pictures of different types of flotation being used? Ive seen under seat foam blocks and I am not real fond of that.

Also what is the best place for the thwart. Should it be on the center of buoyancy? Any advice on rowing ergonomics/geometry would be appreciated as well. I have no idea how high to make the seat in relation to the oar locks. As you can tell I am an amateur with a welder and a little motivation.

[lewisboats]

As far as your rowing seat/thwart goes...you will need to splash it first then get in and have someone take pictures as you systematically place yourself in positions. this will help you determine the proper trim for the boat with you seated in it. Oarlocks should go about the length of your forearm aft (of your aftward facing seated position) of the centerline from your hips to your shoulders. As for height of seated position...this will be different according to your height. Best method is to build a wood box that you know to be too low then stack stuff on top until you get to the height that is comfortable to you. do this after you have determined the lock position so you can have the oars in place and can test things out.

[hobo_hut]

Thanks for the info about the rowing ergonomics and geometry. I spent some time searching and googling but didnt really find anything. Im going to take down to the lake and try what you said as soon as it stops raining, might be another day or two.

Hull coatings: I was thinking about painting the inside with a polyurethane paint maybe white or lite grey. Then polishing the outside hull close too a mirror finish and then clear coating it from waterline up. The bottom half I will just put a heavy coat of wax on and polish out scratches and rust as need be. I have experimented with polishing steel in the past and it has proven to be very good against rusting. Plus I think a shiny hull could look really sleek on the water with a boot stripe.

Still have not decided about the flotation issue.