Wood or Metal

[timnmelinda]

Hello
I am new to this site, not as new to boat building.
My first boat was a 20 ft pontoon, I fabbed aluminum pontoons, aluminum undercarriage, wood decks etc. It turned out well, sold it for honeymoon money for Vegas....should have kept the boat as the marriage sank!

Second boat was a 14 x 45 foot pontoon based houseboat, basically all steel structure except for plywood decking, built this boat for my father he enjoyed it for about 8 or 9 years but did not wish to pay the prices for the dock space, he got out of it.

Now I am in planning and design stages for another for myself. I am planning on a pontoon boat base once again (besides ease of construction, I like the stability of this platform) As I have not finished my rough design estimates, I have not decided if I am going to run with 2 or 3 pontoons as of yet.

Where I am looking for opinions, and everyones 2 cents worth is that I am trying to decide between glassed plywood based pontoons, or steel based pontoons. The last boat used .134 sheet for the pontoons bulkheaded every 4 feet. Had no problems with the boat and of course the pontoons were very durable in hitting rocks or running into shallows. It is just I read of so many that have or are building based upon plywood and glass, so I wonder if it is an option I should consider? Are there pros I am not realizing to the plywood?

This boat will be 48/54 ft with a 15/16 ft beam. The other boats were all outboard powered. This boat I am leaning towards twin diesels (from beta marine) placed within the pontoons for propulsion. I am thinking, and wondering with the twins, if I install a front thruster, if I could actually eliminate fabrication of a rudder system, as most twins I have been aboard were actually steered by the engines, if I add a thruster to the equation it would in theary give me the added flexibility beyond the engines, this is however just a thought.

With this boat I am also going to take further advantage of the wasted space within the pontoons , besides the drives, I intend to place holding tanks etc within, all things I did not do on the last boat. I figure it is both a learning curve as well as a process of refinment!

Well my real question was the thoughts of the wood vs the steel, but I thought I would share a little about the planned project as well.

Tim

[alan white]

Using a thruster is fine until something quits working. A backup rudder should always be at the ready.

I don't think there's any comparison between ply and steel for the hulls themselves. Steel, for your purposes, wins hands down. It forms to any radius, is virtually indestructable, and in the case of pontoons, it's weight is down low, offering stability without ballasting.

On the other hand, abovedecks, it makes no sense to me to use steel, since this is essentially a nearshore-inshore vessel. Strength isn't the issue. Cost and aesthetics are.
Steel is cold to the touch, doesn't allow easy fastening without drilling (in which case rust mustn't bleed, so it goes on and on).

I would build the upper structure from exterior plywood over studwalls of cedar or yellow pine and paint the ply. Perhaps use 1/4" ply inside. Wall thickness would depend on locale, as they would be insulated.
It might make sense to build "posts and beams" of steel which would be hidden within the structure, a means to get a very rigid frame without triangulating the walls with plywood--- this would allow freedom to place windows and doors anywhere without fear of weakening the structure.

I guess the roof would be curved athwartship, rubber membrane, etc..
So in answer to how someone else (me) would do it, I would use both materials, getting the best advantage out of each for the application involved.

Alan

[PAR]

Okay, not pontoons but in the size range you need and better then pontoon in many respects (all machinery and most equipment below the weather deck). A 50' boat is a substantial investment to build and the design must be reasonably calculated or bad things can become of her in short order.
Basic design spec's are available in the gallery here. Further intrest should be conducted through email (click my name).

[timgoz]

Hi Tim,

I agree with PAR in that such a large vessel will be alot of $$$ no matter what type. A true boat would be much more sellable in the future if it came to it.

For a pontoon boat I would definetly go with steel or aluminum for pontoons. Maybe steel pontoons with an aluminum or ply-glass (as Alan suggested) superstructure would be a good combination.

You on the Three Rivers?

Nice to have you on the forum.

Tim

[Guest625101138]

Tim n Melinda
I basically agree with Alan.

You must have good skills to have built two useful boats and obviously have an idea of the costs involved with the methods used. I would be interested in photos of your two previous boats.

I recommend you stick with what you know. Steel probably easy and cheaper but heavier than aluminium. Glass on wood is a different field that you would need to develop some skill in.

Your thoughts on the pontoon make sense. You get a stable, easily driven boat that does not take the design effort involved in a monohull. The most critical component is how you tie the pontoons together. Resale value will depend on finish and practicality for the conditions but then do you plan to sell it.

Diesels in the narrow hulls will require care with ventilation and exhaust plumbing.

Rudders can generate very high steering forces once you get on the move. Two drives plus a thruster would be nice for berthing. Reduces the skill level required.

I would be interested in the proposed hull design. I should be able to give you performance estimates with your selected power if you are interested.

Rick W.