any comments on using aluminum to cut back on weight?

[Georgia Boy]

Just curious thinking about trying it on my next project, but has anyone ever thought of using aluminum tubing for stringers, and to build the transom to cut back on wieght? I know not everyone has the capabilities to cut and weld aluminum, but you would never have to worry about it rotting on you either. I own a welding shop and can do it for little of nothing on my own projects, just curious as to the thoughts and opinions of others. See any drawbacks?

[BarryStrawn]

I would be skeptical you could save much weight. Also wouldn't weld anything, use tempered 2024 or 7075 and bond/rivet joints. Serious engineering to provide adequate strength at minimum weight.

[H2Onut]

I just "poured" any epoxy transom on a vector, put a sheet of aluminum in the material whist it was setting up. IT WORKS !

[Techno]

Tubing wouldn't be that strong. Rectangle box might be.
Just look in a book for the strengths on glass, wood and alluminum. Then the weights they end up being.

[captcarb]

aluminum or steel in the transom and knees.

Good idea!

[Georgia Boy]

Tubing can be round, rectangular, or square, I was refering to square or rectangular, mainly I was thinking taking say 1.5x3 aluminum tubing cut and stack on edge to take the place of the plywood and basically tack weld the peices enough to hold them together, then fiberglass that into the boatfor your transom, for your stringers, take 1/4 plate and breakit with a 1.5" flange at the top, and cut to fit the countour needed and glass inplace. Thanks for your opinoins, H20nut what thickness plate did you use?

[Techno]

I think the stacked idea for the transom would work, just weld on tabs to attach knees to and weld in tubing for the bolts. Maybe some plates to spread the load but sure you have that figured.

I would use the same for the stringers rather than bending flat stock, it seems to be stronger in both directions, possibly some weep holes for drainage.
Fiberglass & wood is as strong as alluminum, but you can get stronger alluminum so there could be a wieght savings if you selected the right alluminum and kept the wall thickness sane.

Do you have any ideas for a dash board? Do you know if glassing it in has any problems? Its the glassing it in at the ends as my only concern, other than being a little harder to chop holes through. Thinking 2 thin plates with a few ribs to seperate and stiffen.

[Georgia Boy]

Techno I have never tried Aluminum in a boat before, this will be a first for me, however I have used fiberglass to patch some aluminum spray tanks to get people thru until we could take the tank off and properly repair it. And what i always have done is take a wire brush on a 4-1/2 inch grinder and brush the area where the fiberglass will be bonding to, and honestly it does pretty well, the brush roughs the finish enough to give the resin a good bonding surface, I have never seen the fiberglass turn loose after I prepared it that way. however I have seen it turn loose on a smooth finish. as far as the dash what I am doing with mine, is I am cutting a piece of 3/16 aluminum diamond plate to cover the front side of my dash, my dash, is about 1/4 inch thick fiberglass and had a 1/2" plywood back, so i think by epoxing the diamond plate on the front of it I will be ok. Just thought the diamond plate would look nice, plus it is something different to break up my interior from just paint, I will post some pics soon, will be painting this week.

[Techno]

If you look at your dash-board it probably goes past the dash and is glassed into the sides. You might want to mimic this underneath, where your dash curves into the sides.
Those curved ends can't take the stress. My last boat had stress cracks there. Mostly from a stress riser-which is what your putting in. The board ended short, didn't go to the sides.
If it is like this then maybe glassing straight over to the side will stiffen it. Underneath.

Might I suggest that damscus or what ever its called? The spirit of st. louis overlapping circle thing. I just don't like diamond plate for glitz.

[Georgia Boy]

You are right Techno, My dash is tied in to the sides Have good strong plywood holding it so i think i will be ok, but i see no problem as to why you could not use an alluminum plate instead of the plywood, I am ready to get on the water, so I am not replacing anything that does not need it yet, might change some noncritical things over the winter just to cut back on some weight, when i add a bigger engine but right now if it is in good shape then i am leaving it. .

[Techno]

I like the idea. I already have 3/16" and 1/4" the 1/4" is t-6? and I don't like it because its a nightmare to cut. Probably don't need that thickness anyway.
Using a plate and only the dash glass opens up some guage mounting/bezeling possibilities for me. The down side is cutting the holes. Some holesaws but others are square.

I'll run it to the sides and glass it in like the wood one.

[Georgia Boy]

Techno what are you cutting your aluminum with? if you are sawing it good luck, you would come out better and a lot less time and effort take it to a welding shop that has a plasma arc and let them cut it, it would not take them five minutes to do it and the plasma arc will cut it fast and if they know what they are doing you probably will not have to dress the sides where it was cut much. Not sure about your area but my shop charges 40 bucks an hour standard rate, but for something like that ten bucks would be a fair price but in my opinoin even the forty would be worth the hassle of not having to saw it and the time it takes, will be painting wednessday and will try to post some pics of my dash and interior I used the diamond plate in a couple of places inside.keep sheck, by the weekend I will have some pics.

[Powercat]

I worked for a company that built a fiberglass
airplane and we used a light weight aluminum
honeycomb material that we sandwiched into layers
of glass and epoxy to make the firewall that the
engine hung off of. Super strong rigid light weight. Would make a great transom... If you
wanted to save every last pound. The whole thing
was vacumn bagged on a flat surface to mold it.
Was a 4 seat single engine retractable gear plane
that would go 280mph.. 1972..
Danny Leger

[Georgia Boy]

I picked up a piece from the place i sell my scrap that sounds a great deal like what you are talking about, i had never seen it in aluminum before, but this is about 1" holes in it and 1 1/2" thick, was just 24x 50 inch piece, but i thought it would work great on a transom.

[Techno]

I ended up laminating black walnut for my dash.

But my present project is a gear shift. With all the areas being machined out for lightening, I suddenly noticed that an aluminum dash doesn't need to be solid like a wood one does. With the steering area being nearly solid You could swiss cheese the rest of it and it would be just as strong but a huge wieght savings. This can be done by anyone with a couple hole saws.