Replacing Wood Transom with Aluminum

[croag]

Hi There - I'm knee deep in a 12' aluminum restoration and after taking off the wooden transom, I can't help but think why I can't use a sheet of aluminum of the same thickness as a replacement. I've got a a close friend who owns a fab shop that can do this for me for next to nothing but I'm interested in your expert opinions. Dumb idea? Too loud, too brittle? what?

I have a 9.9 clamp on motor.

Thanks

 

[Woodonglass]

Re: Replacing Wood Transom with Aluminum

If you have a friend that can supply you with a 3/4" thick piece of Solid Aluminum to use for your transom then IMHO you should accept his offer. You would NOT want to have to Pay for it but if he is givin it to you then go for it. It will be strong enough and it will last forever. I am NOT an Aluminum Boat expert but I see no reason it would be a problem. Some of the "Tin Boat" experts might see it differently so you might want to wait and have them put in their 2 cents worth.

I'm just sayin...

 

[ondarvr]

Re: Replacing Wood Transom with Aluminum

You wouldn't want the same thickness, it would be very heavy, but you could replace it with aluminum.

 

[croag]

Re: Replacing Wood Transom with Aluminum

Thank you very much for your replies!

If i don't need it in the same thickness as the wood, then why are wood transoms so thick?

 

[Comoxsam]

Re: Replacing Wood Transom with Aluminum

Hi,

I'm in the same situation as you and considering just using thick aluminum instead of wood.

My boat is currently set up like this using two 0.25" thick sheets of aluminum. (So 1/2 inch thick) It is very solid and holding a 30hp motor. Problem is it has been cut out for a short shaft motor and I want to use a long. With just a 9.9hp I don't think you need to go up to 3/4" either.

The drawbacks are definitely vibration and noise. I've tried both ways and it is quite a difference without the wood there.

 

[Kiwifisher]

Re: Replacing Wood Transom with Aluminum

The aluminum would be great. If u are really concerned about the weight but want to provide the correct thickness for clamping, let you friend manufacture a hollow transom. ie 2 sheets of aluminum with spacers in between. Personally I don't believe the weight will be such a big issue. I have a Gil or C bracket for my ob and the weight is not excessive.

I would be more concerned about the OB clamps holding securely on the aluminum.

 

[109jb]

Re: Replacing Wood Transom with Aluminum

If I were to do one in aluminum, I would do the same thickness, but would make one out of an sandwich with aluminum honeycomb in the middle (the meat) with aluminum sheet bonded on both sides (bread) to keep the weight down and the strength and stiffness up. Of course it would also cost way more than would be practical.

As for using solid aluminum, you wouldn't need the same thickness as the wood, but you would need the thickness that provided the same strength and same stiffness as the wood did. Or you could use the same thickness and cut lightening holes through it. Any of these options would require a little engineering.

In a nutshell, it jaust ain't worth it in my opinion. If you replace the transom and take care of the boat afterward that transom could lierally last a lifetime. I say make the transom out of wood. Encase it in fiberglass and call it good. That is low cost, not too much additional work, and will have plenty of longevity.

 

[ondarvr]

Re: Replacing Wood Transom with Aluminum

The strength isn't an issue, it can easily be light and strong enough using Aluminum, you just don't need a thick plate, a thinner skin can be separated by some square tubing, my 90hp is mounted that way.

The wood is used for a few reasons, its light, easy to work with, readily available, dampens vibration, makes a very good clamping surface, is low in cost, strong for its weight and for the most part very easy to replace if it ever needs to be.

When left open so it can easily dry out the wood on aluminum transom normally lasts for a decade or two, not bad for less than $10.00 worth of wood.

One of my boats has a 1/4" aluminum plate with 1/2 PT ply on both side for the kicker (9.9) mount, another one has just aluminum plate bent and welded. They both work fine, I just need to watch the aluminum only bracket to make sure the transom clamps don't come loose, because it doesn't take much for the motor to lose its grip on the aluminum and slide up and off. Wood gives a much better clamping surface, but its possibly only a 20 year fix.

 

[ajgraz]

Re: Replacing Wood Transom with Aluminum

Seen a ton of aluminum boats with an aluminum transom the same thickness aluminum as the rest of the boat, with a thick wood "pad" for mounting the motor. Why not do that?

 

[croag]

Re: Replacing Wood Transom with Aluminum

Guys - i really appreciate your answers! Great info - ripping the wood out today, I think using it as a template on a new piece @ the same thickness will be pretty darn easier. I may just put the fiberglass cloth surrounding it as a nice way to top it off.

 

[croag]

Re: Replacing Wood Transom with Aluminum

Seen a ton of aluminum boats with an aluminum transom the same thickness aluminum as the rest of the boat, with a thick wood "pad" for mounting the motor. Why not do that?

AJGraz - That's good info too but when i took that wood off today and had a look at the rear 90 degree angle of aluminum, i came to find that there's a crack there (on both upper corners!) so now i'm really really hesitant to throw any kind of force on that back piece w/o the wood there now. Tonight's activities were rouging the corners up and applying JB weld!...then i can worry about throwing a wood piece back in!

 

[ondarvr]

Re: Replacing Wood Transom with Aluminum

JB Weld isn't going to help with the cracks in the corners, you need to a more structural method of repair.

 

[catfighter]

Re: Replacing Wood Transom with Aluminum

My wooden transom was squishy on my boat; turns out that the plywood had delaminated.

We cut two 1/4" slits into the wood to the bottom of the transom and glued in 1/4" sheets of aluminum plating, then topped it off with some kind of resin (must have been polyurethane but I'm not sure).

It's now stronger than ever; definitely one less thing I have to worry about breaking when I'm out on the water.