C-Forum

I need to make an aluminum thwart for my Whitesell Descender. I have the old thwart from which I can remove the mounting clips. The thwart was badly bent and must be replaced. I have considered buying some 1-1/2" O.D. aluminum tubing from a fab shop that has short drops available. I plan to rivet the old clips to the new thwart after flattening the ends in a press break. Any suggestions on what type of aluminum tubing to use?

Thanks for your replies and advice,

Michael

Aluminum tubing is almost exclusively available in 6061T6 alloys, except for some very expensive aircraft grades. I would use 3/4" OD x .058" wall tubing for up to 20" long, 1" x .065"W for longer, 1.25"OD x .075"W for carrying. 1.5" OD isn't necessary and very difficult to flatten without making a mess.

On my boat (less than 20" wide at the gunnel) I use crossed pieces only 3/8" OD x .065"W. You can't carry the boat with them but it stiffens the gunnels quite nicely.

Be sure, when you're crunching that tube end down flat, to drill a tiny hole where each of the cracks are going to appear in the aluminum tubing. So, after you've started to compress the end of the tube, you will see where the cracks are eventually going to appear. At that point take a little drill and drill a tiny round circle about an inch or so above the end of the tubing on each side. That way, the crack will stop when it reaches that little round hole and not proceed further down the tubing, thereby making it suspect for further stress cracking in the future use of the thwart. I made sliding thwarts; basically two tubes, one of which slid inside the other. I put holes in the section of each tube where they slid inside the other (where the two met in the middle of the boat ), about an inch apart. That way I could widen my hull or narrow my hull depending on the what type of water I was going to be using it on. Since you are going to make the thwarts anyway, that might be something to think about. If you want a more stable, quickly turning boat, you spread the thwarts. If you want a faster, easier to paddle hull, you pull the thwarts in. An inch or two difference in gunnel width can alter a hull remarkably.

Actually, I think you can also just wait until the cracks are in the tubing, and then drill the holes right where the cracks stop. The idea is to keep the crack from spreading further up the tubing.
Good luck,
Ric

Wow! So much good advice! I will look for a smaller tube O.D. than 1-1/2". My thwart will be longer than 26" so it'll need to be strong. The front of my Perception saddle is held with this center thwart. If it was not on this saddle, I would strongly consider making it an adjustable thwart. I've seen Mohawks with the adjustable-type and would like to try that in my next boat.

While I'm flattening the ends I will definitely drill holes at the end of the cracks to prevent them from spreading. I had heard this mentioned before by someone and completely forgot about it. I don't need any problems with this thwart after it is installed with the saddle.

I'll let you know how my thwart comes out.

also remember to sand the cracks and the holes, because you will be putting your hands on the gunnels near there and don't want a cut to occur....
Ric

I will probably finish all the edges of the thwart with my Dremel tool. I've been nicked on sharp edges before .

you can also dip / cover the ends in that plastic coating you an buy at hardware stores, or use a quick duct tape wrap.
My $.01 (cause I can't afford more!!).

A very kind gentleman in Connecticutt read my post on thwart fabrication and notified me that he had a Whitesell thwart in his basement. The thwart had been removed from a Piranha. It is 1-1/8" longer than I need, but it will be easy to shorten. One end clip has to be removed and rivited back on to the thwart after I shorten it.

All the good advice from Space Canoe, PAC and Bob P will probably come in handy in the future. Thank you for taking the time to post great information and instructions on obtaining materials and fabricating an aluminum thwart.

Michael

I am just glad to have the thwart back where it belongs- on the water!

It should arrive by tomorrow. Enjoy.

Jim