Best Material for Experimental dual hull Dinghy Outriggers?

[captain-cowboy]

I'm connecting two self bailing kayaks together into something of a convertible outrigger canoe. That way I can dismantle my dinghy and store it on board (no painter or davit), make use of a single kayak when most convenient, or assemble the whole raft when it's time to row dry goods or gear over from shore.

We used pine 3x2's to prove the concept, it worked brilliantly, so now it's time to invest in final materials. I need outriggers that won't flex and warp too badly. Right now I'm looking at 1/8'' wall 3X2'' aluminium rectangular tube. does that seem robust enough? Round pipe would be more similar to the out riggers on a small catamaran, but a squared shape fits into our setup really well, and it's cheaper.

[HopCar]

I'm not an engineer but I played with ultralight airplanes and hang gliders that were made of aluminum tubing. Just a gut feeling but I think your 3" X 2" rectangular tubing should be fine. I once joined two floats to an ultralight airplane using 1" square tubing. It worked fine. Round tubing looks better but is a little harder to work with.

Have you got a photo of them joined together with the wood?
If the wood worked, why not stay with it?

[Stumble]

If anything that tubing sounds like it is overkill. I would probably price out carbon fiber tubing however. It's going to be more expensive, but have a lot less flex and be lighter which would make carrying it around much easier.

[HopCar]

"If the wood worked, why not stay with it? "
"I would probably price out carbon fiber tubing however. "

Greg, That's funny, I went low tech and you went high tech. I suspect both would work fine. Performance advantage to carbon, price advantage to wood. Aluminum somewhere in the middle?

[captain-cowboy]

man, wish I'd thought to take a picture, but sorry no such luck. The reason I didn't want to stick with wood is because it rots and warps. by the time I over-lay some marine quality lumber with west systems, I'm approaching the cost of aluminium which would be stronger anyway. the wood was strictly just to test the viability of the sit-on-tops as catamaran pontoons.

thanks for the suggestion of carbon fiber. it's a little out of my price range, I'm afraid. It would be nice to cut down on the weight, that's for sure. I originally was hoping to find some kind of perforated channel, but I can't find it in aluminum.

[onestepcsy37]

Originally Posted by HopCar

I'm not an engineer but I played with ultralight airplanes and hang gliders that were made of aluminum tubing.

Hopcar, did you know Don Noble and his son Dan? I kept my boat at his marina - Mandalay Marina at mm 92 in Key Largo - in the 80's. He had owned a crop dusting business in Oklahoma, then sold out and came down to the keys to buy a marina. Said it was his dream. But he couldn't get flying out of his blood.

So he started buying ultralights and equipping them with floats he built at the marina and then reselling them. One day he was making a landing in Rock Harbor, got caught in a wind shift, and tumbled end over end on the rock jetty alongside his marina. Spent a few weeks at Fishermans Hospital.

I lost track of him in the 90's. I know they sold the marina back then but nothing else.

[Snore]

Captain Cowboy

I used to own a Kruger Canoe with a Balogh sail rig. The forces on the member that joins the two hulls is caused by both the two hulls moving differently(think catamaran). Or if you place amas on the end, the aka (pole) will most likely fail where it mounts. I know this because the new owner of Balogh joking called his double walled aka the "Snore Mod". All that said if you paddle places where the waves are one foot or less, you will probably get a longer life cycle out of a lighter pole. Just beware that unless you catch it quick, catastrophic failures of the poles results in a swim.


Feel free to PM

[nimblemotors]

There is never a 'best' material without qualifications.
I suggest fiberglass, cheap, light, strong. But not easy.
Aluminum tubing is easy.

[Stumble]

The issue here isn't strength it's stiffness. Wood, aluminum, and CF are worth looking at, but I wouldn't hesitate on the carbon. You can buy off the shelf CF tubes pretty cheaply.

Another though crossed my mind, see if you can track down replacement beams for a hobie cat. Cheap, easy to find, mounting hardware is everywhere, and replaceable almost anywhere.

[HopCar]

"Hopcar, did you know Don Noble and his son Dan?"
I knew Don very well and flew with him often. I once borrowed one of his planes and tried to take off. The darn engine just wouldn't turn up and the plane just wouldn't leave ground effect. I kept leaving the water then settling back down. I was out past Rodriquez Key and headed to Bimini before I figured out that I could pull the throttle a little farther if I bent it a little around the tube it was mounted on. Had a great flight after that. What a wonderful place that was. Loved the Tiki bar. I've also lost track of Don.

[HopCar]

"One day he was making a landing in Rock Harbor, got caught in a wind shift, and tumbled end over end on the rock jetty alongside his marina. Spent a few weeks at Fishermans Hospital."
I had forgotten that. I wasn't there that day but I remember he was really beat up.

One day we were flying on wheels down near Homestead. Don took off, crossed a canal, lost power and crashed in an orange grove. We had a hell of a time getting his plane out of the trees.

[susswein]

I'd suggest looking into the round aluminum tubing used on whitewater raft frames. That'll give you access to all the different fittings (T's, angle's, etc) available. I've got some superlight titanium tubing that would probably work great (4 oz/ft.) but I doubt it could be shipped economically.

[delmarrey]

In the S. Pacific they use large bamboo for outriggers and will for many more years. But the stuff is hard to get in the western world.

[onestepcsy37]

Originally Posted by HopCar

"One day he was making a landing and tumbled end over end on the rock jetty alongside his marina. Spent a few weeks at Fishermans Hospital."
I had forgotten that. I wasn't there that day but I remember he was really beat up.

I went to visit him in the hospital and he confided to me that he was making a DOWNWIND landing! In an ULTRALIGHT! Said "I should have known better". All I could think of was, here's a guy whose got thousands of hours in crop dusters...

[captain-cowboy]

Hey friends, nimblemotors has nearly sold me on using fiberglass tube; anyone know what OD and wall thickness I should be using? there will be 6 feet of trampoline between the pontoons, 2 feet of outrigger laying on each pontoon to fix to, and about two feet between the outriggers.

Thanks for the help all!