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  #16  
Old 07-08-2008, 07:33 PM
BWD BWD is offline
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Umm, if anybody wants to give advice on those tube brackets, still grateful, although I think I have it pretty much figured out. more or less.

Meanwhile, I have to make the crossbeams, before I make the brackets to fit them. Still want to do them of aluminum that will be light and can be used in a more or less plug-in manner (ok, 4 bolts and one string ).

I have been working on getting a local welder to make them for me in an L shape. I proposed two designs, one butted joint and one mitered joint. Waiting to hear back from welders...

I want whatever design gives enough strength and a good right angle so the angles of both beams will be the same and not concentrate stress more than otherwise and tend to tear the ama up when loaded!
I.e. the ama should be strong and I want it to load up and break like team philips if ever it must, but not crack in the middle like groupama because of "weird loads" in moderate conditions. I know there's a gross oversimplification in this allusion but I think it gets the point across.

Anyone with metal fabrication/welding knowledge, I welcome your comment or insight, drawing attached!
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Outrigger canoe plan....-aluminum-beams.jpg  
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  #17  
Old 07-08-2008, 07:39 PM
BWD BWD is offline
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BTW this is what I am thinking for the beam bracket/tubes now...
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Outrigger canoe plan....-beam_fixation_2.jpg  
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  #18  
Old 07-08-2008, 08:36 PM
Doug Lord
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Quote:
Originally Posted by BWD View Post
Umm, if anybody wants to give advice on those tube brackets, still grateful, although I think I have it pretty much figured out. more or less.

Anyone with metal fabrication/welding knowledge, I welcome your comment or insight, drawing attached!
================
A long time ago I had an aluminum tube welded as the forward cross on a 16' cat I built. I didn't know anything about aluminum so I asked someone who did
and was told to study the bead-if it was symetric and "pretty" then it probably was good. I went out sailing in the intercoastal for a couple of hours flying a hull and having a blast. Came back in and left the boat at the dock- sail luffing. A minute or so later I heard a big bang and the forward cross had collapsed-breaking at the weld. The "moral" of this story is that it is hard if not impossible to look at an aluminum weld and tell if it is any good. I'd use composites-I have ever since that experience with no failures.
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  #19  
Old 07-08-2008, 08:58 PM
BWD BWD is offline
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Thanks, DL.
Will take that under advisement especially if welders' quotes are too high!
Then I would still use Al since I can't afford CF, but do a design around straight tubes with no welding, and build composite brackets to secure 'em.

Update:
Posted a query on the metal boat building sub-forum about using gently bent tubes instead, and I will try to go that way, keeping Al strength and saving weight and complexity. As I gather the long radius bend should not weaken the tubes much, and will be stiff.
ref: http://www.boatdesign.net/forums/sho...d=1#post214359
My thanks to Lazeyjack for advice on this.
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Outrigger canoe plan....-bent-aluminum-beam.jpg  

Last edited by BWD : 07-09-2008 at 10:09 PM. Reason: update
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  #20  
Old 07-12-2008, 09:13 AM
Doug Halsey Doug Halsey is offline
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BWD:

I use welded aluminum tubing in the crossbeam/cockpit assembly of my 15' foiler Broomstick , which as you can see in the thread on Taking Off the Training Wheels, has been taking a lot of beating. So far, the welds are holding up just fine.

I used a local guy in a small town (Fallbrook, CA), but he has a pretty decent metal fabrication business (not just welding).

BTW, for someone who's never built a boat before, it looks like you're doing a great job.

Doug
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  #21  
Old 11-09-2008, 10:54 PM
erikhaha erikhaha is offline
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BWD, I just ran upon this post and it looks like I am just now going through the same problems/design process as you already have.

Here are a few pics of the vaka that I am building, which will eventually be a trimaran. I bought Gary Dierking's book, "building outrigger sailing canoes" and I am basically taking the specs for the Ulua vaka and modifying them to my needs. (under carefull consideration)

Currently I am fiberglassing the interior, but I am trying to design a folding beam system that is fairly simple yet strong enough to withstand the forces that it will see once it is out in the ocean.

Whats your current progress? I would realy like to see a few pics.

So far it looks good. I also used DF for most of the hull, but I used DF clear(no knots). The upper strips are mahogony.
Attached Thumbnails
Outrigger canoe plan....-vaka2.jpg  Outrigger canoe plan....-side-view-w-arch.jpg  Outrigger canoe plan....-varnished-1.jpg  

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  #22  
Old 11-10-2008, 03:12 PM
BWD BWD is offline
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That looks nice. looks like you did 1' molds -good job! I did 2' and therefore spent an extra week sanding. Learned a lesson.

Nothing doing lately. Preocuppied with other projects. As the water gets colder, I will spend more time indoors working on this -I hope.

I'd be concerned about a folding beam system on a tri- so many parts = more work, more weight, and a larger number of "things that must not break." and harder to break down for compact storage. Not that you shouldn't do it, just saying I haven't figured out a good way.

Did you see the pictures on the first page? I have others, if there is something specific you would like to see. Happy to describe any construction details as well.
Still not settled on the crossbeams and landings/brackets, so afraid I can't offer much there...
Good luck with your project -hope it goes faster!!
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  #23  
Old 11-21-2008, 09:53 AM
dstgean dstgean is offline
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Quote:
Originally Posted by erikhaha View Post
Here are a few pics of the vaka that I am building, which will eventually be a trimaran. I bought Gary Dierking's book, "building outrigger sailing canoes" and I am basically taking the specs for the Ulua vaka and modifying them to my needs. (under carefull consideration)

Currently I am fiberglassing the interior, but I am trying to design a folding beam system that is fairly simple yet strong enough to withstand the forces that it will see once it is out in the ocean.

.
What kind of overall beam and length are you talking about? How wide is the vaka beam? I've been considering making a catamaran/double canoe cruiser based on a second Ulua to add to mine or a pair of Tamanu hulls. I ended up building the Ulua to plan but stretched to 21' and have both a single outrigger beam and a set of double outrigger beams at 14'. However the canoe is a little shy on buoyancy for two plus gear and fresh water for extended trips. I love it though!

Dan
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  #24  
Old 11-22-2008, 04:58 PM
erikhaha erikhaha is offline
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dst: the vaka beam is 24" at the widest point and the overall beam will be 12'.
Basically I used the Ulua shape which I got from the book but I scaled the dimensions to give it a little more volume, wider, deeper and longer (20').

Sounds like you will have a nice project ahead of you if you build the cat.
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  #25  
Old 09-04-2009, 03:09 PM
dstgean dstgean is offline
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Originally Posted by erikhaha View Post

Sounds like you will have a nice project ahead of you if you build the cat.
It's been fun so far. My friend and I each built a Tamanu hull and combined it with a H18 for the last Texas 200 cruise. Fun stuff, but the upwind work--there wasn't much of it--beat the crap out of the front beam and broke the beam inside the luff groove retaining the tramp. If we go cat again with the two tamanu hulls it'll be with some beefy tubes lashed, not a combo of lashed and bolted. You can check it out at the link for 2009 at www.t200.com

Dan
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  #26  
Old 09-04-2009, 04:15 PM
BWD BWD is offline
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What are you guys trying to shame me into updating my thread or something?
Seriously, get a room or something (just kiddin...)

I seem to be on a once in a blue moon schedule with this project, but here are couple o' pics in case anybody is looking...

Vaka structure done (a good while back) minus a thwart and beam mounts -waiting to see if vendor can deliver bent Al tubes I want with strength. They've done a few runs of nonstructural bends in applicable tubes but I need to follow up to see if they have tested any of it for strength, from that will flow final aka/connections... ...or else I will reluctantly build some nice clunky wooden ones....

Meanwhile ama is taking shape with a little inspiration from Gougeons and from a Mr. van Belkom who hot rodded his "raptor" proa to include h2o ballast among other things. thought it was a good idea so why not, pic shows the tank, soon to be glassed in...... cheers!
Attached Thumbnails
Outrigger canoe plan....-dsc01442.jpg  Outrigger canoe plan....-dsc01443.jpg  Outrigger canoe plan....-dsc01515.jpg  

Outrigger canoe plan....-after-storm.jpg  
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  #27  
Old 09-04-2009, 08:48 PM
peterAustralia peterAustralia is offline
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hi BWD

I was just wondering why you want bent beams. If you went for simple straight beams and then had some connections going down to the ama, the extra weight would only be 3 or 4 kg at best. Your supply of extra chocolate and water is going to be close to that.

I can understand that a bent beam with a nice curve, be that metal or wood does look nicer. The way you have shown the 90 degree joint looks OK. The normal way to do it, without a bent beam of course, is to have a straight beam and then struts going down. With a V shape ama, the struts can come up parallel with the ama sides, so that at beam level they are a bit wider. This gives a good purchase to distribute loads. The same goes for fore and aft direction. Your connections can start narrow at beam level, and then get wider as you go down to connect with the outrigger.

What progress have you made for the outrigger, what system to you intend to use for getting water into the ama ballast tank and then outside once more

I have an outrigger canoe, not much good
have sketches a much better one. It shows a mechanism for draining water from ama water ballast tank. If you have any comments, be free to fire away. I have Gary's book, it is very good.

http://www.tacking-outrigger.com/replacement_boat.html

on the main page of this website there are also links to 27 different outrigger sailing canoes, from these you might get some ideas.


n peter evans
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  #28  
Old 09-04-2009, 09:04 PM
BWD BWD is offline
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Quote:
What progress have you made for the outrigger, what system to you intend to use for getting water into the ama ballast tank and then outside once more
meaning the vaka? >> there is a pic above. side foam parts made but not glued up or shaped.

water will come in/out through bailer type scoops. If it doesn't work I will plug it up or use a pump.

Not gonna add any extra pounds with the connections if possible! Shooting for a light ama empty, 14 ft x6."

Gonna look like the pic below.
thanks for stopping by gotta run.
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Outrigger canoe plan....-ama-explained-bit.png  
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  #29  
Old 09-04-2009, 11:12 PM
peterAustralia peterAustralia is offline
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hi

By outrigger I meant ama

Your ama looks very nicely shaped. Mine is 14ft deep Vee plywood, overly built, approx 40cm wide, approx 40cm deep, volume 220L.

My guess is that your ama should weigh less than 41 pounds as it seems so thin. My thinking was that for a tacking outrigger a littel extra weight in hte outrigger does no harm. Half the time the weight is aiding is stability. When the outrigger works as a float the narrower hull in the water can aid in speed. So I went with a setup of a little extra volume and a little extra weight.

In the water I found that the outrigger has very little drag when compared to the main hull. because the main hull is fatter (in my case) the speeds that it was limited to, the outrigger had little to slow it down, because the boat speed was much less than the outrigger max theoretical speed (if there is such a thing)

Your main hull looks very nicely shaped, looks super smooth. Should be fast
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  #30  
Old 09-05-2009, 02:14 AM
BWD BWD is offline
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ha ha. by vaka I meant ama, but was literally on the way out the door. and typed the wrong word.

Glad the rendering shows nice; the real thing as you can see still currently looks like a chunk of foam with a rocker to it.

The ama as is is about 9 lbs. Done it will displace 200 lbs and weigh around 20, minus the connections, which I hope will be stubs to take bent Al tubes. Or struts from pieces of windsurf mast, if the bending doesn't work out..

Thanks for your kind words about the vaka. Realistically I'd be pleasantly surprised for it to make 15 knots. 12 probably. We'll see....

I have Dierking's book and corresponded with him a bit. He is helpful and knows a lot. I started this well before the book came out.
It's been fun to work through things, but had I bought a plan a couple years ago I am sure I would have had a boat much, much faster. On the other hand, since then I think I have figured out how to have a faster boat.

The only problem, is this boat will probably not be the faster one. Maybe the next one....
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