Carbon Boom Design

bigbadbevo

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We made a boom last year out of a broken carbon A class cat mast. works really well. just need to reinforce where you put the vang, clew and goose neck fittings.

 

FishAintBiting

Anarchist
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We made a boom last year out of a broken carbon A class cat mast. works really well. just need to reinforce where you put the vang, clew and goose neck fittings.
So how many 50 booms could you get out of an A Class mast? Probably at least three. Even at only two it'd still be a pretty good deal :)

Anyone got a hacksaw lying around :)

Fish

 

skiffboy

Anarchist
Skiffe and Goat - I'm not sure who came up with that but I wish I did as I think credit should be due. I had one on my old boat which had been broken by some prick falling on it. Once I repaired it, it was amazing the difference it made to the boat, especially gybing.

I like the idea of a cut-down A-class rig. Very easy way to get a good carbon boom although I'd have thought it would need to be built up a little around the ends and vang point just for safety.

 

European Bloke

Super Anarchist
3,407
829
When proctor started making carbon booms for our class (smaller with much lower loads than a 505) about 10/12 years ago they were a disaster. They all broke at the kicker as expected, but they all broke laterally not vertically. Even the ‘pros’ had completely underestimated the lateral component in the loading. I have to say I think they had the work experience boys on that project, cos even as a first year engineering student you could see it was a POS before they even rigged it up.

 

bowman81

Super Anarchist
1,412
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Australia
Larson and Eliasson "principles of Yacht design" has a chapter on rig design. How to calculate forces from the vang and sail and the required section modulas. Moreover it is a great book in general.

 

skiffe

Anarchist
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Sydney
Skiffe and Goat - I'm not sure who came up with that but I wish I did as I think credit should be due. I had one on my old boat which had been broken by some prick falling on it. Once I repaired it, it was amazing the difference it made to the boat, especially gybing.
I like the idea of a cut-down A-class rig. Very easy way to get a good carbon boom although I'd have thought it would need to be built up a little around the ends and vang point just for safety.
I cannot claim any credit for that design.

Goat?

 

Bill E Goat

Super Anarchist
4,600
396
Sydney
Mine all mine and nobody else.

One other benefit was when it pissed down with rain and there was no breeze you could tilt it sideways and hide under it and stay dry.

 

Magician

New member
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Whats wrong with your current boom? Better off with some thing you no won't break. Booms are weighted with the hull so there is no weight advantage. Only advantage I see is a lighter boom out of the boat. There is a lot of other things to improve on first before I would worry about a carbon boom. I have heard that some of the top boats in the world are not going to have carbon booms at SF.

My advise is, invest your time on the water, not building your own boom.

 
So y'all don't think I'm a wingnut.

No, I will not be thinking about building a boom for the worlds. That is obviously not intelligent given the proximity to the event. The boatwork list is long enough and aluminum is a damn fine material.

I may be getting a career designing composites and I see this research as personal development. People in sailing don't know enough about working with fiber reinforced composites and they become irrational about them. I'd like to broaden my understanding.

Yes, the side launcher is a higher boatwork priority.

Yes, sailing is a more efficient use of my time.

Thanks for the sermons anyways.

 

DMR

Member
398
0
Annapolis
As has been much fraught over here, the 505 class allows carbon booms and poles. I'm in college and my partner in the boat isn't rich, so we can't quite afford the upgrade.
1) After the requisite research here and elsewhere I have not really found a solid source on boom design. Do any of you have a reference you could direct me too? Really its just a beam with applied loads, and any kid that's a sophomore in engineering can sort it out but the issue here is calculating leech and vang loads so I have a number to put into the engineering analysis. I can design the spar theoretically, but I don't want to go through a big iterative process of not making it strong enough and breaking it because I didn't begin with a good assumption of the applied load.
Doesn't your not-rich partner in the boat have a job where he hangs around people that design sails? Don't they compute leech loads? Wouldn't the vang load be related to that? Maybe he can grab it for you.

Oh, and to keep on with the theme: Don't waste your time. You'd be much better off sailing every day. Its a waste of money, you have a perfectly good metal boom, what's wrong with it? Blah, blah, blah (I don't really give a shit, but you seemed to enjoy the lecture, so...)

See ya in Kingston?

 
fo sho bro

You'd think working with the sailmaker that he does, with the designers literally a shout away, that we'd have this sorted. Sadly, people do not share our enthusiasm:( Its that whole, making money thing that gets in the way I think...

 
Hi

I've made my own masts and booms, takes a bit of trial and error but I've never had one fail on the water. If you take the material thickness from a sucessful carbon boom ( will not be more than 2.5mm)and assume that most of it (bar the first and last plies ) are ud. I use cloth at 0/90 for the first and last ply, 200gsm. An extra ply of cloth at start and finish for high load areas. to make the section take a length of ptfe impregnated glass cloth, work out circumfrance of your section and attach two batterns to cloth at this distance, lay up in side and put a vac tube down with a valve attached to it, wrap layup around tube, bolt batteerns together, and blow up tube, this makes a round section, advantages are that you can make a double tapered section and its fairly cheap. I've used these sections on Phantoms (2.8m booms, lots of kicker) and international canoes

Alistair

 

joell

Member
59
0
HiI've made my own masts and booms, takes a bit of trial and error but I've never had one fail on the water. If you take the material thickness from a sucessful carbon boom ( will not be more than 2.5mm)and assume that most of it (bar the first and last plies ) are ud. I use cloth at 0/90 for the first and last ply, 200gsm. An extra ply of cloth at start and finish for high load areas. to make the section take a length of ptfe impregnated glass cloth, work out circumfrance of your section and attach two batterns to cloth at this distance, lay up in side and put a vac tube down with a valve attached to it, wrap layup around tube, bolt batteerns together, and blow up tube, this makes a round section, advantages are that you can make a double tapered section and its fairly cheap. I've used these sections on Phantoms (2.8m booms, lots of kicker) and international canoes

Alistair

Any pics of this method, I'm just not picturing it.

 

Chris Maas

Member
396
11
HiI've made my own masts and booms, takes a bit of trial and error but I've never had one fail on the water. If you take the material thickness from a sucessful carbon boom ( will not be more than 2.5mm)and assume that most of it (bar the first and last plies ) are ud. I use cloth at 0/90 for the first and last ply, 200gsm. An extra ply of cloth at start and finish for high load areas. to make the section take a length of ptfe impregnated glass cloth, work out circumfrance of your section and attach two batterns to cloth at this distance, lay up in side and put a vac tube down with a valve attached to it, wrap layup around tube, bolt batteerns together, and blow up tube, this makes a round section, advantages are that you can make a double tapered section and its fairly cheap. I've used these sections on Phantoms (2.8m booms, lots of kicker) and international canoes

Alistair
I like that. Is that how you made that very nice boom you had on your IC at the Worlds?

There must have been a fairly steep learning curve to figure this out.

I'm thinking you can't have much overlap in the woven layers or the laminate couldn't expand out to the fabric 'mold'. How do you seal the ends? How much pressure? Those battens must be fairly robust with lots of bolts.

I don't know what a vac tube is. Some Brit thing I guess. But any kind of flexible or expandable tube would work as a bladder wouldn't it? For that matter any kind of strong fabric would work for the mold as long as you had a release film in there.

You could get pretty creative with shapes couldn't you? As long as the section was round or, I suppose, oval if you clamped some sides to it after it was inflated.

Sorry Russell, this doesn't exactly address your questions but you have to admit it's pretty interesting.

 

Phil S

Super Anarchist
2,608
233
Sydney
Alistair,

Thats brilliant. No mandrel or mold.

I did not look closely enough at your canoe in McCrae to notice the product.

My guess is that the ptfe glass cloth is some thing like a polytarp? material, something impervious but strong enough to be bolted together with battens? For inside I have some latex surgical tubing which expands when inflated. Did not work well inside foil molds but would fit inside a tube well. I will have to try this method on some small products first. Thanks for the idea.

Phil S

 
c maas, no worries dude, very useful info there. I had an idea for round sections to layup around an inflatable tube and stick it inside a pvc tube or something, kinda like an inside out mandrel that didn't require a vacuum bag setup. Don't reckon it would work, but an idea non-the-less.

I'd love to see a step-by-step with photos of your build process man.

 

BalticBandit

Super Anarchist
11,114
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c maas, no worries dude, very useful info there. I had an idea for round sections to layup around an inflatable tube and stick it inside a pvc tube or something, kinda like an inside out mandrel that didn't require a vacuum bag setup. Don't reckon it would work, but an idea non-the-less.
I'd love to see a step-by-step with photos of your build process man.
I'm, planning on using exactly what you just described in building my next CF tube. for the interior tube I plan on using bicycle tires glued end to end. with a valve at one end and sealed off at the other. Then a piece of PVC pipe that has been pre-split down its lenght.

each layer is Measured in the layup to have about a 1/4" overlap (I don't plan to compensate for the decrease in diameter of the inner section). inflate the tires until stiff. wrap a layer of Celowrap for release. Then layup around the tube. Once done, into the PVC pipe. Tape up the PVC pipe on the outside. And inflate to 20PSI. (1.5 atm). Once cured, open the PVC tube and voila.

At least that's the plan

 
The only issue I see with that plan is the fiber crimping (minor but research shows just 7 degrees of fiber crimp makes a significant impact on strength) If you wrap tight around the inflatable tube before going into the hard tube, you'd prolly be able to avoid that since the laminate would have to expand and the fiber crimps would get straightened out. this is why Hall spars exclusively use aluminum mandrels, when the part goes into the autoclave the aluminum expands with the heat and straightens any fiber crimps.

 




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