Boom diameter

rich1 · Joined: 10 Apr 2000 Posts: 156

Hi Guys,

It's time for new booms, and all my old ones are standard diameter. I'm curious if anyone knows (or can measure a set) whether the stated grip diameter of 1 1/8" is the tubing or the actual diameter including the grip material? I'm toying with the idea of making 3 sets of fixed length carbon booms and I need a starting point for the finished tube diameter before adding the grip material.

Cheers

Chris.

WaterKook · Posted: Fri Mar 11, 2011 2:20 pm Post subject:

Sounds like fun!
Please post picture of completed project Smile

rich1 · Joined: 10 Apr 2000 Posts: 156

If I actually go through with it, for sure I'll post some pictures. I have enough left over carbon and carbon/kevlar to make a few sets of booms so I thought why not? I never fly with my gear, (they make it next to impossible to do that any more) and a fixed length boom would be lighter and stiffer than it's adjustable counter part. My main point of concern is how thick do the walls need to be and what diameter. I just saw an ad for Severne red line booms and they claim a 26mm grip! If that's after the grip material has been added that means they've got a 3/4" tube. Much smaller than I had originally thought.

Cheers.

outcast · Joined: 04 May 2004 Posts: 2724

I applaud initiatve, but recommend swimming lessons

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DanWeiss · Joined: 24 Jun 2008 Posts: 2296 Location: Connecticut, USA

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isobars · Joined: 12 Dec 1999 Posts: 20935

rich1 · Joined: 10 Apr 2000 Posts: 156

Interesting,

I didn't think this would generate quite so much comment. Firstly, all my sails are pretty much brand new, and I only replace sails when they are falling apart, so I'm ok with building one boom per sail, or at least one each for my 2 most often used sails. As for length, I've rigged these sails and sailed them enough to know how long the booms should be, so that's not a concern.

I'm planning on making at least one of the boom heads as well. I have a perfectly serviceable HPL head that I put on an older set of booms so I can use that if I care to.

I'm a bit shocked how everyone assumes that for some reason I can't make a set of carbon booms that won't break. I've been shaping and building boards using carbon, kevlar and epoxy since 1985. I've built mast bases, repaired my own sails, and on my most recent board, the fin box is actually part of the bottom of the board, molded out of carbon fibre. I've had plenty of failures along the way but that's how we learn.

My post here was to get a starting point. Even though the material I'm using is left over from my last board, it is expensive, and I want to get it right the first time. Because I'm going fixed length, I can over build them and still come up with something lighter than a commercial version. My goal however is to capitalize on the advantage of a one piece boom and make it much lighter. The final result being one boom per sail, harness lines in the right place, half the weight of what I'm currently sailing.

So basically from what Dan wrote, it looks like I'm shooting for a 1" diameter tube in the main body. I'm planning on larger diameter toward the tail and head of the boom, as I'm currently planning on molding them over high density foam which I can shape to any profile I like.

Thanks for all the comments, I'll post some pics as they progress.

Cheers,

Chris

shreddbob · Joined: 31 Mar 1987 Posts: 361 Location: Hawaii

FWIW: I have a caliper and measured some of my booms for tube diameter at the gripping region (with foam grip material included in the measurements).

Maui Sails Wave 140 - 200: 1.165"

HPL Wave 140 - 190: 1.220"

HPL Slalom 170 - 230: 1.270"

Notes:
- For all these booms the diameter increases by about .030" where the tail piece inserts.

- As far as I can tell (by comparing to at an old broken Fiberspar) the gip material thickness for the above 3 booms falls into the range of approximately .040" - .050" --so subtract out .080" - .100" from the above measurements to get bare tube diameters--probably the HPL's have .050" foam and the Maui Sails has closer to .040".

- WALL thickness, where tail inserts, for the HPL booms is about .080" - .090". (Don't know about the Maui Sails wall thickness. And of course I have no idea how the wall thickness may differ in the gripping area of the booms versus where the tail piece inserts.)

Sounds like an interesting project. Good luck!

Bob