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Building a new wooden boom
Ulrich,
It looks like you are trying to create a 3" diameter boom with a foot rope tunnel (I hope that is what you mean by keep). Assuming that this boom in not mid-boom sheeting, and that you are not planning to vang it very hard to flatten the main. Let me make some observations and recommendations. The nature of such a structure is such that the material in the center does very little. A spar of the size you are considering, could easily loose the center 1" of material - almost - the conditional is because I do not have the final dimensions of the keep (tunnel). If you removed material so that the remaining material was no less than 3/4" everwhere with the exception of directly under the tunnel where it could be a little less for just that tangent. The structure is best left solid about 3~4 diameters from both ends this is largely for fittings and fastening. That said, you can take a lot of wood out of that bottom piece and maybe some out of the two upper parts. I am guessing that you all ready have the material. If I were making this spar, I would not make it round. I would make it tall enough to accommodate the tunnel without reducing the loaded section very much. Over very many years, my father and I assembled many such spars some are still in use today and the last was layed up over 25 years ago. We did it much the way you seem to be headed. We would cut staves and route the tunnel and hollow the center then laminate the spar (later with epoxy) and finally plane the final shape. Best of luck Matt Colie Lifelong Waterman, Licensed Mariner and Perpetual Sailor Ulrich G. Kliegis wrote: After 35 summers in a pretty rainy corner of the world (Kiel, Baltic Sea), the old boom has done its job, building a new one has started. Now, weighing the raw timber in my hand on one side and comparing it to the old boom, the question for hollowing the new one to reduce the weight arises. It will be put together from three parts, two adjacent 1.5" * 3" stripes with the rail for the keep (?) routed out, and one 3" * 1.75" in landscape-format below, overall length 11 feet. How deep and over which extent would you take out material, using a router? Thanks in advance for all helpful comments! U. -- target of diversity victim of affirmative action refugee from the war on poverty minimized by political correctness |
#2
posted to rec.boats.building
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Building a new wooden boom
Ulrich,
Sounds like you have a good friend there. When you get it planed round, it will loose even more weight. Have a good time gluing it. You can't have too many clamps. I would lend you an arm load, but the shipping would be a problem. Good Luck Matt Ulrich G. Kliegis wrote: Matt, thank you very much for that explicit and experience-based comment. Yep, keep is the german word, the foot rope is what I had in mind. A quick calculation shows, that I could reduce the wooden volume by about 10 to max. 15% of the whole mass, if I do not work down to the lowest stability level. A friend of mine, carpenter by profession, boat builder by heart, did me the favor to shape the wood down to the final surface, with the tunnel neatly done, and a slot of 1/8" for the sail. Carrying all three parts (which are still 3 feet too long) and comparing that to the old boom showed that the new one does not weigh really more than the old one, rather less, when processed to the final result. So, I guess I will leave the volume solid as it is right now. Even 15% less weight (even less, when looking at the total weight with all the s/l steal fittings) is not worth the extra effort in this case. But the discussion was it - every word. So again, thanks for your comment! Cheers, U. On Wed, 18 Apr 2007 09:03:11 -0400, Matt Colie wrote in rec.boats.building: Ulrich, It looks like you are trying to create a 3" diameter boom with a foot rope tunnel (I hope that is what you mean by keep). Assuming that this boom in not mid-boom sheeting, and that you are not planning to vang it very hard to flatten the main. Let me make some observations and recommendations. The nature of such a structure is such that the material in the center does very little. A spar of the size you are considering, could easily loose the center 1" of material - almost - the conditional is because I do not have the final dimensions of the keep (tunnel). If you removed material so that the remaining material was no less than 3/4" everwhere with the exception of directly under the tunnel where it could be a little less for just that tangent. The structure is best left solid about 3~4 diameters from both ends this is largely for fittings and fastening. That said, you can take a lot of wood out of that bottom piece and maybe some out of the two upper parts. I am guessing that you all ready have the material. If I were making this spar, I would not make it round. I would make it tall enough to accommodate the tunnel without reducing the loaded section very much. Over very many years, my father and I assembled many such spars some are still in use today and the last was layed up over 25 years ago. We did it much the way you seem to be headed. We would cut staves and route the tunnel and hollow the center then laminate the spar (later with epoxy) and finally plane the final shape. Best of luck Matt Colie Lifelong Waterman, Licensed Mariner and Perpetual Sailor Ulrich G. Kliegis wrote: After 35 summers in a pretty rainy corner of the world (Kiel, Baltic Sea), the old boom has done its job, building a new one has started. Now, weighing the raw timber in my hand on one side and comparing it to the old boom, the question for hollowing the new one to reduce the weight arises. It will be put together from three parts, two adjacent 1.5" * 3" stripes with the rail for the keep (?) routed out, and one 3" * 1.75" in landscape-format below, overall length 11 feet. How deep and over which extent would you take out material, using a router? Thanks in advance for all helpful comments! U. -- target of diversity victim of affirmative action refugee from the war on poverty minimized by political correctness |
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