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Building a new wooden boom



 
 
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  #1  
Old April 18th 07, 02:03 PM posted to rec.boats.building
Matt Colie
external usenet poster
 
Posts: 69
Default 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
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  #2  
Old April 18th 07, 09:12 PM posted to rec.boats.building
Matt Colie
external usenet poster
 
Posts: 69
Default 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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