Weekender Bowsprit

[cs]

The plans for a the bowsprit on the weekender call for it to be 2-1/2" square. Now If got an octagonally shaped piece of clear Doug Fir that is 2-1/2". I was thinking about rounding this off for the bowsprit. Can anyone tell me why this wouldn't work.

Chad

ps I will also post this on Frank's site and see if they got any ideas

[Art Read]

No reason at all if you get it absolutely right the first time. In the real world, by the time you've sanded it smooth and fair, it'll measure a bit less. (Or, if you work like me, maybe a LOT less?) Can you afford that? 2 1/2" seems a bit "dainty" for a bowsprit somehow...

[whb]

Why round it?

I always thought an octagonal cross section looked pretty good.

Howard

[Jim Goodine]

That Doug Fir would be much stronger than your little boat needs. My 20' Elver has a bowsprit that tapers from 3" to 2" in 6'6" and it is more than enough. Good luck with the project.

[High C]

Chad, mine is made of ash, and octagonal. I like the way it looks, but when you put those little chocks up against the bitt, they don't seal up the void there. It's too big a space to caulk, and I'm afraid water will get under there and work its way down thru the deck where the bitt passes thru. I'm going to seal up that space somehow, just haven't decided how, yet.

http://www.jtservices.net/images/images2/fd08bec6.jpg.orig.jpg

Also, I wouldn't round it, it wouldn't contact the deck and stem as solidly as it does with a flat face on the bottom. If I were Superman, I could pick up the whole boat and swing it around over my head by that sprit. It's that solid. I lkie that. :D

[ 09-22-2003, 10:16 PM: Message edited by: High C ]

[cs]

Between you guys and Frank's site, I think I've decided to leave it in the octagnol shape at the bits and round it as it comes out toward the "pointy" end.

Chad

[Bruce Hooke]

If I'm doing the math right, a round beam (i.e., the bowsprit subjected to a bending load) with a diameter of a (e.g., 2 1/2" in your case) will only be 59% as strong as a square beam with sides equal to a (e.g., a 2 1/2" square beam in your case). An octagonal beam made from that square piece of wood would be 66% as strong as the square beam. Looked at as a column the round beam is 61% as strong as the square beam and the octagonal beam is 79% as strong as a square beam, however, I suspect that a bowsprit would fail in bending before it would fail in compression.

I'm not an engineer so take these figures with a grain of salt, but unless someone steps in to correct me, I'd be real hesitant to use a bowsprit that would, if my numbers are right, only be around 60 to 80% as strong as what the designer called for. HOWEVER, what wood did the designer specify? If the designer allowed for a wood that is considerably weaker than douglas fir then you might be on safer ground.

[cs]

Bruce you make a good point there. I'll have to check the plans when I get home. I kinda got a feeling that the bowsprit is overdesigned, but I would hate to find out in a good blow that it wasn't.

Chad

[NormMessinger]

Originally posted by cs:
Between you guys and Frank's site, I think I've decided to leave it in the octagnol shape at the bits and round it as it comes out toward the "pointy" end.That is almost ezakly the way I'd like to see you do it. :cool: Oh, not being one to leave nearly perfect alone, I'd leave it square as it comes out of the bits with a gradual transition to octaginal and not round over the bits as HighC did where the bow sprit and bits join. Otherwise, make the bits ezakely as HighC did but ease the ends just a little more and Norm's your uncle.

Dang! You guys do good work.

[cs]

Bruce brought up a good point about the strength. I had cross posted this over on Frank's site and Mike Stevenson (designer of the weekender) posted this reply:


Keep in mind: The original Weekender plans called for 2" full round handrail material for the mast and bowsprit. We went to the heavier style for looks and as the handrail stock doesn't give much safety factor.

I'm sure the solid tent pole will work great. If it doesn't, make a new bowsprit later!

Mike So that answers the stength question.

Chad

[Bruce Hooke]

Chad, that sure does answer the strength question! A 2 1/2" diameter douglas fir bowsprit should be almost twice as strong (loaded as a beam) as 2" diameter stock and probably more because your douglas fir is most likely much better stock than whatever is currently used for handrails.

[High C]

Originally posted by NormMessinger:
Dang! You guys do good work.Thanks, Norm, but I must give credit where credit is due. I bought my Weekender partly built. That sprit and bitt were built by a very skilled feller from south Florida who started the project and lost interest. I was lucky enough to pick up where he left off.

I coulda done it as well, though, really, I coulda, I swear, for true... :D

[Paul Scheuer]

What is "handrail material" ? Is there a handrail tree ? My first trial and error pieces for my 10-foot mast raising bi-pod turned out to be red oak, which I managed to break. Now they're ash, octagonal.

[Bruce Taylor]

I still think the poles look like sitka spruce, which I use fairly often. OTOH, I don't use a lot of douglas fir, so what do I know? smile.gif

[Bruce Hooke]

Originally posted by Paul Scheuer:
What is "handrail material" ? Is there a handrail tree ? My first trial and error pieces for my 10-foot mast raising bi-pod turned out to be red oak, which I managed to break. Now they're ash, octagonal.It seems to me that most of the "handrail stock" that I've seen in lumberyards has been some sort of softwood, but I don't recall which -- probably whatever is available in clear pieces...

[cs]

Bruce does spruce have that reddish tint? If so it may be spruce, it seems real light.

I feel kinda cheated. Last night I went through the stack of free lumber and pulled out a piece for the bowsprit. By the time I took the metal cap off of the end I had about a perfect piece for the bowsprit. Where the metal cap was is already round and already has a pre-drilled hole where I can attach the forestay as per plans. Using that hole as a reference there will be about a foot at the end rounded (the plans call for 7") and the rest will be octagonal. All I got to do is cut to length and clean it up a little with some sandpaper. Now where is the fun in that? :( ;)

Chad

[Bruce Taylor]

Ah, the real fun starts when you launch...and look how much closer you are, all of a sudden!

Yeah, sitka can have a reddish grain. Mind you, it's hard to believe the armed forces wd. spring for sitka tent poles! $$$

[cs]

I've got enough of them "pre-fab" poles to make 4 or 5 bowsprits. Maybe I could make a living re-claiming old army tent poles and selling them as bowsprits. :D

Chad