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Old 16-12-2015, 12:18   #46
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Re: Bowsprit replacement?

That seems like overkill. Adding the spar down the middle would add lots of strength.
Remember it's not a bending load on the bowsprit, it's a compression load. The only time it might bend is if you run into something.
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Old 16-12-2015, 13:15   #47
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Re: Bowsprit replacement?

someone in leaky teaky yacht club, a yahoo group, has done this sprit making job. isn tthat hard. why not join em and learn how to do it yourself....
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Old 16-12-2015, 15:50   #48
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Re: Bowsprit replacement?

I understand about the static, and even the calculatable loads of jib, fore staysail, and even the squaresail reacting with the bowsprit, which I agree is mainly in compression, but not always.
The strength must also account for a broken bobstay, or a severe sending into a head sea - which imposes enormous impact loads in other directions.
I am pretty sure the existing bowsprit is over-engineered, much like the rest of the ship, but I must now manufacture a replacement of the same strength and size.
I am leaning towards aluminum because we do not have to wait for Douglas Fir from the PNW, etc., and the welder can get straight on it from stock material.
It’s just a question of what material thickness and what internal support if any, to compensate for the solidity of wood.
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Old 16-12-2015, 16:31   #49
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Re: Bowsprit replacement?

do not rule out cypress or cedars. both can do well as a sprit. strong, rot resistent, bug resistent--i am in mexico an di will use parota, aka ipe, aka huanacaxtle wood. same reasons. mine are original thai cedar spars.
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Old 17-12-2015, 12:45   #50
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Re: Bowsprit replacement?

If you know about compression posts then you could have a bowsprit like those big ocean racers, almost skinny in the middle. Great for running into waves too. You're probably thinking about running into a shipping container under full sail some night and severing the bob stay.
While you are sitting there thinking, learn how to build a composite bowsprit with rub guards for the chain and anchor, all kinds of custom features. You could even make it to look like wood. You could do that from a wheelchair for $500.
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Old 17-12-2015, 16:09   #51
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Re: Bowsprit replacement?

Yes I’m working on that, and thinking how I could improve the present shape. Maybe with a V shaped bottom, instead of flat, which would add stiffness and deflect waves.
It’s all in the cost, and I’m still waiting for quotes.
I’m pretty sure it will be aluminum, for weight saving, cost, and speed of supply, but we’ll see.
JR
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Old 17-12-2015, 16:41   #52
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Re: Bowsprit replacement?

Quote:
Originally Posted by Jolly Roger View Post
Here’s some interesting figures, for those who have helped me with this problem.
Taking HappyMDRsailor’s middle figure for Douglas Fir at 40 lbs per cubic foot, my existing sprit weighs something like 165 lbs.
The exact same shape in 3/8” 6061 structural aluminum sheet, including a central spine, comes in at 124 lbs. If I made it in 1/4“ aluminum it would be only 80 lbs.
If I had it made in a combination, 3/8” sides and spine, with 1/4“ top and bottom, it would be 111 lbs.
JR
How big is that sprit? 165# seems like it must be huge....
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Old 17-12-2015, 16:45   #53
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Re: Bowsprit replacement?

If you go aluminum, beware to avoid any trapped areas where salt water may accumulate and dry etc. Wet area up there and bare aluminum can corrode fast in some instances.
Fir is good, requires a coating and beware, much sold today is called Hem-Fir.. some kind of rapid growth engineered species. You want old growth fir.
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Old 17-12-2015, 16:52   #54
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Re: Bowsprit replacement?

You could try watching the Emerald Steel YouTube video, he fabricated his own bowsprit, and mast too, with laminated planks rather than one piece. The guy's a genius!
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Old 17-12-2015, 20:40   #55
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Re: Bowsprit replacement?

I replaced our old steel sprit with 316SS. I also took the opportunity to strengthen and stabilize the planking and make it accept next gen anchors.

I know I added some weight but at 20 Tons I think it a fair compromise to the advantages.

I think the Ss was about $1,200. I did the fabrication myself. A bunch of work for sure but a big improvement.

The aluminum will be much cheaper and lighter. I had steel and needed to weld to my deck and sides so al was out for me.

You might want to check with Valmont, see if they have any marine grade poles. They would be able to calculate the compression and deflection limits Easily I would think.
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Old 24-12-2015, 05:48   #56
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Re: Bowsprit replacement?

Quote:
Originally Posted by Jolly Roger View Post
I understand about the static, and even the calculatable loads of jib, fore staysail, and even the squaresail reacting with the bowsprit, which I agree is mainly in compression, but not always.
The strength must also account for a broken bobstay, or a severe sending into a head sea - which imposes enormous impact loads in other directions.
I am pretty sure the existing bowsprit is over-engineered, much like the rest of the ship, but I must now manufacture a replacement of the same strength and size.
I am leaning towards aluminum because we do not have to wait for Douglas Fir from the PNW, etc., and the welder can get straight on it from stock material.
It’s just a question of what material thickness and what internal support if any, to compensate for the solidity of wood.
I think AL would be awesome, quick and easy respecting the corrosion issues etc...

Send me a basic drawing of the current sprit dimensions and fixing points, and I'd be happy to run some numbers for ya!

I'll PM ya with email...
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Old 24-12-2015, 07:06   #57
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Re: Bowsprit replacement?

Quote:
Originally Posted by Cheechako View Post
If you go aluminum, beware to avoid any trapped areas where salt water may accumulate and dry etc. Wet area up there and bare aluminum can corrode fast in some instances.
Fir is good, requires a coating and beware, much sold today is called Hem-Fir.. some kind of rapid growth engineered species. You want old growth fir.

HemFir is a reference to the two species of trees that can be culled at the same time, Hemlock, and Fir. Their structural properties are similar enough that they are considered equal when being harvested.

There's also SPF or, Spruce, Pine, and Fir. You'll see this in a lot of dimensional lumber. Think 2x4s and such.

Old growth Fir is extremely hard to find, and getting more rare, as you can imagine.

Zee is correct in that there are a lot of species of hardwoods coming out of Mexico and central and South America that are great woods and would serve equally as well.
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Old 24-12-2015, 13:09   #58
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Re: Bowsprit replacement?

You could ask these guys too.......http://www.edensaw.com/MainSite/Stor...Home/Main.aspx
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Old 08-02-2016, 20:12   #59
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Re: Bowsprit replacement?

Could anodize the aluminum if go that route.

Or could apply a one part urethane with aluminum pigment. (Master Series Silver Paint) Moisture cures. Seals from moisture, and oxygen. Used on steel also, can then epoxy or paint if you wanted. Used in automotive, and restoring tanks. Fishing fleet has been using inside diesel tanks too.
They've run salt spray & other tests on it.
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Old 09-02-2016, 08:39   #60
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Re: Bowsprit replacement?

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