Back to the dreaded bowsprit material construction considerations

[VChild]

Onlinemetals.com is a good place to find a primer in metals, comparison of grades, standard available sections, weights and prices.[/QUOTE]




I've actually used onlinemetals.com quite a bit for general fabrication projects when I'm in a pinch but beware their prices are sky high compared to local metal suppliers. I have discovered a local (within 50 miles) 316 stainless steel supplier of any shape or dimension. A local Pierce Aluminum warehouse is also within 50 miles and has rock bottom prices on all alloys of aluminum. The only catch with local yards is minimum quantities. Extrusions, bars, angles and tubes usually 20 feet. Sheet and plate at least 4' x 8'.
Not usually a problem for me because I'll always find a use for the remnants.


Another good source of information for metal (and other) fabrication of boats including the various metals, alloys, scantling rules and scantling number is: "The Elements of Boat Strength" by Dave Gerr.

[Eastward ho 24]

Well well well after thinking and rethinking and ordering hundredes of dollars in 316. I think I might start over and go with 6061t6 alu!. 4x4"x1/4" thick. I now have 3/16" thick 4x4" ss square tube and it feels a little thin. I'd like to got up to 1/4" thick 4x4 SS but I fear that'll be to heavy. The 6061t6 is as strong as steel from what I gather. Figure I'll get a square tube and make SS bands to go around it to avoid welding the bands I will through bolt to keep in place. I'm still looking for testimonials on the longevity a 6061 spar constantly doused in salt water would offer. Who knows I might eventually go with the 1/4 SS after all, or at this rate maybe all 3. Haha

[captlloyd]

Originally Posted by Eastward ho 24

Well well well after thinking and rethinking and ordering hundredes of dollars in 316. I think I might start over and go with 6061t6 alu!. 4x4"x1/4" thick. I now have 3/16" thick 4x4" ss square tube and it feels a little thin. I'd like to got up to 1/4" thick 4x4 SS but I fear that'll be to heavy. The 6061t6 is as strong as steel from what I gather. Figure I'll get a square tube and make SS bands to go around it to avoid welding the bands I will through bolt to keep in place. I'm still looking for testimonials on the longevity a 6061 spar constantly doused in salt water would offer. Who knows I might eventually go with the 1/4 SS after all, or at this rate maybe all 3. Haha

No reason the aluminum can’t be properly painted or powder coated and if maintained outlast you.

[VChild]

As you mentioned, it would be constantly dousing in seawater. That's a little different than a 6061 aluminum mast or boom that is positioned further back in the boat and getting occasional spray. The other thing that concerns me is the SS that will be in direct contact with the bowsprit. I looked at a picture (below) of a bowsprit on a Downeaster 32. It looks like there is a lot of stainless attached. Stainless and aluminum do not mix well. Good recipe for corrosion. If you send me the exact dimensions of your proposed bowsprit shape in stainless steel, I can do a virtual build in my engineering software and it will spit out a weight in 1/4" stainless steel (or any other).

[Eastward ho 24]

The SS sprit is pretty basic it's just gonna be 4x4" square tube( I have 3/16 thickness now, which is probably fine. But I'd feel better if it were 1/4" thickness.carribean in hurricane season etc..) That's basically it it's gonna have end caps and 1/2" x2x4 lugs for the bobstay whisker stays headsail and staysail. I haven't seen anything available on the market (that's beefey enough other then the bronze ones made by Davey and co )as far as rollers for the anchors. So I'm gonna have to make something up there to maybe plus 25lbs for that. My concern is I have no windlass and rope rode for my anchor right now. So once the sprit is done I'm gonna have windlass ( lofrans Tigres,) and I'm shooting for 200' of 5/16 ht chain. All that crap is adding up quick which is why the alu is enticeing, but lack of long term testimonials has me back and fourth. As mentioned above the mast being alu is midships where it's not under constant sea spray has me wondering if alu 6061 is a good choice. I've seen most mast fittings are SS to alu and it's not as big a problem as periodicals would suggest. If you can't tell I would second guess and confuse a ham sandwitch..

[VChild]

A 4"x4" square tube in 1/4" wall thickness SS would be about 13.14 pounds per linear foot or about 79 pounds for a 6 foot piece.
The same piece in 6061 aluminum would be about 4.41 pounds per linear foot or about 26.5 pounds for a 6 foot piece.


Agree that stainless attachments on aluminum mast are fine but need to be isolated for instance Tefgel, Loctite etc. where stainless steel screws go into aluminum.

[Eastward ho 24]

I just don't know the boat well enough, and or have the experience in sailing to know if the weight of the ss is gonna be adverse. The boat sails like a dream now I've only had her out a few times in the bay (no waves). But I'm very impressed with it. Don't want to spend a ton of money and make the bow to heavy. I guess my bobstay fittings relation to the water would be a good indicator? Say if I were to put about 300lbs on the bow see if it squats? I assume there's more to it then just that but some you say that's a good indicator?

[Eastward ho 24]

https://www.fisheriessupply.com/dave...temhead-roller

I'll be adding one on each side..

[VChild]

Nice looking hardware.
A different approach would be to have a professional marine carpenter build you a new identical wooden bowsprit. There are woods out there that are as strong as steel on a strength to weight basis. No worries about welding, corrosion or excessive weight. Easy to work with and beautiful. The original one lasted +/-40 years. No reason to think the second one wouldn’t last 40 more years. Probably wouldn’t cost very much.
Let me know if you need any other shapes analyzed for weight with various materials.

[Eastward ho 24]

Thanks

[Benz]

Originally Posted by Eastward ho 24

The SS sprit is pretty basic it's just gonna be 4x4" square tube( I have 3/16 thickness now, which is probably fine. But I'd feel better if it were 1/4" thickness.carribean in hurricane season etc..) That's basically it it's gonna have end caps and 1/2" x2x4 lugs for the bobstay whisker stays headsail and staysail. I haven't seen anything available on the market (that's beefey enough other then the bronze ones made by Davey and co )as far as rollers for the anchors. So I'm gonna have to make something up there to maybe plus 25lbs for that. My concern is I have no windlass and rope rode for my anchor right now. So once the sprit is done I'm gonna have windlass ( lofrans Tigres,) and I'm shooting for 200' of 5/16 ht chain. All that crap is adding up quick which is why the alu is enticeing, but lack of long term testimonials has me back and fourth. As mentioned above the mast being alu is midships where it's not under constant sea spray has me wondering if alu 6061 is a good choice. I've seen most mast fittings are SS to alu and it's not as big a problem as periodicals would suggest. If you can't tell I would second guess and confuse a ham sandwitch..

I have a mooring bitt on deck that my bowsprit deadends at. It is bare 6061 alu, gets washed by salt water constantly, and is fine. As I've mentioned before, keeping weight out of the ends matters most when it's choppy--your boat will hobbyhorse abominably if you weigh down the bows too much.
If you stay with SS, at least keep the 3/16" wall thickness--going to quarter inch is ludicrous. Believe, even if you're unfortunate enough (I won't say dumb, but it's kinda there) to get caught out in a hurricane, whether your bowsprit will buckle is going to be the last of your concerns. It's not like you're gonna fly a sail way out on the jibstay in a serious blow--you'll have a staysail or storm staysail inboard.
If you butter up your fasteners with Tef-Gel, they'll be fine. But I recommend having all your fittings welded to the aluminum tube. You can even have sleeves welded through where the anchor roller pins bear. You'll save a lot of weight by going all aluminum. And you won't get ugly rust streaks.

[Benz]

Oh, incidentally, I have 200 feet of 5/16" anchor chain--I've never used it all, though we cruised for five years and spent more than a thousand nights at anchor. Didn't go South Pacific, but even there I'd be comfy with the thought of 100' of chain (and not using all of that often), with nylon after that. That'll reduce weight nicely.

[bletso]

I have a 150 #ish piece of teak. Pretty but a lot of work.

[VChild]

Originally Posted by Eastward ho 24

Thanks

You’re welcome

[goat]

Take a big friend sailing, get him/her to stand on the bowsprit. Check the characteristics and go from there. Some booze and a towel might be required.

goat