Bowsprit end hardware - cranse iron

[CAM]

Originally Posted by mauro.iachelli

Hi All,

I'm in the process of building a bowsprit for my 1975 Amel Euros 41 ketch, I want her to have a double headsail to improve windward capabilities. My project is to have a 3' long (from stem) bowsprit tubular shape made in carbon fiber/epoxy (wall thickness 1/2") with a "defensive" fbg/epoxy outer layer of 3/16" . I'd like to keep a light 130% furling genoa on the main forestay attached to the cranse iron (1/4" SS316) and just aft to that (max 12" from eye to eye) another fitting to attach a movable stay where to set a Yankee sail. This second "band ring" will be welded to the cranse iron with two lateral bands of the same material to keep it in place and add stiffness. The piece will become one only. Now my questions are:
1) Do I need another bobstay for that? I 'd like to avoid it, if possible and I think the very close proximity between the two stays chainplates should allow that, but I'd like to hear the experts opinion.
2) Do I need to reinforce the linkage between the cranse iron and the second fitting with a lower band? I wanted to avoid it to let water seep through freely, but I understand that this is the place in which the bowsprit head will substain the most stress from the Yankee sail (in case I'm not installing a 2nd bobstay).

Thanks to all who can help.
BTW, I have a little sketch I can email for easier understanding.

All the best
Mauro

I'll add my doubts to this project increasing windward capabilities. Ask for a money back guarantee from this NA?

If your "tubular" shape is more than a couple inches in diameter, then your carbon sprit will be fine (and quite heavy) at that thickness. Consider making the aft end a lot wider than the tip to avoid needing side stays (if attaching directly to the bow). Also consider an internal end fitting (machined aluminum, or fabricated G10) to receive the bobstay and possibly tack lines if you ever fly an asymmetric kite. Can be as simple as a tight-fitting glued-in "slug" with a vertical-cut slot to ring hitch the bobstay and strops through. Your second "chainplate" can be a webbing strop that spiral wraps to the tip, sort of like a vang attaches to a carbon boom. "Cranse iron" and "carbon bowsprit" don't seem compatible to me, and all the places where the hard, sharp edged metal isn't a perfect fit will point load the spar and possibly crush it.

I built a 1 meter bolt-on sprit for a 40' race boat, and its wall thickness was in the 1/4" range. A slightly bigger "glue-on" sprit for a 52' boat had a wall thickness in the 3/8" range. Both were set up to run zero's, so high luff loads were needed. If you are using wet, hand layup methods and cloth instead of uni's, increase the wall thickness by about 75% or so -about what you quoted.

Good luck