I would like to get exact measurements for drilling a hole in the boom for a vang bail on my CD25D. As I measure, it is 26" from the bottom of the mast step to the center position (where I would drill the boom hole) on the gooseneck. Subtract 3" to clear the mast step inset and one has 23" For an exact 45 degree angle, that would put the boom bail hole about 2 feet aft of the centerline on the mast to the spot where I would drill. Seems a bit short. The specs someone kindly sent indicated 3 1/2 feet back from the gooseneck insert into the boom. That makes an angle quite bit less than 45 and so the downward force will be less than at 45. What do others measure for the bail hole position on the 25D boom - aft of where the actual boom inserts into the gooseneck. I also heard that as a rule, 150% of the mast bail to the gooseneck is recommended. Please help me out before I drill holes in the wrong place.
thanks fellow CD25ers
jim
james.jamieson@yale.edu
Bomm Vang on CD25D
Moderator: Jim Walsh
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Bill
Re: Bomm Vang on CD25D
Hello Jim
I just installed my bails on Friday and I followed the spec sheet I have which is from Spartan Marine (or rigging). THe measurement that bothered me was the "y" measurement up the mast of 5" (if I remember corectly). Anyway, when the mast comes down this fall I am going to install a halyard plate under the mast shoe and use it instead of the bail on the mast. I dont know the physics of this set up, just followed the spec on that sheet you have (I think it is the same one).
Did you order your boom bail from Rigrite? I did and it took two months to get it and the boom bail is nowhere as rugged as I had expected. I ordered another one from West Marine (Shafer (sp) 90-10 & 90-08) which is 3/8" rod and much much "beefier" than what Rigrite sent. I'll be tring to send Rigrite's back to them.
Bill
cd25d@clnk.com
I just installed my bails on Friday and I followed the spec sheet I have which is from Spartan Marine (or rigging). THe measurement that bothered me was the "y" measurement up the mast of 5" (if I remember corectly). Anyway, when the mast comes down this fall I am going to install a halyard plate under the mast shoe and use it instead of the bail on the mast. I dont know the physics of this set up, just followed the spec on that sheet you have (I think it is the same one).
Did you order your boom bail from Rigrite? I did and it took two months to get it and the boom bail is nowhere as rugged as I had expected. I ordered another one from West Marine (Shafer (sp) 90-10 & 90-08) which is 3/8" rod and much much "beefier" than what Rigrite sent. I'll be tring to send Rigrite's back to them.
Bill
Jim Jamieson wrote: I would like to get exact measurements for drilling a hole in the boom for a vang bail on my CD25D. As I measure, it is 26" from the bottom of the mast step to the center position (where I would drill the boom hole) on the gooseneck. Subtract 3" to clear the mast step inset and one has 23" For an exact 45 degree angle, that would put the boom bail hole about 2 feet aft of the centerline on the mast to the spot where I would drill. Seems a bit short. The specs someone kindly sent indicated 3 1/2 feet back from the gooseneck insert into the boom. That makes an angle quite bit less than 45 and so the downward force will be less than at 45. What do others measure for the bail hole position on the 25D boom - aft of where the actual boom inserts into the gooseneck. I also heard that as a rule, 150% of the mast bail to the gooseneck is recommended. Please help me out before I drill holes in the wrong place.
thanks fellow CD25ers
jim
cd25d@clnk.com
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Richard Stephens
Re: Boom Vang on CD25D
Jim,
I installed a vang on my Typhoon last year, and it is in my nature to calculate the forces, etc... The surprising result is that, if you assume the boom is horizontal, the tension in the vang is independent of where you attach it to the boom. As you move it away from the mast, the better leverage is cancelled out by the worse angle.
However, the position does affect the force at the gooseneck: nearer the mast you get a greater vertical reaction, away from the mast you get a greater reaction along the boom. If your gooseneck slides, you will get too much luff tension if the vang is too close to the mast.
So, there is nothing special about an angle of 45 degrees. The position of the bail is not that critical - if it looks right, its probably ok. What is critical is attaching the vang to the mast as low as possible.
Regards,
Richard.
rstephens@alexusa.com
I installed a vang on my Typhoon last year, and it is in my nature to calculate the forces, etc... The surprising result is that, if you assume the boom is horizontal, the tension in the vang is independent of where you attach it to the boom. As you move it away from the mast, the better leverage is cancelled out by the worse angle.
However, the position does affect the force at the gooseneck: nearer the mast you get a greater vertical reaction, away from the mast you get a greater reaction along the boom. If your gooseneck slides, you will get too much luff tension if the vang is too close to the mast.
So, there is nothing special about an angle of 45 degrees. The position of the bail is not that critical - if it looks right, its probably ok. What is critical is attaching the vang to the mast as low as possible.
Regards,
Richard.
rstephens@alexusa.com
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Richard Stephens
Correction
Correction: it is the horizontal force at the gooseneck that is independent of where the vang is attached. I judged the gooseneck to be the weakest point in the system, so it was useful to know that moving the vang out does not increase the load on it.
The tension in the vang is (theoretically) infinite if it is attached at the mast, and it tends to a constant value as it is moved out along the boom.
rstephens@alexusa.com
The tension in the vang is (theoretically) infinite if it is attached at the mast, and it tends to a constant value as it is moved out along the boom.
rstephens@alexusa.com
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Kurt
Re: Bomm Vang on CD25D
I mounted a vang to my CD26 last season. I installed a 1/8" stainless plate beneath the mast step and attached the vang to the plate. I also used the plate to attach halyard turning blocks and then ran my halyards back to the cockpit. I would estimate the dimensions of the plate to be around 6"x8"x1/8", drilled and shaped to accept the appropriate fittings. I poitioned the vang on the boom far enough aft of the gooseneck so that I can operate it from the companionway.
KJLGPW@AOL.COM
KJLGPW@AOL.COM
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john churchill
Re: Bomm Vang on CD25D
here is the measurements from my CD26, which looks like a factory installation. mast bail is 3/8" dia, length is 4" from bolt to inside of bail, mounted 2 1/4" above butt of mast with hole in groove of mast. upper bail is 1/4" dia, (looks much less robust) 3 3/4" long
mounted 33" aft of aft face of mast to hole, again in groove in boom. i measure 24 1/2" from deck to underside of boom.
the distance along the boom does matter in terms of the forces placed on the boom. you can draw out the force vectors to show. very close to the boom gets minimal longitudinal force , all is directed down, but very poor mechanical advantage. real far out along the boom is great mechanical advantage, but great longitudinal stress on the boom relative to the desired downward force. i gues the 1.5:1 ratio has seemed best thru trial and error.
mounted 33" aft of aft face of mast to hole, again in groove in boom. i measure 24 1/2" from deck to underside of boom.
the distance along the boom does matter in terms of the forces placed on the boom. you can draw out the force vectors to show. very close to the boom gets minimal longitudinal force , all is directed down, but very poor mechanical advantage. real far out along the boom is great mechanical advantage, but great longitudinal stress on the boom relative to the desired downward force. i gues the 1.5:1 ratio has seemed best thru trial and error.