Topping lift measurement

dfp51

.
Jun 26, 2019
42
O'Day 28 Lorain, Ohio
We are replacing the running rigging on our 1985 O'Day 28 that we purchased at the end of last summer. I have the manual and the attendant rigging measurements. However, the manual lists two lengths for the boom topping lift, Mast, 29 ft and Boom 22 ft. I can not for the life of me figure out what that is supposed to mean. Can any one provide some insight?

Thanks.
 
May 17, 2004
5,031
Beneteau Oceanis 37 Havre de Grace
Our 28 had the TL fixed to the top of the mast, through a sheave at the aft end of the boom, and then leaving the boom under the gooseneck for adjustment. I wonder if there was an alternate configuration where the fixed end was at the aft end of the boom, and the adjustable end in the mast? If so that configuration might be the longer length, and ours would be the shorter.
 

dfp51

.
Jun 26, 2019
42
O'Day 28 Lorain, Ohio
Thanks David. There must be two configurations, since our topping lift is adjusted at the mast. A complication is that we have a dutchman system, which attaches to the topping lift. That line may have to stay the same this year, since I don't have a clear image in my head of how it was rigged, and while I thought I took plenty of pictures when we rigged the boat in September, I was wrong!

And Don, thanks for the geometry primer. 10th grade was a very long time ago. And therein lies my confusion. The P measurement on the 28 is 30.5, and the E is 10. Recognizing that I don't math well, and assuming that I understand P to be the height of the mast above the boom and E to be the length of the boom, the hypotenuse of that triangle is neither 29 nor 22. So how can the topping lift be less than the hypotenuse?
 
Dec 2, 2003
751
Hunter 260 winnipeg, Manitoba
On our Hunter 260 we have a fixed wire from the mast head to a sheave that’s is slightly shorter than mast head to gooseneck. Topping lift adjustment happens at goose neck. Line passes thru boom end sheave, up to sheave on cable then down and tied to end of boom or a bail on the side of the boom.
 
May 17, 2004
5,031
Beneteau Oceanis 37 Havre de Grace
And Don, thanks for the geometry primer. 10th grade was a very long time ago. And therein lies my confusion. The P measurement on the 28 is 30.5, and the E is 10. Recognizing that I don't math well, and assuming that I understand P to be the height of the mast above the boom and E to be the length of the boom, the hypotenuse of that triangle is neither 29 nor 22. So how can the topping lift be less than the hypotenuse?
Good point. That would mean a hypotenuse of 31.6 feet. So you’d need a TL of about 65 feet to run as yours is rigged, or 45 feet as mine was. Now I have no idea where their published lengths come from (Which doesn’t inspire confidence in the other book measurements).
 
Oct 19, 2017
7,732
O'Day 19 Littleton, NH
Here is a wild guess that has no business being taken seriously, but...
The mast length may be a fixed length from masthead to a pulley for a boom adjustment line. Could it be a line that starts and terminates at the gooseneck but runs through a turning block and pulley supported by the mast line.
Just trying out ideas to make the numbers work.

-Will (Dragonfly)