Problem with spreaders resting on lifelines. How to fix ?

[elvatoli]

I added an inch to the mast support. I put a champagne cork under the tube end of the mas support, peeling some of the cork to fit, and this made about 1 inch the mast support higher.
Then I disconected the lifelines at the bow pulpit and reconect it moving to 3 holes loose. Thsi way my spreaders are just touching the lifelines on my 26X.

Hector
RGV, TX

[pokerrick1]

The stock spreader length is 44" and with 8" taken off, they are now 36", not a huge change, and the Genoa's sheeting angle being impoved is significant.

Thats a 20% change, and that is not small.

Excuse me but that's 18.18% - - -oh, never mind - - - I forgot - - - you use French math

Rick

[ALX357]

IF anyone knows offhand the height of the X mast ABOVE the spreaders, and given the length change of spreader from 44 to 36 inches, the original angle and the new angle should be easy to calculate. at 90 degrees spreader to mast angle, it's a right triangle. That angle from the spreader tip to the mast's upper shroud hound does not seem to me to have significantly changed.

IIRC, that height is around 12' ..... I think trigonometry is involved in finding those angles .....

[Catigale]

I put a champagne cork

A real one or that cr** they sell here??

Ill do the math exercise today over lunch

[K9Kampers]

IF anyone knows offhand the height of the X mast ABOVE the spreaders, and given the length change of spreader from 44 to 36 inches, the original angle and the new angle should be easy to calculate. at 90 degrees spreader to mast angle, it's a right triangle. That angle from the spreader tip to the mast's upper shroud hound does not seem to me to have significantly changed.

IIRC, that height is around 12' ..... I think trigonometry is involved in finding those angles .....

On the mast, the distance between the spreaders and the upper shroud hound is 11'-10".
The upper shroud angle difference between a 44" spreader and a 36" spreader is 3 degrees.
The upper shroud length difference between a 44" spreader and a 36" spreader is 2.17 inches.


PS- Skipping lunch Cat? I'm just now having my lunch... bacon wrapped salmon with a peach wine glaze!

[Catigale]

I just got back from lunch. It was very good. Mould, gardon, jambon, with a Burgundy

Andy's angle change seems small. But it will have a big effect on the shroud force since the shroud angle at the top of the mast is small

I confirmed andy's numbers, and find an upper shroud angle of 1&.6 degrees (44inch spreader) and 15.4 degrees (36 inchspreader)

With 300 pounds shroud tension, we get the horizontal shroud force at top of mast to be. Drum roll

F= 95 pounds force for 44 inch spreaders

And

F= 80 pounds force for36 inch spreaders


It is time for lunch, again!!

[ALX357]

95lbs vs. 80 lbs. ..... 'not sure how to interpret that change with regard to the actual sailing forces ....

I must be going way out of my engineering knowledge depth here, but .....

That 15 lbs. difference in force .... might appear to make the mast 84-something percent weaker, but that percentage is not fairly developed in comparing the spreader lengths, due to the added resistance of the masts inherent strength.

With engineering calculations, the mast has it's own resistance to being bent, and the shroud's force vector should be added to that. Over a 12 foot unsupported span of mast, what force would it take to make the mast buckle ? ....
Rough guess, at least 100 lbs. ? Then the vector forces of the upper shroud would be added to the mast's rigidity, and the difference .... 100+95 = 195 cf. 100+80 - 180, gives about an 8% change in strength. If that mast strength guess of 100 lbs. in 12 feet is underestimated, the percentage of weakening is going to decrease that 8%. If that mast rigidity could withstand 200 lbs. without buckling, the change goes to about 5 % .

Yup, these are guesses, and I am not versed in actual engineering calulating ... just trying to keep it real.
Any further clarification would be appreciated.

[Catigale]

..more on that SWAG...the mast sits on the crutch with a 20 foot span or so, and it does bend a bit under its own weight, but does not buckle. However this is along the fore-aft cross section which Im guessing is more stiff than the port-starboard cross section. I would guess 100# force is on the low side for the buckling force though.

I need a Chip Hindes to get a better number.

[Hamin' X]

I need a Chip Hindes to get a better number.