how much will cable stretch

[LordNelson]

i used my new loos gauge and set my stays at 15 before launching and they seemed tight. a day or so later i went to sail the boat and the stays were going slightly slack in calm water with just the roll of the boat.

i retensioned all the stays back to 15 as they had dropped to 10 or under. this is always a pain with the boat in the water trying to lay on the deck avoiding sea gull dropping while undoing the rigging tape i put on the lock nuts to keep them from vibrating off.

the temperature was probable 10+ degrees higher than when i stepped the mast but will stainless stays stretch that much, or do i have something else to worry about?

 

[RichBone]

The bad news is that the stays are not stretching. You've got something else going on. First thing to check is the mast step. It might be sinking. Could be the deck core under it or the cabin sole under the compression post.

Rich

 

[Technodad]

A thing to remember is that our masts are aluminum and with temperature expands and contracts in length a lot more than Stainless steel.
Your shrouds tension will vary according to the days temperature.

Measure the tension on days that are the same temp to get a good comparison.

 

[Joe11688]

Rich is right. Also check the "L" brackets mounted on the bulkhead that reinforce your side stay chain plates to see if they are cracked at the bend.

Bulges on the deck near your chain plates will develop if these brackets are cracked at the bend. Check the floor under the tension post under the mast. If it's sinking, that is a dead give away. Something else is going on. Check these things before you re-tighten the stays again.
Joe

 

[Larsden]

I don't know for sure if it is true, but I read recently on another post that the boat will be distorted on the trailer compared to in the water. It wouldn't take much distortion at all to affect the tension on the stays.

See post #2 of:
http://forums.oday.sailboatowners.com/showthread.php?t=130156&highlight=rigging,+launch

Also, after tensioning up my standing rigging on the trailer at the launch, I noticed that my stays were not as tight once it was in the water and I also have an O'day 20. Of course that could mean that my boat just has the same problem, but I am hoping it is just the difference between being on a trailer and in the water.

 

[Joe11688]

I don't know for sure if it is true, but I read recently on another post that the boat will be distorted on the trailer compared to in the water. It wouldn't take much distortion at all to affect the tension on the stays.

See post #2 of:
http://forums.oday.sailboatowners.com/showthread.php?t=130156&highlight=rigging,+launch

Also, after tensioning up my standing rigging on the trailer at the launch, I noticed that my stays were not as tight once it was in the water and I also have an O'day 20. Of course that could mean that my boat just has the same problem, but I am hoping it is just the difference between being on a trailer and in the water.

I heard the very same thing when I was talking to Rudy Nickerson at D&R Marine one day. He mentioned that very same thing to me. I guess the hull changes when it's in the water because of the force of the water around the hull as compared to being on the trailer. Having the boom with the weight of mainsail and cover set up on the mast must make a some kind of a difference too, I think.
It's hard to get the "like" stays even especially with a roller furler. I use the term "like stays" to differentiate between the uppers and the lowers which the lower stays should have less tension than the upper stays according to the books I've read on this subject.
I think it's important to have the mast straight. So if he has the uppers at 15 and the lowers at 12, he can fudge on the back stay if he has a furler, or try to get the head stay and back stay at a suitable number where the mast isn't bowing. The important thing is to find that happy medium where the stays aren't too tight or too loose and the boat can sail at the same speed on both tacks and it doesn't necessarily have to be #15 and #12 on the Loos Gauge.

 

[LordNelson]

after retensioning, the stays seemed to have kept their tension. chain plates and floor seem fine. i do have so small cracks in the gell coat on the deck around the mast step but it does not appear to be sinking. i am hoping that the change from the trailer to the water caused to difference but am keeping an eye on it.

thanks everyone for your input

 

[James19955]

Horatio - I think everyone's comments have validity. The hull does change shape when it is in the water versus on the trailer. The temperature does not matter much in terms of thermal expansion - for a 25 ft mast the thermal expansion would be 0.075 inches.

I think a key is the overall straightening of the shrouds. When I put my mast up I tighten the shrouds and then go for a sail to lean on everything and try to straighten everything out - then I adjust again.

It seems tha yu have straightened everything out and now its fine.

I'd keep an eye on them over the summer just as a precaution in case anything loosens etc.

James