mast tuning

[Ken Juul]

The Seldon Mast rep at the recent Catalina Rendezvous said all masts should have some aft prebend in them.  Is this true for the older telephone pole masts?  If yes how much, winds in this part of the world are usually under 20 knots.

[DaveM]

Ken
You may want to put this question on this forum.  Always been good answers for me and Brion does participate.

http://www.briontoss.com/spartalk

Good Winds
DaveM

[Stu Jackson]

Bend a telephone pole?

I've always used the guide in the C34 boat manual.  Been working for 18 years.

[Jack Hutteball]

My tall rig came set up with a slight aft bend in it when we purchased the boat.  Left it as I thought it was supposed to be that way.

Jack

[Ron Hill]

Ken : I believe that you had Gerry Douglas at that Rendezvous - why didn't you ask him?

I always thought that with the straight mast that a rake of 3 - 5 inches aft was good.  Always worked for me.

A few thoughts

[Ken Juul]

Gerry listened to the talk, when the question was asked is this applicable to all masts, Selden said yes, Gerry didn't comment.  I'm leaning toward straight, but I did ask the question on the Toss site.  Left my passwords at home, won't be able to check his answer until Monday.

[Ken Juul]

According to Brian Toss all masts should have some prebend to prevent the mast from inverting when the main is full.  He recommends setting the backstay to the correct tension then use the forward lower to pull the center of the mast forward and inch or so.  Have my engineer friends working on how much is the proper tension on each leg of the backstay to exert the correct tension.

[Ron Hill]

Ken : That's funny, because I always tuned the fwd lowers slightly tighter - so the mast would remain  straight when the large 150 genoa was out all the way!! 

A thought

[Ken Juul]

Ron,
I guess it doesn't matter which sail, main or head.  The idea is not to have the head of the mast forward of the foot.  Your last post describes exactly what both the tuning experts said to do.  IIRC the tuning guide that I have been using is from the wiki and probably in the forum, is wrong.  I will publish what my Naval Arch friend at the Naval Academy suggests when he gets back to me.

[Ken Juul]

My Naval Arch/ engineer freinds got back to me.  They agree on the tension.  The legs of my split backstay are about 177".  The correct tension on each leg should be 935#.  Time to break out the Loos guage.