My new crew, brought in from the Tornado school, convinced me to prebend my P19 mast (it now has about 1.5 in between the mast groove and an imaginary line from the top to the base of the mast). He's not going to be present this weekend when I test the modification and I am worried about something breaking. The diamond wires are so tight! I was OK until reading in R Whites book that prebend is used on triradial cut sails and not the existing crosscut dacron.

I will also test my new 16:1 downhaul.

Am I just paranoid?

The prebend and tight diamond wires are a better rig setup for the P-19 so you should leave your rig in that configuration. The best way to tell if you have sufficient diamond tension is to sail the boat upwind in double trapeze conditions. If you see any slack at all in the weather diamond wire, add more tension. 1.5" of pre-bend sounds about right. You should also consider investing in a Loos Gauge to measure rig and diamond tension. The Loos "A" gauge made out of silver andonized aluminum was used in the P-19 tuning guide. I seem to recall a recommended Loos gauge setting of 34 for the diamond wire tension on the P-19. You should be able to purchase a Loos gauge from Annapolis Performance Sailing (www.apsltd.com) and possibly West Marine. Good tool to have.

By the way, I still have the Smyth spinnaker you inquired about but will not be in south Florida until next January for the next A-class midwinter race week. If you are still interested, you can purchase the spinnaker, tramp bag, spinnaker blocks and running rigging and build your spinnaker pole.

Bob Hodges

Thanks Bob,I'll check the settings this weekend.
I'll contact you during December or so and see if we can get you to unload that spinnaker.

Fermin

Check the tangs for the diamond wires, eventually replace them with new longers ones or at least the rivets if they are old. Also check the rivets on your mast hook, and consider replacing it if it seems underdimensioned.
As long as you dont overdo the downhaul and dont go out twin wiring with a high total crew weight you should be ok.

How much pre-bend you should use is also largely dependent on your mainsail luff curve. If your main is cut for a sideways bend setup, you might well be faster that way.

Pre-bend is definately the way to go, but it's not neccesarily much faster if you dont get the right setup for your sails and crew-weight. Mast stiffness is also important to get the right flexing characteristics, so there are a lot of variables to play around with when you start on this path.


Good luck!

Thanks for the comments Rolf. Good idea to check the attachment points. I had replaced one questionable turnbuckle.