I'm trying to gather some information for setting up adjustable diamond wire tension on my A-cat. It has an applied composites mast (which I'm guessing is now FibreFoam) and the diamond wires go through the bottom mast plate to individual nuts on the underside...it's a real PIA to adjust tension. I want to go to the modern a-cat adjustable "from the wire" tensioning system with the lever arm and purchase and such...I'm pretty handy with composites and fabrication, but I don't want to jump into this without doing a little research (i.e. drilling holes in my carbon mast). Can anyone shed some light or point me to some resources?
Jake Kohl
-- Have You Seen This? --
Re: Adjustable Diamonds
[Re: Jake]
#146674 06/25/0808:44 AM06/25/0808:44 AM
It's not THAT special...most new A-cats come with the system...surely someone state-side has had some experience retrofitting the system to an older mast.
Jake Kohl
Re: Adjustable Diamonds
[Re: Jake]
#146677 06/25/0810:28 AM06/25/0810:28 AM
To upgrade, you need to redo your mast base to accomodate the exit sheeves and the cleats for the diamond tensioner.
People also add some positve rotator ears if they want and certainly add a new deck sweeper rotation arm.
This is the prefered location for a veloctoek or compass.
You can get carbon plate from Hall spars or the link tami gave.
A cheaper solution is to take fiberglass G10 and vacumn bag carbon layers top and bottom to get the proper thickness, cut and finish to suit.
The hard piece to find or fabricate is the U shaped strap which wraps around the mast and attaches to the diamonds.
Mark
Manufacturing and composites are no problem. I've got two rolls of carbon, a great mechanical vacuum setup, and I work at a machine manufacturing facility with three steel cutting lasers, finishing, cnc, welding, milling, etc...
I guess I should have been more specific...I really want to know how much does the mast need to be reinforced where blocks enter and exit. What to people like or dislike about the system they have?...I probably need to start taking pictures and studying.
I don't know if this is the same system or not but Bim had a system where the diamonds and the cunningham were attached. Pull the line and the luff and diamonds were tensioned together. Might be an "easy" boat to get to see for an example.
I had the Bimm 2000 combi system when new..not precise--not so good. Eventually I turned the s.s. tubing "stirrup" around 180 degrees in front of the mast and used it for the diamond wire tensioner. Worked fine at 10:1 downhaul.
Later I got several aluminum or s.s. stirrups off old aluminum A-cat masts and used them on CF masts. These old designs work just fine, even better with tiny double bullet blocks and small line. But larger triples and quads are a nuisance in small spaces- do not use them. 9 inch long x 2 inch by 1/8 inch thick aluminum plate works fine- 2 pieces bent into a shallow Z, lightened by drilled holes. None of mine ever broke.... except the first one when I went out in a blow, when two very old, poorly-fastened rivets in the downhaul DID come off the aluminum mast..... Twang-CRUNCH... Splash.
Dacarls: A-class USA 196, USA 21, H18, H16 "Nothing that's any good works by itself. You got to make the damn thing work"- Thomas Edison
Re: Adjustable Diamonds
[Re: Jake]
#146683 06/26/0807:27 AM06/26/0807:27 AM
So part of your question is do you like them, do you use them. I dont, I have fixed diamonds that I rarely touch.
If I was going to do it, I would make each side adjust independantly, give you more flexibility in the adjustment.
I dont think you need to overly reinforce the mast, the point that the lever arm goes into the mast might need some reinforcement, but I'm not sure. The blocks need to be wire line blocks, not regular exit blocks.
All the attached pictures obviously have internal downhaul and diamond tension setups, not sure the purchase or how you fit all those blocks in the mast.
Bill
Re: Adjustable Diamonds
[Re: dacarls]
#146688 06/26/0807:47 AM06/26/0807:47 AM
I had the Bimm 2000 combi system when new..not precise--not so good. Eventually I turned the s.s. tubing "stirrup" around 180 degrees in front of the mast and used it for the diamond wire tensioner. Worked fine at 10:1 downhaul.
Later I got several aluminum or s.s. stirrups off old aluminum A-cat masts and used them on CF masts. These old designs work just fine, even better with tiny double bullet blocks and small line. But larger triples and quads are a nuisance in small spaces- do not use them. 9 inch long x 2 inch by 1/8 inch thick aluminum plate works fine- 2 pieces bent into a shallow Z, lightened by drilled holes. None of mine ever broke.... except the first one when I went out in a blow, when two very old, poorly-fastened rivets in the downhaul DID come off the aluminum mast..... Twang-CRUNCH... Splash.
Yeah, I'm not so sure I want everything combined - rig tuning isn't that simple!
I saw one setup with a single line coming from the yoke into the base of the mast with a bunch of internal purchase - very clean but the innards were a bit mysterious. I'm most uneasy about how to attach things to the carbon mast and what kind of loading the attachment points can handle. Most fittings are riveted to the mast (and it's 7 years old) so I guess that's acceptable. 10:1 sounds like a lot of purchase if you had a lever-arm on the diamonds - did that include the leverage of the arm?
Jake Kohl
Re: Adjustable Diamonds
[Re: Chris9]
#146689 06/26/0807:50 AM06/26/0807:50 AM
One set of exit blocks is for internal downhaul, probably 8 to 1 , the other set is for internal diamond tension setup, probably also 8 to 1 or more. These systems are set up so that you can pull on either line to adjust the tension, so depending on your tack, you can adjust both the downhaul and the diamond from the wire.
I just have one set of blocks for downhaul in my mast, so I only have one exit block on either side and one set of cleats. Check out the picture, the blue line goes into the mast and through an 8 to 1 block set up. The top of the 8 to 1 is tied off to a bolt that runs through the mast. The bottom of the 8 to 1 is ties to the yellow line which comes out the exit block and goes around the blocks in on the sail to make a 16 to 1 downhaul.
Re: Adjustable Diamonds
[Re: Jake]
#146690 06/26/0807:58 AM06/26/0807:58 AM
the innards were a bit mysterious. I'm most uneasy about how to attach things to the carbon mast and what kind of loading the attachment points can handle
Its really not that complicated. PM me and we can talk on the phone. I had the same questions when I set up my mast and someone talked me through it.
Re: Adjustable Diamonds
[Re: bvining]
#146691 06/26/0808:10 AM06/26/0808:10 AM
It has an applied composites mast (which I'm guessing is now FibreFoam) and the diamond wires go through the bottom mast plate to individual nuts on the underside...it's a real PIA to adjust tension.
I had a similar Applied Comp mast on a Boyer 4. I had the diamonds cut short and fitted with a toggle/swage turnbuckle at the bottom. With the toggle removed, the "T" that formerly held the toggle slides through the hole in the mast base. It's not adjustable from the wire, but is easier to adjust than the stock system, quick to implement, and cheap.