Bent A Frame members

[Ron]

Depending on how much they are bent, you may be able to get them straightened. But note that they may not be as strong as before. Once distorted, metals tend to lose something (e.g. - they could bend back to that shape somewhat easier than before).

It sounds like the rig may not have been in proper tune. The A and B frames are meant to be in slight tension on both sides with no loads. If they were in a compressed state then, a significant load could do this kind of damage - especially if the cap and intermediate shrouds were not tight enough. The manual has detailed instructions for tuning it. This part covers the final setup of the two frames -

"Turn the ¾” nut on a frame ‘A’ until locking pin holes are
within 1/2 of a hole from lining up. Do this on both sides.
Either drive in tapered locking pin or have someone pull the
cap shroud so that outer tube on a frame A moves down
over inner tube enabling the insertion of a 3/8” bolt. (This
ensures frame “A” is in tension).

Tighten frame “B” so that it is just in tension and lock as well."

[simonhayes]

I noticed that my port A frame section has also bent under compression load. I actually noticed it while sailing and saw it flexing alarmingly. I have gone through the rigging tuning procedure ( the shrouds had stretched and needed tightening ) but i have a significant issue trying to execute the last requirement to tension the A frame.

The issue is that, when I have tension the cap-shrouds sufficiently and I try to "adjust the ¾” nut on the A frame until locking pin holes are within 1/2 of a hole from lining up" as described in the manual, the hole is now positioned such that the "inner hole" is now on top of the thread at the bottom and is preventing me from re-inserting the 3/8" bolt. This forces me to adjust the nut until the hole on the cylinder it is attached to clears the thread to get the bolt through and this effectively lengthens the A frame and does not allow me to tension it. At best it is neutral and perhaps slight compression. This is a significant contributing factor the flexing / buckling of the A frame imho

Having pondered this, there are two possible issues / solutions I can think of . Either i have to shorten the thread , either by cutting off the end or by buying a new shorter one, or I have to drill new holes. The holes should probably be drilled 90 degrees to the current holes anyway (fore and aft instead of athwart-ships ) . The latter is probably the easier fix.

WRT replacing the bent A frame - this would make sense if the A Frame is really supposed to take much load in compression. (although be complex to do given the C - Frame connection welded at the bottom ) . But the load it should take should theoretically be small as the windward A frame and shroud should take almost all the load ( as happens with a conventional rig ) . If that is the case , and it's main function (apart from mast raising ) is to provide tension support for the mast, then a small bend will make no difference.

This is where talking to Tony would be very helpful as most of these things are in his head.. does anyone know if he is contactable ?

Thanks

Simon

[wingman]

Well, one of the advantages of living in Annapolis, I can go to Kato Marine (http://www.katomarine.com/), who actually built the A frames, and get them to straighten mine! It cost $100 for one, but they did a good job and it only took about three days. I asked if they could build a new one and they replied that they had to special order the original stainless steel as it is a size that they normally do not use. They even had to do some inventive rigging of their equipment to just straighten it as the A frame is larger than most of their tubes. Of course, shipping the A Frame cannot be cheap!

I am now going to slightly over-tighten my shrouds, then do a practice sail to see if I get any sag in the lee shroud. If I do, then I tighten some more. That is what all the rigging information that i can find on the web advises to do.

I saw that one of my B frames is also very slightly bent, but will leave it alone. I can still get it neutral for tuning.

Wingman

[Ron]

Simon - With my boat 1200 miles away in Florida, I'm trying to visualize and understand your problem with the A frame. By rotating the 3/4 inch nut, the holes will wind up around 1/2 hole apart, then you've got to forcibly pull the cap shroud to that side of the boat to move the two holes closer together so you can insert the 3/8 bolt. Flexing the mast will cause this to happen because you are shortening the distance. Or you can get a 3/8 inch tapered clevis and drive it in. I don't understand why you are having a problem. I don't think it's safe to sail the boat with the frames in compression. Wire shrouds are in tension as well, but you don't have a solid tube on the other side to help take the load. The wire will slaken somewhat, but the lee side A (and B) frame will attempt to help.

Wingman - As far as increasing the tension on the cap and intermediate shrouds, this may not be a good idea. Assuming it's 1/4 inch, the maximum you can safely do is probably around 1000 pounds, but that's for a fixed mast without stainless tubing acting as the lowers. You don't have a fixed mast - it's hinged. Overtightening the swept back shrounds will put a lot more effort into raising the mast. If you do it, remember to lower the tension before you lower the mast. Tony seemed to pick 600 pounds as the best number for the cap shrouds. I'd want to stay in that ballpark. Get the A frame straightened out, then follow the procedure to trim all 4 frames. Don't compensate by tightening the 4 wires.

[simonhayes]

Yes - it is a bit tricky to visualize if you can't see it . I will try again and if I fail this time , will take picture next weekend,

There are , as far as I can tell, 4 pieces to an A frame member . Starting at the bottom

1. A steel thread which is connected to the chain plates via clevis pin
2 a 3/4" nut which is welded to an inner steel pipe / cylinder . This has a hole drilled near the top to pass a bolt
3. The main outer steel pip/ cylinder itself that is attached to the mast at the top and has holes drilled near the bottom to pass a bolt
4. A 3/8 bolt and nut

The assembly is such that the 3/4 nut & cylinder combo slides inside the main steel pipe (which is attached to the mast at the top ) and then the nut threads over the thread attached to the chain plates to shorten and lengthen it. The pin is used to fix the inner and out tubes by lining up holes drilled in both . With me so far ?

Now imagine that you keep tightening the nut/cylinder combo piece down (inner tube) over the thread . The nut is at the bottom and the thread is going up through the middle of this pipe. When the nut is far enough down, the thread block the holes drilled at the other end of the cylinder and you can't pass a bolt through it. If you unscrew the the nut to slide the pipe and holes back over the thread until the holes are clear once again to pass a bolt through, you have lengthened the overall frame.

That is in essence, the problem. I cannot set the A frames in tension because the shortest length I can get the bolt through the holes without it being blocked by the inner thread puts them at a length which is makes the A frame at best, neutral, and probably in slight compression. This is clearly a problem which can be resolved by shortening the thread or drilling new holes but unless you do one or the other, tension is impossible .

Did that make any more sense ?

- Simon

[Ron]

Simon -

It makes sense and I can visualize mine, which I've adjusted 3 or 4 times over the last 3 years. What I didn't understand is that I've never had a problem doing it. It's actually a fairly simple procedure. Nothing has ever blocked either set of holes and I just pull the cap shroud to line them up. The two boats are only 4 hulls apart, so I don't think Tony made any intentional changes to it. Maybe they drilled the holes in the slider or main tube in a different place than mine? Get a measurement or two from others on the list and compare the height / location of the drilled holes to yours. I'd do it, but I'm about 2 months away from seeing the boat.

Out of curiosity, did this A frame adjusting procedure use to work? Does this happen on both sides? If not, is the mast pointing straight up?

[simonhayes]

Well, I haven't tried to adjust the A Frames until recently, partly because Tony told me that, once they were set, you shouldn't need to mess with them and could just focus on tightening the shrouds evenly to compensate for stretch. It was only when I saw the buckling that I decided to go through the whole set up procedure.

I doubt the design changed between our hulls but, with while Tony design and engineering was strong and innovative, PCI's manufacturing quality was uneven at best based on my experience of other issues . I suspect that either the thread used was too long and/or that the holes were drilled in the wrong place on one or both of the cylinders . I will take apart the whole A-Frame this weekend and post the measurements of the components to compare with others

It is happening on both sides but is slightly worse on the starboard side. I have messed with this for hours and you can make it worse / better by changing relative tightness of the shrouds . Since we are talking about 1/4" making a difference here, you will notice it long before you see a bend in the mast to the naked eye. My working assumption is that this has always been an issue but only became noticeable when the shrouds stretched too far and hence loaded up the leeward A frame to the point that it buckled.

[Ron]

I would think that a slight bend in the A frames would not be a major problem while sailing as long as both frames are in tension and not compression. Compression would get them to buckle even more and that could cause failure.

Raising and lowering the mast with bent A frames could cause a failure though. They are acting as the fulcrum with the weight of the mast at that point.