Broken flange on A frame

andrewm · Post by **andrewm** » Sat Dec 11, 2010 4:37 pm

I have a broken flange on the base of the "A" frame part of the mast support system and I was wondering if anyone had experienced this, or has an idea how it happened. One side of the flange on the port side is completely broken – see photos - and the one on the starboard is bent.
I put the boat in the water and raised the mast 2 weeks ago, and recall that at one point the backstay got caught up and I could have put too much pressure on the control line, but would be surprised if that had caused the damage.
I’m guessing the A frame doesn’t have any role in supporting the mast while sailing, so I’m assuming I can sail with the frame disconnected, but was wondering if anyone had any thoughts about that as well.

Andrewm

[img]BrokenFlange.jpg[/img]
[img]BrokenFlange.jpg[/img]

Post by **Ron** » Sun Dec 12, 2010 4:42 am

The "A" frame acts as a lower shroud when the mast is up. I think you've got to fix this thing if you want to sail the boat. A good percentage of the mast's weight is on this frame when raising or lowering the mast (it's the fulcrum), so this could have been the cause. The flange looks a little rusty as well - which could have contributed to the failure.

dcarl · Post by **dcarl** » Tue Feb 08, 2011 5:03 pm

I had the same thing happen on Shockwave yesterday. Boat was on the trailer and I was dropping the mast for the trip south and it wouldn't go all the way down. I went forward to check if there was a line caught in something and when I grabbed the roller frame the mast went over the side. The flange on the port side "A" frame broke off at the threads. Luckily the rest of the system kept the mast from going down hard but it landed on the stern of a trailered boat parked next to me. It took 3 of us and two tall ladders to walk the mast up and on to the rear supportand we had to disconnected the starboard A frame at the spreader. Mast is undamaged, but the D frame took most of the load and is bowed.

I had Rick Zern, a local rigger out today and we'll be working on it. There's no sing of rust at the break.

I'll send pictures when I get a chance.

David Carl
Shockwave
#327
Pensacola

Mark · Post by **Mark** » Fri Feb 11, 2011 1:33 pm

The problem may be that the A-frame is designed to to be stretched, not squashed. It should prevent the mast bending to leeward by holding it back, not by pushing it back. When pushed it bends the end and this obviously cannot take the strain. One side of mine is bent, presumable because it was not tight enough at one time. I was promised a new one but never pursued it. Sounds like a very dangerous situation - I presume the mast could have hit someone or knocked them off the boat. An important question is whether this is a design flaw or not - if someone is hurt then what?

Mark

Dan · Post by **Dan** » Fri Feb 11, 2011 1:43 pm

Actually, when you're setting the "A" a-frame, it should be neutral for the most part. They work in both tension and compression when under sail, and that is one reason the tubing is the diameter it is. According to a conversation I had with Tony just before I bought my boat, the original "A" a-frame was narrower diameter and they buckled when under sail.

Commonly, if you aren't careful when lowering or raising the mast, and the mast starts to torque—say by one of the shrouds or other pieces not being free to move properly—you can bend the flange. That combined with crevice corrosion that often begins at the welds can cause it to fail. Passivating the stainless steel, using something like SPOTLESS STAINLESS, helps prevent corrosion issues.

Mark wrote:The problem may be that the A-frame is designed to to be stretched, not squashed. It should prevent the mast bending to leeward by holding it back, not by pushing it back. When pushed it bends the end and this obviously cannot take the strain. One side of mine is bent, presumable because it was not tight enough at one time. I was promised a new one but never pursued it. Sounds like a very dangerous situation - I presume the mast could have hit someone or knocked them off the boat. An important question is whether this is a design flaw or not - if someone is hurt then what?

Mark

dcarl · Post by **dcarl** » Tue Feb 22, 2011 2:11 pm

I've had the A frame repaired and installed but does anyone have any information on tuning the mast raising system? We spent about 3 hours yesterday trying to raise the mast, can't get pass the point where the stopper plate hits the base of the mast. Were any measurements or settings ever published?

/David Carl

dcarl · Post by **dcarl** » Fri Feb 25, 2011 5:23 pm

Got the mast raising system repaired. We've got it working, took a bit of study. Performance was unable to help, "no records no one there who knows anything",

Referred me to USSPAR which checked and referred me to "Seco South did the rigging on those we did some at the very end of the project. Their # is 727-536-1924 and they should be able to help you.". By then we'd adjusted the rigging and didn't follow up with Seco. Rick at USSPAR was very responsive and got right back to me.

First picture shows the damage.

You can see the broken Flanges still on the chain plate. Damage was caused as the mast was being lowered the Stay toggle (just forward of flanges on the chain plate) was rotated aft and jamed into the base of the "A" frame breaking the flanges. We know this because when we got the system working again and were bringing the mast down we the same thing happen, this time we had a lot of eyes on the problem and caught it before anything broke.

The second picture show my repairs to the bottom of the "A" frame, the threaded bolt goes about 3/4 of an inch into the new fittings and is welded in there.

I have more confident in the rig now.

David Carl
ShockWave
#327
Pensacola, FL

International Telstar Owners Association