#342 Linkbox cracks

[dcsailing1]

I sent the below email to Will last Mon night, 8/3. He hasn't gotten back to me yet and is out until Mon according to Sue. Good news is PCI and Will are busy and Tony is on the mend.
I thought the troops may have some insight or experience to help with what PCI comes up with as to cause and the best fix. Nine photos with original email but only 3 here:

> Hi Will: I spoke to you Mon. 8/3/09 AM re: problems closing both amas, in
> the water and not on the trailer, and cracks in the port ama forward linkbox.
> To give you more complete info:
> We bought this boat from Damon ----- in San Diego last year when there was
> going to be a delivery delay from PCI for a new one.
> We have always had some difficulty closing the amas in the water, never on
> the trailer. We recently launched the boat and found we were completely
> unable to close the port ama. While trying to close it by hauling in and
> back with lines we heard cracking and discovered the crack in these
> photos.
> It appears it goes through the second fastener out in the linkbox, next to
> an apparent factory cutout which is not found on the stb. linkbox and is
> widest at the outward end.
> If you follow the photos, the crack is almost invisible when the ama is
> fully open and gets more open as the ama closes. When at it's limit
> because of apparent interference with the hull, the crack is more then 1 inch as
> viewed from the bottom. It appears the crack is opening because of the
> twisting moment on the linkbox as the ama is driven down into the water
> from the angle of the outer pivit.
> If we weighted the ama with 500+lbs. there is no interference and the ama
> will now close and the crack stays closed.
> So we now know the why it won't close, but not the source of the crack.
> As I told you we are not aware of any hull damage and Damon reported none other
> then some "shipping" damage when he first received the boat. We did have
> to jam on the brakes last fall and the boat slid ahead causing minor gel
> damage from the V stop on the trailer to the bow.
>
> So our requests for help are:
>
> 1. Best way to repair this damage?
>
> 2. Best guess why it occurred in the first place and how to prevent a
> re-occurrence?
>
> 3. Why is the non-cracked stb. ama still difficult to close in the water,
> (feels kinda like the Port) but no visible cracks.
>
> I did measure the SS angular braces that appear they may be fitted and
> drilled/bolted as part of final assembly of hull/ama. The way I measured
> the stb. side is 3/8" shorter then the port. Is this normal tuning
> tolerance or could it be part of the problem with interference on the port
> side leading to the crack?
> Which came first, the chicken or the egg?

Comments and concerns welcome.
I believe the crack is from the twisting stress on the box as it tries to hold the ama down when closing and started at the saw cut stress point. The good news is, as Will first told me on the phone, the box is hardly needed when amas are open so the boat is still safe.
I suppose the fix will be to remove the box, open up to get access to inside for proper repair and replace.

[trashpad]

The only times I have had problems moving the amas in or out came from the tramp tie slide. Salt tends to prevent the tram slides from moving freely which makes amas hard to stow. A lil spray silicon and my amas felt smooth as silk.

[Ron]

If I remember, I spray the trampoline slides and all of the hinge pins with McLube (with straw attached) about once every other month. Have been doing that for almost 2 years now. The slides tend to stick a drop if I forget, and that automatically reminds me to do it. I've also used Starbite's Zipper and Snap lube on the slides - It works, but I'm not sure which lasts longer. It's a white (nearly clear) teflon lube. Works great on mast tracks as well.

If these parts are not lubed occasionally, I can see more force having to be applied which could eventually cause some damage to something. But, if the boat was delivered this way, this was obviously not the cause.

[dcsailing1]

Ron;
We do keep the slides lubed quite a bit. Don't think that's the cause as the ama would get "stuck", actually jammed tight against the hull before the slides were taught. Once we started looking her over real good, found where the ama had rubbed the gelcoat off the bottom of the hull and when the crack got this bad it hit on the raised seam there and stopped. When we weight the ama there is around an inch of clearance so it appears the cracking is letting the linkbox twist up and into the hull as the ama lifts, thus the jam.

Dan, if you see this maybe it should move to mechanical systems, Sorry I goofed.

[Dan]

The problem that usually causes that type of cracking is if the ama is left partially extended. If the ama is in the fully extended position or the fully retracted position, there is very little stress on the ama link boxes. However, if the ama is left in the partially extended/retracted position, the geometry of the stainless steel pieces causes them to act as lever arms and causes fairly high stress loading on the link boxes, especially if there is any wave action causing the ama to move up and down.

I would point out that the saw cut is most likely the starting point of the crack/tear, as laminates tend to concentrate stress at such points. Ideally, the link boxes would have cleanly molded or rounded corners on those edges, since that would greatly reduce the chances of such cracks forming.

It is very important to lock the ama locking line clutch and to tension the locking line so that the ama is locked in either the fully retracted or fully extended position.

Repairing the damage is fairly simple. If you have the ama fully extended, you can patch the ama link box in position, by cutting a hole in the back of it and applying the patch to the interior of the link box. If the boat is on the hard, you can remove the ama and repair the box from both sides, but getting the repair depth to match the original ama link box contours is going to be fairly difficult IMHO. I would highly recommend using at least one or two layers of kevlar cloth in the repair, as it is far more resistant to tearing than fiberglass is.

If you have any questions, please let me know.

[dcsailing1]

Thanks Guys:

AFAIK the first owner left the boat in slip year round and this (port) ama was fully extended with the other retracted. He didn't use the trailer except to haul the boat to the yard for bottom paint one time. We operate the amas on the trailer all the time and if the track gets dry it does stick. We have never had to force the amas in or out on the trailer. A good push from the stern is usually all it takes, then complete the arc with the lock line either opening or closing.

As I said, I think Dan is spot on with the stress point at the end of the saw cuts and I will mentioned to PCI that they consider first drilling a hole then sawing to the hole to help with this on future boats. Also apparent is that with the slight list of the engine on port side, there is more up and twisting force from the ama going deeper in the water when closing, then on stb side.

So I guess if there is a lesson learned here it's: Find some light-footed heavy crew to ride the ama nearly closed if it starts to jam on the hull. (We have the weight but not the light footed part). Then figure out whats coming loose and or breaking/cracking ASAP.

I will also ask PCI why the link box cutouts are different and or missing port vs stb, or even there in the first place. I guess you need a drain hole to let the box breath, but cuts inner and outer on port and only one on std? Maybe they will go away during the repair of the port side.

[Mark]

I would suggest checking all the bolts holding the metal hinges. There are lots of them and on mine most were not tight (you need a large phillips screwdriver and a 1/2 in spanner). I had sticking problems due to the corner of the box rubbing on the ama. I cut off ~ 1/4 in and have no problem other than having to repair the gel coat on the amas. There is some rubbing on the underside of the main hull and on top of the box as well which I have ignored.

[trashpad]

I agree with Mark about checking all the bolts. I have noticed once or twice a year one of the amas will start to have a little give when the waves pick up. It does not take long to hit them all. The last time it ended up being the large nut on the forward pivot that was loose.

I do have a 22' wide slip and keep the amas out all the time. I have only had to retract them once in the past year and a half when I pulled into Solomon's Island.

[dcsailing1]

UP DATE: NOTHING FROM PCI.

Well continuing with Ron’s frustration from the trailer threads and no response from PCI for several weeks;
I would think they would have some concern with a T28 suffering major cracking of the link box with no apparent damage or misuse present. I would like some info from PCI as to what kind of normal stresses are on this structure, is it normal now and or what do I need to do during repair to prevent a recurrence? PCI should know better then anyone else at this point.

X2 with Ron’s “Anyone in the Annapolis area who drives by should stop in and see what's happening (Kurt, Bob, etc,).”

If this is all around a major illness or something, then my apologies now. If not, it’s not ok.

Maybe we didn’t buy #342 new from PCI, but we have a ~3 year old boat that has a problem. Will told me on the phone he had received my email and the photos of the failure the day after I sent them, more then a month ago. He also told me he commissioned this boat in San Diego when it was new and didn’t recall any “shipping” damage.

[dcsailing1]

Update on this link box failure.

As Ron has posted on Nov. 1 2009, there are new happenings for Telstar. And new contact info. Here it is again if you should need it:
Phone: (410) 990-0317 = Performance Sailing
Email: sue@telstartrimarans.com

After getting this new contact info, Tony returned my call. He was not aware of our earlier attempt in August to get help with this issue and we talked about this failure.

Tony had seen another failure like I described to him but said he later learned from that owner that the boat had gone through near hurricane winds, in the slip, and the ama had been partially extended during the storm.
As we have observed and been told, there is no twisting moment on the link box structure until the ama is partially open or closed. As can be observed on our boat the crack opens only in the partial open/closed position. When fully open or closed the crack closes up and is nearly invisible from the top. (Not the bottom though as the glass fibers don’t quite line up) The plunging motion on an ama in the highest stress position in a storm, even in a slip, could cause this type of failure.

The ama is being forced down in the water as it closes which results in increasing the up force on the structure and the twisting of the metal “truss” structure. The repeating stress from the plunging motion will eventually cause this kind damage. Kind of like bending a paper clip repeatedly until it breaks.

We are not aware of letting either ama spend any time in the partial open/closed position, while in the water, while we have owned the boat. The first owner kept her in a slip year round with this, port ama, fully extended, AFAWK. Why/how this occurred in our case will ever be a mystery.

We talked about repair plans but this will be fine tuned later when we get closer to actually doing them. The boat is on trailer for the winter and repairs will likely wait for better weather in the spring. Plans now are to install one or two removable “deck” ports in flat surfaces of the box and make the majority of the repairs from the inside. What will happen to the bottom outside is still in the air as the ama has to come off to get the link box off. Perhaps we can partially remove it enough to get at the bottom exterior?

So lessons learned:
1. Don’t have a failure of structure question when the company is in a transition and expect any timely help.
2. Don’t let the T28 sit in the water with amas partially open or closed.
3. We used the boat knowing the crack was there and saw no danger, additional movement or damage.

Bottom line: Very glad Sue and Tony are continuing development and production of this really great design and we will have the support of the best expert available when it comes time to do the repairs.

Added a couple of additional photos to illustrate what I tried to describe above:
The first is the max stress crack, nearly an inch wide at the outer edge of the box with the ama half open.
The second is the nearly invisible closed crack in the aft panel of the link box when the ama is fully open.