C-27 transom re design? - SailNet Community
 
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post #1 of 10 Old 03-09-2010 Thread Starter
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C-27 transom re design?

I have a catalina 27, 1977. It is the outboard model. I've been thinking about switching to a split backstay and opening up the transom since its kind of a pain, and its hard to find a 4 stroke that will be small enough to tilt up and out of the water.

has anyone done this? or is there an engineer familiar with the construction of this boat to tell me how dumb this idea is..?
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post #2 of 10 Old 03-09-2010
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Splitting the transom is really a stupid idea. It takes a lot of structural strength away from the aft end of the boat if you do this, unless you're prepared to seriously beef up and re-engineer the aft end of the boat. The transom acts as a box beam and transfers loads from one side of the boat to the other. If you split it, it will seriously weaken the aft end of the boat

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post #3 of 10 Old 03-09-2010 Thread Starter
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I had a feeling.. there is already a small crack on the top and front of the stern on the cockpit side of the backstay chainplate. not sure what its from. It doesn't go very far down, thats what got me thinking about the split..
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post #4 of 10 Old 03-09-2010
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Post a photo of the crack. It sounds like that there may be damage inside to the support structure for the backstay chainplate.

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post #5 of 10 Old 03-09-2010 Thread Starter
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I removed the chainplate And it didn't go down under it.. under the chainplate is where the real bulky part of the stern.
I've beat the hell out of her in the last year and she didn't change much. I ground out the crack and put in filled epoxy. that ended up cracking again. if you put your finger there when underway, you can feel the two sides moving and pinching..
tell me if the photo didn't attach, i'm new at the forums thing
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post #6 of 10 Old 03-09-2010
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That is a stress crack and definitely caused by the loads on the back stay. There is something failing structurally on that boat and IT NEEDS TO BE REPAIRED ASAP.

If your backstay chainplate gives way, you can lose the mast and get seriously injured or killed. I would highly recommend not sailing the boat until you've had that repaired.

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post #7 of 10 Old 03-09-2010
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For what it's worth, it's a common modification of Moore 24's, and they are still quite seaworthy. I wouldn't take it lightly I suppose but it would make it easier to get to the outboard.

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post #8 of 10 Old 03-09-2010
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I'd split the backstay just to reduce the forces on the transom.

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post #9 of 10 Old 03-09-2010
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Hey jus - welcome to SN dude. I have a C27 myself (OB version too). I have a couple of cracks in my transom from where the OP had mounted the outboard on a bracket without proper backing (instead of using the outboard well). It created a couple of cracks and delams around the outboard well opening and the bracket bolt-holes. Structurally, it's not that big of a deal as there are no direct loads there.

However, your cracks look a lot nastier since they are right where the name plate is. That nameplate could fall off at any moment causing grievous bodily harm and huge embarrassment in front of the ladies. Next time you might want to back off the torque on those screws.

Seriously, you should get that fixed. With the outboard well opening through the transom, that's your main support "beam" across the stern. Splitting the backstay might be a good option in this case - I don't know. But if you leave the backstay as is, in addition to reglassing that area, you may also want to look into installing a horizontal backing plate on the inside of that section since it's already weakened.

PS - Have you been flying a monster spin in 20 knots?


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Last edited by smackdaddy; 03-09-2010 at 08:21 PM.
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post #10 of 10 Old 03-10-2010
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We belonged to a Co-op that sailed C27's for 14 years before upgrading to a Mirage 29'. In all that time, I have never seen anything as bad as that.

I agree with the advice of other posters: get that repaired as soon as possible. From my experience, their concerns about structural integrity are well-founded.

Even more important, forget about opening up the transom. I have never seen that done on a C27, and Sailing Dog is right when he suggests that you will weaken the structural integrity. From your photo, that chain plate looks like it is close to letting go.

Mark
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