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Thrillsbe

Springtime Discovery

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I’m giving the brightwork on Local Honey a redo. While sanding the quarter knees today, I got a good look at a problem I saw earlier.  They are separating from the transom.  (That’s daylight between the knee and the transom.)  The knees are thin, and I didn’t get a good screw connection.  (I sort of missed a key connection.) Port side is the worst, the starboard is half as bad as this.  My question to all of you is— how serious is this?  What do you recommend?

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Edited by Thrillsbe

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Well, I don’t blame you all for looking and not responding.  This does look serious to me.  To respond with an “Aw it’ll be OK” carries a certIn amount of risk.  I’m starting the long process of cutting out the old ones, and fitting in new, thicker ones.  I’ll probably also cut a 3” notch in the starboard side of my transom, to lower the outboard motor.  It cavitates with not too much wave action.  I’d love to hear from Alan or Graham, before I break out the saw.

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I was sort of hoping that my gi-gundous knee brace (plus a little help from the seat tanks) would take all the loads that an outboard might dish out.  FYI- there might be a 9.9 on this transom in the far distant future.

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   Don, I hate that you're the only one commenting on your post.  I'll offer a suggestion that I haven't actually tried in the real world so take it with a grain of salt.

   Maybe you could make a saw cut between the knee and the transom (preferably not a powered saw) to cut out the gap to a uniform thickness.  Then you could insert a shim of the same thickness as the saw kerf.  This would still leave a joint that connected the end-grain of the knee to the long-grain of the transom, so the weak end-grain joint could be reinforced by a glass patch on the surfaces of the parts (maybe you could wrap one layer of glass around the knee to stabilize the opposing surfaces of the joint).

   If I haven't expressed myself well I can try to sketch the idea.

 

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Regarding the knee separating from the transom. I had an old Thompson 15 lapstrake outboard with a 30 hp motor that had the same condition. That knee was only held by screws, no epoxy. I relocated the failing screw into good wood, used thickened epoxy in the joint, and everything was still holding together when I sold the boat 5 years later.  My inclination would be do a similar fix on your boat. Run the saw blade through only where the joint has separated to clean up the surfaces. Then shim/epoxy, or just epoxy, and get a good screw in place. I would leave the rest of the knee untouched because it is holding.
 

 

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I'd go with Reacher's idea, and I think it's what Ken had in mind, too.  Clean out the separated gap a kerf-width, fill with really thick epoxy and a shim if needed, and install a fresh screw.

Your transom, knee and motor plate look quite strong.

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Hi Don,

 

I like the ideas from Ken and Reacher.   Have you thought about a glassed fillet on the underside?  Most of the other joints on the boat have fillets, right?

 

Bob

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I did, Bob.  The flexing on this joint would tend to peel it apart, though.  As an alternative, I’m thinking of adding a thick cleat to the underside.  I’d glue it to the bottom of the quarter knee and the forward surface of the transom.  I can also shoot a screw or two through the back of the transom.  I don’t want to mess with a screw into my pretty quarter knee, if I can help it.

 

Comments?

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Ah, good, more pictures.  I didn't comment was because I didn't know which boat, or even really the full extent of the problem.  No matter what, I would remove the old ones.  Anything you could cobble together without doing so would be less than confidence inspiring. Using screws and epoxy together doesn't add up. Using screws as clamps to squoosh things together and hold them while curing never hurts.  The only instance I can think of where both contribute is for things like outwales.  Good screw fastening keeps the end from pealing away better than epoxy.  So I always screw the ends and epoxy the whole thing. If you built according to speck, I see no reason to make them bigger, your issue was some kind of bonding failure. If you didn't build to spec, well, maybe you just found the problem. Clean the mating surfaces.  Clean the mating surfaces.  And then clean the mating surfaces.  I would venture that not doing so, or insufficiently doing so is almost always the problem. Since flexing is an issue, nothing holds like bolts or glass tabbing both sides. But what ever you do, remove the old ones and start again.

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Last night, I was dream-worrying about this.  That’s when it’s time to get out your Big-Boy Panties, and start cutting wood.  It was a productive morning, and I’m pleased with the reaults.  It is always gratifying to use a lot of your tools to do a job— it helps justify their purchase.  I still need to cut my cleats.  But then I can glue it all together.  Fortunately, I didn’t read your reply u til lunchtime, Hirilonde.  I had already decided on the less difficult path. Not to worry!  If I get separation again, I’ll go the extreme route.

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I shortened the port side to match the starboard.  It wasn’t doing any structural good, anyway.  I think.

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Absolutely!  I’ve been agonizing over this for too long.  it was time to pick up a saw!  Now, I’ve broken the ice.  If I do need to do radical surgery in the future, I’m not worried.  It would be more involved, but I know I can do it.

 

A cold snap is putting on the brakes for a few days.  Those 55-64 degree days got me spoiled.

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Well, I did the dirty deed.  I think it came out well.  Time  tell me how well this repair performs.  If it fails, I will do the more radical repair.  Now it’s on to varnishing

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My springtime maintenance work is coming along quite nicely, thanks to all the COVID-19 closures.  Still have some small parts to paint, but the hard part is now behind me.

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