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I'm reinforcing my transom with knee bracing. Should I used 1/4 or 1/2 ply. 1/4 seems to thin to me...
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Hello,Originally posted by Kentfielddude View Post
One Knee Brace or two? I would suggest 3/4". Do a Google search on wooden boat transom knee bracing. Also try the Wooden Boat magazine web site. They are the wooden boat experts. I saw your boat on the other thread. Cool boat. Definitely run it with a 50's vintage motor. Mercury Mark 20 or Super 10.
I just did a Google search on ... "wooden boat transom knee bracing design"... lots of images.
Good luck on your cool project.Last edited by DeanFHobart; 02-12-2017, 05:06 PM.sigpic
Dean F. Hobart
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I'm doing two 1/2 knee bracing. I'm going to put a kg7 on my boat.Comment
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You really don't want or need knee bracing. The boat wasn't designed for a knee brace and if you put one in you stand a bigger chance of making the bottom hook and that will make a mess out of the boat.
The design of the boat is intended to use the top decks to hold the transom on. If the transom is not tight to the top decks then you need to figure out how to keep it attached properly. That might mean adding some stiffening element under the deck, but you really want the forces to be taken by the top aft decking. Also note that the spray rails (that's what we used to call the pieces that attach to the motor board and form the back part of the cockpit) are an important part of that stiffening element. You need to make sure they are properly attached to the motor board and are properly attached to the stringer that runs along the cockpit. side.
If it's all properly bonded then the boat will be plenty strong for the type of engine that is proper for this boat. The trick is to make sure it is properly attached. If it isn't or if the wood is cracking or not attached you need to make it right.
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Also, in one of your other post you were looking for what kind of trailer you'd need for this boat. Back in the day they typically didn't trailer these boats with the motors on them. The boat is designed to support the motor properly in the water, but hanging the motor off the back can damage it if it isn't properly supported. The basic problem is that the the boat is really light and most trailers are set up for a much heavier boat or jet ski. Your boat weighs about 120 pounds and the motor weighs about 100. or less. A typical jet ski weighs 500 to 600 pounds, so a jet ski trailer is sprung for twice the weight.
I built a custom trailer for my boat and designed it with light coil springs and shocks and it works fine and I can trailer my boat with the motor on it. If you can't get a trailer with light springs then I'd highly recommend that you trailer the boat without the motor on it. If you're bound and determined to trailer the boat with the motor on it you need to get a trailer that will go to the transom of the boat (which isn't hard since the boat is pretty short) and make a support for the motor lower unit that will let you tilt the motor some and support the lower unit. They make those lower unit "transom savers" and that would be a mandatory if you want to trailer it with the motor on the boat.
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Some people say put a knee brace and others say don't. I'm very confused.Comment
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You really don't have much to anchor knees to. You do have a coamings (sp?) supporting the transom. It would be good to see what they are anchored to and how they are constructed. Propery done they will give more support than any knee will do. I built a couple of Airbornes, the first one i built strictly to the plans. The second one I kind of redesigned to have structural coamings to support the transom but I also included knees. Looking at your pcture i would just reinforce your coamings and not worry about knees. I doubt that a KG7 is going to over stress that boat even as it is.
kk
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Could my boat also support a mk20 or 25?Comment
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Little horsepower difference among KG-7, Mark 20, and Mark 25. All are 20 cubic-inch engines and probably develop about 18-20 horsepower at racing RPM with Quicksilver lower units. The main difference among these engines is fuel delivery (gravity feed on the KG-7, pressure feed on the Mark 20, and fuel pump on the Mark 25). The Mark 25 also has a beefier crankshaft-crankcase assembly, but that shouldn't much affect horsepower output. The Mark 20 is also easily adapted to use the Mark 25 fuel pump, and many restorers, including me, have done so because Merc's pressure-feed tanks are considered troublesome as they age.Last edited by dwhitford; 02-13-2017, 01:12 AM.
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From pics posted here and on your previous post your transom looks ok without knees (agree with KK and check what he says). It will be good for the KG7, Mark 20, Mark 25 and Merc 200 type engines. Just make sure which ever engine you use it is securely lashed down, make sure clamps are tight, have a full butterfly, have a kill switch, good helmet and race jacket."Keep Move'n" life is catching up!
No man's life, liberty or property are safe while the legislature is in session.Comment
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That should work. Does your KG7 have a quicksilver racing tower housing and gear case?Originally posted by Kentfielddude View Postsigpic
Dean F. Hobart
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I'm getting a kg7 with the non-racing lower this summer.Comment
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Ok cool...... Keep us up to date on your project with pictures showing the progress.Originally posted by Kentfielddude View Postsigpic
Dean F. Hobart
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Ok. I have a old thread I was posting on.Comment
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