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Thread: baja progress- knee help!!
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03-15-2004, 08:43 PM #1
baja progress- knee help!!
i pulled the floor outa my baja and was wondering how i could marry some knees to the inside of the transom and to the stringers
have west system 105 and 206 hardener
what glass do i use? will 1/2 in ply work for the knees?
full of dust and crap from sawing but only pic i have
thanks
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03-16-2004, 01:46 PM #26000 RPM
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I would use...
3/4" ply for the knees instead of 1/2"...the weight difference won't make a bit of difference but the peace of mind will be priceless. Regular exterior grade ply vs. marine ply has also been discussed...use whatever you're comfortable with.
I only have two suggestions...first, use cardboard as a template and try to get the braces to fit as tightly on the transom and floor as possible...second, once you dry fit the braces you'll notice a very sharp 90 degree angle on the matting surfaces...try to add a nice wide fillet at these angles using your favorite filler, then apply your cloth...this will also add considerable strength.
There are lots of projects in this forum with ideas, designs and pictures of transom/knee braces...Good luck and post some progress pics.
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03-16-2004, 02:12 PM #3
Get Kyntex
Get some Kyntex tape....6". It's a biaxial cloth with mat stitched to it and is stronger than hell. Tab the knees in with it and cover it with whatever you want. Cloth works better with west system. You could get away with some 8 oz E-glass to cover everthing after it is tabbed in with the kyntex. Also add a brace in between the knees a la T-Rex that lines up in between the transom bolts horizontally. If you need help finding the materials let me know...I will post links.
David
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03-16-2004, 04:26 PM #4
Re: Get Kyntex
Originally posted by Liqui-Fly
Get some Kyntex tape....6". It's a biaxial cloth with mat stitched to it and is stronger than hell. Tab the knees in with it and cover it with whatever you want. Cloth works better with west system. You could get away with some 8 oz E-glass to cover everthing after it is tabbed in with the kyntex. Also add a brace in between the knees a la T-Rex that lines up in between the transom bolts horizontally. If you need help finding the materials let me know...I will post links.
David
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03-16-2004, 05:42 PM #5Member
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What about that transom bar??
I noticed in the pic that a transom bar was used by the manufacturer rather than knee braces as most builders employ. Another boat I looked at currently uses a very large transom bar (2" thick and approximately 6" deep to the transom) rather than knee braces. This bar is glassed all the way across the transom and into the sides of the boat. Is one better than the other? Does the large transom bar described cause any long term problems?
Last edited by Perfect-Storm; 03-16-2004 at 05:46 PM.
All bass are good ones, some are just better than others.
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03-16-2004, 11:32 PM #6
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03-17-2004, 09:22 AM #7
My Checkmate has one too. Some kinda inferred that new hulls direct the motor forces into the stringers rather than the sides of the hull...and so likey the knees are a better way to go than the brace idea. If you think about it, with big knees the transom has little else to do and should not have to be that huge. I wonder how heavy the transom is on say an stv from the knee to the side.
Oh, I'm going to take mine out.Last edited by sho305; 03-17-2004 at 09:24 AM.
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03-17-2004, 09:25 AM #8
Link
I like this place. Everything is always well packaged and their prices are pretty good. I don't know why there pic has just the mat side but this is the Stuff.
http://www.jamestowndistributors.com...NO=J1697106510
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03-17-2004, 11:55 AM #9
thanks fly!
sho you are going to take your transom bar out?
and put knees in rite?
i think im going to marry the knees to the bar underneith it because even if i take that bar out i only have 3-4 inches before the bottom of the motor well
post you opinion any better way?
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03-17-2004, 12:17 PM #10
I thought you where selling the boat?
Here is a picture of the knees I installed. I had the "bar" as you call it runnning across the back of the factory transom. It was removed when the new transom was installed. Had to make the knees as wide as possable due to the gas tank fits between them. The trimate only has one stringer in the center. So to add more streanth to the hole mess I boxed in the rear section and tied the knees to the bottom, sides, and top. You could hand twin 300's off the transom now, but I don't think it would float.Fellow G-Man,
Sunshine Syndicate, Mid West Chapter
1975, 16' Checkmate Tri-mate 2.4 200+
Currently undergoing overhaul.
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03-17-2004, 12:31 PM #11
Well I'm no pro at hull structure, but judging by newer hulls I see it like this: With knees on each side of the motor, you have lets say 75% of the motor forces going through the knees into the stringers/bottom. The wide old open transom will flex a little until the force was transfered into the sides and deck the old way. Before that happens now, the knees will not flex at all and the forces go into the knees. So I think the stock 1.5" of wood transom in my checkmate should hold anything left after the knees do their work (since it likely would hold 200hp stock for a little while if in new condition). The only high stress part of the transom then will be from knee to knee, where the motor bolts are. I debate adding another layer there, but I doubt any 235hp or less motor I would put on here will tear up the 1.5" wood plus glass in the short area between knees anyway. I might just because it would not hurt anyway, and give another layer to bond into the knees mostly.
If anyone has any input to that, please chip in
Another thing, is I plan on getting rid of most of my splashwell. the idea is to get the top motor bolts inside, and then have a horizontal piece on top of the knees to tie the top bolts fully into them. Likely this will be the bottom of the new shallow splashwell. B. Mac did this in his thread, and made a whole frame to go in there. With my smaller 17' here, I will not get so radical with it as mine will not have to take the beating he planned for his or hold that much motor. Likely mine will have 200hp or less V6 on it.
I figure a 3/4 knee frame, 2x3/4" transom plus maybe another 3/4" in the transom between the knees, and tie it into the stringers a few foot ahead of the transom. My only problem is I have one center stringer and the existing floor leaves little room for side stringers...so I may change the rear floor or somthing to give me more room to transition to the stringers right...maybe add side stringers too, not sure yet. I will also cut a small relief into the transom/pad, so I will depend on the knees to support that as well. May add more beef in that area depending on how large it is.
Thanks 175Checkmate, that is the idea...and you see how the knees are above the original floor. I may end up beefing that area up under the back seat so I can end the knees there like that. Your boxed area at the drain there will be like my relief, but I'll have to support it with a knee-like structure. No stress cracks for me
I am tempted to go with two stringers so I can lay a fuel tank down in there...I'll get a better idea on that when I get the floor out but I would love to get rid of that tank there on top of the floor.
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03-17-2004, 01:17 PM #12
i am selling it
but over the winter the floor weakened in one spot so i ripped it out and i am figueing since im putting stringers in the hull might as well tie them into the transom good while im in there you know
well we shal see what happens still pretty undesided though
SO MUCH FOR GETTIN SUMTIN DONE TODAY! UHG
HAPPY ST PATTY'S DAY!
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03-18-2004, 07:47 PM #13Member
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What about the bar?
So it seems like the knees are more accepted. But is a significant transom bar still an acceptible way to reinforce a transom or does it cause other problems in the long term? How about with todays heavier motors such as the DFI's?? This particular boat manufacturer I have been considering is putting a 2" by 6" foam filled fiberglass beam across the full width transom and it is fully glassed to the transom and boat sides. However, the boat has no knee braces.
All bass are good ones, some are just better than others.
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03-18-2004, 08:01 PM #14
looks like they work pretty good knees are probly better but my boats an 84 and has been put through its paces and held up pretty good no problems yet!
the scratches in the top left corner of the transom is missing clear cote believe it or not did ti pulling a wake board into the boat exxagerated in picture for some reasonLast edited by baja200merk; 03-18-2004 at 08:04 PM.
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03-19-2004, 09:43 AM #15
I think the beam works, and if you saw my poor trashed '73 checkmate transom you could see how it is still working I hope this doesn't sound dumb, but...
I think part of it has to do with the forces at play on the hull. In a simple way, a vee style hull uses the vee shape to make the sides into stringers of sorts...and the beam also directs transom forces to the sides.
I think the beam could continue to work in my hull but it will not be needed after the knees are there, I also need the knees to support the relief in the pad, and so why hassle with it then? The only advantage to me is the beam gives more room under there for gas tanks/etc.
My last thing about it is my '73 was made for 150hp then...and that was a Merc inline that is lighter than a V6. So I feel I should do something to beef it up even though it is pretty stout, likely strong enough for a V6 if it were in good condition anyway. Just the same, I want to do more than they did to be sure. If it were a new hull and made for it factory approved, I would not worry at all.