Transom Frame Confirmation

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rbrandenstein
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Transom Frame Confirmation

Post by rbrandenstein » Tue Nov 09, 2010 12:54 pm

I am starting the layout and frame cutting for my Malahini. I think the enclosed diagram shows the correct situation concerning the transom frame dimension, but I want to confirm it is correct.

The transom requires a 13 degree angle across the bottom which makes the inside dimension of the transom larger than the full size drawings. This angle then makes the bottom transom frame larger than the drawing on both sides of the frame member as per the diagram.

Let me know if this is how it works out in reality.
Transom plan
Transom plan
Transom.PNG (17.57 KiB) Viewed 1761 times
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Bob
Completed Malahini (launched 6/24/2012)
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vupilot
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Re: Transom Frame Confirmation

Post by vupilot » Tue Nov 09, 2010 4:22 pm

If I follow you correctly that looks correct to me.

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Roberta
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Re: Transom Frame Confirmation

Post by Roberta » Sun Nov 14, 2010 5:13 pm

Take a look at "Roberta's Zip" on page two. I wrote a blurb on how I set up to cut the transom. It is basically the same as a Malahini except the angle is 12 on the Zip. You may need to consider the angle on the sides, as well. I think I used 10 deg, but any excess can be faired out when side panels are set.
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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rbrandenstein
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Re: Transom Frame Confirmation

Post by rbrandenstein » Tue Nov 16, 2010 3:44 pm

Thanks for the advice. Roberta, I checked out your post and understand your procedure. I was concerned about angling the sides as well; the plans don't provide any insight. I also found this write-up on the Glen-L site which somewhat matches your procedure. I think they are suggesting you would mark the transom on the outside, cut out the top part of the transom, and then temporarily attach the cut out frame members to get them in place. There might be some alignment issues. Now you could continue to cut from the outside at the needed angle since you already have the lines.

From Glen-L "Boatbuilding Methods" under "Using full size patterns"
If the edges of the transom require an angle, review the patterns carefully before making any cuts. The layout is made directly on the plywood to be used for the transom by the same method used to transfer the frame contours to the Layout Board (See FRAMES). The transom contour is usually given to the outside back surface of the transom with any angles cut away from, or larger than this shape. However, check the plans and patterns for precise information. Rough cut the plywood transom to the maximum size required allowing for the angle. Temporarily fasten the oversize, rough cut, inner frame on the unmarked side of the transom plywood, leaving the edge projecting over the plywood to allow for the angle. Tack additional doublers in place if required, then saw the assembled transom and frame to the required angle. The frame can then be removed, inner contour and notches cut, and then glued and fastened to the transom as described in the plans.
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Completed Malahini (launched 6/24/2012)
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Roberta
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Re: Transom Frame Confirmation

Post by Roberta » Tue Nov 16, 2010 4:06 pm

The big trick is getting the pattern drawn exactly opposite on each side of the plywood transom board. The locating holes drilled at the vertcal and horizontal axis help place the pattern correctly so you can draw it in the correct position and ,thus, mount the frame members in the correct position and get a good transom assembly when you do the cutting.

Good luck!!

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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Iggy
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Re: Transom Frame Confirmation

Post by Iggy » Tue Nov 16, 2010 4:43 pm

I remember that step. Angle on an angle on the opposite side of my band saw. Blah.. no thanks.

I set my transom frame keel notch in a straight line with my actual keel as per the drawings.. thats the critical dimension, and lined up the top of my frames with the top of my plywood transom, leaving a a good 1/2" extra material on the bottom and (I should have left) about 1/4" on the sides for fairing that bloody angle later.

Basically, I treated the transom sides and bottom like the chine and sheer. Thats an option for you if you prefer.. or if you have good enough equipment to make the angle on angle cut and can calculate the offset, then give it a shot.

I used a 6' straight edge on the bottom of frames 1 and 2 to provide the sightline for fairing the bottom of my transom frame/plywood at the same time. Angle Grinder with sanding disk attachment and/or powerplaner did the trick. No issues.. and no recuts.

For the sides I used a thin cut pine batten (1/4" x 2" x 6'+) to simulate the 'curve' on the transon sides.. but I am sure some guys/gals could probably eyeball the bevel without the batten.

Whats critical when you fair everything is that from frame 3 to the transom is a straight line.. no drops, dips, lumps.. in a line parallel to the keel.
Ian (aka Iggy)
My Malahini Build

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