Building a Malahini

Designs for inboard or outboard power

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chintan
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Joined: Thu Jun 29, 2017 4:03 pm

Building a Malahini

Postby chintan » Fri Jul 21, 2017 4:36 pm

Hi there,
I am building the Malahini design and I was wondering if I can get some help with the transom question that I have, the step describes to cut an angle of 13 degrees in the bottom of transom and I cannot understand how to do that. I tried looking at all the pictures but I am not getting any clue on how to give a 13 degree angle cut.

Can I please get some help?

Thanks,
Chintan

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vupilot
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Re: Building a Malahini

Postby vupilot » Fri Jul 21, 2017 7:03 pm

One way to do this is cut the bottom of the transom long. For a 13 degree angle the math I think works out to something like 3/8" wide on your cut.

Then when you mount the transom to the building form your forms will also be cut with the 13 degree angles in them but that is much easier to do because you are working on a large piece of inexpensive lumber. Then when you put your transom on that form its upside down at a 13 degree angle and all you have to do is block plane your transoms bottom edge flat, or parallel to the floor.

So in short what I am saying is just cut the bottom wide for now and you can get the angle after its mounted to the form. Someone will probably chime in with the exact formula to figure out how much extra exactly that will be but I'm pretty confident 3/8" is going to be pretty darn close.

zip001
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Location: Fredericksburg, VA

Re: Building a Malahini

Postby zip001 » Sat Jul 22, 2017 3:52 am

I did almost the same thing. I had purchased a hand power planer. So I cut my transom and just added about 1/2 inch to be safe. Once mounted to the building frame it is so much easier to see. I then hand planed it close and used a belt sander to finish it out. So much easier to see and I was able to lay a piece of wood from frame one across to the the transom to check the fit.

If you do a search for Maharani transom you will find numerous options and ideas. This forum is a wealth of knowledge and I couldn't have built (or be building) my boat without this available expertise and help from he guys (and gals) when I get stuck. Hope this helps. If you cut it long and take your time it will be an easy fit. One thing I have learned is to take it slow.

Where are you located? I didn't see that in your profile. You will be surprised that sometimes guys are close by and love to help out.
We sleep peacefully in our beds at night because rough men stand ready in the night to visit harm on those who would wish us evil.

PeterG
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Location: Connecticut

Re: Building a Malahini

Postby PeterG » Sat Jul 22, 2017 6:14 am

The pattern for the transom is for the aft face. Extra material has to be added to the bottom edge and the sides so the edge can be beveled for fairing. The bevel on the bottom edge needs to be 13 degrees (12 degrees transom tilt plus 1 degree downward slope of the keel). Basically your transom is about 3/8" undersized along the bottom and a little less on the sides.
When I made my Malahini transom, I drew it out directly on the aft face of the plywood ( I didn't use the patterns but you certainly can) and added 3/8 inch along the bottom and sides but not the top edge, that doesn't need extra. Then I carefully transferred the centerline and setup lines onto the forward/inside face. I then laid out the frame pieces with added 3/8" extra material to the outer edges (you can add more extra, it just needs to be at least 3/8"). I then attached (screwed, not glued) the frame pieces to the inside face of the plywood, laid it down with the aft face up and cut the bottom edge and sides with a saw set to 13 degrees for the bevel. The sides will be faired to less than 13 degrees bevel, but the 13 degrees is a good starting point. Cut the top edge square, no bevel, it will not need any extra material because of the transom tilt and the angle that the deck meets it. One thing I tried before cutting the transom, use a utility knife and precut through the face layer of plywood along the cut lines. This will keep the saw from splintering the face layer as you cut and gives a nice clean corner/edge to fair to.
After I cut the transom out, I prepped the edges back by planing and sanding to the pattern line and made sure the edges still had the 13 degree bevel. I then removed the frame pieces to make the notches for the battens, keel, chines and shears. The keel and batten notches will be angled at 13 degrees like the edge of the frame.
A suggestion: Have you decided whether you are using a long shaft (20" transom height) or short shaft (15" transom height) engine for your boat? The plans are dimensioned for a short shaft but if you are building for long shaft, the cutout will need to be higher up the transom, the horizontal 2 x 4 stiffener will need to be moved up and the top end of the transom knee has to be extended to meet the 2 x 4.
Have fun! The transom is the most complicated part of the structure, all the rest will be easy.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

obd
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Joined: Sun Dec 30, 2012 3:39 pm
Location: Mount Pleasant, SC

Re: Building a Malahini

Postby obd » Sat Jul 22, 2017 3:51 pm

See table saw jig on page 95 of Glen-L's book, "Boat Building With Plywood". This approach worked beautifully for me. Definitely attach transom frame to plywood before cutting bevel. I used steel screws initially and waited on the bronze and epoxy until later so I could still tweak transom frame notches.


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