Malahini transom questions

Designs for inboard or outboard power

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obd
Posts: 34
Joined: Sun Dec 30, 2012 3:39 pm
Location: Mount Pleasant, SC

Malahini transom questions

Postby obd » Sun May 14, 2017 9:16 pm

Is there any reason why the transom motor board cannot be made with lumber instead of plywood? I have a 10 inch wide sapele plank that I think will work and it would match the transom frame width so the knee would not require any additional shaving/fabrication. Also, what should the size of the transom cut out be if I am planning on a Yamaha 60 four stroke? I have seen where others have had to make modifications to accommodate the steering arm. I would like to get it right the first time if possible. Thanks!

Mark-NJ
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Location: New Jersey

Re: Malahini transom questions

Postby Mark-NJ » Mon May 15, 2017 4:25 am

Sure! Why not?

The whole Glen-L 'thing' is about "Plywood boats"....but you surely don't have to use it.

My transom is Sapele, with a few cavaets:

It's three pieces of wood, jointed together, and I would strongly recommend a dadoed slot & a full-size spline:

Image

Next, in addition to the transom frame, the entire center area is filled in with more dadoed Sapele creating a 1-1/2" thick transom throughout. The dado joints are NOT in the same areas...you don't want a seam on a seam. Not sure if it's clear in the picture...

Image

Here's the finished transom:

Image

So, yeah! Go for it! The 'look' will be great

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Roberta
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Re: Malahini transom questions

Postby Roberta » Mon May 15, 2017 5:40 am

The Transom is a very large part of the boat and needs to be strong and stable. Segmenting it with overlapping layers like Mark did will provide the stability similar to plywood and will be strong. I would not suggest making the transom from just large slabs, though. Shrinkage and splitting could be a real issue later on.

You need to make the transom cutout for the motor so the cavitation plate on the motor will be about the level of the bottom of the keel when the motor rests on the transom. Best to have the motor info before cutting the transom. Makes a big difference whether you get a long or short shaft motor. Most likely a newer 4 stroke will be a long shaft. The manual for the motor will have mounting criteria. Generally, about 30" of room will be needed to allow the motor to fully turn, so the sides of the motor well should be spaced that far apart. The pictures show the motor well on a Zip with a Merc 500. The steering arm extends quite a bit, so room, or a cutout is necessary to allow movement. This is a short shaft installation. A long shaft installation might have the steering arm above the decking (because the transom will need to be raised up instead of lowered to get the correct orientation of the cavitation plate) and the well might not need to be as wide.

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

PeterG
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Joined: Mon Dec 03, 2007 7:08 am
Location: Connecticut

Re: Malahini transom questions

Postby PeterG » Mon May 15, 2017 7:10 am

So for the Malahini, it would be OK to use solid wood as the motorboard on the inside face. But I do recommend using the plywood for the added stability like Roberta recommended. Besides, that wood may look nicer someplace where it can be seen :D As far as thickness mismatch between the plywood motorboard and the frame at the transom knee, you may find it easier to do like I did and make a "slot" in the frame that is flush with the motorboard and just wide enough for the knee.
The designed width of the motorwell on the Malahini is 36", which is good for my outboard which needs a miniumum of 32" to clear the steering system I will be using... I recommend looking at the outboard manufacturer's installation instructions for the needed clearances (forward of the transom and port/starboard of the motor) and make adjustments in the motorwell dimensions as needed. For a long shaft motor, you will want to move the 2x4 horizontal brace up about 5". Check the motor install instructions for the lower bolt hole locations, put the brace just above these to clear washers and nuts on those bolts. Be sure when you lay out your transom knee that you extend it up to attach to the brace. That's pretty much it for mods to the design for a long shaft motor.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

PeterG
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Location: Connecticut

Re: Malahini transom questions

Postby PeterG » Mon May 15, 2017 7:48 am

Here is a Malahini transom set up for a long shaft (20 inch) motor...
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Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

Hercdrvr
Posts: 345
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Location: McKinney TX

Re: Malahini transom questions

Postby Hercdrvr » Mon May 15, 2017 3:37 pm

How thick is the lumber you intend to use? The plans call for 1.5" thick transom. I'm guessing your Sapele is 4/4. If it were my transom, I'd make transom 1 piece of 3/4" plywood and laminate the Sapele to the plywood.

Motorwell size, I made mine in accordance with the Glen L motorwell deminsions guide with some minor deviations. The big deal is getting the steering rod to fit. The turning and tilting of the motor takes surprisingly little space. My decking overhangs the motorwell about an 1 1/2. It looks nicer an hides the rigging holes. only change I'd make is cosmetic, would have rounded the decking at the front of the motorwell instead of square corners.
Hope my pictures help,
Matt B
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Hercdrvr
Posts: 345
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Location: McKinney TX

Re: Malahini transom questions

Postby Hercdrvr » Mon May 15, 2017 4:12 pm

One more thing, I'd leave the transom height proud until you have a motor. Cut mine at 20.5" and wish it was taller stillo. I'm running my ventilation plate 1" above the bottom of the boat. If I find $750 in a jacket pocket I may buy a jack plate, different subject though.
Good luck, it's a challenge to put all the pieces together in your head before you have all the pieces.
Matt B
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