Side planking questions

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Thompson
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Side planking questions

Postby Thompson » Fri Feb 24, 2017 6:00 am

I'm building the Malahini. I'm sure this has been covered before on this forum. The side planking calls for 18' of ply for the sides. This means 2 pieces, one 8' and one 10'. Or two 8' and one 2'. One joint or two on each side. I can save little money buying 8' plywood. I'm planning to use okoume. The money saving is not really the big consideration in the over all cost. My concern is the joints. I know that some have had problems with the plywood cracking when wraping the frame near the transom. That's the reason I'm going with the okoume. Is seams to bend easier. I could be wrong. This is my first boat. If i go with 8' ply where is this best place for the joints. I plan on trying scarf joints. It seams there is more stress on the ply in the front and the rear. Stern , aft. Not sure the correct terms. Or do you put both near the middle. Or once the scraf joints are made it doesn't matter where they go.
The next question. I plan on leaving the sides bright. As i under stand. Scraf joint or butt joint, the joint will still be visible. I plan on staining the sides in hopes on making the joints less visible. I know sometimes putting a finish on raw plywood, even the same type of plywood, the color difference can be big. Staining i hope will help this. The question. I think I know the answer. Do you stain before you joint the pieces together if you use scraf joints or after. Does the stain, water base, effect the epoxy bond. Thanks
Lyman

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Roberta
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Re: Side planking questions

Postby Roberta » Fri Feb 24, 2017 6:22 am

LL Johnson's Workbench in Michigan sells the 4X10 Okoume in 3/8" and 1/4" thicknesses if you want to go the two piece route. Joints should be planned at the flattest location on the hull regardless of style. As discussed in another current thread, there are many ways to make the joints less noticeable. I've seen attractively made joints placing the two foot splice section on the three piece hulls in the middle of the hull where the panel will be the flattest. Okoume is less susceptible to fracturing during bending. Do the staining after the hull is ready for finishing. You can wipe lacquer thinner on the plywood to determine color compatibility. This will approximate what a clear varnish will look like on the wood and give you a better idea if the mating woods will be close in color when finished. Water based stains should not affect a glue joint, but if the stain needs any repair due to construction damage, it will be difficult to match, resulting in a blotchy stain job.

http://theworkbench.com/plywood.php#marineply

Roberta
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hoodman
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Re: Side planking questions

Postby hoodman » Fri Feb 24, 2017 7:55 am

On the side planking for my Geronimo I have two butt joints on each side. The rearmost joint is about four feet forward of the transom. I just split a sheet of ply in half and used one half for each side. Then the next sheet forward is about seven feet long. An eight-foot piece would have made the joint land too close to a frame to do a butt joint.

On the Malahini, you can soak the rear section with the towels/boiling water method. That should definitely eliminate any cracking in that area. I wish I would have soaked the forward section of the side panels. It would have made it much easier to bend. It works like a charm. You can scarf the panels but then you have one giant sheet that you have to screw on all at once. It has been done but not by me. Seeing the boats in person at the last gathering, I can tell you that the butt joints don't really detract from the appearance of the interior of the boats in my opinion.

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rbrandenstein
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Re: Side planking questions

Postby rbrandenstein » Fri Feb 24, 2017 10:18 am

I bought 10' Meranti from Homestead and used a scarf joint. Mainly because I wanted to try scarfing plywood. The joint should be between frames 2 and 3 as there is the least side curvature. I would agree with Matt that a butt joint is probably no more noticeable than a scarf... at least mine. Staining will make the color more consistent. I used a water based Mahogany stain from Minwax. It came in a tube, not a can.
It is a challenge to put the whole side piece on. I did it without helpers. I first mounted and cut the piece to shape to remove excess material. I then attached it dry and used steel screws to preform the holes to reduce stress on the SB screws. At the balance point I drilled a hole in the ply and chine and inserted a nail. After applying the epoxy coating and then the thickened epoxy I hung the panel on the nail and proceeded to find the predrilled holes and attach with the SB screws. I found a long, thin ice pick a valuable tool to find and align the holes.
Good luck.
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JimmY
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Re: Side planking questions

Postby JimmY » Fri Feb 24, 2017 10:47 am

FWIW...

If you are set on bright sides, you need to do some planning.

I did scarf joints on my Squirt, but they are covered up with veneer so I didn't spend a lot of time setting up a jig or getting them perfect. The thin edges are hard to hold flat and can result in a wavy edge depending how you cut them. I was working with 1/4", so thicker plywood may help here. Also, a wavy edge may help hide the joint if you are able to match the grain. Also, you will want the joints as flat and perfect as possible, otherwise you will have to fill/fair the joint with clear epoxy to get a smooth joint. My scarf joints had less than a 1/32 dip in them and I'll be applying another coat (7th?) over the joint tonight trying to level it with the surrounding wood. If I don't do this, you would see the dip under the glossy clear coat.

I used Behlen's Solar Lux dyes, which are alcohol based. With this dye, you can make minor repairs and if it doesn't look right you can wipe it down with denatured alcohol to help blend it in. I dyed my veneer before gluing it to the boat. If you get epoxy on the wood, the dye doesn't soak in like raw wood even after sanding it down. I would recommend that you stain the plywood prior to gluing the scarf joints, since it will be very difficult not to get some squeeze out when gluing the joint.

If you pre-dye the wood then:
1.) You need to use the same epoxy that you will glass and encapsulate with for the joint.
2.) You will want to avoid sanding the sides (so you need to sand before dying, but the Behlens is Non-Grain Raising).
3.) Need to avoid getting the structural adhesive on the sides (remember no sanding).
4.) You'll need to be careful with the screws and counter sinking. If they are showing you want them uniform, if they are painted over you can use fillers.

If you don't pre-dye the wood, you might consider the Interlux filler stains. These are oil based but appear to blend better over epoxy spills. You would need to coat with CPES before encapsulating.

Other options to consider, look up Art's Squirt where he covered the joint with paint but left it bright fore and aft. I don't think Art's stained his sides, and the Okoume darkens nicely under clear epoxy. This may be your best option if you can match the hue of the plywood sheets.

Nothing is impossible, just think it through and plan to do some test pieces and create some scrap.
-Jim
Nothing says poor craftsmanship like wrinkles in your duct tape!

Thompson
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Re: Side planking questions

Postby Thompson » Sun Feb 26, 2017 7:38 pm

Thanks Roberta, Matt, Bob and Jim. I value everyone's input. Matt how and what did you use to cut the plywood to get tight joints.
Thanks again.
Lyman

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hoodman
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Re: Side planking questions

Postby hoodman » Sun Feb 26, 2017 7:49 pm

Unfortunately I can't give you advise on tight plywood joints. I didn't end up with any. My side planking will be painted. I would clamp them up tight but by the time they were installed I always ended up with a small crack. I wasn't worried since I have intended to paint all along.

Hercdrvr
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Re: Side planking questions

Postby Hercdrvr » Sun Feb 26, 2017 10:27 pm

My side planking (Okume) exploded when I torqued it down dry.

Used a cloths steamer and trash bag to soften things up and took it easy as I bent it into position. Less muscle and more gentle gradual clamping.

Good luck
Matt B
Attachments
IMG_1077.JPG
Steaming helped things yield to the curve
IMG_1068.JPG
Big split in plywood 1st try

Hercdrvr
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Re: Side planking questions

Postby Hercdrvr » Sun Feb 26, 2017 10:31 pm

After wrestling with it for a week and a wasted sheet of $80 plywood, it bent into position
Attachments
IMG_1075.JPG
Success

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rbrandenstein
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Re: Side planking questions

Postby rbrandenstein » Mon Feb 27, 2017 10:59 am

Matt: that looks like 3/8", definitely harder to bend. The Malahini calls for 1/4" on the sides. Although, even with 1/4", I did get a small crack on one side when I attached it dry. I had to inject epoxy and jury rig a shaped mandrel on the outside and push clamps on the inside.
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Hercdrvr
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Re: Side planking questions

Postby Hercdrvr » Mon Feb 27, 2017 11:40 am

Yes, it is 3/8 side planking. A mistake on my part, I do not advise deviating from the planned material thickness.
Matt

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Bill Edmundson
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Re: Side planking questions

Postby Bill Edmundson » Mon Feb 27, 2017 1:36 pm

3/8 will be over 3 times as hard to bend than 1/4.

Bill
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bob smith
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Re: Side planking questions

Postby bob smith » Tue Feb 28, 2017 7:55 am

I suppose you could cut some shallow longitudinal kerfs in inside of the 3/8" and fill them with epoxy.
Just thinking....
Bob Smith
Chester, SC

Hercdrvr
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Re: Side planking questions

Postby Hercdrvr » Tue Feb 28, 2017 10:02 am

My mistake has hijacked this thread . Don't use 3/8 ply on the sides of a Malahini. 1/4 inch is correct

Matt B


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