Finger Jointed Plywood VS. The Scarf Joint

 

Has anyone used finger jointed marine plywood. I found a site in which you can buy 3,4,6,12mm finger jointed marine plywood. It is a little more that buying the 4 x 8 sheets and doing a scarf joint, but given the free shipping and the lack of labor, it really seems like a good buy.

 

Your thoughts?

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Permalink Reply by Christian Lazarides on June 15, 2011 at 2:26pm

By the way they come in 4x 12,16,20 foot lengths. and can be shipped to your door.

 

Permalink Reply by Lawrence E. Long on June 15, 2011 at 3:44pm

Christian:  I have never used a "factory" scarfed piece of PW.  There have been several reports on this site and another about failures of "factory" scarfed joints.  You don't know what the glue is- donn't know how the "finger" joint is made- any piece of finger jointed wood I have ever seen was made  from smaller sections and did not hold up.  How do you finger joint 6mm PW?

Being a cheap old SOB I much prefer to make my own scarfed joints, know what the glue is and if it fails it is my fault and I can try again.  This is not rocket science- learn how to plane a scarf and glue it properly with epoxy.  You will get much advice from the forum as to how to do it properly.

If you get a factory scarf and it fails  while installing a panel on the boat what do you do?  Call the place, wait 2 weeks for a replacement- argue with the MFG  as to what you did wrong to cause the failure?

In this day and age who in hell ships plywood for "free"?

 

Learn to scarf.  Good Luck

Permalink Reply by Dave Z on June 15, 2011 at 8:04pm

I'm with Lawrence.

 

Scarfs aren't hard to do.  Just have patience.  Shortcuts don't always pay off.

Permalink Reply by Mike Baker on June 16, 2011 at 2:38pm

Hey Christian,

I assume you are talking about the sheets CLC boats sells. A couple of things, I too am intrigued by the finger joint scarf. They claim to have never had a failure but the build Kayaks and the such, far less abuse than our drift boats.

Next, I hate to burst your bubble but there free shiping does not include plywood.

If memory serves those sheets are Okume which is far less durable (and more expensive) than Meranti or Fir. I bought one sheet of Okume when I bought my last supply of Meranti cuz the Meranti was super dark and I wanted the lighter Okume for rub strips and seat backs for the contrast. The Okume is amazing, absolutley PERFECT in construction and much lighter. But like I said not as durable.

Mike

Permalink Reply by Christian Lazarides on June 16, 2011 at 4:23pm
Mike,

Yes you burst my bubble, but fortunately I am just going to do the scarf joint. I have a bunch of 1/4" plywood to practice on. I do have a a question. I just got the Drift Boats and River Dories book today. I have decided to build the Origianl McKenzie Double Ender w a Transom. It calls for 16' plywood, if I scaf joint two 8' sheets it will knock off 3" of my needed 16', what are your thoughts here? Should I butt the sheets and spline them together? Or will it be ok to be a couple inches short
Permalink Reply by Mike Baker on June 16, 2011 at 5:09pm

No problem on the 3" shorter. you might have to slightly adjust where ribs one and/or two go. You can also use the cut offs from the bow cut back scrap to make an additional scarf at the rear of the boat to get the whole 16'. This is what I usually do. The instructions on cutting a scarf in Rogers book are spot on.

Mike

Permalink Reply by Eric Loudenslager on June 18, 2011 at 6:46pm

One of the primary reasons to scarf the plywood is to create a smooth transition from one panel to another, essentially producing a 16' panel.  If you butt join them you will have a hard spot when the panel is bend to shape.  Whether or not the finger jointed panels resolve this problem is not clear from the discussion.  If the panel was not bend to fit the sides of a drift boat finger or butt joints would be fine.  Some wide (54 and 56 inch) drift boat bottoms made of plywood are butt jointed, and held in place during glueing with a spline.

 

Lots of ways to solve all these construction elements.

 

 

Permalink Reply by Dave Z on June 19, 2011 at 5:57am

Christian,

 

You will end up with 15'8" or 15'9" depending on your scarf ratio.

Just build the boat, without a transom, then build a transom to fit after all frames are done. 

Permalink Reply by Christian Lazarides on June 19, 2011 at 8:44am
That being the case, wouldn't that throw off all the height dimensions?
Permalink Reply by Frank R on June 21, 2011 at 5:42am

The fiberglass butt joint is a simple way to join two pieces of plywood smoothly without scarfing:

 http://www.instantboats.com/gbj/index.html   Scroll down to see the original article.

 

You will not lose anything in length like a scarf will cause.

Permalink Reply by Andrew on June 21, 2011 at 5:53am

Thanks for that Frank.

 

I am just about to join up the bottom panels of my skiff.  I was planning on using a  strapped butt joint, but the straps did not line up where I wanted them under the benches so I was considering a FG butt joint. 

 

The wood I am using is faced with aluminum so the aluminum will be over lapped and screwed as well. Since the bottom of the skiff is nearly flat there should be no concern about being able to bend it evenly.

 

Andrew

Permalink Reply by Christian Lazarides on June 21, 2011 at 6:10am
Aluminum faced plywood? Where did you find that? What Ga. Is the alum?

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