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Scarfing Jig WAR Style

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Will Aldridge

Well-Known Member
Joined
Oct 30, 2009
Messages
997
Location
Northern Utah
The weather has finally warmed up enough that it's pleasant to work in the unheated shop(although it's snowing as I write this). I'm getting ready to put the plywood on the faces of my main center spar and that means I had to set up for scarfing. Since I bought the plans for and integrated major portions of the WAR replica Corsair into my design I decided to try using their method for scarfing. I am a very tactile learner and it took me about 10 times reading the instructions before I figured out what exactly it was saying to do. Being a tactile learner I need to be doing it as I am reading. So here are a few pics that might make it easier for the next guy to understand.

First off here is the text and diagram for making your own scarfing jig from the WAR manual:
IMG_0717.jpgIMG_0720.jpg

1. First part is fairly simple: Clamp a piece of plywood to your table saw with the blade retracted. Set blade to 5 degree angle and turn on the saw and raise the blade so it cuts through the plywood as it's being raised (raise the blade all the way).

2. The remove the plywood from the saw and attach a fence right next to the slot in the plywood. The manual said to epoxy the fence in place but I used a bunch of screws instead. Then reinstall the ply and fence back on saw and clamp in place.

IMG_0711.jpg

3. The next step is to make the other fence to sandwich the ply. What took me the longest to understand was that you needed to attach a piece of plywood to the bottom of the second fence so you can screw it down to the first piece of ply. There is no way to accurately place and clamp the jig on the saw with the second fence in place. And you can't secure the second fence in place without the having the ply to screw to the jig. A rare instance of easier done than said.

IMG_0712.jpg

4. The jig must be set for the thickness of ply to be scarfed so here I have a scrap piece of 6 mm ply. The second fence is pushed up against the ply and screwed down.


At this point I tested it out but I forgot one crucial step. If you look at the WAR diagram #6 shows a guide strip stapled to the ply to be scarfed that rides on top of the fence. Perhaps not necessary if scarfing a small piece but I tried it out on the side of a 5 foot long scrap and you see the results below.

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The above is the first 2/3's of the scarf. Not great but makes me think I'm on the right track.
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The really ugly portion of the scarf is seen above. Part of the reason is the lack of the guide strip and part is the fact that enough of the ply was hanging out in space on the far side of the saw (I was attempting this alone) and the weight of the material hanging in space pulled the material still on the saw up and as I pushed it down it made the ugly scallops. My saw is also on the cheap side and not very powerful and I suspect I need a new blade. In any case the cut took a long time and ended up with the saw jamming up with the piece shown in the pic below.
IMG_0715.jpg

So what are the tolerances for scarfing? Is the first few feet of my scarf acceptable? I'm guessing the answer might be in AC 43 if anyone can point me to a specific page I'd appreciate it.

I really need to build some extensions for my saw since I anticipate I will be working solo for 99% of the project. I get the impression this method was designed to eliminate the need for a router or other tool. Working in the vertical is harder I would guess than having the ply flat on the table. So my recommendation is if using this method to cut your material so you have the smallest area to scarf that you can get.
 
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