Form building

[Curtis Haden]

More thinking out loud until my Bingham's order shows up...

Whilst out on my sander-buying lark the other day, I stopped by Grizzly and picked up a pattern-cutting router bit.  The bit has a 3/4" cutting depth.

I'm planning on getting a piece of high-grade 3/4" plywood and routing the limb profile from a template, then just using the original to pattern another piece.  Glue/screw them together, and I have my 1.5" wide form.

That should work, right???  I assume the Bingham plans will have some form building instruction, but right now I'm just dreaming and scheming from some half-remembered build-alongs seen in the past...

[bjansen]

I use a similar method...what i do is glue up the plywood first (i.e...to get 1.5 inches thick), then i take a short piece of MDF cut out my template (one side) and sand it smooth.  Then i screw that MDF form to the plywood, mark a line then go to the bandsaw to get most of the wood off close to the line.  

Then take your pattern bit and make the first pass riding on the MDF form you just made, flip that MDF template over on the other side and do the same.  Then take the MDF pattern off and your flushcut pattern bit will ride on the freshly cut surface you just cut on the top 3/4 of the form.  

Best of luck

 

[Apex Predator]

One note:  3/4" plywood does not measure 3/4".  I was able to make mine work though by gluing on my 1 1/2" aluminum strip.  I then used a small washer under my pivoting alignment washers so that they would pivot around the slightly wider aluminum strip.  Does that make sense?

[RAU]

Im in the process of building a form out of a 1 3/4" glulam beam. Im in the market now for a 2" depth pattern cutting bit. I bet your method will work. Probably a tiny bit better to cut the layers in one swoop with a deeper bit but probably not a real noticable difference if you take your time lining them up right?

[Curtis Haden]

Well, got the stuff from Bingham's today.  Actually came a day or two earlier than I thought it would.  The plans call for 3 sections of 1/2" plywood laminated together for the press.

 

Originally posted by Apex Predator:
One note:  3/4" plywood does not measure 3/4".  I was able to make mine work though by gluing on my 1 1/2" aluminum strip.  I then used a small washer under my pivoting alignment washers so that they would pivot around the slightly wider aluminum strip.  Does that make sense?

It does make sense.  I wasn't sure, but hoping that the AC grade plywood was at or very close to 3/4".  I considered the possibility of using some kind of very thin veneer to sandwich between the plywood to get a true 1.5" laminate.  I think (hope) I can get the form true enough to just use the formica strip that came in the kit for the lower form piece.

Still planning on using the pattern cutting router bit to get the profile.  We'll see how it goes.  Worst case scenario is that I'm out $40 for sheet of 3/4" AC plywood.  Oh.  Wait.  I guess that's $80 if I have to buy another sheet!  And then there's the sheet of plywood I have to buy for the oven...

                 

I could have bought a really nice bow on the Classifieds for what I'm going to have in this first attempt at building one.  Hope the first one turns out good enough to make me want to build another.  Oh.  Wait.  We're still in the form building stage...LOL!

[kennym]

Yep ,the pattern cutter will work,I just screw the template to the form(after marking the entire profile and bandsawing off 1/8" from the line),run it,then drop the fouter down and run on what you just cut for a pattern.

Never keep track of what you spend on this hobby!