Curved Panels - adding another dimension to woodworking. #3: Building a better form for curved panels - 201

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Blog entry by John8059 posted 02-22-2009 04:52 PM 1355 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 2: Building "flat" curved cabinet doors - 101 Part 3 of Curved Panels - adding another dimension to woodworking. series Part 4: Easy Does It - curved panels without a vacuum press »

In Part 2, I introduced the materials and methods. I mentioned that my form had a serious drawback and here I hope to explain why and send you down a better road. Here is the project – at least part of it:

The edges of the panels come out of the bag looking pretty rough. I can’t think of a way to coat 5 sheets of bender with adhesive, stack them perfectly, and keep them stacked perfectly into the bag and through the vacuum process so when they come out you have perfect edge. Even if you could, it is not like you can put a square on it and get a second side at 90 degrees to the first. My solution was to build the form in such a way that I could use it as a guide to put the edges on all the panels that came off of it. Here is how I did it.

Above you can see the beginning of the construction of the form. Using a method similar to that explained in Part 2, I produced a number of identical ribs. Working on the flattest surface I have (it is under the form and perhaps the subject of another blog), I added one rib at a time. Each rib is forced to be perpendicular to the base and parallel to the next by spacers that you can barely make out below the clamp. Ditto on the ends of the ribs which are spaced about 3” on center.

Once again, using left-over pieces of bender I built up the curved surface of the form to about ¾”. This time I got cheap and lazy and decided to use old yellow glue and a pin-nailer to hold the bender in place. I thought I was being careful to get the sheets down tight and all the air out from between, but I ended up costing myself a tough week of sanding and re-shaping.

Now I would have blocked the surface out like this anyway, but it was really bad. So bad I actually had to add bondo to fill in the lows. Here you can see how my auto body-work experience really helped out.

Unfortunately, my block didn’t apply as much pressure as the vacuum bag and the panels I took off the form were horribly wavy. I burned up a lot of time, sand paper, and bondo getting them straight. Like I mentioned in part 2, YOU MUST USE YOUR VACUUM SYSTEM TO APPLY THE BENDER TO YOUR FORM!

For what it is worth, here is one of the panels cooking in the vacuum bag. Notice the bucket of urea formaldehyde glue in the upper right corner and that it has an orange label if you decide to use that product. Also notice I don’t have gapping holes in this form for the bag to get stretched over. I do have holes in every rib to allow air to easily escape.

OK now the good stuff. You’re looking at the form upside down. Notice the marks indicating that those are the corners I really concentrated on getting square. When I put the ribs together, I was very careful to get them perpendicular to the base. At this point, I cleaned up the side and end bender surfaces of the form to match the surfaces of the outer ribs and base ends. So what I should have there is a 3D object that is both square and plumb on one end and 2 sides.

Above I have attached one of the panels to the form with screws so that one side and one end overhang the form. I used a piece of bender lay-up I made on top of a panel (because the radii are different top to bottom) to adapt the router base to the shape of the panel. (I could have made it a little thinner as you can see the bit is protruding dangerously from the router).

Using the side of the form as a guide, I was able to put a straight 90 degree edge on a panel in moments. With the panel’s end hanging off the form, I was then able to trim the end at 90 degrees to the side.

BTW – the center bender board here is really 3/8” thick (not 1/4”). As I mentioned in Part 2, the thicknesses are not what the descriptions state and you must plan ahead for this. Total thickness of this layup is actually 0.78”. Before doing this again, I would try to find a longer ½” shank bit but it worked. I had my fingers crossed the whole time and I was wondering what a hot bit in my gut would feel like. I did it in many passes; although, with the correct bit you probably could knock the whole edge off in one shot. Still attached to the form, you see the result below.

When assembled, the front of the lectern stood perfectly plumb and the top and bottom edges were level for attaching the feet and upper mouldings.

The “un” finished product:

You most likely will need different angles on the ends your panels as I did for the bottom edges of the table sides shown above. At least I had something to reference by sticking to what I showed above. I’m sure you will have no problem modifying the form, creating router base attachments, or coming up with an entirely different twist to this. I am looking forward to hearing your ideas and seeing some more curved projects out there.

-- Cuz

4 comments so far

View kiwi1969's profile


609 posts in 2862 days

#1 posted 02-22-2009 05:05 PM

when you break it down like that it seems a lot less complicated than i thought.Thanks

-- if the hand is not working it is not a pure hand

View cabinetmaster's profile


10874 posts in 2978 days

#2 posted 02-22-2009 06:09 PM

Another great post. Looking forward to the next.

-- Jerry--A man can never have enough tools or clamps

View firecaster's profile


570 posts in 2839 days

#3 posted 02-22-2009 10:09 PM

That was a facinating process.

And a beautiful end result.

-- Father of two sons. Both Eagle Scouts.

View SCOTSMAN's profile


5839 posts in 3005 days

#4 posted 02-22-2009 11:08 PM

Great job well done !! This is an interesting process.Alistair

-- excuse my typing as I have a form of parkinsons disease

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