buildingform

Note: This page covers the building of my original form, but has an update section at the bottom covering, more briefly, the making of my second form and updating of the original.)

I have a double form that JD Berry provided me, which makes a 2" deflexed flatbow on one side and a 1 1/2" reflexed Hill style on the other. I can "flip" either of these if I"m willing to attach a riser after the basic lamination is complete. However, I wanted the experience of building a form and I wanted to try a dead flat bow, since that is something I couldn't make off of the existing form. Part of my motivation was because I found it a pain in the whatever to make a curved riser. I've done two and may go back to that, especially if I do some R/D's, but for right now, I'm deeply into simplicity, and a flat bow with a flat riser on a flat form appeals, so why not?

I also have a complete set of 4" clamps, the standard kind that are called "C" clamps but really aren't, because the top of the C is flat, not hooked, so you have to have a flat, parallel under surface on the form to use them well. I had seen a couple of examples of an application in which 3 way edge clamps were used on bow forms by removing the bottom two screw clamps and running pins through those screw holes and through the form. I really liked the way it looked like this worked, so, again, why not?

I have also seen a couple of examples of machined aluminum forms. Now that's getting advanced! I wasn't prepared to go that far, but it occurred to me that if you're going to have a flat form, you really don't need to go to great lengths to produce a perfect, flat wood surface when there are people who will sell you a flat aluminum surface. For my flatbow, I like a 2" form and 2" glass. For Hill styles, even though most folks use a 1 1/2" form and glass, I think I'll prefer 1 3/4". This is what Louis Armbruster used for all his Hill styles, and he claimed to have made thousands of them. The advantage, as I see it, is that you won't be working so close to the edges when you band saw. Probably something that doesn't need to be worried about, but, hey, I worry...

So, I set out on this project. First thing was to get the clamps. I lucked out there, finding them on sale for $3.49 at the local Harbor Freight. I bought 36. The bottom clamps had to be hacksawed off and the necessary pins had to be cut.

A 3 way edging clamp before modification.	Clamp one of the bottom screws in the vice ...
and saw off the flexible clamp button. One down, only 72 to go. Notice the rigid frame Kobalt hack saw I treated myself to for this job. Great tool!	The finished "conversion"... a 3 way edging clamp is now a bow form clamp. The threaded hole for the screws that were removed is 3/8". It turns out that a 5/16" rod slips right through those holes, without drilling out the threads. Others have drilled these holes out to 7/16" and used 3/8" pins. That seemed excessive to me. I can't see 5/16" pins not being adequate. Note: As you'll see later, I was awfully glad I didn't drill out those threads! They came in handy to bolt hangers onto some of the clamps to increase their depth for use in the riser area.
Here's some 5/16" cold steel rod put into my 4 1/2" vice, 1/2" protruding. Cutting at the left edge of the vice gives me 5" pins for the clamps. I need 36 of these pins. Now you can see why I value a quality hack saw!	A nice little carpenter's box holds the clamps and pins and keeps them organized. Of course, I can hardly lift it!

Next step was to hunt up the aluminum surfaces I wanted on the form. The 2" was no problem. A local metal supplier provided me with a 6' piece of 2" aluminum channel... that's 2" on the top and on each side. Since the material thickness is 1/4", the inside channel is 1 1/2". I envisioned using two thicknesses of 3/4" plywood to provide the wood basis of the form, but discovered that 3/4" plywood is not 3/4", but is undersized. To get a true 3/4" you would have to use one piece of 3/4", one of 1/2" and one of 3/8". Anyway, I gave up and just bought a 2x8 pine plank.

As it turned out, things still didn't go together without effort. I'm not sure whether the channel was a bit small or the plank a bit large, but the fit wasn't an automatic drop in. This actually turned out to be a good thing, because I was dying to try my new Grizzly overhead drum sander. I was concerned that some folks have reported that its power draw blew their circuits, and my garage shop circuits are not robust. I figured that if the machine was going to trip a breaker, running a full sized 6' 2x8 plank through it would show that weakness right off. As it happened, the dust collector was also on that circuit. I started to plug it in on the other side of the garage, and then said, "Nah, let's go for broke... Then we'll know." So I hooked up the collector and turned that on, then turned on the drum sander. Whoa!!! The Grizzly drum sander is so quiet that we didn't hear it over the dust collector, which I consider to be one of the quietest ones of those I've seen! Wonderful. But, what would happen to the circuits when the load took on the plank? Nothing.... Not only did it handle a sanding pass on the plank, with the dust collector hooked up, there was absolutely no sign of sanding dust in the shop... I mean, not one floating mote! Yay, sander; yay collector; yay circuit!

So, OK, I now have a plank that drops snugly into the inside of the 2" aluminum channel. Just to guild the lily as far as the fit goes, I ran both the top and bottom of the plank through a jointer to insure right angle flat surfaces. I then ran the plank through the table saw on a 45 degree angle to just slightly trim the corners that would go into the channel, to insure inside clearance.

The next concern was the bottom surface, which I want to end up as an aluminum covered 1 3/4" surface. This proved more difficult. It seems that no one manufactures an aluminum channel, el angle or even an aluminum strip, that is 1 3/4" wide. They make 1 1/2" and 2", but no 1 3/4". I accepted that there was no channel that would provide just what I wanted. I considered an angle, but I would have had to pay a very healthy fee to have the 2" side machined down to 1 3/4". I may still have that done in the future, but for the moment, I settled for an aluminum strip that is awfully light, 1/16", that a local roofing company was willing to custom cut for me for $20. I would really have liked to have 1/4", so that I could taper sink screws in the surface to hold it onto the form, but that was the thickest material they worked with. For the moment, I'll have to settle for epoxying it on.

The simple part of the problem was getting a 1 3/4" surface to the wood on the bottom side of the form. I just cut a piece of 1/4" plywood the depth of the 1 1/2" plank up to the channel lip and laminated it on, thus ending up with my 1 3/4".

Here's the 1/4" plywood in position where it will be glued. If you look closely at the plank in the channel, you can see where I trimmed the upper corner edges at a 45 degree angle to insure that they'd seat fully into the channel

The holes for the clamp pins will be drilled 1 1/8" below the surface of the top and bottom. On the top, they will go through the aluminum. On the bottom they will go through only wood.

I liked the idea of the lamination on this side of the form. You can see the start of a check in the end of the plank. That doesn't go far, but the lamination seemed a good idea, and a good idea bears repeating... so I cut another piece of 1/4" plywood for the other side. On this side, I couldn't go all the way to the top, or I'd have ended up with a 2" thickness instead of the 1 3/4" that I had gone to some lengths to get.

Here's the fully laminated side. The dark dots are drywall screws holding the lam on till the Titebond III dries. The form is standing on the 2" channel side, and the aluminum strip that will be the 1 3/4" surface is lying on the top. If you look carfully at the lower left end, you can just see that the other side is also laminated, but the lamination stops 2" from the surface, so that the 1 3/4" surface remains 1 3/4" and the clamp pin holes will be the same height on this surface as on the 2" surface.

Here's another view of this "off side" showing the partial lamination.

That pretty much brings all the work up to date. The next operation will be to actually attach the channel with screws from the sides, and the strip with epoxy. I also still have to drill the pin holes, but I already have the pattern laid out for that.

A further report will be made when I complete the rest of the work. So far, I'm really pleased.

Dick

Following Day...

The biggest single part of this job involves drilling the holes for the clamp pins. I have only a small bench top drill press and the holes have to go through 1/4" of aluminum, 1 1/2" of wood, then another 1/4" of aluminum. The form is very heavy, and since I kind of thought it would be nice if the holes went through at true right angles, I had to rig a way to handle the form's weight and still be able to feed it through the drill press. My shop is small, and when I put it together, I made sure that all machines were either on their own wheels or were on shelves where they could be slid out onto a moving work table. For this job, I moved the drill press, on wheels, out ot the middle of the garage and then set up an outboard support roller. Unfortunately, the roller did not raise high enough, but I had a handy section of hollow core door that just made the difference and allowed me to set up and level the form for drilling. I could only drill the holes in one end and one side at a time, then had to rotate the form and/or move the support roller to the other side. All of the drilling through the aluminum had to go slowly, with lots of raising and lowering of the bit to clear waste. It was all a bit awkward and involved, but I went slowly, took basically the whole day to move leisurely and make sure I was thinking ahead, and it all worked out.

The drill press, which is mounted on a roll around cabinet, has been moved out to the center of the garage to provide the space needed to handle the form. Height has been basically adjusted (note the hollow core door section).	As noted, I did feel that truly vertical holes were good, so I made sure the whole rather jury rigged setup was level. The drill bit bears mentioning. I bought a new DeWalt 3/8" pilot point bit, and was very glad I did. The pilot point definiteley helps.
This is where I discovered that the available depth of the working surface of the drill press is not adequate to drill both lines of holes in one setup. You just can't reach them. I'll have to drill the holes on one side of one end, then then turn the form, then move the support to the other side of the drill press and repeat... four setups and operations.	As soon as the first two holes were drilled, of course, I had to test them! This is what the clamping setup will look like in use... direct overhead, centered pressure. Note also the screws along the lower edge of the channel. I drilled the holes for these as well. The screws are what holds the channel to the wood. At this point they are only installed on one side, since they are large head cap screws and the underside of the form has to ride level on the drill press work plate.
Here's the form at this point. The upper, 2" channel surface is installed and all pin holes are drilled. The only thing remaining is to install a 1 3/4" surface on the opposite edge. (see note on this below).	Something to note here is that I drilled ten extra pin holes in the middle of the form, from the center outwards. These, when combined with clamps that have hanger extensions on them (work yet to be done) will give a great deal of flexibility in handling different sizes and shapes of risers. (Note: What appears to be an entire line of holes down the center is actually, except for the ten pin holes noted above, just the head craters left when I removed the drywall screws that I used for laminating the plywood on)
Here's some detail that may help you understand what you're looking at. You can see both rows of pin holes top and bottom, and the screw heads holding the channel in place. I have also added a couple of pin holes on the end of the form. These are for clamping a vertical wood block on the end to keep full length lams from slipping outwards. If working with shorter lams, you can obviously clamp blocks for this purpose to the top edge. You can also clearly see the smaller screw head craters I referred to above running down the center of the plank.

Note re my search for 1 3/4" aluminum strip. I'm still frustrated that the aluminum I have for the bottom is so thin. Today I decided to see just how hard ti would be to remove 1/4" of aluminum from a 2" strip. I dug around in my knife making draw for some aluminum scrap I knew had been in there a long time, and found it. Guess what... it's 1 3/4" by 3/16"! The darn stuff does exist. All I have to do is find a source. So, Monday, I'll rattle all the metal cages I can find in Seattle. Installing this piece and making the hanger extensions for the clamps that will be used in the riser area is really all that's left to do.

Dick

Not that much done today, but what was is important. First, I was successful in getting a piece of 1 3/4" x 1/4" aluminum 6' long to face the bottom side of the form with. I had to have it cut from stock, and had to draw file the cut edge smooth (or mostly smooth). Going across town to get it and then filing it took up a lot of the day. Tomorrow I'll get it installed, which will be the final piece of work.

The other job for the day was to cut up some 1 1/8" steel "hole strap" I got last night and install it on 8 of the clamps as hangers or extensions. This will allow for the extra depth needed for the risers, and also for angle clamping in the fades. If you recall, I chose not to drill out the 3/8 threads from the clamps.... good decision! I bought a supply of 3/8 cap bolts and the hole strap, and cut eight four inch pieces and eight six in pieces and attached them with the cap bolts, which threaded right into the bottoms of the clamps.

Today saw the finish of this project, which has been a bit more than I thought it would but has been really enjoyable. What was remaining to be done today was to attach the aluminum surface to the 1 3/4" side. I found that the folks who had cut the aluminum strip for me had actually cut it about 6' 3/16", so it stuck out off of the end of the form. This bugged me so I carefully hacksawed off the excess. I then positioned appropriately sized holes for #10 x 3/4" flathead screws, drilled those and then chamfered them to sink the heads below surface.

Once the strip was fastened to the plank, I mixed up some Bondo and applied it in two coats, smoothing and sanding between each. I now have a nice surface to apply tape to before starting a layup.

Well, if you've gotten this far, thanks for taking the trip with me. It's been a great project for me. Now I have only a few "big" thinkgs to do before actually using it to create my next bow. I have to make a set of lams and make a riser, and I think I may have a good idea for rearranging the shop so that the oven can have a permanent home that is readily accessible. However, before I can start on these things, I have to make good on a promise to post a mystery quilt for my quilting site folks. That will be a two day job, but I think I can safely say that I can have all of this done this week and be laying up a bow Monday or Tuesday...

I'm one of the few builders who seem to actually favor flat forms. They're kind of looked down on in many quarters as being too simple, kind of an easy way out, but I like them. I like and am making straight D bows, and there are those that favor these with a bit of deflex, and those that favor them with a bit of reflex. Both provide desirable features and good results, so I figure that compromising between them can't be all bad and I'm liking the results that I get. All of my bows that have found their way into other hands have received approval, so there you are. My old form (above) has one side with a 2" top and one with a 1 3/4" top. I don't like to do a layup on a surface that's wider than the limbs as it seems to invite lam shifting, so I wanted another form that would be for working with 1 1/2" glass. That's the new one.

I do have forms with both reflexed and deflexed surfaces, I just haven't been using them. I make my flat forms by using aluminum channel on a plank. For this one, I got some 1 1/2" alum channel, 1/8" wall thickness, and a nice clear fir plank. I planed the plank to a snug slide fit inside the channel, then proceeded to fasten it on and drill the holes for my clamp pins and for what I call "crib fingers" to hold the riser and limbs in alignment.

The most time consuming part of the job was making the crib fingers. I cut them from stock, rounded the finger ends on a little grinder and drilled screw holes in them. You can see that some are longer, for the riser area..

Here's the form, with the channel installed on top, holes drilled in the channel lip for the clamp pins and the crib fingers installer, but in the down position. A series of holes drilled in the plank below the aluminum lip, combined with clamps that have extension hangers on them, provide for clamping any angle needed on the riser fades.

These two pics show the crib fingers up, for lamination retention. On my original form, I had been using washers, but I didn't feel they were high enough.

Since I was, in effect, "in the area", I updated the old form as well, adding the new longer crib fingers to both of its surfaces.

My oven is on wheels, and in order to provide stability, I put the wheels on "outriggers", to extend the base. Today I added lips to the outriggers, providing a nice storage place for forms. I did the back outriggers, as well, so there's room for more forms.