Tips on building a Form (Pictures of finished Bow added)

[rmorris]

Last week or so I noticed a few people had some questions on building a form. I had a new bow design I have been wanting to build so here is a build along of a bow form. I prefer the forms that use an air hose  so that is they style I will be building. This form is also for a one piece bow because they are much more complicated and that is where many people have problems.
I start off by picking up a 7’ by 9.5” of LVL beam from by local building supply store. This piece of lumber should only cost you about $35. LVL comes is 1.75” thick so if you are building a recurve it is perfect. I need it to be 1.5” thick so I give it a few passes in the plainer to get it down to 1.5”.
 
 
I then take a long strip off of a roll of butcher paper and tape it to a sheet of corrian (the counter top material in ½” thick) and draw out the design I want.
 
I then take a razor blade and cut out the limb shape also scribing the corrian.  After removing the butcher paper I trace the scribed line with a marker.
 

[JSMOFFITT03]

Thanks for sharing,   Always nice to see how others build there jigs/ forms.....

Looks good so far,  quick question,  how will the LVL handle in a oven?  Any worries of delamination with the heat of the oven?

[rmorris]

Jerrod, I have used the LVL in all my forms for many years now and have never had a problem. I heat each bow for 4 hours at 180 deg. and the forms have never flexed, delaminataed or had any other problems. if anyone has had any problems with LVL please let me know..

[rmorris]

In the last picture also noticed that there is a wedge I cut out of corrian , this will be used later to make the exact angle I need for the riser jig I also built. I then took the corrian over to the bandsaw and cut it out along the marker line. After a few more cuts on the table saw I now had a template for the radius part of the limb and one for the correct angel I needed. All I need to do now is fasten them together.

 

 I then took the radius part of the template and cleaned it up on the oscillating sander.

 

Now this is where things get a little tricky. I need to make sure that the two pieces of the template match up perfectly before they are connected together.

 

Now that they are lined up I take a small block of corrian and a few drops of super glue to attach all three pieces. Once the super glue has set I drill and tap the corrian and mechanally fasten all the pieces together.

[rmorris]

Alright now we have the template for ½ of a bow and it is time to make the form. If you look in the center of the LVL you will see a small blue rectangle of corrian that I attached and this will act as a guide. I drilled 4 holes in the template ( 2 in the radius side and 2 in the angle  side). I then made sure my template touched the guide with no gaps and then screwed the template to the form. Once properly fastened I used a marker to trace out the template on the form.

 

 

I then unscrewed the form from the LVL and got another small block of corrian and fastened it to the otherside of the joint on the template. Do not remove the original connection until you have the one on the other side drilled – tapped and securely fastened.

 

Now remove the original brace and you have an exact and opposite template for the other limb.

 

Once again place the template angst you guide block , fasten down and draw out the template with a marker.

[rmorris]

Now it is time to remove your template (don’t remove the guide block) and you have the pattern to cut out with you band saw or jig saw whatever you feel the most comfortable with. Make sure you cut on the correct side of the live otherwise you will be very angry with yourself.

 

Now it is time to pull out that pattern you made and re attach it to your LVL with the same holes you used last time. This will not give you a guide for a flush trim router bit to use.

 

 

After you have done one side you will to remove your template and place the original brace back on before removing the current brace. Now re attach the template to the other side using the original holes you made and use the router once again to cut the form.

 

 

[rmorris]

Now you have the hardest part of the form done and all you need to do now is sand out any rough spots and add fixturings.

 

I made this little sander and it helps me sand things that I need to keep square and not round edges. It is a little awkward to use but well worth the extra time.

 

 

Once you made you form perfect you have a few options. You can attach you hardware to use the c-clamp method or any other method you prefer or take the other half of that LVL you cut off the band saw and use it for the air hose method form.
 

[rmorris]

I now cut 16 of these ½” bamboo blocks and drill holes in them to attach them to the form

 

I them also drill all my guide holes for my bolt and washer system I use to keep everything in place for glue ups. Next I attach all the bamboo blocks and drill the holes in them for the hardware I purchased from Bingham projects online.

 

 
My wife’s cousin came over while I was working so I put him to work and here is a picture of him holding the near final project. Thanks for your help Bobby!

 

[rmorris]

Now last I will add  2 eye bolts so I can hang the form from inside my oven.

 

 

Now what I do is every time I make a bow with this form I will look over the bow very carefully for any imperfections or waves in the bow caused by imperfections in the form and try to sand them out before I make the next bow. After I get a few good bows with no imperfections I will glue a piece of fiberglass to the form and that will make it more durable.
Hopefully anyone who had questions about building a one piece form has a good idea on how to do it now and if you have more questions feel free to post them and  myself or someone more knowledgeable will answer them for you.

[monterey]

Thanks for taking the time to document this.  Every form build a long has a few new gems in it, at least for me!  

[bobzila]

thank you rmorris that is a big help to me.

[JSMOFFITT03]

Great job on the thread....   Can't wait to see your builds from the form....

[rmorris]

Alright so I just ordered a few sheets of black glass and I am going to make a bow on this new form. I could use some help on choosing the wood combination. My family has started refusing to help me with this process so I need some input. The first picture is what the new riser will look like, the options for part “A” are in the second picture and are cocobolo, bocote, marble wood, goncalo  alves, dalmatian wood, Bolivian rosewood, osage and curly maple. The  third picture is the options for “B” purple heart, wenge, walnut,marble wood,  Bolovian Rosewwod, zebra wood,  jatoba, padauk and osage . For option “C” anything listed above will work. Thanks for your help.

 

 

 

[dmikeyj]

A- Osage
B- Rosewood
C- Purpleheart

Its a light- to dark theme, could also switch B and C.

[Crooked Stic]

On form building one thing I do before cutting the two halves is drill the holes for the hardware.I made a jig out of hardwood (maple) about 2 in. tall with the hardware holes drilled on a press. Then attach it to the form with long wood screws. This lets you drill right on the bench and not have to wrestle the form in a drill press. Attach the spacer block ( predrilled) later by holding them in place with your hardware bolts. This method for me has prevented little line up tweaks on the dry run.
Thanks for the build a long. Our Menards has finaly started carring the good LVL. I will use it on my next form.

[rmorris]

Mike, that is a great idea because when it come to wrestling a drill press a drill press never get tired. I sat up my drill press next to my bench so the work area of the drill press and the bench was the same height. The bench was too low so I did not have enough travel to drill all the way into the 2.5" of form so I had to unload all the lumber off my shelf to get to my larger lengths and thicker lumber. I was then able to get my form high enough to drill the holes by placing my expensive lumber on the table and drill press work area and placing the form on top of that. I then had to make sure I did not drill into my nice 1.5" slab of Bolivian Rosewood. Your way sounds much simpler and I think I will try it next time. Thanks.

[rmorris]

Made a bow with this new form over the last week. I think it turned out pretty nice hope you enjoy the pictures. BTW I went with goncalo alves for part "A" leopard wood for part "C" and Bolivian rosewood for part "B" with an overlay of leopard wood. Hope you enjoy.

 

 

 

[jsweka]

Well done.  How's it shoot?  It looks like it would really zing an arrow.

[**DONOTDELETE**]

DuPont™ Corian makes some of the best router jigs and straight edges you can build. the cool part about that stuff is if you oooops and get into the stuff, you can build it back out with bondo and bring it back to glass smoothness.

I've actually looked into building the forms themselves out of laminated Corian. TD limb forms that is... a one piece form would weight too much.

Good build along there.  

[rmorris]

Kirk , I have also thought of making a form out of corian also.  The weight would be an issue but I have heated it up to 220 deg and had no warping issues. I have also thought about  making a template out the 1/2" stuff and then laminating it between 2 pieces of 1/2 " plywood and then using the router to cut off the excess wood. The LVL is just too easy and then I get to keep my template incase I need it again but it is always fun to think about new cool ideas.