More on bow forms

[kennym]

Just added a form that we built today to my site.
You can see it here....... The bottom one..
  http://kennyscustomarchery.com/Bow_forms.html  

This one uses a template and router made to the actual profile of the bow.

[Dick in Seattle]

Kenny.... very nice presentation... makes me think I might be able to do it.

[PV]

Nicely done Kenny.I use the same technique.With a 2" pattern bit and 1 1/2" thick laminated beam.

[Dmaxshawn]

Thanks for the info Kenny.  I have bottom mounted bits I am glad I looked at that as it will make things alot easier.

Shawn

[BMN]

Nice job Kenny. Let me know how that MDF works out. I'm thinking of using it myself.

[eman614]

thats a sweet looking form kenny. hope the mdf works well for you. i used it on my form and it seems to work well. it's nice that it is actually and inch and a half instead of something just short of.
eric

[kennym]

Thanks guys,one thing I forgot is to make sure the template is really flush at center when you flip it!
I think the MDF will work fine,and it isn't warped like plywood either!

[PV]

Originally posted by kennym:

I think the MDF will work fine,and it isn't warped like plywood either!

I'm hoping it does Kenny.
Had a microlam form warp on me today. Fourth bow out of the form (R/D) Set the bow on the bench and she rocked. First three were perfect. Form still reads square on the glueing surface. The whole micro lam warped. Took me a couple of hours of head scratching to figure it out.    Doesn't take much to throw the bow off.

[eman614]

what did you use to glue the mdf together?

[kennym]

PV, is that common on MDF?  This is my first experience with it.

Eric,Not sure on the glue,my bud Kerry glued it up at his house and brought it over. Maybe he will be along and tell us what he used.

[PV]

I don't know Kenny.Haven't tried it in a form. I think once the MDF is glued up it shouldn't move.I use MDF for all my templates and base plates for jigs.

The form that warped was a microlam or LVL is another name for it. Basicly 12 ply 1 1/2" thick plywood.Extremely stable most times. This one had some bad glue joints in it. Didn't think it would be a problem. Usually isn't

[wihill]

MDF (Medium Density Fiberboard) is compressed cardboard.  I made countless, countless speaker boxes from it in my youth.  Could have started a job with it actually...

Provided it doesn't get wet and swell, MDF is very ridgid and stable.

We used to coat the insides of the larger speaker boxes with FG resin and sand to strengthen them up, and the MDF would just eat up the resin.  Once it finally cured up it was almost as strong as concrete I swear...

Heavy stuff, and makes an ungodly mess with a router (very fine particles), so make sure to head outdoors or wear a good mask when you're cutting it.  You'll have dust in the garage for months.  

Have you guys ever thought to use birch lam plywood?  I found it to be very stable, straight and incredibly stiff - just very very expensive.

[Walt Francis]

PV,
Are you putting a 5-6 foot x 1 1/2" angle iron on both pieces (top & bottom) of the form to keep it from moving / bending laterally?  I did this with the forms I made from LVL and haven't had any problems.  LVL isn't as stable to the sides and if it bends, even slightly, it could cause the twist in the limbs; most likely at the narrowest part of form, which is mid limb on most forms.  If you do not use angle iron it might be important the form is standing straight while in the heat box during curing and not leaning on the side of hte heat box.

 
As Wihill suggested, birch lam plywood would work fine but is a little expensive.  If you want to try a different type of material that is less expensive (I get them for $18/ sheet) for your forms, the building industry recently came out with a new subfloor material called ADVANTEC.  It comes in 4' x 8' x 3/4" sheets and works similar to plywood but is heavier and more stable.  I built a new form out of it last week but haven’t had a chance to actually test it with a bow, but so far I like it better then the LVL.  Not all lumber suppliers carry it so you may have to call around to locate a local source.  The main reason I am trying this material is all my bows are 1 ½” wide and it is easier to glue up a bow on a form this width then the 1 ¾” LVL.  That and the fact I am frugal (okay cheep) and I get the material from the scrap plies for free at my projects.
Regardless of the wood/laminate used, angle iron should be used to insure the form is straight and remains that way while in the oven.

[monterey]

I used chipboard once and it worked out pretty well.  I came across some stuff that was 3/4" true dimension and lammed it into a true 1.5 form.  It's stored in an unheated but weathered in shed and is holding up fine.

I like the MDF idea and since a new form is needed in the near future it's going to get a try.

[PV]

Thanks for the tip Walt.Was planning on using it on the next one. This is my first one piece form. My other LVL forms are takedowns.There are base plates on the bottom to keep the form upright and for clamping to the bench. I can see where the longer form is more susceptible to warping.Are you running the angle iron up as high as you can on the form or bolting it to the side at the bottom for a base?

[Walt Francis]

I bolt it to both the bottom and the side.

[PV]

Thanks for the help Walt. Nothing wrong with going green and recycling.We've the avantec here also. I like the LVL's (altough not all are created equal)and want to continue to use them. A couple of runs through the planer and you've got a trued up form. Call me lazy but I get enough glue action with the bows  

[TNstickn]

I started screwing a piece of angle Iron to the bottom and sides in the hopes to keep'em from warping in between uses. Dont lean your forms on anything. All plywood, microlams, anything made of wood will warp if left un supported. You also might want to seal'em up with some poly. Humidity will wreak havoc on wood more than anything, except leaning it in a corner.

Kenny, your site keeps gettin better and better!!
Whats that osage edge grain look like??

[kennym]

Hey Greg,I don't have a pic of edge osage,here is edge and flat red elm, the grain color diff on the osage is not so pronounced as in the red elm edge....

 

[Cupcake]

I have built both my one-piece and take-down forms from MDF using carpenters wood glue, Tite-Bond II or III or Elmer's.  They have worked great and the true 1.5" width has probably kept the swear jar from getting too full.  I hang my forms on the garage wall using a big hook like the kind one would use to hang a bicycle.