Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: eman614 on January 17, 2009, 09:09:00 PM
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i tried your method for making the press for my bow, but when i got to the part where i move my form lower to use as a guide things didn't workout well. i don't know if i misunderstood your directions or not, but i measured the distance from the edge of the router to the bit, made a couple marks, lined up my form and clamped it, then began to make the cut with the router. first problem was that the bit didn't even touch the end of the press, but once i got to the middle of the first hump it was back on target. it seemed to do fine until i got to the other end of the form where it faded away again. in order to fix it i had to take some of the bend out of the limb. i was wondering if maybe you had some trick that i didn't know. thanks for the help.
eric
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Hmmmm..... If you drew out your limb profile and made the router pattern off it,it should cut right to your profile line.I marked square off the bow profile line about every inch or so,then connected the dots to make the pattern line. You can see where I was marking the dots on the pattern piece. Maybe I'm not understanding what happened..........
How wide was your form blank?
Feel free to call me sometime tomorrow,if you like.I'm about wore down tonite,hauled osage logs to the mill and then went to pick some lumber up at the kiln today!
Kenny
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You have to adjust your pattern to compensate for the curves. The more curve the more your template will be off. Think of it as a race track. The template edge would be the shortest "lap" and the router bit would be the outside car traveling the greater distance, even with the exact same spacing the entire distance, given the same vertical starting pts and stoping pts.
If you took your bow pattern and made a box. then ran you router around the outside. The line the router cut would be longer than the pattern length, changing the radius a little as you went. The less reflx/ deflex in the curves the less you would notice this.
Put a quarter on a peice of paper, trace around it. Now try and draw another line with equal distance spacing using the same quarter(radius).
Cant be done, best you get is a crescent shape. You would need a great radius to keep the equal distance.
When you router bit goes over a "hump it is making a larger radius. When it goes down in the curves it is shorting the radius
Hope this helps. Wish I could articulate it better. Took me a while to get my patterns right after I ran into the same problem. :thumbsup:
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thanks to both of you. tnstickn that made perfect since. do i need to change the shape of my form to fix it or do i just move my form differently.
thanks eric
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When I did mine. The area around the end of my limbs was very close. I measured the difference of the line of my pattern and the route that wasnt what I intended and corrected that amount. It took me a couple of tries with my quater inch pattern, but wasnt that difficult to adjust it till it was the same as my original drawings. After work tomarrow I'll find the drawings and lay my pattern on it so you can see what kind of differnce I was dealing with.
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Look at the 4th pic down here...
http://kennyscustomarchery.com/Bow_forms.html
The line on the plywood form is a different radius than the pattern,but the router will cut to the profile because the pattern is marked 2 7/8" - 90 degrees(as close as possible) off the line of the intended bow. You cant just move the profile line down or as Greg said,it changes things.
Hope this helps!
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I use a 2" bottom bearing pattern router bit for forms. Place your pattern where you want it and it duplicates it.
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PV, you are exactly right,I just used what I had!
That bottom bearing bit would make the pattern much easier to make,you could trace it right off the plan if you have one!! Old dogs CAN learn new tricks,just takes this one a while sometimes!! LOL
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thanks guys. you all helped out alot, i got the form made and, i am very pleased with the outcome. again thanks for all the help.
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Glad it worked out for ya Eric. If it wasnt for all the great guys and gals here on Tradgang, I would have never even started trying some of the stuff I can do now. Post us some pics of your bow when you finish!
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Originally posted by kennym:
[QB] PV, you are exactly right,I just used what I had!
I also Kenny
My first forms were built with a jigsaw, paper pattern, 1"drum sander chucked up in a handdrill and a whole lot of plastic wood!!!!
This old dog learned about the pattern bit from another old dog :)
Good luck with your new form enman614.Welcome to the adventures of bowyering.While not compulsory picture's are greatly appreciated ;)
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i'm not great with computers, but i'll try to figure it out and get some pictures for you guys