I have mentioned in another post my ongoing Frankenbow project, an experiment in maximizing the potential of a 1977 Polar LTD compound for a second life as a recurve. I launched this project after a post and some photos by another Trad Ganger of a couple Polar compound risers with bolted-on limbs that he was giving to the grandkids as practice bows.
Some of you may remember the Polar II and Polar LTD's as engineering masterpieces in the wild and crazy explosion compound technology for the masses. It had round wheels, four additional pulleys mounted on adjustable brackets that bolted into a magnesium riser, and draw length could be adjusted from 26-32 inches and draw weight from 25-65 pounds . But it sounded like a farm gate opening up when you you drew back and by 1980 I would have paid someone to haul it off.
I started with a lefty bow spray painted with three colors of flat camo paint...the original riser is a shiny black and silver pebble finish. Figuring I would lose some weight due to a less steep limb attachment angles, I found a pair of like-new Samick Sage limbs rated @ 60#. After disssassembly, I realized a simple bolt on wouldnt work ...the orignal limbs were aligned with a half round plastic spacer that was slotted on the exterior circumference to match ridges machined into the riser . Those alignment spacers mount onto the limb belley by two fingers that fit snuggly into holes drilled into the limb bases. But I read at several places that Samick Sage limbs should not be drilled with additional holes for alignment pins, etc., and another tinkerer used epoxy glue, so that's how I planned to do it.Also, the mold lines on the magnesium riser had not been filed completely smooth , so I did that and then added self-adhesive moleskin onto the riser face to create a self-smoothing mating surface with a bit of vibration dampening.
Another issue is the limb bolt does not run perpendicular to the belly side of the limb and both faces of the Samick Sage limb are close to parallel. So I removed the metal bushing from the limb bolt holes in the Sage limbs so the bolt could pass through at an angle about 15 degrees from perpendicular. That laft the issue of the washer for the limb bolt would likewise be about 15 degrees off from parallel with the limb face, so I needed a wedge/ spacer of sufficient strength to withstand a firm attachment torque. Seeing that the original Polar compound limb bases had the exactly correct angle, were already slotted to accomodate the limb bolt and were clearly strong enough to withstand the pressure without cracking, I simply lopped off the last 3/25 inches of the base of the orignal limbs ; I used a 45 degree mitered cut to make it a little less clunky. Since I didn't want these spacers sliding around separate from the limbs, I epoxied these onto the outer face of the Sage limb base, using the limb bolt to hold position while the epoxy set and cured.
In the meantime, I estimated my final product would be about 63.5 " AMO length and 50-54 # draw, so I ordered a fast flight string made to those specs. I had read a board suggestion to use 5 minute epoxy to glue the spacers onto the limbs and to string the bow up to hold everything together while making sure the limb alignment was good before the glue dried. This worked great, and I was as careful as I could be to make sure the epoxy glue didn't get in between the spacers and the bow and glue them permanently into the riser alignment slots.
When it was assembled, aligned and cured, I added a Centerest to enable sight window adjustmnet...the original Bear WeatherRest had fallen off.
The finished product is rock solid in your hand at full draw and slings arrows at approx. 53# @ 28". I think the wedges mounted at the ends of the risers significantly stabilize the bow. My interim quieting strategy is to ties some long cat whiskers onto the string with an overhand knot. The only hiccup is that the cast riser is noticeably top-heavy...I am studying potential for removal of excess metal without compromising strength.
Part 2 of the experiment was borne from my discovery last fall that my dominant eye had shifted from left to right eye. I figured it was time to get a RH riser and see if the bolt ons would line up. A WTB ad revealed several Trad guys with Polar LTD's in their basements as well, and I pickled up an entire bow,disassembled for shipment, for $25, complete with a lunger rest and flat camo paint! It lined up perfectly , but the two bows had different rests so the nocking points were slightly different. Also the RH bow was missing its grip so I got one of the big auction site for an outrageous price...those plastic grips go for more than a complete bow!
The net result is that I have a solid, straight shooting takedown, and another solid straight shooting takedown that is its mirror image, for a total investment of $155 , including the highway robbery to acquire a RH plastic 2R grip .
Topic: Frankenbow (Read 1655 times)
