Wednesday, March 21, 2012

Reflex / Deflex Longbow Build #1 (tutorial)


After I got some experience by building a couple 1-piece recurve bows (Build 1, Build 2), I wanted to expand my knowledge and test my abilities some more. So, I started researching how to build a longer recurve ( more than 60"), and also how to build a longbow.  I will put the results of the longer recurve design in another blog.  I really like the looks of the reflex-deflex  (r/d) style longbows.  There are great examples from commercial builders as well as hobby builders like the ones I have connected with on the Trad Gang forum and other archery forums.

These r/d longbows are not cheap to buy, so I assume there is significant work that goes into them. Still, I decided to build one to see if I can pull it off.  I spent a couple weeks just looking at all the bow designs, asking questions, looking for supplies, and reading build tutorials.  At this point, I could easily have gone back to Bingham's for a complete kit and instructions. However, I like the curved style risers that I see better than the flat ones like Bingham's.  So, I started looking at how to get started into building one of those, which meant building my own 'kit'; no instructions.

I contacted KennyM on the TradGang forum, who is a supplier of laminates (lams) and other bow building materials.  He is great to work with and gave me a lot of help.  He has a web site which shows a nice r/d form; one he has been developing for years.  He is nice enough to sell the pattern to newbies like me, saving a lot of time on developing a pattern. Also, since I wanted to build a 66" bow on a 64" form, he helped with that.  I also wanted to try the power lam and tip wedge design ideas on this bow.  A tip wedge is supposed to stiffen up the tip section of the limbs and the power lam is supposed to stiffen up the area just past the fades. Kenny can make a "super lam" that combines both of these elements into one lam, making the assembly less complicated and less costly.


Here are the stats for this bow:
- target stats: 66", 47# @ 28", 1.5" wide
- achieved stats: 66", 47# @28" (53# @30"), 192fps with a 378gr arrow (at my 30" draw)
- black ULS glass: .040 x 72" (2)
- maple parallel lam: .055 x 36" (4)
- maple super lam (belly power lam + tip wedge combo), .060 x 36"  (2)
  (.060" for 2" past fades, then taper .001/1", then fade thicker at tips, .042" in center)
- maple taper lam: .115 x 36, (taper: .002/1" on back) (2)
- riser: 1.5 x 2 x 18", zebra

KennyM was very helpful with the specs.  He took the stack height for 45# limbs (.355"), added .010” to it to compensate for the extra 2” of  length, added another 2#  from the super lam effect: so it should be around 47# (if the S/L has as much effect on a 66” bow). And as we can see, it was right on the money!





The main issue with building a new design is that there is a significant up-front effort required to build a new bow press for each design.  I don't mind building presses, but they are not as much fun as building an actual bow.  Also, there is cost associated with each form.  To save a little $$, I decided to build my own press hardware for this new press.

(click any picture for full-size image)

The form has to be 1 1/2 inches wide for this style of bow. I had to calculate what layers of ply would get me that thickness.  I ended up being over by 1/32, so I made sure all the screws were sunk deep and ran it thru the planer. Perfect thickness.


The KennyM form is easy to use. It's 1/2 of the pattern and you just have to lay it out on both sides of a center line and 1 " off the bottom.

I cut it out with a bandsaw as close to the line as possible.


Then, I used the template to flush up the edge. I used a 2" flush cutting bit from MLCS Woodworking that works beautifully.  The upper or lower bushing rides along the form/template and the blades create a perfect surface.


I had some Formica laying around from when we did our counters, so I ripped a strip on my saw and used it on the form.  It helps create a nice, square surface that is more non-stick than just the plywood.Before glue-up, I wipe a thin coat of grease on it.


After I figured out the lower part of the press, I needed to create a template for the riser so that I could cut out the top of the press correctly.  I started by cutting and sanding on a block of ply until it would fit nicely on the press with the lower 2 lams under it.  Here it is being tested.  It has to be tweaked until there is no light under the curve. Then I know it will glue up nicely.


With the back of the riser curved to fit, I had to figure out a nice curve for the belly-side.  It is not easy because there are only a few guidelines and a diagram to follow.  I guess the exact curve is not that critical as long as it is the same on both ends and has the required taper at the ends (1/8" at 2" from tip, 1/16" at 1" from tip). Before glue-up, the tips have to be faded to paper-thin to blend with the lams correctly. I use a board behind the wood to keep if from breaking while I create these fades.  I didn't take a picture of it, but it's shown in my other build.

Also not shown is the detail added to the riser.  I cut the riser lengthwise and glued in a piece of hickory.  Then, I also cut a curve on the bandsaw, sanded it smooth, and put a strip of black phenolic in there. I am not as creative as some builders are, so this will have to suffice for now.  I hope it looks good when finished.


With the riser done, the top of the press can be finished and hardware installed.  It takes a lot of time to get the press setup correctly so that the bows will come out right. I was surprised how much tweaking I actually did. 



After a "dry run" test of the glue-up, everything looked good for the real thing.  I decided to put a few little blocks of wood on the edges of the press to keep the layers from sliding around during the "squishing" process of the glue-up.  The hose is inflated to 60psi and really puts a lot of pressure on all the layers.  Since the longbow has 2 more lam layers that a recurve, there is more that might move around.  I had to deflate and re-inflate the hose a couple times to get everything the way I wanted.  Finally, it went into the bow oven for 4 hours.


Info on building an oven and using it are in my other bow building blogs.  I did have to modify my oven to accept this  longer form and the hoses sticking out of the ends.  My wife says it looks like a long casket now.

Out of the oven, the bow is removed from the press and cleaned up from all the tape, plastic, and glue.



Based on directions from other bowyers, I drew my profile lines on the taped-up limbs.  About 2" from the fade-outs the limbs are 1 1/2" wide.  From there it tapers straight to the tip, leaving it 5/8" wide at the string grooves. 

I switched the bandsaw to my "beater" blade for sawing glass.  Bingham says that a 4 TPI, skip toothed, neutral rake blade will last the longest, even though it will smoke and squeal a bit.  So I keep one blade just for this chore, which keeps my other blades sharper for wood.


After sanding down to the line with the drum sander, I used a long sanding block to remove any wavy bumps from the limb sides that were created during the sanding process.


Then, using an angle finder, I marked 55 degrees at the grooves.


The grooves are cut with a  3/16" chainsaw file.


I forgot to take pictures because I was in a hurry before work.  I used a piece of maple lam, black phenolic, and a thin piece of Zebra wood to add detail to the tips.



 After they heat cured (smooth-on epoxy), I finished cutting the grooves and sanding the tips. I also shortened the tips, as recommended by some bowyers. I think it will look good when finished.


Another step that I didn't show was adding details to the riser.  I put some maple and a black strip across the back side of the riser.

I also put some maple, black, and zebra strips on the belly side above and below the grip area.  I was trying to build up the heel area of the grip a bit.  I hope it comes out nice when I do the final shaping.  This picture is of the rough cut out of the riser shape and sight window.


After some time on the shaping drum w/ 80 grit .


And also some filing.


And lots of hand-sanding with paper from 100 to 220 grit.






For a finish, I have to do a hand-rubbed method, since I am not setup to spray one on. It takes a lot longer and sometimes it can be frustrating dealing with flaws and dust, but it will eventually come out looking nice.  I have been learning patience. I used several coats of Tru-Oil, sanding between coats to remove high spots. After the surface was smooth enough, I put on several coats of Minwax Wipe-On Poly to finish it up.









OK, I got back from the range last night, where I setup and tested the bow. I got final measurements on pull weight and arrow speed as well (posted at top).  I have to say that I am very pleased with how well this bow shoots.  It is faster than I expected and very smooth shooting.  I have a Flemish string coming and I may try some string dampeners.


7 comments:

  1. Great job.... very nice shooter there !!

    ReplyDelete
  2. I want to make a recurve bow for myself. I cant afford to buy a kit but I am able to make most of the parts needed. I have a large trunk of a maple tree that I cut down for this. I want to use it after it is try of course. I am so confused, do I put the glass on the front and back with maple in between the 2? Or can you put glass in the middle and maple on the front and back? I have searched the internet for 3 days and I cant find any detaild directions on how the build up goes from start to finish. Any info or advice would help me a great deal. THANKS...

    ReplyDelete
    Replies
    1. The glass goes on the outside, with the hardwood sandwiched in the middle. If you read some of my other recurve builds, I think it shows it better. Also, if you go to tradgang.com, there are lots of build-a-longs there that you can see, and friendly people to help with questions. I have learned a lot from them,

      Delete
  3. I really like the riser profile. What kind of fps are you getting out of the bow and at how many grains per pound of draw weight? Is is possible to get the template off of you to build one of these? I plan on builing a few of these this summer. I was looking for a template for a riser just like you have here. BTW what is the mass weight of the bow now that it is finished?
    Thanks for the buildalong
    Greg

    ReplyDelete
    Replies
    1. Hi, thanks for the post.

      I am getting 192fps with a 378gr arrow (at my 30" draw).

      You can get the design info from Kennym at: http://www.kennyscustomarchery.com/

      He is a great guy to work with. I had to make my own riser template, based on drawings that he included with the bow press pattern. So that was a little extra work, but not horrible. The pattern for the press was the main thing that I needed.

      I haven't weighed the actual bow yet, but I will have to do that and post it. It is a feather weight compared to by big recurves, of course. I could carry it all day.

      Delete
  4. Thanks much for the info. What does the bow have for draw weight? That is plenty of speed for sure. I am making the switch to a RD longbow due to likeing the light weight. I find I can shoot just as accurate w a lighter bow as a heavy one provided the poundage isnt too high.
    Thanks much
    Greg

    ReplyDelete
    Replies
    1. Greg,
      This bow pulls 47# @28".
      I also like the ease of shooting a lighter bow, and if I start trad hunting, it will be a big advantage to carry a RD. I used mine in a 3D target league last winter and I did just as well with it as I did with the recurves.

      Delete