Ozbow

Evening all,

Glued up a little experiment today... been toying with the idea of doing a bamboo back and belly bow for a while and then decided to make a deflex reflex as well because I've never tried making one.. SO MANY LESSONS LEARNED ALREADY!! A few include:

Lesson 1, Need to make the fades longer next time and finer curves so the bamboo belly conforms to them easier...

Lesson 2, I need LOTS more clamps for these bows

Lesson 3, you use a heap of glue on these bows

The bow will be 66"ntn when completed and the construction method was as follows:

1. Cut a 2mm thick lemonwood core lam and mark out the profile of the bow
2. Cut out the profile of the bow on the outside of the lines
3. Flatten bamboo for back and belly laminations
4. Transfer profile to back and belly laminations and cut them out, again on the outside of the lines
5. Taper the bamboo with the profile to make almost a sharp edge around the outside (ensuring the tips taper out enough to get them bending I HOPE!!)
6. Quickly design and cut out a riser block (then find a issue mentioned above and try to fix it on the fly )
7. mix and apply glue to the backing lam then add the core lam and then apply glue to it.
8. apply glue to the riser block and put it in place
9. Apply glue to the belly lam and then set it in place on the riser block. Tape the centre of the bow so the lams cant slip and also tape the tips. cling wrap the lot so the bands wont stick.

Heres where things got interesting

10. Discover that the "remedied" curves on the riser block are still too sharp (I think) and slightly freak out because everything has glue on it now and cant be re shaped.
11. Decide to persevere and strap up the limbs to the problem area and then battle with clamps trying to get the bamboo to neatly wrap around the curves on the belly side.
12. get the belly clamped almost there at the fade curves and decide that's as good as i'll get it and then discover I cant use the form method I wanted to because of the clamps being in the way...
13. add more strap to the limbs and then use the strap tension to hold the reflex curves (worked surprisingly well!! )
14. leave the bow to do a gym session

15. mid gym session have an idea to remove the clamps by strapping right beside them to hold the lams close then remove the clamps and bind over where the clamps were.
16. Put clamps back on a crank them as tight as I possibly could and I think I got the bamboo in place (i'll know tomorrow when it all comes back off)

17. quickly cut some blocks of timber to use as the original form design and put them in place...

Here's the end result!!
more to come!

Col

Tough way to learn Colin but the lessons tend to stick hey :]

I used to have a copy of Dean Torges Hunting the Bamboo Backed Bow which is an excellent reference when making these Laminated Bows. I'll have a look and see if I still have it packed away somewhere. I have made quite a few of these years ago Mate and have plenty of clamps sitting here and a Jig I doubt I'd use again sitting here. Drop me a line if you have need of anything Mate

regards Perry

Cheers Perry!

Was a big learning curve but I would never know if I hadn't tried

Next one will be better but we'll see what this one does in any case.

Colin

The main battle with these Laminates is ensuring the Bamboo once it's cut to profile is thinned down as near a knife edge as possible. You've done that so I predict the Tillering will go quickly. Bamboo is not the greatest under compression but generally the end result is a Bow with a little string follow more than desired initially but shoots very well.

regards Perry

You did that after i left ? Man i would have liked to hang around and watched that :'-(

Hi Colin,

The bamboo back and belly bows are a bit of a challenge first up but are quite easily mastered.

After trial and error I found it easier to use two forms, one rigid and one adjustable.

To give the core more integrity I prefer to use a minimum of two laminations cut from the same piece of timber and end for end them to help balance out variations within the timber.

The rigid form is used to glue the handle, core laminations and belly bamboo together. When the glue has cured I place this ‘back up’ on the adjustable form.

If some reflex has been lost in the initial glue-up it can be replaced in the second glue-up by using taller posts at the tips when applying the back bamboo. When applying clamps to the crown of the bamboo I use little blocks with a concave face which stop the clamps sliding off or damaging the bamboo. Spring clamps work well with sandpaper to stop them sliding.

Although I don't have the statistical data there seems to be little noticeable performance increase when applying bamboo to the belly. Heat treated bamboo however may be a different story.

Daryl.

Well the one went a bit haywire... and by a bit I mean ALOT!! hahaha

Learned a heap from it and will be having another crack at some stage. The bow does shoot, only around 25-30 lbs (haven't checked) at 28 inches and ended up at 62"ntn (don't ask where the other 4 inches went!) Big fret in one of the fades which I believe happened when I glued it up.

Need to re design the riser block and pay more attention to the curves at the fades and the length of the fades. Also need to take more time in prepping all the laminations. Next one will be either 2 core strips or a single thicker one for some more weight.

Might stick a photo up tomorrow.

Colin