First spotted gum bow

[albatross]

Hi ,
Here is my first go at a spotted gum bow. Still unfinished, need tillering, final sanding and maybe backing as the grain runs off a bit. What is the best material to back the bow with?
The bow seems really heavy at the moment and im thinking I might need to reduce the thickness down from 3/8" , but not sure as it is my first try.
Been a great learning curve and if it shoots an arrow it will be a bonus.
Cheers Matt

[hunterguy1991]

That sucker will go around 70-80lbs judging off the thickness you have there in the limbs... Might have to bring the fade outs down into the limb board and thin the limbs to drop the weight a bit.

Linen fabric or Jute strips would be a cheap means of backing the bow. Just glued on with PVA.

[perry]

Sorry to be negative Nelly here Matt but you have created an Albatross with the Built up Riser with the Fadeouts being too Steep. The Riser will also Pop Off after a short time when it is Drawn as the Fadeouts meet the Limbs too abruptly. It is likely the Bow will also break where you have Cut out the Shelf when the Riser Block Pops off. You may be able to Salvage it by working the Fadeouts to a shallower Angle so they Taper into the Limbs more and then Glue a Timber Lamination along the Length of the Belly that covers the reworked shallower Fadeouts. This will mean the greatest majority of Tillering will be on Back of the Bow, a problem if the Timbers Grain is not Spot on.

It is a very common for Newby's to Wood Bows to copy the Design they are most Familiar with - the Hill Style Long Bow. It can work and work very well but the Riser must be between Laminations IMO. Check out this Link http://www.primitivearcher.com/smf/inde ... ic=50195.0 The Riser is not Laminated over in this Link but the big thing is the Fadeouts are gradual and Laminations are quite thick under the Riser so it is not prone to Bending. I still think you'd be better off with the Riser Sandwiched between Laminations with this type of Bow

regards Jacko

[albatross]

Thanks for the feedback perry ,much appreciated, this one is a learning project. I will probably do alot of things differently with my next bow. I wont worry about salvaging to much with this bow, but enjoyed playing around with it. I might just increase the fade out and throw some backing on it, if it breaks ill try again.
Cheers again Matt

[yeoman]

I agree with Perry's assessment.

I think what many bowyer pups don't realise is that gluing on a bit of extra wood to make a built up riser should not comprise the totality of the riser. Rather, the added wood should complement a riser which is built up from the stave's own material to begin with.

Let's have a look here:



The added wood is only some 5 mm thick. By the time the added riser material is reached by the outline of the bow, the stave is already pretty much double the thickness of the bending portion of the limb. This one's quite subtle, and the added material doesn't add much.

Here's another:



Done more thoughtfully, the riser block should be a couple of inches longer than this. Fortunately, we got away with it this time.

Note how much thicker the stave is where the riser block starts compared to a couple of inches out past the riser where the limbs start to bend:



But don't be discouraged. Perry's advice about laying a lamination on the belly and running it up the riser is a sound one.

How thick is the stave where the riser block starts?

[albatross]

Thanks Yoeman,
The stave is 3/4" thick were the fades meets, I had thout about maybe cutting some of the riser off so I can gradually work the fades in, but it will probably break were the rest is im guessing? Live and learn I guess. I have another piece of spotted gum, i will start on another when i get back from work in a few weeks.

[yeoman]

19 mm should work. Your limb's thickness, where it starts to work, likely will be around 12 mm thick or so. Taking it up to 19 mm makes it about four times as stiff. This is a good base on which to build a riser, but the riser doesn't have to be substantial in order to give a (functionally) perfectly stiff riser. Maybe only another 10 mm or so.

Keep at it!

[greybeard]

Hi Matt, welcome to Ozbow. Take time to browse some of the earlier posts as they contain a lot of useful information.

From my observations most new comers wanting to learn the skills of the bowyer seem to have problems with handle design and the transition of fadeouts into the limbs.

If you must have a shelf, profile it to a more gentle shape. Although the photo is of a shelf in a laminated bow it will give you an idea of what I mean.

Shelf Front View.JPG (55.93 KiB) Viewed 5553 times

Daryl.

[albatross]

Thanks guys for all the useful feedback, I increased the length of the fades and reduced the thickness of the riser, thinned the limbs out quite a bit. Had a go at tillering which is alot harder than I thought it would be.
I have put about 100 arrows through it now and it seems to shoot ok.
It is 35 lbs @26", i am reasonably happy for my first go and cant wait to get my next bow underway. Its been a great learning curve.
Cheers
Matt

[yeoman]

Congratulations on getting a bow to full draw!

If I might make a suggestion:

Suggestion.JPG (62.63 KiB) Viewed 5475 times

If the bow is tillered such that the areas bounded by the shabby red lines bends quite a bit more, then you will have a faster shooting, smoother drawing, more evenly stressed bow.

To do that to this bow might reduce the draw weight down to 28 lb or so. That being the case, you might prefer to aim for a different tiller shape on your next bow.

When I was starting with milled timber it was a hard habit to break to move the bending section of the limb close to the handle, but I eventually made it after a while.

I look forward to seeing more progress!

[albatross]

Thanks Yoeman, I will have a go at tillering the section in question. Just a bit worried that the riser might come off as the fades could be a bit shallower and then it may break where I cut the arrow shelf. Im not to fussed about the weight so its worth a shot. I will do a few things different with my next bow.

[albatross]

I re-tillered the section Yeomans highlighted and the bow came in at just over 30lbs, after another 100 or so arrows it looks like the riser may be starting to lift and a splinter has appeared on the edge/ back of the upper limb. It seems to have occured after I applied Linseed oil, probably just co-incidence though as the oil shows the inperfections easily once applied.
I have glued the splinter back down with not much hope, I am pretty sure the backing is the only that stopped it from breaking .
Im not to dissapointed as from most of your assessments, everything you said looks to be happening.
Started next bow already, hopefully this one will be better.
Matt

[albatross]

Still hanging in there, had alot of fun with it.
Have started next bow, still have apiece of spotted gum from the same board left over and was thinking about using some rock maple laminate strips for the backing. Will this work or should I use bamboo, I would rather use the maple because itis readily available in laminate strips.

[Nezwin]

Have started next bow, still have apiece of spotted gum from the same board left over and was thinking about using some rock maple laminate strips for the backing. Will this work or should I use bamboo, I would rather use the maple because it is readily available in laminate strips.

Rock Maple is easily available in laminate strips?! I'd love to know where!

For anything over 40#@28" (or thereabouts) I'd advise against timber backings with Ironbark & Spotted Gum. The dense, stiff eucalypts are not suited to using them, in my opinion. I know that Hunterguy Colin used a Hickory backing on Ironbark (or was it Spotted Gum?) which caused the back to splinter - very, very difficult with Hickory. You'd be better using bamboo.

[albatross]

Thanks Nezwin,
I have a baboo pole 100 diameter lined up, just have to machine it up.

Ottos timber in adelaide sell 1.8 meter x 50 x 3 strips, i think they have a few other timbers as well in strips. I am going there later in the week to ckeck it out.