Ozbow

Been a while since I posted fellas so here is my latest project. A new flatbow form with a lot of deflex/reflex. The string nocks are inline with the back of the riser overall when cut to 60" NTN. The longer it is cut the more net reflex (i.e. preload) it has. The riser is built up in 2 stages in a similar fashion to a Dan Toelke "Whip". The fun part of this project is development of a new heat strip system that I started to document months ago and will finish in the previous thread. This is the maiden layup (prototype) for this form and I am looking forward to finishing the bow off and finding out how it shoots.
Cheers... Rod

This is the shape I have planned for the remainder of the riser that glues onto the belly glass lamination. All constructive criticism (or otherwise ) is invited? Cheers... Rod

Rod I am really liking what I see. looks pretty dang fine to me. Nothing like a good ol' deflex/ reflex, modern longbow, hybrid, semi recurve to get the juices flowing!!!

Hi Rod, I hope this reply is constructive.

My first impression of the design suggests a trade off of stability for speed, just an impression.

If you check out the Fox Triple Crown which has a similar side view profile the riser represents approximately 30% of the n to n length. I believe the overbuilt riser is required to dissipate hand shock and create a more stable shooting platform; just my opinion.

From Elmont Bingham;

"How do I get rid of hand shock?
I am asked repeatedly about hand shock. You often notice this when shooting a longbow for the first time. After you have shot for a while, you will become less aware of this when you release the arrow. You are less likely to notice this when shooting a recurve, take-down recurve or even a take-down longbow. It is a simple law of physics, relating to weight and mass. The flat longbow has a heavy, long limb and a short, light riser. The motion of the long limb cannot be absorbed by the smaller riser, thus the hand shock. When compared to the longbow, the recurve and take-down recurve limb is shorter and lighter with a larger and heavier riser; the shock of the lighter limb moving forward is absorbed by the riser, thus lessening the hand shock and giving the “soft feel”."

I will admit that I do not totally agree with the above statement but there are some elements of truth.

Hopefully the build will go to plan.

Daryl.

[quote="greybeard"]Hi Rod, I hope this reply is constructive.

My first impression of the design suggests a trade off of stability for speed, just an impression.
I would not worry about that too much . the profile is very similar to the deflex/reflex I make and they are very quick with really steady stability. Obviously a flat laid, narrow but deep 'traditional' longbow will inherently allow through its design parameters more stability and be more forgiving of bad form but certainly not such as to render the D/R unsuitable. As i mentioned it seems very similar to the design I work with and I have no complaints from any one who has one.

Daryl, It may end up being twitchy but I am hoping not if decent weight wood is used in the riser (16" long = 25% of a 64" NTN bow so not too far off). That Fox triple Crown looks to be all riser to me, and though it may add stability, it looks like overkill to me. I have made a 64" D/R bow with a lot more subtle design and used low density timber in the riser. It was stable to shoot and in the end I wished I wasn't making it for someone else. If it does turn out to be unstable I can lengthen the riser (i.e. shorten the working length of the limbs) with a power lam between the riser and the belly lam, but I am hoping that instead of achieving great speed, it is capable of launching heavy arrows (e.g. 15 g.p.p.) at normal speeds. That should take some of the buck out of it I hope.

Thank for your feedback, it will be in the front of my mind when I finally get to fling some arrows with the new bow. Here it is out of the form. Note when I cut the 72" blank to 64" long it will only have a bit over an inch of net reflex. Cheers... Rod

Thanks for the support Bob, I appreciate it. I think Daryl may have considered the bow would have all of the 3 inches of reflex that is in the blank, which would probably make it a handful. I will be cutting it back to 64" NTN so it may behave more kindly.

Cheers... Rod.

no worries Rod, I'm simply re affirming my experience with similar bows.As I mainly shoot targets these days I would use one myself in a heartbeat but don't want to have to shoot from the red peg in ABA events.Some of mine have approached 200fps in the heavier draw weights so have no doubt that they would generate some pretty decent kinetic energy suitable for hunting. The only down side to these is the meticulous requirement for accuracy in fitting back of riser to lams in form. I usually have to do up 1/2 dozen 'dry runs' to get it right.Did you find it a little harder than normal?

Looking good! Almost makes a bloke want to build a D/R trilam...

Top stuff Rod

Thanks fellas. It is making slow progress, got plenty of work on at the moment.

Rod I don't think you'll have any problems with it. My takedown back mount bows have that much reflex and they shoot fine just get the grip to fit your hand repeatedly and it will be a fast tac driver. I did add a power lam about 2" past the wedge but it really doesn't need it with .003"/inch taper. The 67# shoots a 675 gr arrow at 188fps. Don't have any heavier arrows so can't get numbers for you. Though my 47# belly mount bow using the same limb shoots that 675gr arrow at 158fps and thats 14+ grains per pound. What kind of speed are you looking for?

Hi Ben,

I don't have a particular speed in mind, but I would like to see the bow launch heavy arrows with authority.

I am mainly into hunting but lost access to my usual block and recently I have been club shooting a bit. So many of the shots are well outside my comfortable hunting range. My main problem is getting the elevation right, most of my arrows end up in the grass before the target on long shots. It would be nice to have a bow that shoots reasonably flat and is stable enough with lighter arrows.

Cheers... Rod

Rod I think you'll enjoy the bow your building it looks fast . It will require you to be attentive to your shooting form but that will help your shooting overall.

Well this is a new one on me. Before stringing the bow is dimensionally symmetrical apart from the top limb being a fraction narrower than the bottom and also fraction longer (the riser slipped to one side about 1/8" after loading the air hose). There is no twist in the limbs and they appear straight when using a string line along the centre, both before stringing and after unstringing.

After stringing, the top limb has a minor amount of twist and a major sideways bend in the outer third.

The bow came in at 45#@28" which is a little under target weight (50#), but I did make it narrower (1.15" at fades and 0.5" at tips) than I had originally planned (1.25" at fades and 0.65" at tips). Perhaps the more flat bow layout would suit this design better than a deep cored longbow layout.

I am going to research how to correct this problem that appears to be a material issue. If in the process I can reduce the draw weight to 35#@28" the bow might still be a shooter for my wife. Any advice on methods to correct the sideways bend would be appreciated. Note the string nocks have very little room for sideways movement as the tips are quite thin and the grooves are already quite deep. Cheers... Rod

Going great guns Rod. That's quite a twist you've got going on there. I would be getting as much adjustment out of the nock tip as possible, it's surprising how narrow you can make them, just have a look at any Nick Lintern long bow and you will see what I mean, I've seen some that are flat out being 6mm wide.
Apart from that the only other thing I can suggest is grab the tip in one hand and the limb where it is not twisted in the other hand and twist it the other way. You can do this while the string is on the bow, feels a little scary though. This works to correct minor twists in recuve limbs, not sure it will have the same result with a thick stacked narrow limb.
Or you could cut an inch off both limbs and cut new nocks,,, might bring the poundage up to the 50# you were after.

Rob.

My suggestions would echo Robs. With my very similar [in profile at least] D/R the width of the limbs are 1 1/2'' for 2'' past fades and then taper progressively to the tips where they are about 1/2''. Being so narrow as yours is then it might be wanting to induce twist.You can probably salvage this even if it is a lighter poundage bow.

Bugger!!!!!

Why one limb and not both? different mechanical properties in core material?

Daryl.

That's what i can't work out Daryl, and it doesn't have a lot of propeller type twist in the bent limb, mostly just a sideways bend which is really weird. Maybe there is a soft spot in the fibreglass or the core. The core is three tapered lams of bamboo floorboard.

It is starting to come back into line by just stringing it up every no and then and heaving on it. Don't know i it will be a permanent fix but looking like working so far. I might even finish shaping the grip on this one and fling a few through it if it straightens u a bit more. Cheers... Rod

That bow's really impressive, and unique to boot!

Despite the little set back with the twist, it seems to have worked really well. Do you have a chronograph?

Thanks Dave. Yes, I have a chrony. I have shaped the riser and slowly pulled some of the twist out of this bow. I am going to find out if it is a shooter this weekend before I spend time finish sanding and coating. It feels good in the hand so I am looking forward to shooting it... It fills in the gap in my bow rack nicely It think it would be OK out to 30" draw no worries. I must do a DF Vs DL curve for it to compare with the next flatter limb design.

Cheers... Rod

Rod how is your bow coming out? Hadn't heard anything so tought I'd ask.

It shoots fine BenBow. Quite steady in the hand and seems quick enough for 45#. I haven't even finished it yet because I moved onto the next prototype that will have a wider & flatter limb section. I'll probably have a go with 2 lams instead of 3, so it will have less taper as well.

I thought I had most of the twist out of it, shot about 100 arrows and it was back. Didn't seem to affect performance too much though.

Hope you post more on the new version

The second iteration is looking much better. I have the limbs shaped to 64" NTN, tillered and weighed in at 48.5#@28". It has 1/8" positive tiller on the right hand limb with 8" brace height. The buff horn tip overlays are curing tonight. Maybe this one is a candidate for shooting at the muster, being 10# lighter than my other bows should give my elbow a chance of holding up for the weekend. The full draw photo is at roughly 29" AMO. Seems to have plenty of string angle left for a longer draw length.
Tasmanian Blackwood, Black Wattle, Black Botuff, Black Phenolic accents and black buffalo horn tip overlays. Has to be called a Black "something"? We'll see how she shoots...

Hope to see it at the Muster.

Eddie

Rod the braced picture reminds me of a cape buffalo frontal silhouette. Look forward to seeing it complete.

A few photos of the finished bow below. It has been to the Gladstone Muster and the ABA Branch B Safari before being properly finished. It is a lot more comfortable to shoot at only 47#@28" than my other bows. The light weight doesn't seem to be any penalty when proportionately lighter arrows are made to match it. I am happy to be able to shoot without too much pain in the elbow . Sorry for the poor photography, still haven't got past the phone camera stage yet

looks pretty schmick to me!