Help needed with Dimensions for Laminations reflex / Deflex Bow with Boo

[globalmark]

Hi Guys

i hope someone can help – I have made a couple Bows – one with Bowyer “Chris Boyton” here in the UK , but would like to Make a reflex .deflex recurve or longbow (whatever you call them) – I am also a cabinet maker so have no problem with making forms , Glue ups or anything like that  and have started making the form .

However I dont want to use Glass (bo-flex) this time but have bought some 2.4m lengths of bamboo slats 45mm wide from a bamboo supplier who sees to Bowyers – so good looking stuff needs tiny bit flattening but pretty close already .

I need a long bow as 6’3″ and draw like 32″ when measured my arms – so came up i needed a 70-72” bow one long bow i have is 80+ lbs I cannot draw all the way , my other 50+lbs i can draw just about (had dislocated shoulder before) , and friends recurve bow easy to draw – I enjoy making rather then using so Dont care about draw strength , I DONT hunt so just a decent strength bow 40-50lbs maybe but whatever works ok .

But as only made long bow types before have no idea of the lamination thickness – how much taper etc

So can anyone help just recommendations on how many laminations , thickness of laminations , what taper to put in them and which ones – I was thinking maybe either “all Bamboo – with timber handle” , or “bamboo belly and Bamboo back” with core or timber ? or other suggestions ?

SO width’s , thickness total at handle and tips , what recommend etc .

Any help would be great

Thanks Mark

[wood carver 2]

Welcome to Trad Gang, Mark.
I can give you some measurements taken from bamboo/wood tri-lams that I have built. I can't give you an exact formula because they all come out a bit different from one another, but it should help you to get close to what you're looking for. I build my longbows with a bamboo back and belly and a wood core. I have used bamboo for the core, but it made for a sluggish shooter.
Starting with the back, I will flatten a bamboo slat on my jointer ( carefully!), then taper it so that it is 1/8" thick in the center and 1/16" thick at the ends. A belt sander will do this as well, but I am comfortable doing it on the jointer. Draw the bow's profile on this and cut it to shape. I like my bows to be 1 3/8" wide and taper after the fades to 1/2" or a bit less when finished, so for now I taper it to 5/8" at the tips. I prepare the belly slats next. After flattening my belly slat, I take it outside and burn the outer face black with a torch. Once it cools, you will notice that it has cupped backwards. That's ok. Flatten it again. I find that this reduces the crown of the natural bamboo and the blackening ( I'm told by better bowyers than myself ) adds resilience to the belly. I cut my belly slats in half so that I can run them up the fadeout ramps of the riser.
I have made cores out of many woods. I look for something inherently strong and springy. Hard maple, hickory, yew, black walnut, purple heart, jatoba, etc. My favorite shooter has a cherry core. The core thickness is the biggest variable as two pieces of the same type of wood can have very different properties. I make the core 1/4" to 5/16" thick and I will taper it to about half of that at the tips. I leave the core and belly full width until the bow is glued up.
I also like to include a thin power lam between the back and core. I make it 1/8" thick and taper it to 0 and make it 4" longer than the riser.
I don't have much of a form, since the bamboo belly won't conform to one anyway. I use a straight beam with a raised area in the center where I clamp the riser, and posts at each end to give the bow it's reflex. Two large parallel jaw clamps pull the mid limbs down to the beam for deflex.
For glue, I have used EA40, Unibond and Titebond3. They all work well but I prefer TB3 for it's simplicity and water cleanup.
I have a couple of bows I can measure for you. #1 is 67" tip to tip, 65"NTN, 1 3/8" wide, 1/2" at the tips, 1/4" hickory core, tapering to 1/8", 19" riser and a 23" walnut power lam. It also has tip wedges made of walnut 8"long tapering from 0 to 1/16". This bow draws 65# @ 28".
#2 is 68" tip to tip, 66"NTN, 1 3/8" wide tapering to 1/2", 5/16" cherry core with no power lam or tip wedges, and a 17" riser. This one draws 57# @ 28".
I have a third bow here that I can measure. It's incomplete, so I can only guess at it's draw weight which feels like mid 50# range. It is 65" NTN and should be 67"tip to tip when finished, 1/4" maple core tapering to 1/8", 1/8" osage power lam 24" long over an 18" riser and also 8" by 1/16" tip wedges.
You are going to need a bit of trial and error to get your target weight at your draw length, but I hope this helps .
Dave.

[globalmark]

HI Dave

Thanks you so Much for that Info - it gives me alot of great Info to think about -
I have also heard about Burning the belly Lamination -
Just couple extra questions so got the clear

Do you think the length of mine 70-72" is OK

the Back Tapered 1/8 - to - 1/16
the core  Tapered 1/4, 5/16" - to - approx 1/8", 3/16
the Power Lam - tapered 1/8 -to - 0"   But -(what do you make this from Timber or BOO ) - Sorry not sure what you mean make the Power lam 4" longer the the riser ? why ? as i was thinking all timber lengths would be long enough to cover the 70" bow
The Belly - Burn But what dimensions should this Be ?? thickness and is this also Tapered ?

DO you also leave the Nodes on Both Back and belly - if so how do you do the Tillering - from the side ??

And Last thing - do you sandwich the Riser in the middle of the 4 Lams ?? or other ?

Thanks again
Mark

[wood carver 2]

To be honest, I don't know what draw weight you will end up with at your length, but if I were to guess, I would say that you will end up a few pounds lower in draw weight. I'm no expert and the bamboo and wood you choose will be a determining factor. I came up with the thickness I use mostly by trial and error. The power lam is a thin, short lam that runs about 2 inches past either end of your riser fades and, if I understand correctly, it helps in the transition area between the riser and the working limbs. Since I started including a power lam, I have seen an improvement in my bows.  [ Invalid Attachment ]  [ Invalid Attachment ] I make power lams from the same woods that I use in core lams. I usually use a contrasting wood to look good.
There are people here who are far more knowledgeable than I am, so if I'm wrong here, please correct me.
I plane the belly lams to 1/8" and taper to 1/16" and cut them in two so I can run them up the belly fades. The back, power lam and the core are glued over the riser.
Glueing the belly lams under the riser makes it impossible to pop a riser off. You would have to break the entire bow.
Hopefully some other bowyers will chime in. My way is certainly not the only way to build tri-lams.
Dave.

[globalmark]

HI Dave

Thanks so much for the Help - I get 99% now an think I can make something
I really dont care that much about Draw weights as long as shoots a arrow for fun - I only Kill Hay bales occasionally anyway - the fun is in the building stuff for me .

1.So just to confirm ALL laminations are Tapered - I ask as many people seem to have at least 1-2  Parallel Laminations not tapered - .
No bother I will Taper all if best (use a very Long No-7 Hand plane and can get Perfect joint)

2.Also I have read that Belly is usually thicker then Back - Does this not matter with BOO or no difference ??

3.Also Just to confirm my overall Thicknesses - the Tips without extra tips wedges is approx 1/4" -to- 5/16" (6.3mm-7.9mm)
and Centre of bow NOT inc riser approx 5/8" -to- 11/16" thick (15.9mm - 17.1mm)

This bit maybe you or others have a Answer as was wondering ..
Also I see you and Others Cut some laminations in Half before Tapering ?? is there any reason for doing this as from a Cabinetmakers point of view seems its would weaken the Bow - and really not that Hard to Taper from the centre to Tip keeping 1 full length of timber (apart from Belly as will get sanded away probably) - But core and Power Lams - would they not benefit as keeping full length ??


Thanks For Help so much - really appreciated

Mark

[wood carver 2]

#1, It's just the way I build bows. Through trial and error, I found that this works for me>
#2, I make the belly the same thickness and taper as the back. Because of the bamboo belly, you can only tiller this type of bow from the edges.
#3, That's what mine add up to. This should get you into the ball park, then you can make adjustments on future bows. ( And there will be future bows, trust me, this is highly addictive! ).
#4, If you are able to taper your lams whole, there is no reason not to. I cut my belly lams in half because they ride up the fades on the riser.
Good luck. I look forward to seeing pictures.
Dave.

[globalmark]

Hi Dave

Thanks so Much for the Help - will definitely try and do like you suggested or as much as I can and upload couple pics also when get around to it ..
Thanks Mark

[globalmark]

Hi dave - or anyone

Just a question on the Bamboo shaping -
1. also Dimensions given on Bamboo thicknesses are these measured in the edge or the middle (obviously bamboo is thicker in the Middle (so am i trying to get edge knife sharp or leave edge 1/8" - 1/16" etc ?


2.I Just started to try and taper them -
but due to the Nodes on one side and as its a natural shape when you plain or sand them how do you get it a even Parallel or even Taper - as at looking from the side it looks like waves a bit if you know what i mean ..
do i need to put something in-between the nodes to stop dipping or is it really not that important (being a cabinet maker i like it precise )

3. if temper/ heat treat the bamboo - how much should it be done as had a go today with blow torch and goes brown pretty quick - i left all just a medium brown as even as possible - as didn't want to do to much .

Thanks Mark

[wood carver 2]

Measure the thickness at the crown. I don't worry too much about the edges. If you're using large diameter bamboo, the edges will be knife edge or very thin.
I do most of my tapers on the jointer. Start at one end and plane about 1/3. Start again and go 2/3.
F
Dave.lip it around and do the same thing on the other end, then plane all the way through. After this, I take it to the belt sander and refine it. I tend to work by eye and I find it to be pretty accurate. In order to get a nice flat job on the jointer, I use two rubber soled sanding pads to push the slat through. I keep even pressure by " walking " the pads along one right after the other as I push.
Burn the bugger black!! Just don't set it on fire or reduce it to ash. 
As I blacken the slat, I usually have steam coming out from the ends. The rapid drying will cause the slat to cup backwards. Once it cools, plane it again. I forgot to mention before, for the belly slat, I plane it flat, but I don't taper it until I have blackened it.
Dave.

[globalmark]

Hi Dave

Thanks again for all That - still doing it with a Hand Plane No-7 long heavy plane gets it to thickness very accurately and flat in a few minutes - just wondered about the measuring - So at the crown .Thanks

Burn it black - sorry forgot to ask and googled it but conflicting info -

Do i burn the outside (with nodes sticking up) or flat Inside of BOO ? - and presuming I dont want a Black bow do i sand this black off again ?
thanks Mark

[wood carver 2]

Burn the outside till it's black. I lightly sand it to remove the small amount of char that you will get, but I like the black colour. I think it looks really good under varnish. I guess that you could sand off the blackened layer to get a lighter colour, but be careful not to sand too much. You could weaken the bamboo, especially if you take off too much at the nodes.
Dave.

[globalmark]

Hi Dave

Yes that does look Nice looking Bow looks like some PNG rosewood in handle? - i will give it another burn today if get time .. and just very light sand after THANKS for that .
I will try and get some pictures up after as Might help someone else .
Mark