Massaranduba Board Bow. Information needed.

[AlexanderArcher]

Hello everyone, this is my very first post and I'd just like to take the time to make it known that I love this site, it has been instrumental to the success of my bow crafting experiences and is full of incredibly interesting and helpful information.

Ok, so I really wanted to make a longbow that i could practice my accuracy and eventually get very good with so upon reading many of the crafting articles posted [and drooling over your successes] I decided to try to make my own bow. I knew that my best bet, other than cutting and drying my own wood, would be to find some hardwood decking and shape a bow out of that. I went on down to bunnings and found that there was only one type of hardwood decking that they had left and that was this veritable mound of massaranduba planks. I searched the lot and found one with perfect grain, what is interesting to note is that most of the planks had incredibly straight and tight grain. I got home and measured up my bow, used a wood lathe to grind down above the levels i wanted and started tillering. I left a handle space approximately 1 inch below the center line so as to put an arrow rest and grip on it. I made a pretty bad mistake while tillering [took off too much near the handle] and had to drastically reduce the poundage of my bow now it shoots 22# at 28'' i glued a piece of spotted gum on to the back of the handle to give it slightly more depth and strength and shaped the handle and arrow sights with a circular rasp. Sanded it all down and strung it up ready to shoot. It feels incredibly smooth in hand and has no chrysals. This is only my second bow and i am incredibly proud of it, chrysals broke my spotted gum board bow
I only have some cheap arrows i bought from an archery store and has plastic flights\feathers on it, so when i shoot it, the arrows knock against the wood of the sights and the arrow flies askew, if im standing 1O-15m in front of the target, the arrow will land in the target at a 45degree angle.
What should i do to remedy this?

Also, should I oil the wood with, say, linseed oil? if this is not appropriate, could you please recommend another type of oil.

Thanks all

[Dennis La Varenne]

Welcome to Ozbow Alex and well done on your first working bow.

That 'massaranduba' is a new one on me. I will have to look it up.

With regard to the arrows knocking against the 'sights' which I take to mean your sight window and flying askew, this is the hallmark of an arrow which is severely over-spined for this particular bow. The arrows you have purchased are most probably indeterminate spine.

Do you know what diameter your shafts are?

I must qualify the above statement to some extent in that I have not had any problem with my bows using heavily over-spined arrows up to 15lbs and sometimes 20 lbs over-spine, but I have never seriously used a bow of such low draw weight either, so there is possibly another dynamic going on here. For instance, I get good straight flight with 55-60 lb spine arrows from my 40-45 lb bows. However, I encounter exactly the phenomenon you are describing with severely UNDER-SPINED arrows, but it is hard to imagine that under-spined shafts is a problem with a 22lb bow.

With regard to applying a finish, just about any reasonable commercially available furniture finish will work. Some are easier than others to apply but there will be plenty of suggestions from other members. The main thing with an all wood bow is to have an effective seal against moisture loss and gain. Ordinary linseed is NOT a good seal against moisture movement, but it looks nice. Currently, I am using Minwax Wipe-on Poly which I got from Bunnings. It is oil-based with a polyurethane compound added. Mine is the satin finish.

Also, if you can, lose the plastic vanes and replace them with feather vanes. You could also try using an arrow of narrower diameter too. If you can get somebody to make some for you, try using some 6mm Bunnings hardwood dowel. You may be able to adapt one of the heads designed for carbon or aluminium shafts to suit. Small diameter nocks won't be a problem. A small amount of hand fitting will sort things out.

[AlexanderArcher]

Dennis,

I looked up the type of arrows i have and found this:
http://www.bowhunterssuperstore.com/eas ... 71942.html

When i say that the flights\feathers are knocking against the wood, i have no padding on my arrow sights so as the semi-rigid plastic flights pass through the sights, they physically hit the side of the wood displacing the end of the arrow. There is a region on my sights where the colors of the flights have been superimposed on the wood because of this knocking and two flights have been knocked off of the shafts because of this. I don't believe there is a problem with the arrow being under the draw poundage weight.

Thanks again,
Alex

P.S. thank you for the quick and detailed reply, I really appreciate it :]

[bigbob]

I would say unless you can get some feathers you will continue to have a problem. Feathers 'fold' as the arrow passes the shelf, whereas vanes remain rigid and kick as they counteract the non yielding wood of the shelf, rsulting in an errant arrow. This will happen regardless of spine.

[AlexanderArcher]

I'm going to make another Massaranduba board bow in the very near future, the wood is incredibly flexible and has great straight grain, should i take some pictures and do a step by step process? I am hoping to get a 4O# at 28" this time.

[AlexanderArcher]

thanks bob, i will look into getting some feather flights as i believe your right. Do you think it would be worthwhile trying to cut multiple tiny slits in the plastic then flay them out a little bit, so as to make them imitate feathers and give them a bit more bend?

[bigbob]

I'm going to make another Massaranduba board bow in the very near future, the wood is incredibly flexible and has great straight grain, should i take some pictures and do a step by step process? I am hoping to get a 4O# at 28" this time.

I for one would be interested in seeing a buildalong with this timber.

[Dennis La Varenne]

Alex,

Before we proceed any further, we need to get some basic terminology sorted out so we can understand what each other is talking about. Could I refer you to A Glossary of Traditional Archery Terms in the Resources section. There, you will find almost all of the terms applicable to traditional archery and their explanation.

When you refer to your 'sights', what do you mean? If you do not use standard archery terms, you will not be understood when you ask a question and that will make it difficult for us to help you out.

You said above that -

There is a region on my sights where the colors of the flights have been superimposed on the wood because of this knocking and two flights have been knocked off of the shafts because of this.

The only places where I have seen this phenomenon occur are either on the arrow shelf or the leading edge of the sight window. You need to explain which it is. If it is on the leading edge of the arrow shelf nearest to you, all you need to do is to raise the nock point on the bowstring about 2 - 3mm and try again. If it occurs again raise the nock point a little more.

What I am trying to advise you on above is possibly/probably due to a tillering problem involving the upper limb of your bow. Moving the nock point is the easiest way to go about it, but if you need to shift the nock point higher than 4 - 5 mm above where it is now, then we need to see some pictures of your bow both at brace height and at full draw similar to those supplied by KellyG in his thread - http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=12567

A picture of you drawing your bow is an excellent way of assessing how YOU draw your own bow and the effect your style is having on the dynamics of its limbs. That way, we can analyse what your bowlimbs are doing and whether or not they are in correct timing.

However, you need to to take the picture with the bow held as vertically as possible and with the camera positioned at 90 degrees to the bow and at the height of the handle area to minimise camera distortion of the limbs. If this is difficult, then pictures of your bow on a tiller at brace height and again at full draw or nearly so are satisfactory.

If the problem is that the arrow is striking the leading edge of the sight window, which is very rare, you probably have either arrow spine problems or, more than likely, you have cut your sight window incorrectly.

If you can describe with of these is occurring using the correct terms, we can proceed from there.

In regard to the plastic vanes, bigbob is correct. They do not fold down like feather vanes when passing over the arrow shelf and often bump vertically up off the arrow plate a small amount which will give wobbly arrow flight. But you seem to be describing what seems to me to be the arrow scraping heavily against some part of your bow. If that is the symptom, then plastic vanes are NOT the problem. I doubt then that turning your plastic vanes into lettuce strips will achieve much. It won't make it any worse, but neither will it improve things.

The vanes at the rear of an arrow correct and stabilise its flight by inducing drag so that the head stays in front of the tail of the arrow. It is similar to how a shuttlecock works. There are other factors involved, but this is the most fundamental of the principles involved in arrow flight.

Anyway, could you supply some pictures of the marks from the arrows you describe above and that will help us to help you.

[AlexanderArcher]

Ok, so heres some photos of my bow and the arrow rest that i have cut out, the orange fluffy stuff is my attempt at softening the knocking effect and raising the arrow a tiny bit.

grip, arrow shelf and very small sight window

IMG_0857.jpg (168.57 KiB) Viewed 11262 times

nocking point and handle\arrow shelf\sight window

IMG_0860.JPG (143.83 KiB) Viewed 11262 times

Bow at brace

IMG_0858.jpg (126.59 KiB) Viewed 11262 times

Bow at full draw

IMG_0859.jpg (127.68 KiB) Viewed 11262 times

if you need more photos, let me know.

Again, thanks for all the help it is VERY much appreciated. :]

[AlexanderArcher]

Ok, it was hitting the leading edge of the arrow shelf. I was told by the archery store owner, where i bought my string and arrows from, to nock the arrow underneath the little gold ring he put on my string. When i read that i needed to lift the arrow a few mm, i nocked the arrow above the golden ring instead; fired off a few arrows and i got quite a few straight shots off but there are still about half of them skewing to the right a little bit as they land in the target, could this be caused by that fluffy stuff i padded the arrow shelf with?

thanks again

P.S. ok i removed the fluffy stuff from the arrow shelf and tried a few more shots, now they bend back the other way, to the left [before it was to the right] but the bend is not nearly as much, so im getting closer. I have some of that paint edgers hair stuff which was posted in the flatline opus takedown buildalong post, seeing as it is alot less thick, i will try to apply some of that and see if it rights the [now left] swing of the arrow.

cheers

[Dennis La Varenne]

Alex,

Firstly, the tillering job you have done is excellent. I have drawn some lines over your pictures which show the distribution of the bending shape of the limbs and the highpoint of the bend is at mid-limb which is most desirable for optimum stress distribution along the length of the limb. You have no problems there.

IMG_0858_2.jpg (113.17 KiB) Viewed 11239 times

IMG_0859_2.jpg (115.07 KiB) Viewed 11239 times

Below, I have overdrawn a small circle where I can see in your other picture where your arrows have been striking the leading edge of the arrow-shelf. Here is my suggestion for correcting your problem.

IMG_0857_2.jpg (87.26 KiB) Viewed 11239 times

You have cut your arrow shelf in way too much and your arrow does not have the necessary control over how it paradoxes past the arrow plate. On a trad bow, the sight window should never be cut past the mid-lline of the bow. This is to ensure that the paradoxing movement of the arrow is controlled to bend in one direction only as it passes the bow.

The way you have cut your sight window well past centre means that the arrow can bend in an uncontrolled manner as it passes the bow. With a sight window which is no deeper than the centre line of the bow, the arrow can only bend in the one direction which is away from the bow.

This sounds counter-intuitive, but in fact, your arrows will actually fly straighter as a result of this outwards pressure exerted on the arrow as it passes the bow. So, get rid of alll that fluffy stuff and fill in your sight window with a block of wood which you can glue into place so that it fills out the sight window area to the level of the blue line which I have marked.

Make sure that this piece of wood is thick enough to be about 3mm to the left of the mid-line of the bow. This is an average amount for a trad bow to be out-of-centre. You should round this piece of wood slightly from back to belly so that the arrow touches the sight window at the smallest possible point. Many archers cover this spot with a small piece of leather to prevent the arrow from scratching the finish on the wood. This piece of leather is called an 'arrow plate' and is applied once the arrow is flying well.

If the arrow strikes too far to the left at the target, you can sand a little bit at a time off the sight window to bring it closer to centre, but it MUST NOT ever be past centre (as it is now) to have the correct effect on your arrow so that it will bend properly as it passes your bow.

I suggest that you google the words 'archer's paradox' to get an understanding of the principle involved. The Ozbow glossary also has a brief explanation, but there are some excellent videos on Youtube showing it in slow motion.

By the way, that little gold ring on the string is called either the 'string nock' or 'nocking point'. You can carefully open it up a bit with a knife and move it up or down to suit your shooting style. Very commonly, we trad archers will simply use a bit of dental floss which we wind around the string to form a small lump about the same size as what you have and cover it with superglue to form a hard ball. That way is easily removed if it needs to be changed and they never slip on the string which the metal ones sometimes do if the serving loosens.

By the way, there is a simple reliable method for working out exactly where to place your string nock based on the geometry of the limbs. I will it explain later if you wish.

Lastly, how did you come to burn the surface of your sight window and part of your handle area???

[greybeard]

Hi Alex,

The following is a fairly simple explanation,

Archer’s Paradox.

"The term archer's paradox refers to the flexing of an arrow shaft that occurs when it is shot from a non-centreshot bow. Coined by Robert P. Elmer in the 1930s, the archer's paradox centres around the idea that, in order to be accurate, an arrow must have the correct stiffness, or "spine", to flex and return back to the correct path as it leaves the bow. The word paradox refers to the fact that in order to strike the center of the target, the arrow must be pointed slightly to its side.
Less powerful bows require arrows with more spine (literally, the ability of an arrow to curve - like a spine). Less powerful bows have less effect in deforming the arrow as it is accelerated from the bow and the arrow must be "easier" to flex around the riser of the bow before settling to its path. Conversely, powerful bows need stiffer arrows, with less spine as the bow will have a much greater effect on the arrow as it is accelerated around the riser.
As the diagram shows, an arrow with too little spine for the bow will not flex and as the string comes closer to the bow stave, the arrow will be forced off to one side. Too much spine, or flexure, will result in the arrow deforming too much and being propelled off to the other side of the target.
In archery, compensation of the archer's paradox led to the invention of the Plunger button, also known as a pressure button or Berger button (after its inventor, Vic Berger)."

Archers Paradox.jpg (25.79 KiB) Viewed 11231 times

Daryl.

[Hamish]

Ian, who goes by "Kombikid" has been making lots of bows from this stuff, over the last couple of years, bought from Bunnings in Qld. It was known as bulletwood in the 20th century, and comes from South America. Although he has made unbacked bows he mainly backs his wood with bamboo. From what he tells me it is a pretty good wood, will make almost any design of bow, though it will sometimes chrysal.
Hamish.

[Dennis La Varenne]

Hamish,

I did a bit of a google search and came up with this Wikipedia reference among lots of others pretty much saying the same thing - http://en.wikipedia.org/wiki/Manilkara_bidentata

The US Forests Products 1999 Handbook of wood properties lists it on Chapter 4 page 16 as Bulletwood with the following properties -

Bulletwood (Manilkara bidentata)
Specific gravity 0.85 which equates roughly to an Air Dried Density of 950 kg/m^3 (Conversion: S.G.x1120=kg/m^3)
Modulus of Rupture (MoR) at 12% moisture content - 188,200 kPa
Janka (side) hardness at 12% moisture content - 14,200 N

It isn't listed in the current edition of Bootle's 'Wood in Australia' unfortunately.

By comparison to Australian Spotted Gum (Eucalyptus maculata, aka Corymbia maculata) for instance (see Bootle 2010, pp418) which is a fairly available indigenous bow wood, we have these mechanical properties -
Air Dried Density (ADD) of 950 kg/m^3
Modulus of Rupture (MoR) at 12% moisture content - 150 MPa
Janka (side) hardness at 12% moisture content - 11 kN

So, Massaranduba is a bit stronger than Spotted Gum, about as strong as both Red and Grey Ironbark but slightly lighter then either, but its strength to mass ration is actually lower. It is also slightly more resistant to crushing and bumps than Spotted Gum and equivalent to the Ironbarks.

Here are the mass to strength ratios (ADD/MoR) of the wood species above -

Massaranduba: 950/188 = 5.05
Spotted Gum: 950/150 = 6.33
Red Ironbark: 1220/135 = 9.04
Grey Ironbark: 1210/181 = 6.68

You can see from the above ratios, that Massaranduba is quite strong per unit of mass meaning that on average, for a bows of given dimensions, a relatively heavy draw weight bow could be made having a relatively low mass and if of equal draw weight, it would be quicker.

For every unit of strength, Massaranduba has just over 5 units of mass, compared to Red Ironbark, for instance which has just over 9 units - almost twice the mass. Hypothetically then, for a bow of equal dimensions to another bow of Red Ironbark, the Massaranduba bow could be almost half the mass and therefore somewhat quicker.

I might have to give it a go myself if I can find any at the Shepparton Bunnings in Victoria. I have attached two downloaded PDF documents from the CIRAD specs for this wood which give it a greater mass and similar strength.

Massaranduba_FSC.pdf

(262.08 KiB) Downloaded 187 times

Massaranduba_kilde_Cirad.pdf

(12.59 KiB) Downloaded 195 times

[AlexanderArcher]

Wow, thank you all for your guidance. For someone like me who is only just starting out, but has a great passion for the creation of bows and also the shooting of them, this information is truly gold.

It has been a few days and some trial and error has occurred. Firstly, i visited my local archery store and bought some feather flights for my arrows, then i promptly removed the plastic vanes and glued on the feather flights. It has been raining constantly in Brisbane the last few days so i have had to do my shooting under my verandah with a hay bale haha, but the feather fletching is working wonders. Now that the suns out i can move my hay bale further away. I have moved the nock point slightly higher up on my bowstring and find that this has eliminated the problem with the arrows hitting the leading edge of the arrow shelf. I am not an expert archer and thus my accuracy needs improvement [which i hope to remedy with time and practice] but i can get very decent groupage with my shots from 2Om, i find that the power is lacking in my bow and i have to compensate for a 1Ocm drop in the arrow flight. All that this means is i need to start my next bow

Dennis,
Thank you for your excellent advice, i will try to build up my sight window to the point you have specified as i fully and wholly believe you. Thank you Daryl for the information you have supplied, it has helped me to understand flight mechanics to a greater degree.

In regards to burning my sight window and part of my handle that piece of wood which i have glued on to thicken my handle area is actually a piece of wood leftover from my first spotted gum bow and that very dark area is actually just where the wood was left out in the weather the lighter areas are where i have rasped clean the wood to make the handle.

again, thanks everyone for your instrumental advice, it has helped me enormously. I will probably start my new massaranduba board bow in the next few days, i will try to take some pictures and create a buildalong :]

[Dennis La Varenne]

Good on you Alex. We are all very glad to help in any way. Do get onto No. 2 bow as soon as you can. Here is a basic principle to remember in self-bow making -

Twice as wide is twice as heavy, but twice as thick is 8 times as heavy.

thickness-draw weight ratio for 20lb bow.jpg (108.89 KiB) Viewed 11174 times

If you make another bow exactly the same length and width as the one you have just made, for every 14% thicker approximately, the bow will increase its draw weight approximately by 20 lbs. 14% thicker is not very much at all. Using an outside caliper is a way to control limb thickness. Here is a picture of one which I drew up in Photoshop if you are not familiar with the tool.

Outside-caliper.jpg (33.92 KiB) Viewed 11174 times

[bigbob]

Yet again some priceless information Dennis. That data should be of use to all who muck about with bow building.

[greybeard]

Alex,

As Dennis pointed out you did well at tillering the bow.

Your photos indicate that the handle area could be improved. When timber is added to thicken the handle this added piece needs to have a gentle transition into the main limb. By doing this you lessen the possibility of creating a stress area.

Cutting the handle fades before gluing to the board will make the job easier.

The following photos may be helpful. By the way the finish is a little rough but the bow was built to evaluate the suitability of horizontal laminated bamboo flooring as limb material.

01 Back Of Bow Handle Area.JPG (29.28 KiB) Viewed 11146 times

04 Fadeout And Transition To Grip Area.JPG (57.24 KiB) Viewed 11146 times

03 Fadeout Side On.JPG (45.09 KiB) Viewed 11146 times

You may notice that in the photo of the braced bow the finer end of the fadeout has started to bend and will bend more as the bow is taken to full draw.

05 Fadeout On Braced Bow.JPG (40.36 KiB) Viewed 11146 times

Daryl.

[AlexanderArcher]

Thanks Daryl,

yeah you are right, i wasn't thinking very clearly when i started this bow, i just really really wanted a bow that i could take out and shoot, so i scrambled to get it all done, but when it came time to put a handle on, there just wasnt enough room for a serious fadeout. Im starting my new massaranduba board bow tomorrow so i'll leave more room for a serious handle. I want to make a recurve but i have next to zip experience so i will probably just end up making another longbow :S I am quite happy with the bow i have now but i cant help but feel like there are serious improvements to be made and i just dont know how. Which is why i vastly appreciate all the help i can get.

In terms of glueing on a good handle, what type of glue should i use? as the glue i used to stick on my current handle has come loose.... twice...
But all i did was stick it straight onto the bare wood i had marked out for the handle area. Any suggestions on making the glue slightly more... permanent?

Thanks all.

[Dennis La Varenne]

Daryl (through Alex),

How did the horizontally laminated bamboo material go in the bow?

I remember somewhere else that you remarked that Craig Ekin used it, but on all 7 of my HH bows that I have bought over time from Craig Ekin (I sold an eighth bow a while ago), they are conventional bamboo laminations with the nodes running across the full width of the lam from side to side and the full thickness of the lamination. There are no nodes which seem to be staggered in any way within a lamination when viewed from side to side.

I have not seen any of this horizontal stuff in timber yards to understand what it is. Would you have any pics or diagrams? I have seen vertically laminated board. I am a bit curious about it.

I am interested in how much set your bow has taken as I have hopes for a project using laminations I bought from Craig Ekin which have been glued up on Jeff Challacombe's form. This blank has 37mm of reflex shaped in a shallow parabola which accelerates toward the tips. To overcome the problem of the nodes on the back, we glued it up with the hose under the back so it would conform to the shape of the nodes as the glue cured.

The limbs are presently 18mm thick for their full length. I will treat the blank as it if is a self-bow and thin it down through the laminations as they did in the old days pre-fibreglass.

Craig also sent me some parallel lengths of offcut with which to do some bending tests which I still have not done yet (but will). I also propose to use the Supertiller Excel programme which Dave Clarke (Yeoman) uses to work out limb thicknesses based on the bending tests to see how well it predicts an end result. Dave seems to be getting very reliable results from it.

Also, I use a different system to making fadeouts on a glued up handle which doesn't need repeating in detail here so that Alex does't get confused as this early stage. Suffice to say that my limb material starts off much thicker at the handle section to which I add the handle in the old fashioned way. The bulk of my fadeout is part of the limbs. However, I like the way yours flexes like it does and opens the possibility of using much thinner limb material.

[AlexanderArcher]

Ok fellows, bow number 2 is on the way. I've cut out a stave from a rather large plank but I have a few questions about dimensions for the limbs, fadeouts, grip and sight window.

With my first bow and a rather large dose of browsing on these forums, it has come to my attention how little i know about bow making and so I've decided to leave the buildalong\tutorials to those more experienced than I. There is nothing worse than someone [that would be myself] teaching new people how to do something WRONG, so i humbly step down. Maybe with time and more experience

Ok, so my current stave dimensions are:
Length: 19OOmm
Width: 44mm
Depth: 21mm

Edit:
Come to the conclusion that i will probably just have to sand the 4Ocm ive marked out for my riser down to an appropriate [and flat] level then glue on my fadeouts, start tillering and sand away at it :S

Sorry to ask for some rough dimensions, i know its an inexact art so im just going to give it a shot.

Thanks all again, I really love making bows and i want to get good at it, i just cant help but feel a little useless\inexperienced all i can do is ask questions, so thank you.

Also, will araldite work to glue on the extra handle wood?

[greybeard]

Dennis,

As a stand alone product used in a selfbow type situation I believe the board that I used failed in all criteria required in a good selfbow, its only redeeming feature was in the spoke shave and sanding department.
Of the thousand or so species of bamboo there is only a hand full suited to produce quality bows.
I would go so far as to say that I would be sceptical in using it as laminations in a glass backed and bellied bow.
Having said this we must remember that the product in question has been engineered for flooring and not bow making.
Node spacing is too close and with three laminations making up the 15mm thickness some nodes can almost lay on top of each other.

Horizontal Bamboo Board.JPG (36.06 KiB) Viewed 11108 times

With regards to the add on handle I have used your method but with the above I only had 15mm to play with.

Daryl.

[Dennis La Varenne]

Daryl,

Yes, I can see from the pictures that there would be structural problems in regard to bending strength for a non-glass bow. At least you had a go and found out though. The kind of riser you have used would need to be long in the fadeouts to work. Mine have often popped off because they were not long and thin enough like yours. That is why I tended to stick with the add-on handles and started with a thicker middle section from which I could shape my dips.

Alex,
With your new bow, you can make it a bit longer than your present bow, because you may want to cut off the bowtip nocks when you have finished. Your board is 21mm thick which is plenty enough to give you a stiff centre section with good fadeouts. Before you start shaping a bow from your board, make sure you glue a block of wood on the side which is to be the belly of the bow. This block of wood should be at least 300m long and deep enough to give you a handle which is anything from 35 to 50mm deep. Glue it in the exact middle of the board so you get something which looks like this -

Basic blank.jpg (42.04 KiB) Viewed 11089 times

After that, you can begin shaping the handle area by blending the handle down into the limbs in the following fashion. This way, there is no danger that the glued on handle will pop off as the bow bends which can happen with glued on handles if one is not careful.

Side profile showing dips.jpg (56.59 KiB) Viewed 11089 times

Next I have a schematic I drew up for another person once before base on using Spotted Gum for a 50lb bow. You can still use the same width dimensions and just make it a little bit thinner to bring it down to your 45 lbs which is 20.4kg.

Spotted Gum 50lb flatbow schematic.jpg (150.25 KiB) Viewed 11089 times

You will notice that the middle section of the limbs is parallel in width. This helps the bow take the huge bending load on the limb in the inner half of the limb. The outer half of the limb becomes progressively narrow to reduce the mass of the outer limbs. Thick and wide outer limbs are slow limbs. We can safely make this part of the bowlimb quite narrow and pretty thin because the amount of bending done in this region is much less than the inner half. There are exceptions of course, but you have enough on your plate with the above for the time being.

In my earlier post above, I recommended you get yourself a cheap outside caliper. This is where you will save yourself a lot of trial and error getting your tiller right. Mark your limbs in 75mm intervals as in the diagram above, and ALWAYS match those thickness dimensions on the other limb exactly. Use your caliper to measure them and scrape the other identical position to match the first or whichever is the THINNER.

Next, you need to make sure that all your thicknesses progressively decrease as you move toward the tips. If there is a thickness anywhere which is thinner than the what comes after it toward the tip, then you have created a weak area which will inevitably break from compression failure. So be very careful as you thin your limbs. Floor tiller your bow often to see that the limbs appear to be bending evenly BEFORE applying a low brace-height string called a 'tillering string' - of no more than 3 or 4 inches of brace height to start with.

The first time you apply the 'tillering string' as we call it, you will see immediately if there is any dys-symmentry in the bends of the limbs. They MUST be symmetrical in shape.

Once they are symmetrical in shape, then you commence sinking your bow to the draw weight you want. 'Sinking' a bow is the bowyers term for reducing the draw weight of a bow. The process is this -

If you want your bow to be 45lbs and the limbs are bending symmetrically at a low brace height, then you draw your bow out gently with the tillering string hooked onto a scale and gently draw it out until it shows 45lbs THEN STOP IMMEDIATELY and take it off the scale.

Check the draw length at which you reached 45lbs. If it is less than your intended draw length (whatever it is), then you need to continue reducing the thickness of the limbs of the stave a bit at a time until the draw weight you desire and the draw length you desire coincide. LIttle and often is the go because you cannot put back on what you take off. Make sure that you scrape the belly side of the stave only for its full length once the limbs are symmetrical in shape. That way, you will preserve the existing tiller of the bow. In this case, the tiller refers to the symmetricallity of the shape of both limbs as they are drawn out when viewed from the side as in your pics above.

A stave, by the way, is the bowyer's term usually for a shaped unfinished bow which is still in the making. It is also used to refer to a log of wood which will be made into a bow.

Anyway, have a good read and get back to us with any questions. I have given you a fairly basic but sound diagram from which you can make a well-functioning bow of pretty much any kind of wood. The draw weight it finishes up with depends upon the density of the wood used. Its speed, apart from the bow's design is a function of some of the mechanical properties of that wood such as its 'modulus of elasticity' or stiffness.

[AlexanderArcher]

Thanks again Dennis for your instruction, sorry for the late reply, ive been busy the past few days. Ok so I've started shaping the bow and I'm following a general outline of the schematics supplied by Dennis [thanks again] and im already up to the tillering stage unfortunately the tillering string i used to tiller my first bow wasnt long enough to fit my 19Ocm stave so I've had to make a flemish string, which turned out quite nicely

Well i ended up using fletching glue to stick on my handle thickening piece as I was rather impatient and wanted to get onto shaping. If it comes loose then ill just sand it down and use araldite.

Thanks again, I'll post some pictures soon :]

[Dennis La Varenne]

Alex,

Here are some pictures from eBay which are good illustrations of the classic method of adding a glued-on handle block. This is a picture of an old Bear lemonwood flatbow from the 1940s. This method of building up a handle is the standard method from those times up until the 1950s and the advent of the fibreglass era.

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The old bow depicted is one of the most beautifully elegant designs I have seen in a factory made bow from that era. Here are some pics of its shape. I believe it is about 64 inches long and has the characteristically narrow handle from that era which is not much more than 1 1/2 inches (38 mm) deep. Note in the last picture that the amount of string follow is only the same amount as the depth of the handle which is quite good even by today's standards and particularly so since in those times, Lemonwood was regarded as one of the worst performing of the bow woods, even though it was one of the most reliable against breakage and could be used for the mass production of bows, just as this one was.

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The back of this bow is dead flat, while on the belly it is slightly rounded as you can see in the following picture. There is no particular performance advantage to a rounded belly, but it does make tillering much easier and quicker because it is easier to remove thickness from the top of a convex surface than a flat one - a significant labour/time saving when producing bows in a factory.

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[AlexanderArcher]

Thank you again dennis,

Ive incorporated some serious fadeouts into my handle section now and ive had a problem with the handles constantly falling off and i determined it was because they werent bending enough with the bow and\or the glue isnt strong enough so i lathed down my glue-on piece so it should bend a little now.

I tillered my bow now and it bends well with a 48-5O# approx. draw weight ^_^ which is about perfect. All i have to do is glue on my handle and rasp out a grasp and arrow rest\sight window. Then comes the shooting

I promised pictures but my dads iphone [which i was using before] is currently in sydney :\ and not available to me. but they shall come

[Dennis La Varenne]

Alex,

It would have been better had you glued on your handle block BEFORE you started work on your bow - not after. Also, as you can see from the pictures of the old Bear Lemonwood bow above, you do not need to cut an arrow shelf into your bow. The one in the picture has a small leather wedge glued to the shooting side of the bow at the level of the arrow pass. Your arrow will sit on such a wedge well enough and shoot fine.

The handles popping off is a combination of unfortunate glue type and/or the handle block being able to flex too much when the bow is drawn. The style of glue-on handle shown in the pics above get around this problem.

[AlexanderArcher]

Sorry, it was an unfortunate use of words, i had in fact glued on the handle before i started work and sanded it all down as one, but during the very final stages of development the handle fell off again bloody damn it. oh well.

[Dennis La Varenne]

Alex,

Seems like the glue wasn't up to the job.

[greybeard]

Alex,

I checked a couple of web sites and found the following;

HOW WELL DOES IT WORK?
Despite having a high density, the wood is easy to work with in all operations. Gluing Massaranduba requires extra care. Lumber has excellent steam bending properties.

WORKING PROPERTIES: Bores, planes, moulds, carves and screws easily. May be difficult to cut and sand. Does not glue well.

The timber may be greasy / oily by nature and being extremely dense may not readily absorb glue very well.

If you haven’t already done so roughen the areas to be glued to aid the bond, wash the areas with mentholated sprits and allow to dry. Apply a two part epoxy to both surfaces, bring together and clamp. Use as many clamps as needed to obtain an even pressure. Do not apply excess pressure with the clamps as you may squeeze out too much glue and end up with a dry joint.

The steam bending properties of the timber may make it suitable for a semi recurve style of bow.

Daryl.