Arrow weight for longbows

[woodsplitter]

I've read in few places about bows needing the arrows to "Slow the bow down" so that it is not damaged when being shot. Does anyone know how to calculate the minimum weight of arrows for a particular bow. I mean physical weight, not spine.
My birthday is coming up soon, so now might be a good time to start dropping hints to the nearest and dearest about books - any suggestions,? Mind you, I spent about a month every year for about ten years using words like "book", "poetry" "First" "World" and "War", as in the sentence "I should get myself a good book of First World War poetry.". Eventually I did.

[jaselpool]

Originally Posted by woodsplitter

I've read in few places about bows needing the arrows to "Slow the bow down" so that it is not damaged when being shot. Does anyone know how to calculate the minimum weight of arrows for a particular bow. I mean physical weight, not spine.
My birthday is coming up soon, so now might be a good time to start dropping hints to the nearest and dearest about books - any suggestions,? Mind you, I spent about a month every year for about ten years using words like "book", "poetry" "First" "World" and "War", as in the sentence "I should get myself a good book of First World War poetry.". Eventually I did.

Hi there - IMO it's not the weight of the arrows it's the arrow spine that matters. Hunters in US etc use heavier arrow weights because they want the penetration and are shooting much closer distances whereas we target/clout/field archers generally prefer a lighter arrow that can travel various distances with the correct flight pattern. The arrow spine is what affects the 'Archers Paradox' which is the way an arrow bends around the bow and then straightens out. If you are shooting a heavy poundage and try shooting a spine that is too low for your bow it has the same affect as 'dry shooting' your bow which will cause serious damage. Various diameters of shafting start at certain spine weights as in 5/16 comes usually from 15-50lb, 11/32 usually comes in 40-70lb and 23/64, 3/8ths upwards from there. Different woods also have different weights Port Orford Cedar probably being the lightest and something like an Australian Victorian Ash hardwood being one of the heaviest in density. Sorry if I'm teaching you to suck eggs but not sure on how much knowledge you have so trying to be as basic as possible!

Just my opinion though and I'm sure there are others that will disagree and have their own thoughts

[jb.68]

I agree that the spine is important as it generally determines the weight. I.e as it gets stiffer, it gets thicker and therefore it also gets heavier as it gets thicker.

[jaselpool]

Originally Posted by jb.68

I agree that the spine is important as it generally determines the weight. I.e as it gets stiffer, it gets thicker and therefore it also gets heavier as it gets thicker.

Hi - nope disagree there sorry. You can have different diameter of shafts and they will weigh the same and have the same spine it depends on your choice of wood. I can have a 5/16 victorian ash hardwood shaft measure in the 450s and have a 23/64 POC shaft measure in the 300s. It's just as much down to wood density for weight not necessarily diameter.

[alanesq]

If an arrow is too light for a bow, when the arrow leaves the bow there will still be a lot of energy in the bow which will be released as hand shock and could damage the bow

So I guess there is a perfect weight of arrow for any bow where the arrow will just be leaving the bow when all the available energy has been given up by the bow ?

I figure that if the bow doesn't complain when I loose an arrow then it's ok
if I get a lot of hand shock/noise then I will look at increasing the arrows weight

[Ceri Jones]

alanesq: do the eyes on your avatar flash or is my screen on the way out?

[alanesq]

Originally Posted by Ceri Jones

alanesq: do the eyes on your avatar flash or is my screen on the way out?

Yes !
You wouldnt believe how long I spent getting this completely pointless feature set up :-)

Its an animated GIF file - easiest way to make one is with UnFREEz.exe http://www.whitsoftdev.com/files/unfreez.zip

[jb.68]

Originally Posted by jaselpool

Hi - nope disagree there sorry. You can have different diameter of shafts and they will weigh the same and have the same spine it depends on your choice of wood. I can have a 5/16 victorian ash hardwood shaft measure in the 450s and have a 23/64 POC shaft measure in the 300s. It's just as much down to wood density for weight not necessarily diameter.

You are of course quite right. I was talking generally and was not differentiating between species. Hardwoods are (again generally) denser than softwoods, and therefore will weigh more.

[steve58]

Originally Posted by jaselpool

Hi there - IMO it's not the weight of the arrows it's the arrow spine that matters. The arrow spine is what affects the 'Archers Paradox' which is the way an arrow bends around the bow and then straightens out. If you are shooting a heavy poundage and try shooting a spine that is too low for your bow it has the same affect as 'dry shooting' your bow which will cause serious damage.

Hi Jaselpool. This is a new piece of information to me. I thought that the only likely problem with low spined arrows was that they went right (for a RH shooter). I have some Sitka Spruce arrows, 5/16", rear taper, 3" low shield fletch, 63 grain points, probably weigh about 28 grams an arrow. The heaviest spine HiForce had in 5/16" Sitka was 35/39# so I used those. They fly as nice as you like and do not go right at all. I reckon I have 52# on my fingers now, as the bow has followed the string a little. Now you have me worried that I may be damaging the bow shooting these off it... Should I be worried?

[jaselpool]

Originally Posted by steve58

Hi Jaselpool. This is a new piece of information to me. I thought that the only likely problem with low spined arrows was that they went right (for a RH shooter). I have some Sitka Spruce arrows, 5/16", rear taper, 3" low shield fletch, 63 grain points, probably weigh about 28 grams an arrow. The heaviest spine HiForce had in 5/16" Sitka was 35/39# so I used those. They fly as nice as you like and do not go right at all. I reckon I have 52# on my fingers now, as the bow has followed the string a little. Now you have me worried that I may be damaging the bow shooting these off it... Should I be worried?

I wouldn't be overly worried personally about shooting a spine that low on a 52lb bow as long as your spine is nearer the 39 mark than the 35. General rule of thumb is 10lb lower than bow weight for english longbow and around the same as the bow weight for AFB. You don't mention your draw length? Your draw length will affect overall spine a little. If you are drawing 28" then your arrows will be actually a little stiffer due to the low weight on your points. You are more than likely adding about 3-4lb extra dynamic spine with points that light which would bring you in line with a spine close to your bow poundage. If you are shorter or longer draw than 28 this will also affect spine ratio. 1" longer add 5lb spine, 1" under subtract 5lb. So if you were drawing 28" with those points you'd be looking around 39-43lb spine. if you draw 29" you are looking at 34-39 (a bit too low IMO) If you are drawing 27" then you're looking at 42-47lb (slightly too high). All this of course is a rough guide and things such as shooting style needs to be taken into account.

Again just my opinion as there are several school of thoughts and as with most trad stuff there are always several ways to do things

J