Main Discussion Area > Arrows
Shaft compression...why?
mikebarg:
Does anyone know of any videos out there showing the compression process?
Pat B:
I think 3Rivers sells a compression block. I have poplar shafts Charlie Jefferson sent me. I think he chucked the end of the shaft in an electric drill and drove them through the tapered hole in the compression block. As the shaft is spun and compressed it heats up which also burnishes the shaft. The company that makes the compression block may have a video or you could check out You Tube.
TSA:
if i may be so bold as to offer some input here.
some fact, some opinion, and some conjecture ;D )P(
so there are two types of compression here- besides the "compression straightening"
1. as P D says, where a good shaft is reduced in size by using a compression block.
heres something to bear in mind with spine, it is dictated , primarily by two principle factors
a. the actual chord depth, so like a roof truss, the deeper the chord, the greater the stiffness, in turn the bigger the diameter of a tube, the greater the stiffness.
b. the greater the quantity of material, the greater the stiffness.
both these factors work hand in hand, as when you increase the diameter of a dowel, so you also inadvertently also increase the volume of material.
However based on my experience the volume of material seems to be the greatest factor at play- any engineers please give input!
so, in turn, if you take a 23/64 shaft, and you reduce it to 11/32 you should retain a lot of the higher spine value of the original 23/64. due to the fact that you have retained all the original material, but simply reduced the diameter a wee bit.
in my experience you lose a bit of spine, but not as much as if you were going to simply sand it to 11/32, removing the extra material for good.
many shafts are also burnished, because the maker cant, or wont sand them.
As the dowel exits from the cutter heads, marginally oversize, they are then immediately put through a compression block ( same machine , compression block is right behind the dowel head). to reduce them to final size, and to create a smooth surface, as the cutters leave a rough surface.
Pitchy woods like Pine, are really difficult to sand, so they are doweled oversize, then compressed to final size.
then compression process no. 2.
this is full compression of the wood, ie: the old Sweetland Forgewood process.
Where an entire flitch ( board) is compressed by a factor of as much as 3 ( in other words a 3" thick board compressed to 1" thick), blanks are cut from this processed board, and then shafts spun up from the blanks.
Pro's of this process are incredibly high spine in smaller diameters- Bill Sweetland was getting 100# shafts in 5/16, but they do come with higher mass, which is not entirely a bad thing for hunting.
they are tough, durable, and of very high spine.
contrary to some misinformation out there, the POC is not the only wood able to be compressed, Bill ran many tests, he like the POC best, but many other woods were equally suitable.
he even compressed Western Red Cedar , to such an extent that it wouldnt float!!
i have seen some hemlock shafts made by this process, and they performed incredibly well.
cheers ;)
Todd Mathis:
--- Quote from: Deerhunter21 on November 12, 2019, 09:09:52 am ---wait, do you mean compression straightening, or compressing the whole shaft?
--- End quote ---
I'm actually not sure...I have been reading here and other places about compressing wooden shafts, and I was wondering why they do this.
Todd Mathis:
--- Quote from: TSA on November 14, 2019, 12:13:58 pm ---if i may be so bold as to offer some input here.
some fact, some opinion, and some conjecture ;D )P(
so there are two types of compression here- besides the "compression straightening"
1. as P D says, where a good shaft is reduced in size by using a compression block.
heres something to bear in mind with spine, it is dictated , primarily by two principle factors
a. the actual chord depth, so like a roof truss, the deeper the chord, the greater the stiffness, in turn the bigger the diameter of a tube, the greater the stiffness.
b. the greater the quantity of material, the greater the stiffness.
both these factors work hand in hand, as when you increase the diameter of a dowel, so you also inadvertently also increase the volume of material.
However based on my experience the volume of material seems to be the greatest factor at play- any engineers please give input!
so, in turn, if you take a 23/64 shaft, and you reduce it to 11/32 you should retain a lot of the higher spine value of the original 23/64. due to the fact that you have retained all the original material, but simply reduced the diameter a wee bit.
in my experience you lose a bit of spine, but not as much as if you were going to simply sand it to 11/32, removing the extra material for good.
many shafts are also burnished, because the maker cant, or wont sand them.
As the dowel exits from the cutter heads, marginally oversize, they are then immediately put through a compression block ( same machine , compression block is right behind the dowel head). to reduce them to final size, and to create a smooth surface, as the cutters leave a rough surface.
Pitchy woods like Pine, are really difficult to sand, so they are doweled oversize, then compressed to final size.
then compression process no. 2.
this is full compression of the wood, ie: the old Sweetland Forgewood process.
Where an entire flitch ( board) is compressed by a factor of as much as 3 ( in other words a 3" thick board compressed to 1" thick), blanks are cut from this processed board, and then shafts spun up from the blanks.
Pro's of this process are incredibly high spine in smaller diameters- Bill Sweetland was getting 100# shafts in 5/16, but they do come with higher mass, which is not entirely a bad thing for hunting.
they are tough, durable, and of very high spine.
contrary to some misinformation out there, the POC is not the only wood able to be compressed, Bill ran many tests, he like the POC best, but many other woods were equally suitable.
he even compressed Western Red Cedar , to such an extent that it wouldnt float!!
i have seen some hemlock shafts made by this process, and they performed incredibly well.
cheers ;)
--- End quote ---
Thanks very much! I think I have a better understanding now. Don't know if if means anything for bamboo, but I do LOVE to shoot wooden shafts.
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