How much sap?

[rodlonq]

Hello All,

I have an opportunity to get some grey ironbark staves cut by a bloke who has a mobile saw mill. When I discussed the requirements with him he asked "how much sap do you want". Apparently the thickness of the sap layer depends a lot on the local conditions and varies from less than 3 mm out to 13 mm or more on trees grown in "softer" country.

Could someone kindly advise what would be the most suitable amount of sap to ask for? Thanks.

I am going to pick up the staves as soon as they are cut so I can have a go at forcing a bit of shape into some of them while drying., ie. some amount of reflex for long bows and perhaps try to recurve a stave as shown in TBB1. Does this work for grey ironbark?

I think I will rough one out for quick drying so I can get started sooner. Do I need to seal the length of any cuts across grain such as the along the belly and the curve leading into the riser etc?

These are probably only the first few questions I will be asking. I hope you guys & gals don't mind a lot of extra reading over the next few months! I'm really looking forward to getting the first one built

Thanks, Rod

[ichiban]

just sealing the ends should be fine, in regards to sap i may be wron but i dont think it would matter as iron bark is tough stuff but im not sure

[longbow steve]

Hi Rod, Probably less sap wood would be better otherwise you run the risk of the whole limb being sapwood on a 50# flat bow. An deep limb narrow longbow should pick up the heart wood.
Seal the back and ends. Steve

[ichiban]

ahh good point

[rodlonq]

Thanks Ichi and Steve,

I am aiming for around 45-50#@28", but it doesn't matter what style of bow I end up with. In fact it would be good to try various types.

I gather it is the sap that is elastic and better in tension while the heart wood is better in compression than the sap, is this right? If so I guess it would be a case of building the bow so the sap/heart interface is along the neutral axis of the working parts of the limbs. The amount of sap on a given stave would possibly dictate whether the design is to be flat or deep????

Perhaps I should ask the gentleman for some of each and experiment with them.

Cheers, Rod

[longbow steve]

I dont think there is much of a discernable difference between heart wood and sap wood on Grey iron bark. I gave some staves to a friend to test the timber and one flatbow ended up being 100% sapwood limbs and it was functional.
Heart wood looks better and probably is better?? Steve

[Glenn]

Rod, I have made several selfbows from red and grey ironbark. One bow I have which is a flat bow has the sapwood running around into the belly, this bow has had many shots put through it and I have taken several game animals with it and it has taken very little set. I woud do as you say and try different thicknesses of sapwood to see what works...Glenn...

[rodlonq]

Thanks to you both, Steve and Glenn.

[ichiban]

i think the major difrence between the sap and heart wood in yew stems from the fact that its a conifer and a soft wood where as things like ironbark both sap and heart wood are HARD!!!