Foam wing - balsa skin ve obeche

[Graham Bowers]

The Kaos 90 plan on Outerzone specifies a foam core wing skinned with 3/32 balsa.

 

I'd use a supplier for the wing and skinned with obeche at around 0.7mm seems to be what passes for normal.

 

As far as I can tell, the mechanical properties for obeche are around triple that of balsa so thickness for thickness they seem to be equivalent. So tempted to just do it with no other compensations, other than growing the cross section to make up for the lost thickness.

 

Any other views please?

 

https://outerzone.co.uk/plan_details.asp?ID=5216

https://www.wood-database.com/obeche/

https://www.wood-database.com/balsa/

[Engine Doctor]

Balsa gives a much better finish , doesnt ripple like obeche if glue fails and doesnt split open like the current obechi seems to. 

Years ago i would definatetly have gone with obeche as is seemed much more consistent than the present offeringsof obeche but would now opt for balsa every time.

Of course since our winnd farms have collard the market for balsa our choice of weight , grain etc has been severly affected. 

Others may have different views or experiences but it would be balsa for me.

 

[kc]

USA designs almost always used balsa to cover foam wings, whilst British designs normally used obeche veneer.   In Britain wings were supplied ready veneered, but USA supplied plain foam for the builder to skin with balsa.

Obeche veneer used to be cheap but not now.   Balsa is expensive but the balsa offcuts can be used for other things but obeche offcuts are less useful except for tailplanes or fins.

 

The glassfibre or other centre section reinforcement is the important thing in foam wings.

Edited June 29, 2023 by kc

[Graham Bowers]

9 hours ago, Engine Doctor said:

Balsa gives a much better finish , doesnt ripple like obeche if glue fails and doesnt split open like the current obechi seems to. 

Years ago i would definatetly have gone with obeche as is seemed much more consistent than the present offeringsof obeche but would now opt for balsa every time.

Of course since our winnd farms have collard the market for balsa our choice of weight , grain etc has been severly affected. 

Others may have different views or experiences but it would be balsa for me.

 

Thanks for that. I did re-skin in balsa an old foam wing that had suffered glue failure - albeit after a couple of decades.

 

[Graham Bowers]

9 hours ago, kc said:

USA designs almost always used balsa to cover foam wings, whilst British designs normally used obeche veneer.   In Britain wings were supplied ready veneered, but USA supplied plain foam for the builder to skin with balsa.

Obeche veneer used to be cheap but not now.   Balsa is expensive but the balsa offcuts can be used for other things but obeche offcuts are less useful except for tailplanes or fins.

 

The glassfibre or other centre section reinforcement is the important thing in foam wings.

An interesting insight into why balsa was probably chosen in the first instance, thanks.

[Nigel R]

I would happily use a wing skinned with either balsa or obeche.

 

Or poplar seems to be available at reasonable cost, too. Never used it though. 

[Graham Bowers]

8 hours ago, Nigel R said:

I would happily use a wing skinned with either balsa or obeche.

 

Or poplar seems to be available at reasonable cost, too. Never used it though. 

Poplar is an interesting option, thanks for drawing that to my attention.

[Paul De Tourtoulon]

I have only used Samba, unless I want something really light, then it's balsa.

 

 Opps, Obeche in English,,,

Edited June 30, 2023 by Paul De Tourtoulon
opps