blue foam - cell size

[jpolenek]

Has anybody else noticed that the Styrofoam that Aircraft Spruce sells for wing cores is NOT the same product as Dow STYROFOAM Buoyancy Billets? Buoyancy Billets have a smuch smaller cell size. Should I expect a different cutting speed for the same wire temperature?

 

Joe Polenek

[rickh]

Sort of!

 

I think the boyancy billets are 2 lb /ft.^2 (same/similar as the wall foam sheets you get at the home center), the wing foam is 1.6 lb ft.^2 from what I read.

 

ACS says their foam is 2.0 lb. (edit: I think this is a typo in their description), Wicks says theirs is 1.6 lb. At least in my catalogs.

 

Related, Dow also makes a pipe insulation billet, which is 1.6 lb., and is sold by them in blocks which are the same size as the longest/widest/thickest ACS sells.

 

Confused?

 

Rick

[jpolenek]

Has anyone successfully used the 2.0 lb/cu.ft. buoyancy billet with the smaller cell size and can reassure me that it is OK???

 

Having cut a good portion of my cores using the buoyancy billets, I'm having some serious doubts about the suitability of the material and could use some reassurance (if it is warranted). When I compare the two foams, the product from ACS feels "crunchier" when I crush it, snap it or drive nails into it to attach templates. When I take similar sized slivers of each and bend them, they seem to be the same, but for some reason, the ACS material just feels stiffer when I try to crush it. It's hard to tell how much of that is just perception becuse of the different cell size.

 

Part of me is considering cutting my losses and scrapping it all out and doing the cores over again with the plans-prescribed material from ACS. On the other hand, I'd hate to waste all that time and money if it's not necessary.

 

Any advise would be greatly appreciated.

 

Joe Polenek

[rviglierchio]

The fellow doing CNC wing and winglet parts should be able to help you.

 

http://www.eurekacnc.com/

[Lynn Erickson]

Has anyone successfully used the 2.0 lb/cu.ft. buoyancy billet with the smaller cell size and can reassure me that it is OK???

 

Having cut a good portion of my cores using the buoyancy billets, I'm having some serious doubts about the suitability of the material and could use some reassurance (if it is warranted). When I compare the two foams, the product from ACS feels "crunchier" when I crush it, snap it or drive nails into it to attach templates. When I take similar sized slivers of each and bend them, they seem to be the same, but for some reason, the ACS material just feels stiffer when I try to crush it. It's hard to tell how much of that is just perception becuse of the different cell size.

 

Part of me is considering cutting my losses and scrapping it all out and doing the cores over again with the plans-prescribed material from ACS. On the other hand, I'd hate to waste all that time and money if it's not necessary.

 

Any advise would be greatly appreciated.

 

Joe Polenek

Thats what my wings are made of. the smaller cell foam is what most of the long ezes are made of. the larger cell foam was not used until the 90's. I like the smaller cell stuff better, it sands smoother and takes less micro to fill the cells.

[jpolenek]

Thats what my wings are made of. the smaller cell foam is what most of the long ezes are made of. the larger cell foam was not used until the 90's. I like the smaller cell stuff better, it sands smoother and takes less micro to fill the cells.

THANK YOU!!! :banana: :banana:

 

I would have used more dancing bananas, but that's all that the program would allow. (Can you tell I'm relieved? )

 

Joe Polenek

[jpolenek]

Just for shits&giggles I cut some sample pieces of the various Styrofoam types and weighed them to get the density. Here's the summary:

 

Group 1 (4 pieces)

Styrofoam Buoyancy Billet

purchased around 2004

*** slightly lighter blue colour than Groups 2 & 3

avg. density = 1.95 lb/cu.ft.

 

Group 2 (4 pieces)

Styrofoam Buoyancy Billet

purchased in 2007

*** identical Product Code and Dow manufacturing plant as Group 1 (printed on billet)

avg. density = 1.83 lb/cu.ft.

 

Group 3 (4 pieces)

Styrofoam block from Aircraft Spruce

*** larger cell size than groups 1 & 2

avg. density = 1.98 lb/cu.ft.

 

The samples were cut to around 1.25" x 1.25" x 14" and I did a deflection test by cantilevering 12" of it and putting a 0.3920 weight (my measuring tape) at the end. The deflection ranged from 3/8" to 7/16" without any correlation to sample group, so they seem to have a similar modulus of elasticity.

 

So it turns out that my BB foam may be slightly lower in density than the ACS product. (I say "may be" because of the statistical (in-)significance of such a small sample size). Therefore, weight shouldn't be a concern, but the potential effects of the smaller cell size on peel strength may still exist.

 

Has anybody else verified the density of their Styrofoam (Buoyancy Billets or ACS blocks)?

 

Joe Polenek

[macleodm3]

Now you need to do a sample peel test pull. Has anyone seen a good way to do a peel/pull test?

[JCPJCP]

Here's and interesting link to some foam info:

 

http://www.diversifoam.com/cfproperties.htm

 

Not specific to our application, but shows the ASTM foam insulation standard.

 

JCP