Wing Styrofoam for EZ/Cozy

[ColdLake-Tim]

Checking Aircraft Spruce on-line

 

One of the selections of large styrofoam blue blocks has round corners........Floatation Billets have round corners...(?)

 

Tim

Cold Lake

[EZ AHAB]

Well, I never heard back from RAF or ACS or Wicks but now I've seen quite a bit of foam from a number of sources. What I've found is that there is some variation not only between batches but sometimes even within a batch. I'm now convinced that the foam I've sampled from each source (including Wicks, ACS, and Featherlite) is the same stuff and it's the same stuff I'm using as well. This explains the different densities given from Wicks vs. ACS.

[EZ AHAB]

Oh, BTW, I also sampled some floatation billet foam. It is obviously not the same stuff as the wing foam called for in the plans. It has smaller cells and looks more (but not exactly) like the blue DOW squaredge you can get at Lowes or other building supply stores.

[ErlendM]

I'm still looking for alternative sources for the wing-foam and discovered something interesting today.

 

I have a friend that builds an Europa (http://www.europa-aircraft.co.uk/).

I asked him to send me a sample of the foam his wings are buildt of. It turns out that this styrofoam is not the "large-cell"-type that are used in the Cozy/Long-EZ but the small-cell. I bought samples of the small-cell and the large-cell from AircraftSpruce to compare, and it's no doubt about the type beeing small-cell.

 

The question is then: If small-cell is used in the Europa - would it be safe to use it in a Cozy?

 

Here is a link I found to a site where they build the wings: http://www.loginet.nl/europa/eurowing.htm

[Marc Zeitlin]

The question is then: If small-cell is used in the Europa - would it be safe to use it in a Cozy?

Having used the plans foam for my wings, and having used what I believe to be the "small cell" foam for a few odds and ends, I certainly wouldn't use the small cell foam for my wings. It is not nearly as stiff (whatever the density equivalence) as the large cell polystyrene foam, and I'd be worried about it's skin support capabilities with respect to skin buckling. The Europa is a much slower plane than the COZY - the dynamic pressures on the skin are far lower, so the small cell foam may be perfectly adequate there, where it might not be for the COZY.

 

Now, I know that there are folks in other parts of the world (South Africa, for one example) where people have used Styrafoams other than the plans specified ones for wings, and seem to have had no issues (yet). But I wouldn't do it. The density is NOT the only characteristic property of the foam that's important.

[Lynn Erickson]

Having used the plans foam for my wings, and having used what I believe to be the "small cell" foam for a few odds and ends, I certainly wouldn't use the small cell foam for my wings. It is not nearly as stiff (whatever the density equivalence) as the large cell polystyrene foam, and I'd be worried about it's skin support capabilities with respect to skin buckling. The Europa is a much slower plane than the COZY - the dynamic pressures on the skin are far lower, so the small cell foam may be perfectly adequate there, where it might not be for the COZY.

 

Now, I know that there are folks in other parts of the world (South Africa, for one example) where people have used Styrafoams other than the plans specified ones for wings, and seem to have had no issues (yet). But I wouldn't do it. The density is NOT the only characteristic property of the foam that's important.

Most Vari ezs and long ezs wings are made with the small cell foam that is what the suppliers sold until early 90s when we starting seeing both large and small both sold as the same thing. it has only be recent that the suppliers have learned that there is a difference. my wings are made with the small cell and I have not seen any problems.

[ErlendM]

I've been talking to Chris in South Africa. He will send me a sample so I can compare with the foam I already have. I guess that with their 540-machines it has to be good enough?

I am also going to talk to the local EAA to see what they feel. Not many EZ's have been built in Norway, so it's rather easy to track the builders down and ask them as well.

The saga continues...

[steve]

i have both small and large and in the testing i have done, there is nothing that the eye can see. the peel on the small cell seams to hold up better them the large. but it is so close you could change the results with room heat. so i could not find a difference.

[ErlendM]

i have both small and large and in the testing i have done, there is nothing that the eye can see. the peel on the small cell seams to hold up better them the large. but it is so close you could change the results with room heat. so i could not find a difference.

I am going to perform tests myself with the plans foam and my local foam. Will test both peel-strength and compression. I have already tested that the plans foam are much more brittle and will break off / snap with less pressure than my local foam. If I press with a finger on the plans foam the cells will chrush leaving a big indentation while the same pressure on my local foam will result in a much smaller indentation as the cells will decompress slightly when the pressure is gone.

 

What I need to know is the compressive-strength on the plans foam. This value is not mentioned anywhere as far as I have managed to search. I have found tech-specs of the Dow Styrofoam FB - but this is the small-cell foam as far as I know. Does anyone have the brand-name of the large-cell-foam? Or even better - does anyone know the values of the compressive-strength? My local foam - with the same density as the plans foam (2lbs/cu.feet) has a compressive-strength at 300kN/m2 (43.5 PSI). Styrofoam FB has a compressive-strength at 200kN/m2 (29 PSI) at the same density.

[steve]

I am going to perform tests myself with the plans foam and my local foam. Will test both peel-strength and compression. I have already tested that the plans foam are much more brittle and will break off / snap with less pressure than my local foam. If I press with a finger on the plans foam the cells will chrush leaving a big indentation while the same pressure on my local foam will result in a much smaller indentation as the cells will decompress slightly when the pressure is gone.

 

What I need to know is the compressive-strength on the plans foam. This value is not mentioned anywhere as far as I have managed to search. I have found tech-specs of the Dow Styrofoam FB - but this is the small-cell foam as far as I know. Does anyone have the brand-name of the large-cell-foam? Or even better - does anyone know the values of the compressive-strength? My local foam - with the same density as the plans foam (2lbs/cu.feet) has a compressive-strength at 300kN/m2 (43.5 PSI). Styrofoam FB has a compressive-strength at 200kN/m2 (29 PSI) at the same density.

could you plz tell me how to lay out the foam to do the psi test?

i have both foams and can do it tonight.

[ErlendM]

could you plz tell me how to lay out the foam to do the psi test?

i have both foams and can do it tonight.

Well - my plan was to cut a piece of 2" x 2" of each foam and weigh them down with the same weight and then see how much weight it takes until I can actually measure the compression. My foam is rated at 300kN/m2 = 43.5 PSI. I need quite some weight since my test-area is 4 sq. inch, but I have access to a lot of lead, so I will make some blocks that I later can use as ballast in my Cozy :-)

 

It would of course be a lot easier if I was able to get the figures from Aircraft Spruce, but that seems to be very difficult.

[swpletcher]

A couple of years ago, I spoke with Fred Keller by phone. He is the one that drew the plans for the Defiant. He told me that he used the Dow floatation billets for his wings. However, I have found that if you call Dow and ask questions DO NOT use say anything about planes, or they will hang up on you. They don't want the liability. I haven't been able to build yet due to my daughter still in college so I can't say how this foam performs, however unless there is concrete evidence that it is dangerous to use,  I plan on using it. If Bert and Fred used it on the Defiant, then it must be ok.

 

Steve

[ErlendM]

Well - I ended up travelling the safe road and bought the right stuff from Dow in Germany. Had to pay lots of $$$ in freight. But better safe than sorry... :-)

[Jon Matcho]

Wow... this thread is a history lesson in more ways than one!

 

Well - I ended up travelling the safe road and bought the right stuff from Dow in Germany.

 

So what are the specs of the 'right stuff'?

 

 Had to pay lots of $$$ in freight.

 

Yes, bulky but light items costs a lot to ship here in the U.S. as well.  I had to leave a bunch behind recently that I just couldn't figure out how to ship economically. 

[ErlendM]

So what are the specs of the 'right stuff'?

 

That is a very good question, Jon.

 

I have tried without success to find complete specs on the various type of foam.

I ended up buying the "Flotation Billet" type of Styrofoam, with large cell structure. Since this is what's recommended in the plans, I figured this was the safest/easiest way to go. 

Even though I know planes have been successfully built and flown with other types of Styrofoam. 

 

I did test the large cell and the small cell. I didn't find any particular difference in peel strength. I found the compression-strength to be almost identical, with one big difference: The large cell crushes more easily than the small cell when I tested with heavy weights placed on the foam.

 

Since these tests were very unscientific, I decided to just bite the bullet and buy the large cell foam and go on with the build. But I am pretty sure that the small cell is more than adequate for us, especially when people claims that this was the "right stuff" before the large cell foam appeared on the market.

[Kent Ashton]

The spec'd foam is 2 lbs per CF. It is probably this stuff which works out as the same wt

http://building.dow.com/na/en/products/specialty/billets.htm

[Jon Matcho]

Kent, that is the stuff, and comes out to ~1.8 lbs/ft^3.

I grabbed a foam billet I had lying around (which I thought was the 1.6 lb/ft^3 I bought from Wicks -- I could be wrong), measured and weighed it, and came out with 1.96 lbs/ft^3 (essentially 2 lbs/ft^3).

The original plans (all EZs and Cosy/Cozys) do not specify anything more than "Styrofoam blocks". I could not find anything more specific in the Cozy newsletters other than a clarification that Styrofoam is a brand name (from Dow Chemical) of Polystyrene foam. However, in Canard Pusher #10 I found the following:
 

If you are searching for substitutes do not accept any material which has lower strength or other physical properties than the recommended materials as follows:

Blue Styrene: Dow Chemical Co. Brand F.B. Styrofoam, 2 +/- 0.2 lb/ft^3 density, cell size 1.4 to 2.4 mm.

 

Note the "F.B." abbreviation which I assume means 'floatation billet'.

So there we have it, except for the Wicks 1.6 lb/ft^3 foam that Wicks is selling (and many are using for wings). I wonder if it truly is 1.6 lb/ft^3, and weather it matters assuming the cell size is correct.

 

I'll end with the three important points I gleaned from this thread:

1. Open cells are essential to having a mechanical bond between the skin and the foam, and
2. 'small cell' or 'large cell' is not mentioned in the plans and is essentially meaningless (define "small", etc.) -- ensure the foam you decide to use has cell sizes of 1.4 to 2.4 mm, and
3. do not use Polystyrene/Styrofoam anywhere near where fuel is (or can be).  Fuel dissolves this foam, and the tiniest pinhole leak could end up transforming structural boxes/members/etc. into debris at a crash site.

Be safe!

Edited October 4, 2014 by Jon Matcho
Changed "two" to "three" (points)

[Patchntx]

I had an off the record conversation with a rep at ITW insulation systems. Dow doesn't make this stuff anymore. Period. They have franchised it out to hundreds of manufacturers across the country and around the world. There are going to be variations from every one of them. Here is what I know for sure. 

 

What used to be called FB stood for Fabrication Billet. Not flotation billet. It is now officially called XPS PIB as sold in the big blocks.

http://www.itwinsulation.com/Trymer/library/Data_Sheets/ITW_XPS_new_Data_Sheet.pdf

 

Flotation billet or Dock Billet is now officially called Buoyancy Billet. Kent posted the link in the above post. 

 

FB and BB are NOT the same thing. 

 

If you want a high compression strength of 40 PSI you are now talking about Building products. Highload and Roofmate. Most are over 2pcf.

http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/815/kw/compression%20strength

http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/665/kw/compression%20strength/related/1

 

XPS PIB is closest to what is called for in the plans with regard to density, cell size, and compression strength. It is available all over the place relatively cheap. 

 

I understand there has been some testing regarding peel strength with respect to cell size and large cell is greatly preferred. However, due to variations in the extruding process and the newest EPA certified blowing agents and methods, there is no guarantee that any particular type of Styrofoam is going to have the cell size you are looking for but is most closely associated with XPS PIB. It just isn't a value that manufacturers control for. There is some luck involved. You need to look at a sample before you buy. 

 

ACS and Wick's could have a supplier or manufacturer that is trying to supply what our plans call for. I wouldn't bet that they would tell anyone who the supplier is. 

 

There isn't any source I can find that would have a product with the guaranteed specifications of 1.6 pcf, 40psi, large cell size. 

 

Additionally, the density of the product determines the compression strength. According to Dow's tables,

1.55 PCF has a compression strength of ~20 psi,

1.80 PCF has a compression strength of ~40 psi 

2.20 PCF has a compression strength of ~60 psi.

 

http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/848/kw/dock/related/1

 

ITW is the largest supplier.

http://www.itwinsulation.com/wheretobuy/wheretobuy.asp

Edited October 13, 2014 by Patchntx

[Jon Matcho]

Thanks for the most excellent information!

Personally, I would consider 20 psi compression strength to be 'quite good enough'. For example, based on 20 psi, a 3" diameter area of bare foam would support up to 188 pounds.  As point of reference, the Cozy IV main wing area is 88.3 square feet (according to www.cozyaircraft.com) which equates to the 1.6 lb/ft^3 density bare wing foam (20 psi, the 'lowest' strength/weight) being able to support over 250,000 lbs (evenly distributed) before it fails.  While this is a rather meaningless calculation, it brings the topic back to the local forces where the foam is essentially acting as a series of wing ribs.

 

I understand the primary in-flight concern is for bird strikes (or other foreign objects) where the local forces would exceed the psi compression strengths.  Even with the fiberglass skins in the mix birds will break into the structure.  Still, all the bird strikes I have seen have been kept to very local areas of damage (~3-6") allowing for safe landings.

 

Perhaps if you have a choice you might want the 2.0 or 2.2 lb/ft^3 foam, but again, if it were my plane I personally would not have a problem building with the 1.6 lb/ft^3 foam as many have done and have not experienced any adverse effects.

[JL07]

On 10/31/2006 at 2:27 PM, EZ AHAB said:

I've been doing some research on the foam used in the flying surfaces of both the Long-EZ and the Cozy. What I've found is that the original "2 lb/ft^3 Styrofoam FB" called for in the plans doesn't seem to be made any longer. A/C Spruce still sells what they call 2 lb/ft^3 Styrofoam FB so maybe they stocked up on it? Wicks sells "POLYSTYRENE Blue Large Cell expanded 1.6 lb. density". I called both suppliers and the lady I talked to at A/C Spruce had no knowledge beyond what was printed in their catalogue. She gave me a phone number to their distributer which led to a dead end. Wicks sells 1.6 lb/ft^3 pipe insulation. I ordered samples from both suppliers and they are indeed different. The foam from A/C Spruce

is, in fact 2 lb/ft^3 and has a larger cell size than the stuff from Wicks. What concerns me is that the original Styrofoam FB had a compressive strength of 35 psi while 1.6 lb/ft^3 pipe insulation has only 20 psi. That's less then 60% of the strength. Also, there are warnings in the old canard pushers about using only the correct type of wing styrofoam called for in the plans. It specifically says not to use different types with less strength. There is also, by the way, a specific warning against using dock floatation foam which I have heard others say is the same stuff.

 

I would just order the stuff from A/C Spruce and be done with it but A/C Spruce is really expensive. The price difference between suppliers for foam for 1 airplane is $260. Add to that the fact that I would have to pay for shipping from A/C Spruce while I could go pick up the other stuff in my truck and you get probably more like $500 in price difference. Do any of you have any further insight/information on this? Perhaps a Cozy builder could find out since it is still a supported design.

Hi EZ Ahab,  

Since the Cozy Mark IV design plans only mentioned Wicks Aircraft and Aircraft Spruce, who did you end up ordering your foam from?  

Or, did you end up using floatation foam from your local dealer since you are able to bring your foam back home with your truck?

[Ron Springer]

On 12/24/2020 at 1:42 PM, JL07 said:

Hi EZ Ahab,  

Since the Cozy Mark IV design plans only mentioned Wicks Aircraft and Aircraft Spruce, who did you end up ordering your foam from?  

Or, did you end up using floatation foam from your local dealer since you are able to bring your foam back home with your truck?

Hi JL07,

EZ Ahab (Steve James) hasn't posted on here in over a decade, but he has certainly bought lots and lots of foam. Try reaching him over at his website:

http://www.eurekacnc.com/

Ron