P-helmet foam
Latest update 29 December 2006
Message 25139, Dec 29, 2006
Hi all, As a follow-up to a discussion I had with a couple of
members on discrete frequency, here is some more information about the foam that was used
in early P-helmets (I am uncertain about P-1 helmets but at least from P-1A through to
P-4).
T.O.13-1-37 Use and Maintenance of Type P-3 Flying Helmet, dated 18 October 1951 describes
the foam as "rubber sponge foam, Grade C, Type 2, medium density, Spec. no.
MIL-R-5001". When I look it up in MIL-R-5001 that translates into an open cell latex
foam, uncored (whatever that means), with a density of .0055 pounds per cubic inch.
According to my limited maths skills that should be equal to around 152 kilos per cubic
metre, quite a heavy foam.
I have a fairly well-preserved P-3 helmet in front of me as I write this and both the
padding and earphone spacers are made of a light yellow, almost cream coloured, rubber
foam, around 6.4 mm thick equal to 1/4 inch. The attached picture is a scan of three of
the earphone spacers from the P-3 helmet in question. The rubber foam is generally well
preserved due to the fact that it has been protected from light by the earphones. It is
therefore fresh and spongy except along the edges where it is darker and dryer due to more
exposure to air and light. The edges feel just like the foam padding glued into the helmet
shell.
So, if any of you is looking for P-helmet foam, you should be looking for 1/4 inch thick
cream-coloured latex rubber foam. The foam used in P-4A and P-4B helmets is described as
Ensolite, Type A, just in case you should wonder.
Cheers, Bluelight
Message 3046, Jun 19, 2001
DocBoink - I was inclined to concur with you - after looking at both early & late
P-helmets, long before I found the Ensolite - but my most recent P-1 acquisition had foam
which seemed to be in so much better shape than earlier examples (particularly the
earphone pads) theat the composition seemed much closer to the Ensolite than to other
"open cell" foam rubber.
Any thoughts? Maggot
Message 3021, Jun 19, 2001
Yo Maggot, Gato, and Bluelight..... I have reservations about using Ensolite on helmets
earlier than P-4A, since that (P-1 through P-4) sponge was open cell (5#, I believe Rich
M. spec'd it out as) and very different from Ensolite (which is closed cell and much
denser). For P-4A and B shells Ensolite is perfect, as that is pretty much what the
fiberglass P-helmet shells used on the interior, anyway. The old P-1 through P-4 helmets,
however, would be unsuitable for use with Ensolite (as it would not even be close to the
original open cell sponge foam used therein).
I keep searching for a suitable substitute, but thus far I have had no luck at all finding
a 5# open cell sponge foam of the correct thickness. The quest goes on, naturally.
Cheers, DocBoink
Message 3010, Jun 18, 2001
Hi Maggot and all, This is great news to all who don't know what to do about all that
rotting foam. I have always believed that I could fashion replacement parts, given a photo
or pattern and very similar material to make the replacements from. My motto is: If I
can't find the original or replica, then I make it myself. Although, I am finding that,
somewhere out there, someone else has probably thought of this too. I just need to find
those individuals. This forum has been very handy in getting those in need together with
those who have done it!
Gato
Message 3008, Jun 18, 2001
Hi, Gang - Just returned from my local aircraft trim/upholstery store (they have been
doing more building and automotive awning-type stuff lately) and found 1/4" ENSOLITE
- a very dense foam rubber padding which, for MY tastes, is a suitable replacement for
early P-helmet shell padding. The stuff measures about 58" wide and ran me $25/yd (I
figured a yard ought to get me through at least two helmets ;-).
The stuff seems to be about 1/16" thinner than what I find in later P-helmets, but I
would be inclined to use it all the way around and I believe only the most anal among us
would complain about the difference. I plan to start cutting patterns to make padding sets
- although the helmets ranged in three different sizes, I think a one-size pattern will
accomodate any of them (the stuff has enough stretch to meet ends between the forehead and
nape pieces as you mate them around the rear lobe area). Just be patient with me... I'm
still working on the visor frame spring issue, but believe I'm pretty darn close. I think
you'll be pleased.
Maggot
Message 1871:
(((((Sound of DocBoink's jaw hitting the ground as he contemplates his NEXT step....))))
Thanks for this information, Rich. It is an unhappy bit of news; If the 5# foam is no
longer available, the logic of this proposition would dictate that 'poor' restorations are
the only alternative. Well, we shall see. Maybe there is still some of this material
floating around abroad (say in Yugoslavia?).
Cheers, DocBoink
Message 1869:
There are 2 types of foam used in the P series--5-pound yellow foam used until P-4B, which
used the sort of foam still used in aircraft interior work. Yellow 5# is no longer made,
period. A lighter grade is, but that is a sure tip-off to a poor restoration. I sent a
mint sample from a PIECE of a P-helmet (and before you go nuts, that's ALL there was) to a
foam manufacturer, and that was his response. However, one occasionally sees earlier
helmets with the later foam, but not often, and I never documented the incidents in order
to descern a pattern. When it's gone, it's gone, and it IS gone. Unless, of course, the
guy hoarding mint HGU-17/P liners also has some stock laying around.
Rich
Message 1869:
Hi Doc, I will endeavor to look for the foam; however, I fear that you have already tried
all the places around Sacramento and Northern CA. I have seen something similar at TAP
plastics, but in very bright colors, in close to 1 inch thickness. BTW-I am having a
similar problem locating open cell neoprene (black) 1/8 to 1/4 inch, to repair the
faceshield of my Mark IV. Anyone having information on this, please let me know.
Much thanks, Gato
Message 1865:
Good morning group, I have a request for some information concerning possible sources for
obtaining the sort of old fashioned, tan-colored, open-cell sponge rubber (half inch
thick) that was used inside the P-series shells on the crown, front, and back of head
areas. You know the sort I refer to--it was soft, crushable foam, not rigid like Ensolite?
It was practically the only kind of sponge rubber available back in the 50s, although now,
due to subsequent advances in polymeric chemistry that have made available a wide range of
sponge foam types, this old style sponge foam is practically impossible to find. I have
called a number of so-called "Foam Rubber" shops and discussed this need with
well over a half dozen retail sponge foam sellers (all dim-bulbs, too, I might add), all
of whom have stated with all the spare eloquence of a Calvin Cooledge clone: "Nope,
don't got it; cain't git it."
What I need is a small piece about half an inch thick and just a few square feet in area
(enough to fabricate the sponge shell liners for a P-series helmet). Any help or
information leading to successful source of possible procurement would be most
appreciated. Surely some of you have encountered a similar situation in the past, in your
own restoration attempts in which the existing sponge lining a P-series shell has
deteriorated completely away into friable dust?
Thanks, DocBoink