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fklein(at)orcasonline.com
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 Posted: Wed Jan 10, 2007 8:21 pm Post subject: bouyancy |
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All,
Posted points are well taken...as I said, I intend to do some research
on the subject and will report back any information I gather...adding
foam may well be one of those seemingly simple notions which, upon
investigation, is fraught with peril.
Fred
On Wednesday, January 10, 2007, at 03:51 PM, NevEyre(at)aol.com wrote:
| Quote: | Hi Bob / All.
The blue foam is pretty well closed cell, the type that is definately
closed cell is coloured orange, and sold as ''Flotation Billet'' as
opposed to ''Insulation Billet of the blue, as used in the Europa.
The blue will not pick up too much water unless immersed at great
depth, where the pressure will force the water into the cells, so fine
at sea level ! It weighs 2lb. cu.ft, and a cu.ft will support 60lbs in
fresh water.
Most of the foams that are injected, are open cell, so will soak up
water like a sponge, the pour in types supplied to the marine trade
for bouyancy are very inconsistant in use, sometimes they tend to
expand to ''open cell'', which again will soak up water. [I have seen
boats foamed with this ''TOUCAN'' foam that have absorbed so much
water they barely floated]
The other problem with the ''pour in'' foams [ as opposed to the blow
in, injected types] is that the finnished volume can vary, you can
never be sure how far it will go. I have witnessed floors ripped from
hulls. Temperature of the two foam components. and the space being
foamed will have an effect. The warmer the foam and / or space, the
further it will go.What can happen, is that it fills a space entirely,
and ''gells'',[ so cant escape from the vent hole] then carries on
expanding, with sometimes disasterous results.The power of foam
expanding has to be seen to be believed! I have seen a Range Rover
that someone with a grievence had poured some of this two pack foam
into, puffed it out like a hedgehog, totally round by the time it had
finnished!
A Classic, I am sure , will have more than enough volume of foam to
stay afloat indefinately, an XS will eventually fill up, but possibly
''lurk'' nose down just below the surface.
Cheers,
Nev.
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grahamsingleton(at)btinte
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| Posted: Thu Jan 11, 2007 2:06 am Post subject: bouyancy |
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Fred
as Neville suggests, there is probably enough foam in an XS to float the
engine. All you need to be sure is 2 cubic ft of blue foam, which you
could put in behind the wing spar.
You could estimate the amount of PVC foam, (about 5 lbs/cu ft,?) from
the wetted area of the aircraft. It's 3mm thick. You know the weight,
1370lbs.
Graham
Fred Klein wrote:
| Quote: | All,
Posted points are well taken...as I said, I intend to do some research
on the subject and will report back any information I gather...adding
foam may well be one of those seemingly simple notions which, upon
investigation, is fraught with peril.
Fred
On Wednesday, January 10, 2007, at 03:51 PM, NevEyre(at)aol.com wrote:
Hi Bob / All.
The blue foam is pretty well closed cell, the type that is
definately closed cell is coloured orange, and sold as ''Flotation
Billet'' as opposed to ''Insulation Billet of the blue, as used in
the Europa.
The blue will not pick up too much water unless immersed at great
depth, where the pressure will force the water into the cells, so
fine at sea level ! It weighs 2lb. cu.ft, and a cu.ft will support
60lbs in fresh water.
Most of the foams that are injected, are open cell, so will soak
up water like a sponge, the pour in types supplied to the marine
trade for bouyancy are very inconsistant in use, sometimes they
tend to expand to ''open cell'', which again will soak up water.
[I have seen boats foamed with this ''TOUCAN'' foam that
have absorbed so much water they barely floated]
The other problem with the ''pour in'' foams [ as opposed to the
blow in, injected types] is that the finnished volume can vary,
you can never be sure how far it will go. I have witnessed floors
ripped from hulls. Temperature of the two foam components. and the
space being foamed will have an effect. The warmer the foam and /
or space, the further it will go.What can happen, is that it fills
a space entirely, and ''gells'',[ so cant escape from the vent
hole] then carries on expanding, with sometimes disasterous
results.The power of foam expanding has to be seen to be believed!
I have seen a Range Rover that someone with a grievence had poured
some of this two pack foam into, puffed it out like a hedgehog,
totally round by the time it had finnished!
A Classic, I am sure , will have more than enough volume of foam
to stay afloat indefinately, an XS will eventually fill up, but
possibly ''lurk'' nose down just below the surface.
Cheers,
Nev.
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Randerson(at)skewstacks.f
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| Posted: Thu Jan 11, 2007 3:17 am Post subject: bouyancy |
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Has anybody devised a mod. to mount an outboard motor protruding through the botom of the baggage bay for self retrieval following a ditching?
Do not archive.
[quote][b]
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ami(at)mcfadyean.freeserv
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| Posted: Thu Jan 11, 2007 9:33 am Post subject: bouyancy |
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Or 5mm thick in hte XS wing(?).
In passing, I recall that Ivan claimed 9lbs(?) had been saved in coring out
the blue foam of the Classic wing. So if a lb of foam provides 30lbs of
buoyancy, then 270lbs of potential buoyancy has been lost from the Classic
wings; if/when the hollowed-out sections inundate after a ditching.
Duncan McF.
Duncan McF.
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fklein(at)orcasonline.com
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| Posted: Thu Jan 11, 2007 10:38 am Post subject: bouyancy |
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Graham,
My interest in investigating injecting foam forward of the spar was to
create buoyancy to offset the engine weight...I'm ignorant of the
relation of the spar location vis a vis the c.g.
Blissfully,
Fred
On Thursday, January 11, 2007, at 02:04 AM, Graham Singleton wrote:
| Quote: |
<grahamsingleton(at)btinternet.com>
Fred
as Neville suggests, there is probably enough foam in an XS to float
the engine. All you need to be sure is 2 cubic ft of blue foam, which
you could put in behind the wing spar.
You could estimate the amount of PVC foam, (about 5 lbs/cu ft,?) from
the wetted area of the aircraft. It's 3mm thick. You know the weight,
1370lbs.
Graham
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Trevpond(at)aol.com
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| Posted: Thu Jan 11, 2007 11:37 am Post subject: bouyancy |
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I look forward to witnessing the first test float of a classic!!!
Best regards to all
Trev
[quote][b]
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jan.de.jong(at)xs4all.nl
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| Posted: Fri Jan 12, 2007 2:20 pm Post subject: bouyancy |
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I'm also intrigued because I'm finally getting close to putting the lids
on my XS wings and now there may be just one more and very last thing to do.
If and when I reach a positive decision that there is not that will be
fine. I can do a little more filling and sanding of flaps and ailerons
in the interim.
In theory one could just close off the space forward of the XS wing
spar. The only remaining task would then be to assure pressure
equalisation for those times one wants to fly instead of float. I
thought of:
- Tubing from wing root to fuselage roof
- Float valve at wing tip
- Multiple, redundant, tubing to fuselage roof
- Construct close-off as weakpoint (safety valve)
Difficulty is knowing quality of any 1-off design.
Safety lost could easily exceed safety gained?
B.t.w., maintaining pressure equalisation will probably be an issue with
foam filling as well, I'm thinking.
Jan de Jong
461
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ami(at)mcfadyean.freeserv
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| Posted: Sat Jan 13, 2007 1:38 am Post subject: bouyancy |
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<<B.t.w., maintaining pressure equalisation will probably be an issue with
foam filling as well, I'm thinking.>>
It is, and the build manual requires these internal spaces to be vented.
There was a case a few years ago where a Lancair 'popped' its tailplane in a
climb to high altitude, because of inadequate venting.
Duncan McF.
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