[rebel-builders] Amphib Questions
Posted: Sun Feb 19, 2012 5:11 pm
I will answer some of your questions below with my experience and opinion.
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Eric
Fogelin
Sent: January 16, 2009 3:32 PM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Amphib Questions
Stuck on the ground and can't continue flight testing due to weeks of bad
weather and dense fog, so thought I'd post a few questions that have come up
during past amphib testing:
1)
The floats need to be water tight but not air tight according to the manual.
This way air can enter and leave during large altitude changes. Since waves
roll over the floats, how are people solving this? I'll be flying from sea
level to 10,000 due to mountains.
WK... I don't get much water in mine from waves, except in the front. This
happens when taxiing in rough water, which splashes into the front gear
well. Then after you take off, it drains to the back, and through the hose
grommets.
2)
I'd like to get more rubber doughnuts for the amphib main gear shocks. What
material are these made from? Is there a US source for the doughnuts?
WK... I replaced mine with the blue Elite front nose gear suspension
doughnuts. These are stiffer and twice the thickness of the original yellow
amphib ones. Have worked great on mine for 500 hours. Good stiff suspension,
but you won't bottom out on these ones.
3)
The main amphib axles are held in place with clamps. Friction and the method
of attaching the gear arms to the floats is the only thing that keeps the
axles from sliding out. One of my axles likes to slide about 1/8-1/4". It
seems to stay in this position. I worry what will happen when I side load
the wheel during landing. Anyone else have this problem, concern or fix?
Seems like the design should have a pin or the axle machined with groove or
have a captive end.
WK... Have heard of this problem before, can't remember who now, but don't
know how or why this would happen. Mine are solid, and have never moved.
4)
Hydraulic pressure in the up/down lines for the gear is temperature
sensitive. The change in daytime temperature of 20 or 30 degrees can have a
100psi effect. I worry that if I have the wheels down and pump to 150psi and
the sun comes out, that the pressure could easily go over the 250psi limit
and blow lines. Also see (5) below. Or gets real cold at night and I lose my
pressure and the gear could collapse. I have 3/8" OD lines (90% nylon lines
with the other 10% aluminum in the cabin.)
WK... This is indeed a problem, and I was with another Rebel amphib (Bruce
G.) that had a line blow on him, when we were high up on a mountain lake in
the middle of nowhere. He used to position his valve in the up position, and
I think that would not allow any pressure release. I keep mine in the
neutral middle position, which I think then just causes the pressure to go
to the gear cylinders where it will dissipate. At least they do on mine, as
I think my piston O rings leak a bit. They don't hold pressure for very long
anyway. You don't have to worry about the gear collapsing while on the
ground, due to them being over centre.
5)
Anybody installing a pressure bypass valve incase of getting too
enthusiastic and over-muscling the handpump past the 250psi max?
6)
Do amphib builders keep their floats on blocks and weight off the wheels
when parked for long periods to keep the rubber shock absorbers from being
permanently deformed and the small amphib wheels from getting flat spots?
WK... Nope, and no impact after 500 hours.
7)
I find the amphib brakes to be ineffective and easy to overheat. They are
small so I'm not surprised, but I wish they were a bit more effective. I
don't think I glazed my pads during break in. Do others share this
experience?
WK... They are not great brakes, but do work enough to slow down and turn.
They will never skid, though, if you expect that. I just replaced my pads
recently, as one side was completely worn out. I have also had problems with
the brake lines blowing. Has happened at least 3 times on me so far. Makes
for some tricky handling when trying to come to a stop. You need to shut off
your engine, as soon as it slows down enough that you lose rudder
effectiveness. I think I had some lines that were not up to standard. Am
still planning to replace them before summer.
Eric Fogelin
Elite Amphib N645E
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-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Eric
Fogelin
Sent: January 16, 2009 3:32 PM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Amphib Questions
Stuck on the ground and can't continue flight testing due to weeks of bad
weather and dense fog, so thought I'd post a few questions that have come up
during past amphib testing:
1)
The floats need to be water tight but not air tight according to the manual.
This way air can enter and leave during large altitude changes. Since waves
roll over the floats, how are people solving this? I'll be flying from sea
level to 10,000 due to mountains.
WK... I don't get much water in mine from waves, except in the front. This
happens when taxiing in rough water, which splashes into the front gear
well. Then after you take off, it drains to the back, and through the hose
grommets.
2)
I'd like to get more rubber doughnuts for the amphib main gear shocks. What
material are these made from? Is there a US source for the doughnuts?
WK... I replaced mine with the blue Elite front nose gear suspension
doughnuts. These are stiffer and twice the thickness of the original yellow
amphib ones. Have worked great on mine for 500 hours. Good stiff suspension,
but you won't bottom out on these ones.
3)
The main amphib axles are held in place with clamps. Friction and the method
of attaching the gear arms to the floats is the only thing that keeps the
axles from sliding out. One of my axles likes to slide about 1/8-1/4". It
seems to stay in this position. I worry what will happen when I side load
the wheel during landing. Anyone else have this problem, concern or fix?
Seems like the design should have a pin or the axle machined with groove or
have a captive end.
WK... Have heard of this problem before, can't remember who now, but don't
know how or why this would happen. Mine are solid, and have never moved.
4)
Hydraulic pressure in the up/down lines for the gear is temperature
sensitive. The change in daytime temperature of 20 or 30 degrees can have a
100psi effect. I worry that if I have the wheels down and pump to 150psi and
the sun comes out, that the pressure could easily go over the 250psi limit
and blow lines. Also see (5) below. Or gets real cold at night and I lose my
pressure and the gear could collapse. I have 3/8" OD lines (90% nylon lines
with the other 10% aluminum in the cabin.)
WK... This is indeed a problem, and I was with another Rebel amphib (Bruce
G.) that had a line blow on him, when we were high up on a mountain lake in
the middle of nowhere. He used to position his valve in the up position, and
I think that would not allow any pressure release. I keep mine in the
neutral middle position, which I think then just causes the pressure to go
to the gear cylinders where it will dissipate. At least they do on mine, as
I think my piston O rings leak a bit. They don't hold pressure for very long
anyway. You don't have to worry about the gear collapsing while on the
ground, due to them being over centre.
5)
Anybody installing a pressure bypass valve incase of getting too
enthusiastic and over-muscling the handpump past the 250psi max?
6)
Do amphib builders keep their floats on blocks and weight off the wheels
when parked for long periods to keep the rubber shock absorbers from being
permanently deformed and the small amphib wheels from getting flat spots?
WK... Nope, and no impact after 500 hours.
7)
I find the amphib brakes to be ineffective and easy to overheat. They are
small so I'm not surprised, but I wish they were a bit more effective. I
don't think I glazed my pads during break in. Do others share this
experience?
WK... They are not great brakes, but do work enough to slow down and turn.
They will never skid, though, if you expect that. I just replaced my pads
recently, as one side was completely worn out. I have also had problems with
the brake lines blowing. Has happened at least 3 times on me so far. Makes
for some tricky handling when trying to come to a stop. You need to shut off
your engine, as soon as it slows down enough that you lose rudder
effectiveness. I think I had some lines that were not up to standard. Am
still planning to replace them before summer.
Eric Fogelin
Elite Amphib N645E
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