1800 Amphibs - mounting height
Posted: Fri Feb 17, 2012 11:15 pm
I know there has been lots of discussion on this
subject, and in the end, I think it comes down to
personal preference and opinion.
I have seen Steve Sloan's plane, and it is indeed very
slick and neatly finished. However, if I did it again,
I would still stick with MAM's recommended installation
height for these reasons.
First, I have found no undesirable take-off or landing
characteristics with this set-up. In fact, I have had
high time Cessna and Super Cub float pilots that have
flown with me comment on how stable the Rebel is on the
water. I have taken off (and landed) on one float with
no problem. I have had it loaded very, very heavy on
water and it gets up on the step, no problem at all. I
have landed downwind, done firm glassy water
touchdowns, all with no tendency for the bows to dig
in. Of course, you have to have your airspeed and angle
of attack right when touching down on the water, but
that is easy since you don't have to contend with any
turbulence that you get on hot land runways. It doesn't
porpoise or bounce. In fact, I don't think I have ever
done a bounce on the water (unlike my taildragger
days). This thing really is a dream to fly on the
water. I think having a higher angle of incidence on
your floats helps as well. It allows for a higher wing
angle of attack on touchdown, therefore lower speed,
and maybe a more rearward c of g on touchdown, too.
Anyway, it just planes along like a boat after
touchdown, without any need for a sudden pull back on
the stick to counter nose down tendencies. I still
remember flying my ultralight on floats, and I had to
watch that one pretty carefully on touchdown, despite
the slower stall speed, probably because the floats
were pretty short.
When moored at a public dock, height is definitely an
advantage. When in Manitoba, I docked at a lake where
there were a bunch of kids swimming. The smaller ones
weren't tall enough to reach the flaperons to play
with, and the older ones knew better. By the way, if
you want to keep the kids from touching and playing
with your airplane when docked, here's what works for
me. Kids love to see an airplane, and know all about
it, like can I fly it upside down, etc. Anyway there is
usually one kid that really wants to help with docking,
etc, and if you take some time to talk to him, then you
can ask him to guard your plane and not let anyone
touch anything. I've done that a couple of times now,
and it really works. Seems to work best with about 11
year olds.
Also, when docked with other float planes (excluding
ultralights), I noticed that they were all higher or
the same. I think making it lower would be a nuisance
to duck under when at a dock. As it is, on a high dock,
you can still hit your head on a flaperon if you're not
paying attention. Again, this is my personal opinion.
If you ever want to mount a Borer prop, you will want
the extra clearance.
I am sure you will get some more speed and save some
weight with a lower stance, so I guess each person has
to consider all this and decide for themselves. Speed
was not the priority in my case, and I am still quite
happy with my cruise.
Walter
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subject, and in the end, I think it comes down to
personal preference and opinion.
I have seen Steve Sloan's plane, and it is indeed very
slick and neatly finished. However, if I did it again,
I would still stick with MAM's recommended installation
height for these reasons.
First, I have found no undesirable take-off or landing
characteristics with this set-up. In fact, I have had
high time Cessna and Super Cub float pilots that have
flown with me comment on how stable the Rebel is on the
water. I have taken off (and landed) on one float with
no problem. I have had it loaded very, very heavy on
water and it gets up on the step, no problem at all. I
have landed downwind, done firm glassy water
touchdowns, all with no tendency for the bows to dig
in. Of course, you have to have your airspeed and angle
of attack right when touching down on the water, but
that is easy since you don't have to contend with any
turbulence that you get on hot land runways. It doesn't
porpoise or bounce. In fact, I don't think I have ever
done a bounce on the water (unlike my taildragger
days). This thing really is a dream to fly on the
water. I think having a higher angle of incidence on
your floats helps as well. It allows for a higher wing
angle of attack on touchdown, therefore lower speed,
and maybe a more rearward c of g on touchdown, too.
Anyway, it just planes along like a boat after
touchdown, without any need for a sudden pull back on
the stick to counter nose down tendencies. I still
remember flying my ultralight on floats, and I had to
watch that one pretty carefully on touchdown, despite
the slower stall speed, probably because the floats
were pretty short.
When moored at a public dock, height is definitely an
advantage. When in Manitoba, I docked at a lake where
there were a bunch of kids swimming. The smaller ones
weren't tall enough to reach the flaperons to play
with, and the older ones knew better. By the way, if
you want to keep the kids from touching and playing
with your airplane when docked, here's what works for
me. Kids love to see an airplane, and know all about
it, like can I fly it upside down, etc. Anyway there is
usually one kid that really wants to help with docking,
etc, and if you take some time to talk to him, then you
can ask him to guard your plane and not let anyone
touch anything. I've done that a couple of times now,
and it really works. Seems to work best with about 11
year olds.
Also, when docked with other float planes (excluding
ultralights), I noticed that they were all higher or
the same. I think making it lower would be a nuisance
to duck under when at a dock. As it is, on a high dock,
you can still hit your head on a flaperon if you're not
paying attention. Again, this is my personal opinion.
If you ever want to mount a Borer prop, you will want
the extra clearance.
I am sure you will get some more speed and save some
weight with a lower stance, so I guess each person has
to consider all this and decide for themselves. Speed
was not the priority in my case, and I am still quite
happy with my cruise.
Walter
http://www.dcsol.com:81/public/code/html-subscribe.wcx-----Original Message-----
From: mike.davis@dcsol.com
[mailto:mike.davis@dcsol.com]On Behalf Of
Wayne G. O'Shea
Sent: Thursday, July 17, 2003 7:58 PM
To: murphy-rebel@dcsol.com
Subject: Re: 1800 Amphibs
The high mounting height has lots of
advantages...prop up out of water,
missing dock posts, wider float stance for
more stability and looking bigger
on the ramp!!
Cons are further to fall when you miss the
first step, longer mounting
struts (thus more chance of compression
collapse from bowing out during
compression load), higher thrust line that
in a flat landing can help you
dig in (due to the rotational moment from
the water that has grabbed your
floats, to prop height that is trying to
pull you forward) and throw you
forward into your harness (not a great
feeling and requires pant clean out
afterwards if you are lucky enough to stay
upright and not get them washed
for you!).
Lower mounting has the advantages of the
lower thrust line (thus less moment
arm from water level to the thrust line),
shorter thus slightly stronger
struts, and of course a shorter ladder is
required to fuel.
Cons are of course prop closer to water
(erosion), narrower float stance
(but still probably wider than a C185!!),
less wing clearance for dock
posts, etc
Every aircraft mechanic I have come across
that works on floats states that
"the Rebel is mounted a WAY too high on
floats and looks dangerous"! Haven't
heard any complaints from all the guys that
are flying them mounted per
MAM's original height though, although I
must admit that they do look less
awkward when lowered down about a foot to a
similar height of a C172 on
floats.
Flip a coin and go for it! Remember also
that the front strut is on a pretty
good angle to begin with (when viewed from
the side) and the shorter you
make the strut the steeper this angle gets
causing less chance that the
supplied end fittings will fit and more
chance of collapse in a hard
landing.
Cheers,
Wayne
----- Original Message -----
From: <Legeorgen@aol.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, July 17, 2003 8:37 AM
Subject: Re: 1800 Amphibs
struts is important. I believe IWayne,
I understand keeping the 45*angle on theany cuts until I'm sure. But areunderstand the geometry and I won't make
thereor flight in altering theany benefits or disadvantages to handling
originaloriginal MAM stock floats and I surlyMAM design.
I'm really not one to mess with thehaving more than a few hours asdon't want to be a real test pilot. Not
passengermy rating I would have to seein a float plane and having to still get
somerisk to change it.real advantage to take the extra time and*--------------------------------------------Bruce
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