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1. 09:47 AM - Engine selection for float plane (Paul Seehafer)
2. 02:22 PM - Re: Engine selection for float plane (Chris In Madison)
Message 1
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| Subject: | Engine selection for float plane |
Chris,
My kitfox amphib is flying better and better with that little ol 80 hp 912
Rotax 912, as I continue to tweak it for performance. And being that it is
a heavy model IV (has everything but the kitchen sink in it), the
performance is nothing short of amazing. In perfect conditions (72 degrees
with a 10 mile per hour headwind, a little chop, and only me with 10 gallons
of fuel) I can get it off the water in 5-6 seconds, and climb out at a 1000+
fpm at a pretty steep angle (30-35 degrees I'm guessing). And as I've said
before, this little plane will go 120+ miles per hour flat out. ON AMPHIBS!
Load it up with a 200+ pound passenger in the same conditions, and the
takeoff run will be in the 13-15 second range. And that's been proven as
lately as this last weekend by me taking a few of my friends flying. Oh
yeah, I also did a solo takeoff the other day with full fuel (28 gallons)
and it took 10 seconds off the water without even trying hard. And I took
off crosswind, with a 90+ degree temperature (density altitude was 3600 feet
as I recall). Fuel burn with the 912 is nothing short of amazing - I
average 3.2 gph in all of my flying. And my typical flying speeds are
95-100 mph. I also do A LOT of water work. So I'd burn less if I could
resist playing more. I do have the advantage of using an inflight
adjustable IVO prop, but I am going to compare a warp ground adjustable one
of these days as I really like the water resistance that blade offers for
seaplane use. Personally I don't believe I will see less than a 5-10%
performance reduction. And that's not gonna kill me as I've alway said if I
can have a seaplane do 100 mph, it becomes a practical cross country
airplane you will use to go places. This kitfox has proven to be all that
and then some. It is an awesome little seaplane!! I have no regrets. In
fact, it makes such a good seaplane with that 80 hp 912 and the IVO prop,
that even though I have a 100 hp 912 sitting ready to bolt into it, I think
I'm going to save that for another project. From all I can tell, I really
don't need the 100 hp on this airplane. Sure, more power is good, but that
80 hp 912 is one sweet motor, and a mizer on fuel.
So, would I use an aircraft engine in a Kitfox? No way. Not if I were
planning on using it on floats. Particularly if it were going to be an
amphib. Don't get me wrong, I like the old tried and true aircraft engines.
They are well proven and are less expensive to obtain than a good 912. But
they make airplanes like a Kitfox too heavy. That's not a huge thing on
wheels, but it is a very huge thing on floats. That's not to say it won't
work, but why accept mediocre performance when you can have stellar
performance on less fuel per hour? The small diffence in price between a
used 912 and a used o-200 will be well worth the difference in my opinion.
There's a reason so many light sport airplanes use the Rotax. It just plain
works better than the other choices.
Fwiw - I have a friend that flies a Kitfox just like mine, but built much
lighter (lesser equipped, no shiny paint, etc), with probably the worlds
lightest Lycoming 0-235 in it. And it's on straight floats. So with 118+
hp on tap, on straight floats it should be a real rocket....right? Nope.
It is a good little float plane, and flies well. But it flies much like
most other aircraft engine equipped seaplanes. You won't see it doing 5-6
second takeoffs. It may (?) fly as fast as mine, although honestly I can't
say as we've never compared. So even though my 80 hp Fox will outperform
that 0-235 airplane in most every aspect, to be fairly comparing an aircraft
engine against the Rotax, you would need to put the 115 hp 914 Rotax in my
fox, and remove the 80+ pounds of landing gear from my floats. I will
guarantee you if I did that, I would have a seaplane that would awe most any
seaplane enthusiast. I actually think my Kitfox would be "overpowered" if
you can imagine such a thing?
Last comment on the 912 choice; As much as I love the 912's performance, it
does have it's limits. Many of the newer airplanes are getting heavy. So I
think we are starting to reach the upper limits of what the 912's horsepower
range can effectively fly. While you can put a 912 in a Cessna 150 and fly
all day (has been proven fwiw), it is not going to be a rocket ship. Until
Rotax comes out with a 150 hp 912, Lycomings and continentals will rule the
larger aircraft. But for planes like my Kitfox, I think the 912 is the
perfect engine. Horsepower is horsepower technically. But only if at the
same
weight. Weight, and longer prop capability is wear the 912 shines imho.
And fwiw, I also fly a Lake amphibian with a Lycoming 0-360. I love that
airplane too. It is a good performer for a 180 hp four seat amphibian. But
I always wonder how much better it might fly if Rotax were to build an
engine that weighed 100 pounds less and had the same or more power????
Paul Seehafer
Attached are a few pictures of a small seaplane fly in that was held in
Phillips Wisconsin last weekend (we had 17 airplanes total if I counted
right - some aren't showing in these photos). The Kitfox, the Zenair, and
the Rans in the picture are all 912 powered, and can all fly 100 mph on
floats, burn half or less the fuel any of the other 100 mph floatplanes,
while still providing STOL performance and good load hauling ability.
Further testimony to the effectiveness of the 912's. They do the job
well...
----- Original Message -----
From: "Chris In Madison" <cowens@cnw.com>
Sent: Saturday, July 07, 2007 10:21 AM
Subject: Seaplane-List: Engine selection for float plane
>
> Good morning all,
>
> I've decided upon the Light Miniature Aircraft Super Cub replica as a
> building project, and I want to ensure that the aircraft is suitable for
> safe, reliable float operation. The designer has told me that it would
> work well on floats, so there's the first hurdle, and building manual
> describes that the airframe has been updated in the plans to accommodate
> larger/heavier engines than the plans originally called for some 25 years
> ago (originally the 65hp Rotax 532).
>
> A number of builder are installing engines from the A-65 through the O-200
> on their aircraft, and the designer also suggests that there has been
> interest in the Rotax 912. I'm presuming that all are suitable engines
> for a floatplane, however I'm curious if some are better suited than
> others.
>
> As I recall, Paul S. is using a Rotax 912 on his aircraft and that seems
> to be a popular choice on a number of LSAs that are going on floats these
> days. With the 912 being a newer engine, however, I suspect that the
> availability of them on the used market is lower, and I've noted that the
> prices are quite a bit higher than a quality used Continental.
>
> Are there any schools of thought in this regard? Does 100hp from a 912
> equal 100hp from an O-200 equal 100hp from a VW conversion? If the engine
> develops rated horsepower with the same length prop, does it really matter
> which one you choose?
>
> Thanks and best regards,
> Chris
>
> --------
> Chris Owens
> Waunakee, WI
>
Message 2
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| Subject: | Re: Engine selection for float plane |
Hi Paul,
Thanks for your input. I greatly appreciate it. A side benefit of the Rotax is
the nice, warm winter heat source. As a Wisconsiner yourself, I'm sure you
can appreciate that as well :-)
Will you be at OSH this year? I'll be camping with Al and Lori B. and plan to
spend some time at the seaplane base. I'd like to meet with you and see your
Kitfox if you'll be there.
Best regards,
Chris
--------
Chris Owens
Waunakee, WI
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