Tom Smythe wrote:
Hi,
I'm the guy that was going to drop a 3 rotor into a Moose a while ago
but, have been having second
thoughts as I just don't think the performance is what it could be (I
also looked at the Aerocomp
birds but, again, think performance is lacking...).
So, I've undertaken designing a nice little six place plane of my own.
Probably a composite bird
as I believe composites allow much more freedom and an aerodynamically
clean airframe overall. To
that end, I still would like a powerplant in the 400HP range (like the
Moose had with the latest
Russian radial but not the fuel hungry turbine on the Aerocomp models).
Given the ability of the rotary to handle quite a bit of boost, I've
come up with the table below
(standard day):
2-Rotor 3-Rotor
13B 20B
NA HP @ 6,500 RPM 195 290
(guestimated)
Fuel Flow (lbs/min) 1.4625 2.175
Air Flow (ft^3/min) (59* 285.1875 424.125
day)
(air flow volume changes
with temp, but mass
stays the same and thus
the MAP)
400 HP Fuel Flow 3.0000 3.0000
(lbs/min)
400 HP Air Flow 585 585
(ft^3/min)
MAP @ Sea Level 2.05 1.38
MAP @ 10,000' 3.02 2.03
MAP @ 15,000' 3.64 2.45
MAP @ 20,000' 4.46 3.00
400 HP Air Flow 45 45
(lbs/min)
Recommended Turbocharger T61 T61
100% Power Ceiling 17,000' 26,000
The T61 is operating near the surge limit to achieve the HP required on
the 13B. However, on the
20B, it's actually loafing along fairly nicely. Assuming the above
numbers are correct, I'll be
planning the airframe around the 20B. Otherwise, it's back to the
drawing board.
As an FYI, the airframe is a high wing design with fixed gear and a
gross weight at 4,400 lbs
(give or take...) and usefull load of 1,800 lbs (600 lbs fuel). The
initial design was created in
AirplanePDQ and is being evaluated in X-Plane (5.61).
Thanks,
tom
Barnhart wrote:
Tom,
I'm the guy putting the 20bt in a Murphy Super Rebel. No second thoughts
here at all. Just want to get it flying.
You are right the Moose could be a little improved in the performance area.
All of those rivets, float and ski brackets, struts, and big tires add up
quick in drag.
Where are you going to find a PRSU for 400 hp? Any idea on hp needed to
cruise on?
Are you thinking about a STOL or fast wing? At least 150 gallon tanks for
fuel. You won't get too far with only 100 gallons of fuel. I wish I had more
than the 80 gallons I have now. Should have an empty weight of 1700lbs,
with a gross of 3200 lbs. I'll have a useful of 1500 lbs on proven
components based on turboed 300 hp. The 20bt will be hardly working at
cruise, and not working hard on takeoff.
Barny
Super Rebel 2500, Mean Green Drag Queen.
Hi Barny,
The wing is between 36' and 38' span (still going back and forth on that) based on the Wortman FX
082-512. 6' root and 4' tip chords, 5 degrees dihedral and -5.5 degrees incidence at the root to
-6.1 at the tip. Also, was planning on single-slot fowler flaps spanning appr 50% of the available
wing running 30% of the chord.
The 100 gallons I've planned for should run me around 4 hours to dry tanks if I"m figuring the
fuel burn properly @ 75% (147lbs/hr). If it flies the way the simulator figures (actual calcs, not
numbers punched in like the MS version), then I should see 75% cruise up in the 190-200 KTAS range
@ 4,000 (the sim shows it up to 215 KTAS, but I know things add drag like antennas, cooling
ductwork, exhaust stack(s), window/door seals/joints, etc...). Backing down to 50% (98lbs/hr) only
drops to 175 KTAS in the sim, but gives endurance out to 6 hours. The stall with power off/clean
is around 60 KTAS and with full flaps (45 degrees) ends up down around 54 KTAS. Power on drops it
down to 37 KTAS with all the air hitting the flaps but a 20 degree deck angle makes for a fun ride
over the fence.
In the sim, I've found a 3-blade 82 inch constant speed prop with 2.5" root and 8.5" tips works
well (Clark Y on the props, but I haven't done a lot of trials with other foils in the prop area
yet). I've toyed with pressurization (in my mind, that is), but haven't seen much on how to
accomplish it on the Web. Maybe that's somebody's way of telling me to stick with the original
design concept - 6 place, 4 hours, high wing, fixed gear with true six place, full fuel capability
(thus the 1,800 lbs & 100 gal numbers). The fuselage is figuring to be about 32' long (prop
spinner to tail) and is about 5' wide in the passenger section. It's a rounded design versus the
square versions you see in the Murphy/Aerocomp lines. I know front plate area is the largest area
of the airframe presented to the wind, but I wanted to give folks lots of room inside. I like to
take care of the folks travelling with me :-)
With regards to the gear box, I haven't done much with that yet. I'm of the opinion that I can
probably have one built (or do it myself after I read up on the subject LOTS!) to handle the HP
and hopefully get some good advice from folks on the group on how to accomplish that. It's also an
important piece of the puzzle but, I wanted to ensure the engine calcs I'd come up with were close
to what I could expect (fuel burn, turbo requirements, HP output, etc...) Thus, the note to the
group asking for comments.
I figured if I was going to stick a bunch of time into building a plane to do more than what you
could by buying certified, then I wanted it to be built using the latest information and airfoils.
The Clark Y they use on the Aerocomps is a huge drag bucket in process when it starts going fast
(thus the turbines and altitude numbers) and the Moose was just plain draggy with the way it was
built. The 4415 (modified) was an improvement over the Clark Y, but still old tech stuff. They
both work, but I think they could be improved upon using some of the tools available today. Who
knows, I may end up figuring out that what I'm planning won't work (for whatever reason). But,
I've got to give it a shot.
I'm VERY interested in finding out how your project works out. Radiators, intercooler(s), constant
speed prop selection, did you include A/C off the engine rather than that electric thing you see
in some planes (or did you include A/C?), are you running dual alternators with separate buss's,
etc... Maybe we could talk about more offline if it doesn't fit in with the newsletter?
tommy@bizpost.com
Thanks,
tom
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