P85 - A New Aircraft

Discussion in 'Chevy' started by Jeffd, Jul 24, 2013.

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  1. Jul 26, 2015 #81

    Jeffd

    Jeffd

    Jeffd

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    Current performance has to be qualified by the fact that the current prop is very definitely a "climb prop"

    That being said, some observed performance:

    On the way to Oshkosh we flew up on the wing of a friend with a nice RV-10. At 7500 ft MSL he was running 190 mph TAS or so on 12.5 gph. I was matching him with 15" Hg x 1950 prop rpm, 9.3 GPH running rich of peak and a bit richer than best power AFR (initial conservatism). I would call this super duper economy cruise and it is really slower than the speed the plane is set up for.

    At the same altitude, max rpm (2800 prop rpm) gives about 260-265mph TAS Vmax, but I still have 4" or so MP left due to the climb prop maxing out rpm. I have the new Catto cruise prop in a box in the hangar - testing with it is the next step.

    Sea Level takeoff runs look like 900 ft or so. SL climb rate about 3000 fpm. Both at mid weights.

    Zero cooling issues with the current radiator set-up and air-to-oil cooling. I do want to test a coolant-to-oil cooler though for comparison. Worked well on the V8 Legend and should be lower drag.

    The finish on the plane is currently very rough primer, i.e. the primer on the wings has been applied with a roller (not so good with a NLF airfoil) and some of the fuselage primer has been brushed on.

    I think it is a good bet that with the cruise prop, a smooth waxed paint job and a handful of fairing/aero clean-ups we will see Vmax of 285 mph TAS or so at 7500 ft MSL. Little things count for a lot at these speeds.

    Will focus much more closely on the performance spreadsheet once we are flying with the cruise prop.

    Jeff
     
  2. Jul 26, 2015 #82

    PTAirco

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    I'm really curious how you got that cooling system to work so well. The picture shows the radiator only inches forward of the firewall and it makes one wonder how the air is actually going through it. That it works is obvious, but it doesn't seem an obvious set-up. Are there fans involved?

    p85.jpg
     
  3. Jul 26, 2015 #83

    DRLPatrol

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    Jeff,
    First off, thanks for doing all this experimenting for us all. Your project looks great. I am interested in the Ballistic redrive but did not want to call them until I checked with you to see how they felt about using they stuff on aircraft. The 2 things I was wondering about.

    1. Airboats are a pusher configuration, did they do anything different for you or is it their off the shelf gear box.

    2. Their website does not say much about the coupling between the engine and gear box. How does it work and I would love some pictures.

    Again Thanks
    Doug
     
  4. Jul 26, 2015 #84

    Topaz

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    Or that firewall isn't solid behind the radiator, and the flow does a nice little "S" curve headed out that bulge in the bottom, aided by extractor effect from the exhaust. Just guessing.
     
  5. Jul 26, 2015 #85

    Jeffd

    Jeffd

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    Yep, Thats it. Diverging duct ahead of the radiator. The converging duct aft of the radiator extends through the firewall and "S" turns down/aft. Placing the exhaust in the air outlet duct adds heat and serves as an aerodynamically clean method of getting the exhaust out. The exhaust pipe also points directly aft. The prop does a great job of pushing air through the radiator for ground cooling - can run on the ground indefinitely.

    Jeff
     
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  6. Jul 26, 2015 #86

    Jeffd

    Jeffd

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    The drive vendor has no issues with use in EAB planes - very supportive.

    OK for tractor configurations.

    The drive install requires a specific, readily available aftermarket heavy duty flex plate, which mates to the drive using six flexible bushings.

    Jeff
     
  7. Jul 26, 2015 #87

    Jeffd

    Jeffd

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    Here is a shot of the complete installation, showing the inlet duct:
     

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  8. Jul 26, 2015 #88

    DRLPatrol

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    Thanks for the info.

    Doug
     
  9. Sep 6, 2015 #89

    Goatherder

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    Jeff, if you'd be so kind:

    1. Did you use the standard mounting points on the Ballistic box or fabricate something different?

    2. What did you do for the forward mount on the LS block?

    3. What size is the chromoly tube on your engine mount?

    4. Would you happen to have any pics of the engine mount by itself.

    I've got a V6 w/ airboat box that I need to connect to the back of my canard project. Building a mount is on the list for this winter.
     
  10. Sep 8, 2015 #90

    jac

    jac

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    Question similar to Goatherders in relation to the 'Ballistic Drive unit'. Since most Airboats are pushers do they change the 'helix angle' on the reduction gears from left to right or vice versa for your tractor application. Attached pics taken from their FB page which shows only the one helix angle. Assuming your still running your engine in the OE clockwise rotation at the crank looking at the front pulley end, the gear in pic would tend to add to the thrust load on the prop shaft whereas a reverse helix would/should reduce it. Not too concerned myself and if OK I will consider a revisit to using the Ford Probe final drive gears ( pic with ruler on top) I have that share the same helix direction .
     

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    Last edited: Sep 8, 2015
  11. Mar 28, 2016 #91

    hangarrat101

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    What's the latest news with the project? Looks pretty exciting but seems to have gone very quiet lately!
     
  12. Mar 29, 2016 #92

    Jeffd

    Jeffd

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    Over a full year of flying since the first flight - very happy with the V8 engine installation.

    Kits are now available!

    Jeff
     
  13. Mar 29, 2016 #93

    Toobuilder

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    I assume you now have some decent cross country data - what kind of numbers are you seeing WRT fuel burn/speed? Also, are you playing with LOP ops or staying fat?

    How many hours on it now?
     
  14. Apr 3, 2016 #94

    Jeffd

    Jeffd

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    Installed the new cruise prop last Fall and picked up significant speed at Vmax / 7500 ft. - now seeing 273-275 mph TAS WOT. Have also been attending to some drag reduction items, with 3-4 more items still to be looked at. Have a few ready to check out in the air, hopefully this coming week, so maybe I can get the latest speed vs fuel flow posted following a few more flights. I think another 10 mph is reasonable following completion of aero clean-up.

    I have been conservative, running ROP at AFR of 12.2 or so. Seems like I should be able to run LOP at lower power settings, but I am still looking at what Power % to draw the line between ROP/LOP ops. With the fixed pitch prop, makes sense that I could reduce pumping losses by running LOP with more throttle for the same power seen running ROP with less throttle.

    Did not get much flying in over the winter, lots of work in the shop then and now. About 65-70 hrs TT to date. Very pleased with the engine installation though. When I first set goals for this power plant installation in this airframe, I was looking for at least 250 mph top speed at 7500 ft with a total firewall forward cost less than $25K. Have met those goals with a significant margin.

    Jeff
     
    Last edited: Apr 3, 2016
  15. Apr 3, 2016 #95

    Toobuilder

    Toobuilder

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    275 MPH is pretty impressive for a fixed gear bird. That is better than the Radial Rocket RG, isnt it?

    Running pretty fat at 12.2 translates to what - about 18 - 20 GPH at 7500 feet?

    Good stuff!
     
  16. Apr 3, 2016 #96

    Jeffd

    Jeffd

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    Yes, more than happy with the speed, especially given the very reasonable firewall forward cost and the ability to run 91 ethanol-free Mogas (currently 1/2 the price of 100LL here in the Kansas City area). HP for HP The fixed gear P85 will end up being about 10-15 mph faster than the Radial Rocket RG at WOT / 7500 ft. Attribute this to the cowl shape and lower cooling drag. Interest in the Radial vs V8 seems to run about 50 / 50 right now. I like both.

    12.2 AFR translates into about .50-.52 bsfc, so yes somewhat rich. GPH just depends upon how much HP is dialed up. Last time I checked, 205-210 mph TAS on 11 gph, 230-235 mph TAS on 14-15 gph. LOP operation should put a dent in those fuel flows for sure. Does not take much MP at those speeds, so I would think LOP is possible. I need to do more research on where the LOP / ROP % power demarcation line is before I try it.

    Jeff
     
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  17. Apr 3, 2016 #97

    nucleus

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  18. Apr 4, 2016 #98

    rv6ejguy

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  19. Apr 4, 2016 #99

    nucleus

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    The combustion process is the same regardless of how you cool. Unless you have a wide-band on each cylinder, an EGT on each cylinder is still the way to go, regardless of how rich or lean you run your engine.
     
  20. Apr 5, 2016 #100

    rv6ejguy

    rv6ejguy

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    Yes, the combustion process is the same but the thermal loading (primarily piston crowns) on auto engines is far higher due to the much higher specific output of these engines. EGT is only an accurate measure of AFR at stoich due to other factors such as variable ignition timing vs. often fixed timing on aero engines. The big question is- below what power setting is safe to run LOP on an engine like this? No data exists to answer that question at this time. With engines like the LS, we have a proper intake manifold and EFI to start with, so average AFR read by a single WB is likely close to individual cylinder AFR.

    One Subaru user did some flight testing recently running LOP at around 52% power. The FF and TAS reductions were in line with what we see on Lycoming engines running LOP. Interesting stuff.
     
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