P85 - A New Aircraft

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Jeffd

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Dec 15, 2011
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Overland Park, Kansas USA
This one is just weeks away from being on the gear - fuselage ready for the wing install - wing currently being primed while on sawhorses so it can be flipped over easily. The P85 is a derivation of the well tested Radial Rocket airframe, using a small block Chevy firewall forward package. Airframe changes are of course the more streamlined cowl, as well as a different rudder shape and swept wingtips. Focus with this plane is on relatively economical firewall forward cost in the 350-400 HP category. Engine of choice for this first ship is based on a 400 cid Dart SHP block, with a mild build (cowl is sized for a big block Chevy as well). A fixed pitch prop and simple re-drive contribute to the overall economy theme, although I am sure some may opt for a constant speed installation. My personal interest though is in simplicity and economy in this performance class. Even with the fixed pitch prop, the associated power/wing loading should provide great performance. Looking for a top speed of 270+mph with this ship, although the proof is always in the flying, so I am looking forward to seeing how this one peforms.P85 3 View  with logo jpeg.jpg
 

Jeffd

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Dec 15, 2011
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Overland Park, Kansas USA
Thanks to all for the nice words. I'll post firewall forward photos as soon as progress allows. Right now we have a mock-up small block Chevy engine fixtured in front of the firewall in prep for engine mount fab (Thanks Rob!). I came of age as a "muscle car" kid in the early '70's and have always wanted to combine that interest with the 3 dimensional arena of high performance flight - in a simple, relatively affordable package.

Jeff
 

Jay Kempf

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Warren, VT USA
Thanks to all for the nice words. I'll post firewall forward photos as soon as progress allows. Right now we have a mock-up small block Chevy engine fixtured in front of the firewall in prep for engine mount fab (Thanks Rob!). I came of age as a "muscle car" kid in the early '70's and have always wanted to combine that interest with the 3 dimensional arena of high performance flight - in a simple, relatively affordable package.

Jeff
You folks are responsible for the Radial Rocket offering. Are there any parts or technology shared between the two designs?
 

Jeffd

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Dec 15, 2011
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Location
Overland Park, Kansas USA
You folks are responsible for the Radial Rocket offering. Are there any parts or technology shared between the two designs?
My original post fairly well summed it up. Lots of Radial Rocket tech in this new plane, and this is a good thing! This airframe is well engineered and very tough. We recently submitted a 250 page engineering report to the Swiss authorities in support of a new customer there. The swiss engineer tasked with reviewing the report was complimentary. The company test pilot and chief floor sweeper (me) insists on solid engineering.:)
 

RJW

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Feb 9, 2011
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Wisconsin and Kansas
This is an excellent variation on a beautiful and proven theme. It is nothing less than spectacular. My heart is certainly in it.;)


Rob
 

Aviator168

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Sep 21, 2012
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2,205
Location
Brookville, NY. USA
This one is just weeks away from being on the gear - fuselage ready for the wing install - wing currently being primed while on sawhorses so it can be flipped over easily. The P85 is a derivation of the well tested Radial Rocket airframe, using a small block Chevy firewall forward package. Airframe changes are of course the more streamlined cowl, as well as a different rudder shape and swept wingtips. Focus with this plane is on relatively economical firewall forward cost in the 350-400 HP category. Engine of choice for this first ship is based on a 400 cid Dart SHP block, with a mild build (cowl is sized for a big block Chevy as well). A fixed pitch prop and simple re-drive contribute to the overall economy theme, although I am sure some may opt for a constant speed installation. My personal interest though is in simplicity and economy in this performance class. Even with the fixed pitch prop, the associated power/wing loading should provide great performance. Looking for a top speed of 270+mph with this ship, although the proof is always in the flying, so I am looking forward to seeing how this one peforms.View attachment 25479
Very nice. Two place?
 

Jeffd

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Dec 15, 2011
Messages
115
Location
Overland Park, Kansas USA
Here is the engine re-drive package for the P85, The drive is manufactured by Ballistic Drives. Single mesh gear drive, 1.8:1 reduction ratio.

We plan 5000 max crank rpm to keep the max prop rpm at approx. 2775 rpm. The engine is a stroked 402 cid LS2 block with LS3 heads and intake. Lots of upgrades to the rotating package for this application. Dyno results showed that it more than exceeded our goal of 425 hp at the prop. 10:1 CR and a mild cam. Tons of torque from 3500-5000 pm.

Weight: 414 lbs dry, as shown in the photo with alternator, water pump, starter, flywheel and headers. Re-drive is a additional 65 lbs.

Note that the intake manifold has been swapped end for end, orienting the throttle body forward.

Jeff Ackland
 

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Richard6

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Aug 14, 2010
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696
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Plymouth, MN USA
Jeff,

Looks great. Have a question. I don't believe that the LS2 came with a distributor sticking out the top. How did you get that to work?

Richard
 

Toobuilder

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Jan 19, 2010
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Mojave, Ca
Indeed. What was the reasoning to go with a distributor? Seems like a step backwards in weight, complexity and cost.

The fact that you ended up at less than 500 pounds for more than 425 HP is a very favorable power/weight. Certainly better than other typical aircraft piston power plants.

Is this a C/S prop, or fixed?
 

RJW

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Feb 9, 2011
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708
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Wisconsin and Kansas
Beautiful motor. That’s how I would’ve done it.

I just had a coil pack from a 6-cylinder in my hands—pretty heavy. Four packs or eight coils add up. Electronic distributors never break and supply plenty of accurate spark in a low-rpm aero application. It’s what I’d use.

Rob
 

Jeffd

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Joined
Dec 15, 2011
Messages
115
Location
Overland Park, Kansas USA
Jeff,

Looks great. Have a question. I don't believe that the LS2 came with a distributor sticking out the top. How did you get that to work?

Richard

The distributor mod is a readily available kit made by Wegner Automotive. Dual pickups in it to allow use of two MSD ignition systems. I think that most of the folks running the distributor also use a carb so as to eliminate use of an ECM. Personal preference in the decision to use the distributor on this one. May or may not use it on the next engine depending upon various factors - we'll see.

Yes, very happy with the power/weight ratio, even after adding projected weight of cooling system components.

Going fixed pitch with this one - the idea is to minimize firewall forward cost while maximizing performance for the cost. Think Spitfire I/Hurricane I with the fixed pitch props. They performed well. P85 wing loading at gross (approx 25 lbs/sq ft) and power loading (approx 5.8 lbs/hp) is very similar to these ships. Of course the Spit and Hurricane were quickly fitted with CS props - in combat a very small performance gain could mean the difference between victory and defeat. But we are not fighting a war with the P85 - just looking for that "fighter feel" with simplicity and relatively low cost in a high performance kit aircraft.

Jeff Ackland
 
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