SPORT CLASS; i/o720, 2nd seat, keybird

[Unregistered]

Since the s-class is synominiss (sp?) with Greenamyer..... a few questions.

#1. the i/o 720 (adding the 4th bank).. the motor is HUGE and weighs a TON.... back in the day.... looked good on paper, but the performance benes did not out-weigh the package vol and hp gains. FEED BACK?

Are the gains in performance = 2 the down sides, in stuffing a monster motor (package volume) on to a kite?

Humm ......... RR merlin vs. RR Grifon ?

To get to the 650 limit you need to reduce the bore from 5.125 to 4.875.... can you sleeve the existing cylungers down 1/4" , that would adding an additional cylinder wall thickness of .125" ??? Too much mass / heat transfer problems , if you sleeve it. Any varient Lyc cylinder bores a workable deal?

OK.... weld up the crank and de-stroke it you say? Noooo, cause it is a undersquare bore/stroke already (5.125 x 4.375).......... if you do weld and regrind the crank ( this is real dooable with the race motor technology today ) will a super-under square relationship of 5.125 x 3.950 work welll in a low rpm , high torque situations (and dealing with recip mass acceleration with stock rods and pistons????????

Sure, the over square deal works in other forms of racing.... but the rpm deal is in a totally different realm. MOTOR HEAD FEED BACK

Good example was the 906 porsche and its flat 6 (and a bunch of varients).... the 908 was a flat 8 and worked sorrta ok, but was never that popular in-leu of the flat 6 performance, weight, reliablity.
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#2
In my day... in sport car racing.... the 2nd seat rule was cramming a small plastic seat into the "passenger?" area. Worked for the rules, but my 5 foot, 90# wife didnt even start to fit in the space..... maybe my 8 yr old would. FEED BACK

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#3

OKay... the BIG question..... if the Keybird "thing" was to have been a total success.... would the semi-wet snow / washboard surface /1,700 foot "short" runway have been enough?

O & O

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[W J Pearce]

Re: SPORT CLASS; i/o720, 2nd seat, keybird

Taking a shot here:

#1 The 720 is over the 650, limit as you know. I don't think it makes any sense to apply the amount of work needed to bring that engine into regs. Then there is that fact that the engine itself in not allowed. So by reducing the CU IN make it legal? Seems a grey area. Why not take a 540 or 550 and spend the time and energy (and money) that would have been spent to make the 720 legal and make the 540 or 550 really awesome?

#2 There is no 2 seat rule in the sport class. It is a common misconception.

#3 It's Keebird, and I think Darryl could have done it. Obviously he thought he could do it, he wouldn't have gone to take off after 2 years of work and lot of money if he thought "I'm gunna plow this into the end".

[Apteryx]

Re: SPORT CLASS; i/o720, 2nd seat, keybird

OKay... the BIG question..... if the Keybird was to have been a total success.... would the semi-wet snow / washboard surface /1,700 foot "short" runway have been enough?

Don't forget, it DOES get a bit windy down there

[MustangScott]

Re: SPORT CLASS; i/o720, 2nd seat, keybird

D.G. 's " KEE BIRD " B-29
Not to nit pick. Hell of an effort.

[FlyKidChris]

Re: SPORT CLASS; i/o720, 2nd seat, keybird

The Lycoming IO-720... "...looked good on paper, but the performance benes did not out-weigh the package vol and hp gains. FEED BACK"

I'd respectfully disagree. I flew a few different Twin Commanders with the "Mr. RPM" conversion (Lyc IO-720s) and a few with the stock engines (a few hundred hours between the two). In every aspect, except acceleration on the runway, the converted aircraft were superior, in my opinion.

You should also note the price of the Piper Comanche 400s. No doubt that the Comanche aficionados hold the Comanche 400 in very high regard.