REFLECTOR: Re: Props

[Chuck Harbert]

Jim, I've got a similar setup (200 hp IO-360 in Std RG) and I'm also 
overproped (2200 static), but I'm doing over 180 kts @2700 rpm using a Catto 
prop. I have a turbo system ready to install which will bring up the static 
to 2,400 rpm and I'm expecting higher speeds at higher altitudes at below 
normalized MP which is what Catto designed my prop for. My t/o roll is a bit 
longer, but still less than 2,000'.

I think the combination of FG (w/o wheel pants) and the 173 wings can 
significantlty reduce the top speed. I definitely would not switch to a 
Mazda rotary (I switched from a rotary) as it will take a long time to 
install, and will not produce the power, fuel burn, or reliability you're 
looking for. If you want higher speeds, the only realistic way is to 
turbocharge and take advantage of the reduced drag (thin air) at higher 
altitudes. This assumes you've done everything aerodynamically possible.

If you're only getting 2,550 max rpm, you're losing 20 hp compared to 2,700, 
and probably 5-7kts. Catto told me he can modify the prop to get higher 
cruise rpms, plus you'll pick up some static rpm and better t/o performance.

Good luck.

Chuck H

--------------------------------------
> Date: Thu, 23 Jun 2005 23:54:26 -0500
> From: Jim Sower <canarder at frontiernet.net>
> Subject: Re: REFLECTOR: Props ...
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Message-ID: <42BB9202.9060403 at frontiernet.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Scott,
> Where'd you get 180 ktas?  You got an RG?  If not, I'm humiliated.  Mine
> (w/o wheel pants) won't do a yard over 150 kts.  I have to file 145 or
> 140.  It's embarrassing.  Looks like I might have to bite the bullet and
> do all that work and install a 220 hp Mazda.
>
> Love the engine, hate all that work ... Jim S.
>
> Scott Derrick wrote:
>
>> Jim,
>>
>> "I had" the same engine, rated 200HP.  I was running a Catto, 64x74.
>> I would get 2350 static, and WOT 8000,  2800 RPM, 180 KTAS. That was
>> with a LSE ignition which I think added to my performance.
>>
>> I never cruised at 2800, I would normally cruise at 2700-2750,  at apx
>> 175 KTAS, 75 LOP.
>> You could cut a 1/2 inch at a time, off of it,  and see how it
>> increases your RPM?  2550 WOT is definitly over propped. You get that
>> static up to 2350 you'll cut 500+ ft off your take off roll.  Your
>> cruise speed would be less because of your bigger wing.
>>
>> Scott
>>
>> BTW, my prop with a Saber 8" extension is for sale $1500 + shipping.
>> 300 hours. I'll put a new coat of PPG on it before shipping. You pick
>> the tip color.
>>
>> Jim Sower wrote:
>>
>>> All,
>>> I am running an angle valve IO-360 with a Catto 66x72 on my 173-FG.
>>> I find I'm overpropped about 200 rpm,.  I get 2200 - 2250 static and
>>> 2500 - 2550 WOT at >8000'.  I think I'd be a lot happier with closer
>>> to 2400 - 2450 static and 2700 or more at 8000'.
>>>
>>> Who's got a similar engine, what kind of prop are you using, what
>>> static and cruise (>8000' WOT) rpm are you getting?  I think my
>>> engine's pretty sorry, but I don't have any other data points from
>>> similar engine prop combinations.
>>>
>>> Thanks in advance ... Jim S.
>>> _______________________________________________