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  #1  
Old 12-21-2019, 03:10 PM
Westerhuis Westerhuis is offline
 
Join Date: Sep 2016
Location: Boston (MA)
Posts: 81
Default Is the O-235-C2A a suitable engine and what to look for when buying and RV3

Hi

A good friend is thinking to buy himself an RV3B. It will be his first Vans.

The aircraft he's got his eyes on is a 15 year old 'B' model equipped with a Lycoming O-235-C2A, which I believe is a 115 HP engine. Its empty weight is 738 lbs, which seems very reasonable. However, and I don't know much about RV3s, 150 HP engines seem to be more commonly used?

Could anyone give some idea and his (or her) opinion on an RV3 with this particular engine. Would it be under-powered?

What are the other pitfalls one would lookout for when looking into buying and RV3 (he is an AP), and last but not least, what would be a fair price for a machine that is in great condition, with a Dynon D100, Garmin 296 and just over 600 hours total sime since 2004?

Thanks

Rogier
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  #2  
Old 12-21-2019, 03:36 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,416
Default

My guess is that at sea level, that RV-3B will be okay, but not as fast as the higher-powered ones, and it won't climb as well. Van's original had 125 hp, I think, and was certainly acceptable. This is 10 hp less.

This one is light enough, and that's in its favor.

Price? Not a clue.

Dave
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  #3  
Old 12-21-2019, 04:15 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,388
Default 0 235

The 0 235 C series engines are not very popular in EAB. The parts are extremely expensive and availability of certain parts is not as good as 0 320 and 0 360. They are all conical mount engines.
The 0 235 L series used in the Cessna 152 are dynafocal mount engines and can be upgraded to 125 horsepower.
The 0 235 should work fine on a lightweight RV3 but the purchase price should reflect the much less desirable engine.
The Piper PA16 and PA14 carried four people with 0 235C engine. I know of one PA16 that carried five adults. The PA12 was three seat with 0 235.
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  #4  
Old 12-22-2019, 04:52 AM
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Lufthans Lufthans is offline
 
Join Date: Dec 2017
Location: Hilversum, The Netherlands
Posts: 132
Default

Rogier,

Obviously top speed and climb rate suffer. Let's approach this from a theoretical standpoint.

Horse power required goes with the cube of speed.

If a 150 hp RV3 does 200 mph flat out, then this one with 115 hp will do 200 x (115/150)^1/3, or 183 mph. Not a tremendous price to pay.

Climb rate will be a different matter, although the light weight will work in your favour there.

Switching to proper standards:
738 lbs = 335 kg
A typical 150 hp -3 will be around 780 lbs, or 355 kg
115 hp = 85 kW
150 hp = 112 kW
Let's assume a 80% efficient prop, which is about typical.
Let's assume the aircraft needs 60 hp (or: 45 kW) to fly straight & level at Vy.
Let's on both aircraft assume a fixed pitch prop, which will not let the engine operate in its max power rpm. Say you can do 2250 rpm at Vy, rather than the 2700 where you have max power. So - assuming more or less linearity on power output - that 150 hp becomes (2250/2700) * 150 = 125 hp or 93 kW and that 115 hp becomes (2250/2700) * 115 = 96 hp or 71 kW

Now do the math (and where the proper SI units come in handy). 

First on the 150 hp version:
Available power is 93 kW, of which 45 kW is required to fly straight & level, so 48 kW is left for climbing. With a prop efficiency of 80%, that means 0.8*48 =38.4 kW is actually for climbing.

That is 38,400 J/s
And this equals M*g*dh. So dh (delta of the height in meters, in 1 second) = 38400/(355*10) = 10.8 m/s or 2100 fpm. This is slightly more than typical, but in reasonable ballpark of what a 150 hp -3 can do.

Now for the 115 hp version:
Available power is 71 kW, of which 45 kW is for flying straight & level. Leaving 26 kW for climbing. With 80% prop efficiency, this means 20,800 J/s. So dh = 20800/(335*10) = 6.2 m/s or 1220 fpm.

So there you have it - top speed suffers slightly, but it is climb rate where you pay the price.

Incidentally, I know of a Rotex 912 powered RV4 in Italy. Supposedly, the owner is pretty happy with that aircraft. Very light, and still quite good performance.
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Last edited by Lufthans : 12-22-2019 at 05:20 AM.
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  #5  
Old 12-30-2019, 09:47 AM
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smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,887
Default Enough Stuff..

Quote:
Originally Posted by Westerhuis View Post
Hi

Could anyone give some idea and his (or her) opinion on an RV3 with this particular engine. Would it be under-powered?

Thanks
Roger
Hey Rog,
While building my RV4 in the late 90's I shared a hangar with a Squadron mate who owned a very early RV3. It had an 0-235 with a Sterba Wood climb prop, very little accessories and VERY light empty weight, 715lbs if I remember right.
I flew (and tweaked) it extensively and found it performed very well with a climb prop, 1/2 fuel load and me (170lbs) flying it.
Performance at 3000 MSL was (as I remember) sprightly compared to my 65HP Taylorcraft. 1000fpm climb, 130 Knot cruise (5GPH) at 2400, 150Knots at 2800 RPM (6.6GPH), and the prop would allow 3000 RPM flat out which I could keep up with a 180HP RV6 with no worries indicating 170. Not bad for 115HP.
The 0-235 is plenty if the airframe is light and you plan local flights with a lighter fuel load.

Bottom Line? I think it would be a great airplane if your friend is an experienced Tailwheel Pilot, with high performance airplane experience, single seat time helps (Pitts, etc). The price range of $25K to $35K for a nice one would be acceptable given a low time engine and solid build.
Questions? PM me and I'll be glad to share my experiences.
V/R
Smokey

PS:The 0-235 has a "Sparrowhawk" conversion designed by Lycoming to bump up the HP of C-152's. It brings the engine up to 125HP, a viable consideration for the future.

PSS:
The original RV3 kit had a less than robust main spar attach point and carry through that had several wing failures due to over G in the early 90's. Rapid G onset was blamed but isn't good in any airplane not designed for it. The only one I've flown capable is the F16 and that only when it's not carrying external stores. I never had an issue in my friends early Three as I kept it under 3.5G's and used a easy G onset never "snatching" the stick during acro. It's still flying today at 44 years young.
Yours being a B is an excellent purchase consideration
All that said, Van came out with a spar mod in the mid 1990's he sent to early RV3 owners free, requiring the wings to be removed to install properly. The strap on mod denoting the RV3 "A" designation.
Later Van would redesign a new wing making it standard on later kits and retrofit earlier RV3's denoting the RV3 "B" designation (like yours). All current Three kits are RV3B's.

Last edited by smokyray : 12-30-2019 at 10:01 AM.
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  #6  
Old 01-06-2020, 11:23 AM
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gmcjetpilot gmcjetpilot is offline
 
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The O-235 is/was popular on C-152, Tomahawk, Grumman Yankee. It is not as good as a O320 150/160HP from stand point of parts and obviously power. I believe the parts are more expensive for the O-235. An RV-3 with 115 HP would be fine but 150/160HP way better. Also the O-235-L2C was subject to lead fouling with 100LL.

The O-235 is super popular with the Long EZ crowd. You could sale it and get a O320....
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  #7  
Old 01-06-2020, 01:04 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,388
Default 0 235

Cessna 152 and Tomahawk are very different from Yankee. Cessna is L series, Tomahawk similar but different series.
The L series type are upgraded engines with dynafocal mounts. The Yankee engine is a C series with conical mounts.
The L series engines can be upgraded to 125 horsepower and remain certified. The C series can be also but then are experimental. C series can be 100 hp, 108 hp and 115 hp. Minor changes between the three versions.
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