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  #21  
Old 12-25-2017, 08:17 AM
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGG
Posts: 2,178
Default missing ponies?

Quote:
Originally Posted by Northernliving View Post
I have a 180hp PV O-360, but when it comes time to replace it, I think I would go with the IO-375 PV 200hp. Light weight, PV, and 200 hp. Sounds like a winner to me.
Just curious - do you have times where you feel like that missing 20-30 hp would make a big difference?
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  #22  
Old 12-25-2017, 08:37 AM
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DanH DanH is offline
 
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Location: 08A
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Actually, I rarely recommend any specific choice. I think the key is to think hard about intended mission, then factor in the strengths and weaknesses of the various choices, and tailor to that mission.

Not much question, a RV-8 with a light nose is the more pleasant sport flyer. A heavy nose puts the CG against the forward limit when solo. Most run out of nose up trim when slowed for final, flaps fully extended. Maneuvers like a simple 3.5 G loop entry are better done two-handed, as the required stick force is high, which feeds a one-handed tendency to pull in a little right roll. A heavy metal prop boosts gyro forces, noticeable in rapid maneuvers or simply picking up the tail on takeoff, and it's hard on the crank at high pitch or yaw rates.

Downsides? Rear seat and baggage capability is reduced. An RV-8 loaded to the rear limit has very little pitch stability when slowed, and little stick force gradient with G increase. It's not difficult to fly, or unsafe for the aware, but it isn't pleasant.

Power: Angle valve 360's, 390's, and 400's with a constant speed pull like draft horses. Do a formation takeoff behind a parallel valve 360 fixed pitch, and you find yourself at partial throttle, wondering what is wrong with that guy's airplane. Build tip; an angle valve motor just barely fits in the standard RV-8 cowl.

Ahh, so pick a hot-rodded lightweight engine? Let's get real. It's not hard to get more power out of a Lycoming, but nobody installs upgraded parts. In addition, a pumped up parallel valve can be a challenge to cool; limited fin area, and you can't use the power if CHT is too high. I usually suggest against mods strictly for increased HP, and besides, most of the HP claims heard on the FBO porch are BS anyway. I'm not sayin' mods are bad. Things like porting for flow balance and electronic ignition make the engine a pleasure to use; any little power boost is gravy.

So, back to mission. If the airplane is going to spend most of it hours solo, mixing it up with the other local lunatics, giving rides with zero baggage, etc, I'd look at a composite constant speed and a parallel IO-360-M1B. Build it light, and you're talking Big Fun.

If the mission focus is cross country with wife and baggage, an angle valve with a metal Hartzell is the better hauler. In a pinch, either choice can do either mission.

My own is a 390 with a metal Hartzell. The mission was hauling Ms. Patti, complete with, ahhh, stuff, or a buddy and an heap of camping gear, or a few cases of Spotted Cow. The fastback increases rear baggage volume. I don't fly aggressive acro, and rarely G past 3, so the required stick force for pitch isn't a big deal. It can be hot where I live; the 390/CS combination bullets up to altitude quickly, at gross. Light, solo, cold air? No such thing as too much power, here made with displacement, not high cylinder pressure.

It fits my mission. Think about yours.
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Last edited by DanH : 12-25-2017 at 08:44 AM.
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  #23  
Old 12-25-2017, 05:16 PM
Capt Capt is offline
 
Join Date: Feb 2017
Location: Australia
Posts: 123
Default

Quote:
Originally Posted by DanH View Post
Actually, I rarely recommend any specific choice. I think the key is to think hard about intended mission, then factor in the strengths and weaknesses of the various choices, and tailor to that mission.

Not much question, a RV-8 with a light nose is the more pleasant sport flyer. A heavy nose puts the CG against the forward limit when solo. Most run out of nose up trim when slowed for final, flaps fully extended. Maneuvers like a simple 3.5 G loop entry are better done two-handed, as the required stick force is high, which feeds a one-handed tendency to pull in a little right roll. A heavy metal prop boosts gyro forces, noticeable in rapid maneuvers or simply picking up the tail on takeoff, and it's hard on the crank at high pitch or yaw rates.

Downsides? Rear seat and baggage capability is reduced. An RV-8 loaded to the rear limit has very little pitch stability when slowed, and little stick force gradient with G increase. It's not difficult to fly, or unsafe for the aware, but it isn't pleasant.

Power: Angle valve 360's, 390's, and 400's with a constant speed pull like draft horses. Do a formation takeoff behind a parallel valve 360 fixed pitch, and you find yourself at partial throttle, wondering what is wrong with that guy's airplane. Build tip; an angle valve motor just barely fits in the standard RV-8 cowl.

Ahh, so pick a hot-rodded lightweight engine? Let's get real. It's not hard to get more power out of a Lycoming, but nobody installs upgraded parts. In addition, a pumped up parallel valve can be a challenge to cool; limited fin area, and you can't use the power if CHT is too high. I usually suggest against mods strictly for increased HP, and besides, most of the HP claims heard on the FBO porch are BS anyway. I'm not sayin' mods are bad. Things like porting for flow balance and electronic ignition make the engine a pleasure to use; any little power boost is gravy.

So, back to mission. If the airplane is going to spend most of it hours solo, mixing it up with the other local lunatics, giving rides with zero baggage, etc, I'd look at a composite constant speed and a parallel IO-360-M1B. Build it light, and you're talking Big Fun.

If the mission focus is cross country with wife and baggage, an angle valve with a metal Hartzell is the better hauler. In a pinch, either choice can do either mission.

My own is a 390 with a metal Hartzell. The mission was hauling Ms. Patti, complete with, ahhh, stuff, or a buddy and an heap of camping gear, or a few cases of Spotted Cow. The fastback increases rear baggage volume. I don't fly aggressive acro, and rarely G past 3, so the required stick force for pitch isn't a big deal. It can be hot where I live; the 390/CS combination bullets up to altitude quickly, at gross. Light, solo, cold air? No such thing as too much power, here made with displacement, not high cylinder pressure.

It fits my mission. Think about yours.

Excellent post, enjoyed that & learned even more. As we all know anything to do with aviation is a trade off, just how uch you are willing to trade is personal choice:-) Thanks for posting that very good read:-)

Last edited by Capt : 12-25-2017 at 05:52 PM.
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  #24  
Old 12-26-2017, 07:34 AM
Northernliving Northernliving is offline
 
Join Date: May 2005
Location: Boston, MA
Posts: 57
Default Yeah, I think so...

Quote:
Originally Posted by rv8ch View Post
Just curious - do you have times where you feel like that missing 20-30 hp would make a big difference?
There are lots of variables, but I believe that all things equal, lighter and more HP is desirable. I've only flown in half a dozen RV-8's. One of them was light AND had an AV 200hp IO-360. It performed really well. The others were all 180hp 360's with either CS or FP props. I have a 180hp with a FP prop that is pretty light (1012 EW), and I'd say that what I have is in the middle of the pack.

Dan's write up is excellent - and considering the mission no doubt important. I almost always have my bride in the back. Performance is fine - but if I could add a 20 more HP with/out a weight penalty, and then add a CS Carbon Fiber Prop on the front, I think that would be ideal. I could actually use a little more weight up front, and that would probably put my CG right where I want it.
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RV8 - The Dream - Under Construction

Last edited by Northernliving : 12-26-2017 at 09:19 PM.
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  #25  
Old 12-26-2017, 11:34 AM
dbuds2's Avatar
dbuds2 dbuds2 is offline
 
Join Date: Nov 2005
Location: Palm Beach Gardens, Fl
Posts: 372
Default Light and Parallel

ECI IO360, couldn't be happier.
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  #26  
Old 12-26-2017, 08:31 PM
usafmd usafmd is offline
 
Join Date: Sep 2014
Location: Astoria
Posts: 3
Default

Thanks to all of you for taking the time to weigh in. It's a steep learning curve and I've learned a lot already. At present, I'm soliciting bids for a IO375 with vertical induction and emags. Constant speed prop, with a Whirlwind. Don't know yet about pistons/cylinders; still reading. Did a quick once-through Dan H's engine survey in Kitplanes during work today; will re-read more slowly tonight over a beer. And I really appreciate Dan's thoughts regarding weight/balance and flying characteristics which, frankly, weren't even on my radar screen but should have been. My intention is to spend my retirement flying around the country with my bags/camping gear in the back; not doing hammerheads and inverted flight behind the Barrett-tuned 360 I had in my Pitts years ago. Learning formation flying sounds like a lot of fun. I'd like to learn more by being involved in building the engine: Superior still has that option (for $1000 extra), Titan no longer has that option (but kudos to J.B. at Continental for being helpful and upfront about it), and Aerosport has engine school for $500 with, it seems, supplies from both Titan and Superior (again, still learning on this). Overthinking all this is probably, on balance, more useful than underthinking it, so the research continues. Please feel free to keep the comments coming and thanks again.
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  #27  
Old 01-05-2018, 12:52 AM
Berchmans Berchmans is offline
 
Join Date: Nov 2009
Location: Anchorage, Alaska
Posts: 402
Default My real reason

I didn't want the scoop on the bottom of the cowl...I think it looks better without...drove me the M1B...
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Flying RV 8
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  #28  
Old 01-05-2018, 08:42 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,188
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Quote:
Originally Posted by Berchmans View Post
I didn't want the scoop on the bottom of the cowl...I think it looks better without...drove me the M1B...
+1. First RV-8A was a vertical AFP injection system as Vanís only sold the O-360-A1A (with carb) at the time. I sold the carb without ever taking it out of the box.

The new project has the M1B engine. A vertical intake engine works, but (in my opinion) distracts from the graceful RV-8 lines.

Carl
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