Bigger Engines ... why?

Post by **Spike** » Fri Jan 07, 2005 3:34 pm

I just read the article on this month's RVator concerning why Vans discourages putting turbo charged / turbo normalized engines on their aircraft. I found it to be a very well written article with some very good points and justification.

Personally I dont want to anything bigger than a 160HP on my 9. I dont want the associated fuel burn and honestly I dont have the confidence in myself to justify such a decision from a safety or practicality standpoint.

However, what I did question while reading the article was why builders who choose larger engines do so despite Vans strong stance against such a move. I think we hear a good amount of why not to, but we dont hear much about why people are doing it. Hence, I thought it would be a fun question to ask here. So, if you went bigger, what did you do and how did you come to that decision? I'm interested in hearing from the other side of the fence.

-- John

4kilo · Post by **4kilo** » Fri Jan 07, 2005 4:17 pm

John,

One of the greatest things about building your own airplane is that it allows you to express your individuality in ways that most people are unable to. As I am sure you can guess from my responses to the turbine engine question, I am a big advocate of keeping things simple on an RV. I will most likely put a standard 180 HP Lycoming on my RV. But there are others for whom having the biggest baddest engine is a major part of what they want out of their aircraft. I say, "more power to them."

Just as you cannot justify a massively "chopped" motorcycle from a practicality standpoint, there are still people who desire the image these vehicles project. The beauty of home-built aviation is that even though an over-engined airplane may not have many practical advantages, it not only gives its builder the pride of having accomplished something that others said was impossible or impractical, but every once and a while one of these one of a kind creations will result in a technological or practical advancement which can benefit us all.

If everyone wanted the same things, we wouldn't be building our own airplanes now, would we?

Pat

Post by **Spike** » Fri Jan 07, 2005 4:33 pm

Pat, I agree with what you are saying..

Please know that I am not posing this question in an effort to have builders "justify" themselves, etc. I tried to make sure I worded my question such that this would be apparent but I'm thinking I didnt do such a good of a job.

Obviously people can build (and should build) what they want to. Thats why its experimental after all. I am just trying to listen to the other side. There is definately some value in going outside of the cookie cutter recipe and doing it a different way. Frankly I posed this question out of my own ignorance than anything. Ive heard much about why not to do it and so now I want to here why to do it.

-- John

4kilo · Post by **4kilo** » Fri Jan 07, 2005 5:20 pm

John,

I didn't take your question to be critical in any way, and I would not expect others to do so, either.

Just putting my two cents worth in.

Remember that free advice is always worth at least as much as you paid for it!

Pat

captain_john · Post by **captain_john** » Fri Jan 07, 2005 5:56 pm

Being someone who ALWAYS buys the engine option in everything, I am planning on max-ing out my -7 with 200hp. Exceeding that... well I thought about it just for a minute as I have previously stated elsewhere on this BBS. Needless to say, I adhere to Van's guidelines and suggestions for a standard installation. I DID however, purchase the -7 instead of the -9 specifially FOR the engine option.

Anyways... I think people savvy themselves as engineers and are comfortable enough in their decisions that they do install greater power than the company suggests. Maybe they are right? After all, they are truly betting their A$$ on it!

CJ

hngrflyr · Post by **hngrflyr** » Sat Jan 08, 2005 12:45 am

Van's article in this last issue of RVator revealed a couple of engineering facts of life that I was not aware of. I am not a newcomer to aviation.

Safety is the number one priority for me. If I choose to deviate from the designers parameters is some way, I need to become as knowlegeable as I can about what the true implications of my deviation really are, then make my choice, knowing if I am in untested territory, I'm on my own.

I like that proposition ok, and respect the opinions and experience of those who truly know more than I do. Nontheless, the final choice is mine alone. It's MY airplane.

mustang · Post by **mustang** » Sat Jan 08, 2005 1:05 pm

I am probably a bit outspoken about not going bigger than the recommended engine size. I just have a few years of aviation experience and about 20,000 hours. The one thing I can tell you about flying, is that $hit happens! It's one thing when a guy with my experience level chooses to put a massive engine in an RV. Quite another when a guy with less than 2 or 300 hours does the same thing.

I don't think it is very difficult to bend an RV. After all, we have lost an RV-8 already, without a big engine, to structural failure. Vans engineering team has proven to be very close in their stress failure testing. The RV-3 wing tests turned out to be within a couple of hundred pounds to failure. I saw the RV-9 wings that were tested to bending at Vans when down there in August 2003.

I have owned a Pitts Special that was rated at 10 G's. However, I had a partner that would go out and exceed ten G's about once a month. I spent a lot of time repairing broken ribs!?!? I even had to repair the G meter? The lesson here is that any airplane can be bent or broken by a hamfisted pilot.

I will be operating in the high mountains, so I go on the old premise, "There aint no substitute for cubic inches". That said, having flown the Maule Rocket with an IO-540 in the nose, there is a no way I would ever consider such a lump of iron in the nose in our 1100 lb RV. We will install the recommended O-360 which will pull that RV-8 off any mountain strip that I would care to land on.

Trust the engineers, they do know what they are talking about.

OK, I'm off my soapbox now.
Cheers, Pete

Reheat · Post by **Reheat** » Sun Jan 16, 2005 10:38 am

Pete makes some great points. I belive there is ONE substitute for cu in and that is LIGHTER WEIGHT. Light weight won't make you go much faster, but if you can already reach Vne then the only thing the extra horses will bring is better climb and acceleration and both can be purchased by keeping the weight down which will help structurally as well under G-load.

Light weight is also cheap (if you don't count those al gear made by Grove).

Still... custom choppers are pretty cool

arffguy · Post by **arffguy** » Sun Jan 16, 2005 9:30 pm

I think "bigger motor" equals mostly "bragging rights" and whoop ass climb of course. But I know a guy who got his RV-4 wing wrinkled when a backseat passenger did something stupid suddenly and his airplane was not grossly overpowered either. I agree with Mustang in that he states "I don't think it is very difficult to bend an RV." Remember those famous last words "Hey y'all watch this!"

svanarts · Post by **svanarts** » Mon Jan 17, 2005 1:48 pm

Reheat wrote:I belive there is ONE substitute for cu in and that is LIGHTER WEIGHT.

Amen brother Reheat! My RV-4 has a stock O320-D2A, wood prop, nuthin' special. But my plane came in at 872 lbs BEW. I need to reweigh it since I added a harmonic dampener and gear leg fairings but it should still come in at right around 900 lbs. Does my plane fly any better? I don't have anything to compare it to so hard to say. I do know that I can climb about as well as my buddy's RV-8 with O360 and CS prop.

Just seems that when you're trying to defy gravity, lighter is better. Just my opinion.

Reheat · Post by **Reheat** » Tue Jan 18, 2005 10:23 am

roger that! I just took the plunge and ordered a 3-blade Catto (17lb) and the Grove AL gear. I'm goin' lite baby. Now if I could only find someone to anodize the entire airframe in the color I want.....