The No Alternative section

[rv6ejguy]

Originally Posted by tjo

What they assume is that they will be able to achieve these goals while maintaining the reliability performance the same as a traditional AC engine based on the reliability performance of the machine the engine was designed for. It is a flawed assumption, but the promises usually overwhelm the desire to critically challenge them.

Not really flawed as many people you probably don't know about have shown. Here is a good example (skip to page 27 and pages 29-33): http://www.glidingclub.org.au/Docume...3%20Spring.pdf

http://www.glidingclub.org.au/member...aircraft/etug/

The 200 less cubic inch LS1 did this demanding job much cheaper and better with far less maintenance than the 540 Lycoming. Previous to this, a V6 Ford also did it cheaper and better, paving the way for the later V8 conversions. http://victoriancollections.net.au/i...62ef11145dba31

I could list a bunch of others but I'd be repeating myself.

Yes, not something that anyone can do but it's been done more times than most of the readership here on VAF know so it's certainly possible with the right background.

[tjo]

rv6ejguy, I also said:

"In the end, yes, you can make an auto (or other) conversion work and we all know that. What is not known is how much resource will be burned."

What I mean is that there are very few people who are qualified to estimate how much knowledge and resource it will take so that they can really know what they are getting into from the beginning. Not that it can't be done, we know it can be done, there are plenty of examples of that.

I have a lot of respect for what you have done and continue to do, so I hope I don't come across as argumentative. I am supportive of people willing to go down the alternate power path, I just think there are a good many people who either are thinking that way, or went that way, that went in with a goal in mind, but didn't go in with visibility to the knowledge and resources it requires to succeed or if their goal was realistic. I guess my basic position on the subject is that:

1) I agree with the post that started the thread in that I think we as a group should be supportive of those that want to try to use alternative power.
2) I believe that we also probably have some responsibility to help others understand the challenges that may be in front of them, in a positive way, so they can accurately plan for how they will get (if they need to) the knowledge and resources necessary.
3) I also believe we can help people talk through why they want alternative power and whether it looks like they will achieve that goal or not. In the end, it is always their choice.

Tim

[sblack]

That sums up my thinking very well. Unfortunately when we follow point 2) it sounds like we are badmouthing alternative engines. It's not the case for me, but I can see how it would be interpreted that way.

[rv6ejguy]

My point was that VAF is not the forum to get the big picture about successful auto conversions but there is a whole world out there most folks here know little about. There are literally thousands of auto engines flying worldwide very successfully, so it's not like there are just 12 in the whole world. Thousands means lots of people have done it and found it worthwhile in some way- lower costs usually. Many of these are vendor supplied VW, Subaru, Corvair, Suzuki etc., some are one-offs. Sonex in particular has been very successful with their Aerovee offerings which power the majority of their kits.

I think there has been enough negative experiences with alternative vendor engines here and elsewhere that most RV people considering buying one before, would not now. I doubt if more than 1% of new build RV 7, 8, 9, 10 and 14s have alternative engines fitted these days. It just doesn't make sense for the majority of RV builders which have the money to buy a relatively expensive kit and Lycoming engine to go with it, keeping it all easy and predictable- which is what most RV builders want.

For less expensive kits, the price of a Lycoming, Jabiru or Rotax is hard to swallow, hence you see a lot with VW power here. Engine kits are below $4K: http://www.greatplainsas.com/sclgblock.html all new parts, forged cranks and pistons, ready to assemble. They have this down to a science. That's very appealing in my view and it seems many in that market agree.

When we have crate engines at around $6000 for 400hp and PSRUs for just over $3K. It's hard not to think about the possibilities with a new IO-540 hovering around $48K. The attraction of spending $15K FF vs. $50K is too much for some... Gotta give it a try. You're certain to learn a few things and a few lessons along the way.

[Infidel]

I've yet to build an RV, but I suspect most builders consider the resale value of their hard work and investment. The engine is the heart of the machine. And what engine is the general aviation populous familiar with and most likely to consider in a purchase?

[rv7charlie]

Tim, I think you're pretty close to the mark, but I think my phrasing would be 'probability of success' instead of 'reliability'.

I think someone else in this thread pointed out (and I've said for years), the people most qualified to go down the alternate path are the least likely to do so, and the inverse tends to apply, as well. I don't consider myself qualified, but I'm fortunate to have several good friends who are multi-discipline mechanical engineer/gearhead/welder/scratch-builder. Their offers of assistance was the final nudge I needed to try the alternate path.

Van used to say 'convert your money into a used Lyc' (probably still does), and he's right, for the vast majority. But Snowflake is also right; by now, RV's are pretty much high quality aluminum IKEA. :-) I wanted to experiment, beyond proving to myself that I could assemble something. I feel far more comfortable in a proven airframe design with a reasonable and docile stall speed/handling and an experimental engine, than I would in a totally fabricated (or even self-designed) airframe with a certified engine. The only real downside of the airframe is the obvious fact that it's designed with air cooling in mind. Unfortunately, I don't know of any airframes that fit the mission and were designed for liquid cooled engines; certainly none that handle and perform like an RV.

Thanks to Ross for chiming in about how many alt engines are actually flying successfully.

For an amusing read (at least for me), see if anything in this thread sounds familiar. The 3rd post has the 'richest' content.

http://www.boatdesign.net/forums/diy...ation-650.html


Charlie

[rv6ejguy]

The resale price concept surfaces frequently in these discussions. I'd submit that you may get out what you put in in the end but Lycomings are poor investment opportunities as are RVs.

If people are more worried about how much money they will lose buying the kit, building and selling an RV, perhaps they shouldn't start. You're not going to get out what you put in. One minute with your calculator and the average selling price of a used RV will tell you that. Few people are actually getting the $85-100+K they put into a 2 place RV, 10 years down the road.

We could also look at how many hours most people are flying and how long they keep their aircraft. I doubt if the majority of RVs get more than 500 hours on them in the first decade looking at the typical sales ad. It seems most start out flying lots in the first few years, then usage drops off.
In my case, I dropped about $15K less on my FF than a typical Lycoming installation of the era and was able to make 12% on that money in investments. That was about $40K at the end of 10 years for me. These days, you'd be fairly fortunate to make 6%, depending on your investments but you can see in the end, you may end up with about the same amount of money in your pocket even if you get 30-40% less when you sell the aircraft with an auto conversion.

I built my RV to fly it, not sell it. In the end, if I sell it at the 20 year mark for $25K even, I'll come out fine since the money I saved has been earning interest for 20 years.

[rvbuilder2002]

Originally Posted by rv7charlie

But Snowflake is also right; by now, RV's are pretty much high quality aluminum IKEA. :-)

I don't want to hijack the main subject of the thread but since this has come up in the discussion....

The above statement is only true to a certain point.
As soon as a builder deviates from the plans in any way, they could be inducing a design problem that will unknowingly bite them later.

That is the whole premise of certificated airplanes. The have evolved into a proven design (either over time, or by lots of testing; or both) and every one of them is the same, so they should all have the same known level of reliability.

RV's have somewhat evolved in the same way and builders can benefit from that.
When they deviate from the plans they are loosing some of that benefit (to what degree depends on how extreme the deviation is).

Example - The fuel systems for all the RV's has now been pretty well proven. A large percentage of the fuel starvation accidents in RV's have been airplanes that had fuel systems modified to some degree from what is in the plans.

This same dynamic exists with any of the systems or structure in an RV. Choose a different power plant... you reset the experience and testing clock to zero (or what ever value exists from others if you exactly copy an installation others have done).

Not saying that people shouldn't experiment. Just pointing out that when you do, you are influencing the level of comfort that you should have regarding your IKEA airplane

[rv6ejguy]

Originally Posted by rvbuilder2002

I don't want to hijack the main subject of the thread but since this has come up in the discussion....

The above statement is only true to a certain point.
As soon as a builder deviates from the plans in any way, they could be inducing a design problem that will unknowingly bite them later.

That is the whole premise of certificated airplanes. The have evolved into a proven design (either over time, or by lots of testing; or both) and every one of them is the same, so they should all have the same known level of reliability.

RV's have somewhat evolved in the same way and builders can benefit from that.
When they deviate from the plans they are loosing some of that benefit (to what degree depends on how extreme the deviation is).

Example - The fuel systems for all the RV's has now been pretty well proven. A large percentage of the fuel starvation accidents in RV's have been airplanes that had fuel systems modified to some degree from what is in the plans.

This same dynamic exists with any of the systems or structure in an RV. Choose a different power plant... you reset the experience and testing clock to zero (or what ever value exists from others if you exactly copy an installation others have done).

Not saying that people shouldn't experiment. Just pointing out that when you do, you are influencing the level of comfort that you should have regarding your IKEA airplane

Agreed. Most people know a different engine will involve a lot more testing and work now after reading various trials and tribulations.

The second point is very important. Things like fuel system changes can readily bite you. I suggest anyone using an alternative engine check with other successful people on what to do and what not to do. Good systems design is critical to keep the prop turning. We have some proven rules here which have been validated by tens of thousands of flight hours. Benefit from that knowledge and experience. Same goes for cooling and electrical/ignition.

[deej]

Originally Posted by rv6ejguy

When we have crate engines at around $6000 for 400hp and PSRUs for just over $3K. .

Where can we find good PSRUs for around $3k? Will they fit an H6 Subaru?

Thanks,

-Dj