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Engine Choices - 1500 lb GW/1650 lb w/Floats

I'd have a hot C-85/90/O-200 built with dependability in mind. Anybody experienced that works on engines can maintain them. High flow exhaust and intake, proper carb jetting and ignition setup, and enough fuel onboard to meet the expected range radius and consumption. Adjustable prop to meet the mission. Flaps are nice but simple VG's can help. Keep it light as possible. Others have floated Christavia's so there's some potential support for that gear. Might make for a fun project, but I'd rather fly than build so my experience is lacking.

Gary
 
I posted this thread in an attempt to define engine options better and this has helped. All I can do is continue to identify and refine the effort.
 
I looked up the Aeromomentum engine because I'd never heard of it. https://aeromomentum.com I see why it intrigues you. I can also see that it could be a good engine. The company is owned and operated by what appears to be a husband and wife team. She appears to have come from Russia where she was educated. Nothing wrong with that. Both of them appear to be well qualified. The engine components appear to be imported from that part of the world. Nothing wrong with that either. What happens if something happens to them? Will you be able to easily find replacement parts? The whole company could easily go poof, leaving you with a boat anchor. The propeller they recommend is sourced from Ukraine, a war torn country. Another big question mark.

Cessna made thousands of 150s. Other companies also used the 0-200. Parts are plentiful. There are many overhaul shops which know the 0-200. Salvage yards often have good used engines available. I think I would lean in this direction.
Good points all. My primary reason for prioritizing them is I want liquid cooled. Air cooled is fine but if you look at the work done by HRC (Honda Racing) in the 80's you'll see a host of reasons to prefer liquid cooling. HRC found that virtually every engine they tested had over designed - and consequently heavy - cooling fin structure. Even after re-engineering the fins to reduce weight and maximize efficiency they still found that a properly designed water cooled system can be lighter. Back in the 80's I was a club racer for Honda - and what I found was that liquid cooled was easier in every regard than air cooled had been - to a shocking degree. I didn't want to like it, but I did. What I prefer about it is the heat sink aspect. Liquid cooled is much harder to shock cool - but more to the point a slower thermal change is infinitely preferable than a quick one - whether cooling or heating. Engine operation is much more stable and that's a very good thing. You get much more time to troubleshoot a problem before you wind up with a dead engine in an inopportune location like the bottom of a jump. Add the lessons learned over 100 years plus of automotive cooling experience, and it just seems so much more aware to use liquid.

Your cautions about the tenuous nature of a small company are quite reasonable. I would however suggest that almost every GA specific company encounters much the same degree of risk due to size. That doesn't negate the validity of your point, merely pointing out that it's a common situation in aviation. I do completely agree with your suggestion about the prop - but as long as other props can be used it becomes a non issue. I understand the basic engine components are produced by an otherwise automotive company - which would appear to inure them to some degree from the volatility that is aviation business. If they're producing hundreds of thousands of unit a year and have been - well parts ought not be a problem. In fact I would argue that virtually any typical automotive producer will produce more per year than even the most popular legacy Aviation engine producer. That would appear to create a greater demand pool - and a greater likelihood of continued supply. The last I heard they were primarily using Suzuki and Toyota parts. Neither of them are going out of business anytime soon.


But all this is me. If the OP has any concerns at all it's better to go the non-adventurous non-innovative route. If something's been being done the same way for years, we know it can work and there's plenty of folks out there with experience making it work. Non traditional power is not for everyone in Aviation. But in recent years we've seen examples of previously non traditional engines becoming main stream - so it can happen. I would also caution anyone considering such a move to evaluate carefully. Mistakes can be expensive in aviation.
 
Good points all. My primary reason for prioritizing them is I want liquid cooled. Air cooled is fine but if you look at the work done by HRC (Honda Racing) in the 80's you'll see a host of reasons to prefer liquid cooling. HRC found that virtually every engine they tested had over designed - and consequently heavy - cooling fin structure. Even after re-engineering the fins to reduce weight and maximize efficiency they still found that a properly designed water cooled system can be lighter. Back in the 80's I was a club racer for Honda - and what I found was that liquid cooled was easier in every regard than air cooled had been - to a shocking degree. I didn't want to like it, but I did. What I prefer about it is the heat sink aspect. Liquid cooled is much harder to shock cool - but more to the point a slower thermal change is infinitely preferable than a quick one - whether cooling or heating. Engine operation is much more stable and that's a very good thing. You get much more time to troubleshoot a problem before you wind up with a dead engine in an inopportune location like the bottom of a jump. Add the lessons learned over 100 years plus of automotive cooling experience, and it just seems so much more aware to use liquid.

Your cautions about the tenuous nature of a small company are quite reasonable. I would however suggest that almost every GA specific company encounters much the same degree of risk due to size. That doesn't negate the validity of your point, merely pointing out that it's a common situation in aviation. I do completely agree with your suggestion about the prop - but as long as other props can be used it becomes a non issue. I understand the basic engine components are produced by an otherwise automotive company - which would appear to inure them to some degree from the volatility that is aviation business. If they're producing hundreds of thousands of unit a year and have been - well parts ought not be a problem. In fact I would argue that virtually any typical automotive producer will produce more per year than even the most popular legacy Aviation engine producer. That would appear to create a greater demand pool - and a greater likelihood of continued supply. The last I heard they were primarily using Suzuki and Toyota parts. Neither of them are going out of business anytime soon.


But all this is me. If the OP has any concerns at all it's better to go the non-adventurous non-innovative route. If something's been being done the same way for years, we know it can work and there's plenty of folks out there with experience making it work. Non traditional power is not for everyone in Aviation. But in recent years we've seen examples of previously non traditional engines becoming main stream - so it can happen. I would also caution anyone considering such a move to evaluate carefully. Mistakes can be expensive in aviation.
All valid points. If one knows of alternative sources for normal wear items as you've determined, then these engines have more promise. The propeller question is a non issue, as simple adapters can be made to accommodate a variety of props. My skepticism comes from being around aviation too long, and having been to places where the failure of any parts makes for a long slog home.......if even possible.
 
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I built a Cub with an O-200 that didn’t turn out as light as I wanted. I put a Catto prop on it and amphibious floats. According to my plans I’m good up to 1600lbs on wheels. My floats are Mead 1430 and buoyancy is 1536 per float. It gets off the water in 12 seconds lightly loaded and I have flown it over 1600lbs a number of times with no ill effects. My engine is a stock O200A with stock PA11 exhaust, it’s no carbon Cub but it’s safe and fun. I’d like a little more floatation but small amphibs are hard to come by and weight saving is important. Maybe someday I’ll throw my C90 on there and see what a difference it really makes…I only know this…I tried my 76-36 Catto prop on both engines, and the O200 spins it faster….I know, they say a C90 makes its horsepower at a lower rpm…but the O200 has a higher static with the same prop…so it always confused me why I’m told the C90 will perform better. Won’t my plane climb better if I spin the same prop faster with one engine vs the other? If my O200 has a higher static rpm than the C90 with that exact prop isn’t that supposed to be the ticket? Sometimes this comparison confuses me….early on when I was first flight testing I found that the tachs on these two engines were not accurate…a digital tach gave me the answers I needed. Anyway, good luck on your journey…be careful not to compromise too much on reliability chasing performance.
 
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My skepticism comes from being around aviation too long, and having been to palaces where the failure of any parts makes for a long slog home.......if even possible.
Skepticism is a good thing. It keeps a lot of folks alive! As long as it doesn't turn into intractability it's a very desirable attribute.
 
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