Continental in Avid MK-IV?

[Luked 71]

I started another thread asking about real world Avid empty weights because I was concerned about my empty weight if I go with a Continental engine that is heavier than the plane was designed for. The question of the trade offs of using a heavier engine came up, so I thought it might be good to start a thread on the subject. It might be interesting to others too, or people searching the archives in the future.

 

The other thread about empty weight: http://www.avidfoxflyers.com/index.php?/topic/2805-empty-weights/

 

I don't want to come off sounding too defensive about my plan to use a Continental, but I have put quite a bit of thought into it. Also, everyone's situation is different, and the trade offs that work for one person might not be right for someone else. I know the Continental won't be the most popular choice of engine for most people. I have to decide if I will be happy with the trade offs when all is said and done, and I have a finished airplane.

 

All that being said, I'm at an early enough stage that I could still change my plan (I'm only part way down the Continental road at this point), so I'm open to other peoples thoughts. If I do put a Continental on the front of my plane, I want to do it with my eyes wide open to all of the potential negative aspects.

 

I'll give a little background on my thinking. When I bought the partial kit, the previous owner had already lengthened the fuselage by 16". His plane had been to put an O-200 on. In addition, he had added extensive sheet metal to the area behind the seats that extended most of the way back on the tail to make a huge baggage compartment. In addition to this, he had built the wings to be "convertible" from speed wings to long wings with removable tip and flaperon extensions. also, I measured the washout on the wings that he had already built, and they had slightly over 2" of washout on the short wings alone.

 

This whole thing seemed like a recipe for hugely overweight Avid with poor performance. I basically considered the wings a write off, and decided I would build new ones. Having the stretched tail made me think that a smaller Continental might be a decent fit, and might work with my budget. My first thought was an A-75 with no electrical. This is about the lightest Continental that would be in the right HP range. My thinking was that it should perform like a 582 powered Avid that's carrying some extra weight.

 

The more I got to thinking about it, I wondered if I would regret not having an electrical system. I am also considering a C-85 with lightweight accessories. I already have a flanged crankshaft that will work for either engine. In any case, I am planning to keep the airframe as light as possible (a tall order I know) because I know I am already going to be suffering from having more weight than what was intended.

 

Anyway, any additional information would be welcomed and appreciated, and better information leads to better decision making.

 

Luke D.

 

Edit: forgot to add that I've already removed all of the extra weight that the previous builder added that was not stock. More weight saving ideas are in the works.

Edited 11 Apr 2014 by Luked

[akflyer 1427]

I love my extended baggage and would not trade it for anything.. Other than maybe making it out of kidex instead. Plus a little weight in the tail will help you. A buddy has the c90 in his tcrate and it's a one flip wonder. I don't think I have ever seen him have to flip it more than once. It is a bugger on floats sometimes though. You can get 100 +hp out of it pretty easy.

I think on a stretched fuse with a climb prop it will perform every bit as good as Randy's fat avid, and that is pretty damn impressive if you ask me.

[Luked 71]

I love my extended baggage and would not trade it for anything.. 

 

Well, I remember you mentioned how nice it was having a large baggage area when I first posted about my project. So, I'm planning to have a larger than stock baggage compartment, but it should weigh a lot less than what was in the plane, and be much closer to the CG... Don't know if I want to share details yet though in case the idea is a flop 

[akflyer 1427]

well if you share details, it may be a great idea.. or it could be one that someone had already tried and has input on what they would different and why.  I really am not too sure that much more could be done to these planes that has not been done before.  I don't like running a biasply tire when I can get a smooth riding radial for a few bucks more

 

[Av8r3400 1179]

I believe that even though a Continental Cxx is heavy, it could be a good match to the plane.

What would make it a real winner would be to have the extended fuselage modification done first. This adds 15" to the back of the fuselage just behind the cabin. It will allow for a better balance without the need for ballast in the tail.

[Av8r3400 1179]

This mod originally came about to facilitate the install of a Subaru motor. (I think)

[Luked 71]

Leni, I guess I shouldn't have brought up the baggage idea until I had more figured out. It was mainly just to say that I'm not planning to have only a stock baggage area. I probably won't have a ton of useful load, but I might want to stick some light weight bulky stuff in there like some sleeping bags or something.

 

Larry, my plane's got the tail extended 16". I'm not planning on doing any more stretching at this point, but I'm curious about the stretch right behind the cockpit. What are the advantages over the stretch back by the tail? Or, is this done in addition to the stretch at the tail?

[akflyer 1427]

I wouldnt be afraid to do a little beef up in a few key areas and give yourself a lot more weight carrying capacity without much worries.  Mine says 1085 but I have been over 1300 more than once... Other than a little slower on the climb out, and the fact that it was a bit on the tail heavy side needing a bit of forward stick (read extended baggage and just how much you can load in it) she flew fine.  I am damn sure not going to be pulling 4 gs at that weight, but I was not too worried about it in slightly bumpy air.

 

[EDMO 1078]

Luke,

     You already have the stretch they added in order to run the Subaru - Your Conti weighs less than the Soob.

I would say that the only downside is that you will burn 2 or 3 times the fuel for the same performance as the Soob.

EdMO

[akflyer 1427]

No too sure on the fuel burn issue.  My buddy burns right around 5 or under in his tcrate.  It is a pretty sweet setup and works well on floats.

[EDMO 1078]

We burn more down here in the hot wetlands - You have all that cold dry air bottled up and wont share it....Well, maybe only 2x burn if you are careful - Randy is getting about 3.? gph.

EDMO

Oh, I forgot - you did share it this winter - coldest, most snow in years here - but you can have it back now!

Edited 12 Apr 2014 by Ed In Missouri

[Luked 71]

Luke,

     You already have the stretch they added in order to run the Subaru - Your Conti weighs less than the Soob.

I would say that the only downside is that you will burn 2 or 3 times the fuel for the same performance as the Soob.

EdMO

 

Okay, I wasn't sure if the stretch Larry was talking about was something different than what I have. He mentioned the stretch being right behind the cabin. Mine is stretched closer to the tail. Maybe he was just describing the same thing.

 

On the fuel burn, I guess you can't expect that great of fuel econemy from an engine with a carburetor that's about as advanced as the valve in a toilet boil

[Bandit 286]

I do not think fuel burn is much of a concern for most of us. I have a feeling most pilots don't log that many hours a year to make that much difference.

[Av8r3400 1179]

The C85 in my buddy's Champ only burns 4-5 GPH.  Not too bad...