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I am digging this one out of the grave again...Kestrel, did you ever make the switch to a Catto? Heath...do you have any long-term reports on how the Catto is working on the 540?
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Sorry but at the risk of being a negative-Nancy,
I can't see the point of installing a -540 with a fixed pitch prop. It's like putting $50 tires on your quarter million dollar sports car. It raises the question - why even have the sports car in the first place?
The logic to me seems clear:
If you want less weight, less cost, and less maintenance - then you want a -360 with a fixed pitch.
A fixed pitch on a -360 makes some sense to me, at least then you are sacrificing everything to save weight and cost.
If you want the benefits of a -540, then you are accepting a weight penalty to get more performance at both ends of the airspeed range. You need a variable pitch prop to get that performance. It's as simple as that.
Unless I've missed some other reason why a person might want a 6 cylinder fuel guzzler?
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As mentioned earlier, here in the States, you can quite often find a decent used 540 for less than an 0 360,
Probably 8 out of 10 non LSA experimentals being built today(most RVs and the like, Supercub derivatives, etc.) are 0-360 or 0-320 powered.
There isn't as much demand or competition for used 0-540's
So for considerably less money, you can have an 0-540 and a new fixed pitch prop compared to an 0-360 with a constant speed. You would need to decide if you want to "Cruise like an 0-360, climb like an 0-540", vice-versa, or some compromise of the two.
And if some day you wanted to "upgrade performance', it would likely be easier to change out the fixed pitch to a constant speed then changing an 0-360 to a 540Comment
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We're talking about saving a few thousand bucks though right? On a 20 grand engine, at used mid-life prices. Bob sells 'em re manufactured zero timed for not much more.
In about 200 hours of flying, a fixed pitch prop -540 will definitely waste a few thousand bucks of fuel (based on the performance numbers in this thread).
False economy. Just saying.
So in 200hrs of flying, you've paid for the variable pitch prop with your fuel savings.Last edited by Battson; 10-04-2017, 07:47 PM.Comment
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But that was my first point, the -360 fixed pitch is the lighter option, the -540 C/S is the better option for balance and CG (and performance across the speed range).
The fixed pitch is 20% less fuel efficient by the numbers here, in round numbers. Multiply your fuel cost by 20% and you'll know.Last edited by Battson; 10-04-2017, 09:36 PM.Comment
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Hi Heath,
I also have a catto prop / O-540 combo....not flying yet. Can you share more info on your float set-up. Straight or amphib? Displacement and weight?
I also want to go the float way eventually. Any wear issue on the LE. You have the nickel LE right?
mikeComment
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The wider the speed range, the more benefit you get from a CS prop. A bush plane on huge wheels or floats? Less of a benefit. Your limitation with a fixed pitch 540 Bearhawk probably won't be takeoff performance, but landing. If you can land there, you can take off. Flying an RV with a fixed pitch prop I question much more than a Bearhawk, but lots of RV's do it every day and are happy.
As far as CG, that was my first question about the airplane. But then I realized I will be flying over cities almost 0 percent of the time, and in the middle of nowhere the vast majority of the time. Carrying a few gallons of drinking water, and a little camping/survival gear all the way in the back of the baggage compartment will be SOP. A nose heavy airplane, when totally empty, is not only acceptable, but maybe a goal for me.
More than likely I will buy a brand new CS prop and put it on a Bob built 540. But it is overkill. I think I could also talk myself into thinking of a 540 as a much cheaper version of a o-360 with a built in CS prop and turbo-normalized. The 540 will take off shorter than a 360 with CS, and out climb the turbo engine through 7 or 8 thousand feet.Comment
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I was concerned about CG and it was my first question here. But my one and only purpose for the airplane is to go where only a bush plane or floatplane can go. I will always carry 50-100 lbs of kit in case I go down, or just find someplace that I just have to spend the night because it is too cool, or too good of a place to fish.
The airplane can carry a LOT, but the more you carry, the more you have aft CG problems unless you weigh 400 lbs (I am 215). I am going to build with almost no options. No aux tanks, 10 lb instrument panel, oratex fabric. No lights. An electrical system only big enough to start the engine with a button. I will start with no paint, and add as little as possible later.
I want a CS prop, and could care less about the weight on the front. I will just carry more camping/survival gear. But I will always have big tires/ or floats. The "stuck in second gear" is completely applicable to that scenario. I will rarely, if ever, exceed 120 IAS. A fixed pitch climb prop might be 95% as good for what I want.
Other builders, with different dreams of how they will use their birds, are free to express their opinion. I will still probably do a CS prop, but might have a bit of buyers remorse. I could have bought a Honda Africa Twin instead. Or a lot of really good beer.
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The Bearhawk has a wide CG range. You can expand it by building it nose-heavy, and carrying "something" in the rear baggage. It is still a screamer flying solo, but you can remove that and carry "something else", people, baggage, water, a dead moose. If you build it so that flying solo or 2 up, you are in the middle of the CG range, you will forever be useful load limited by CG.Comment
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Thanks Heath.
is your Catto prop 2 or 3 blades? Mine is 2 blades. I've asked Craig about clocking and he doesn't have any recommendation...which is strange. How did you clock yours, 10-4 o'clock ?
MikeComment
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