H9's Sundowner

[mfuess]

The BME 50 being installed:

[mfuess]

The Sundowner now has a cowling to cover up the BME 50, OK only partially cover...



I did manage to locate a 17x18 prop! This may be too much pitch though. I also added extra mounting screws on the cowling.

The engine fired up easily on the very first start, about 18 flips. This is one super potent engine! I have owned many BME 50 engines but this one is a little more powerful. It uses a CM-6 sparkplug like a DA-50. BME also changed their Ignition over to Falkon/CH, and they changed to a slightly bigger Walbro carb (WT-546)

[Sparky69]

Mfess,
Looks good, Pitty it doesn't fit better in the cowl. Is the prop an APC? If you are not getting the RPM up were you desire start cutting the prop down 1/4 inch at a time. Caution the spark plug hitting the ground on less than graceful landing. The Stock gear may not be stout enough, I have rebent the stock gear many times maybe some sort of wood piece on the top of the cly to prevent contact with the ground. Also you can tape over the cowl intakes they won't do any good in your setup and may help overpresure your cowl. Use 3M Cat. 190 tape available at Ace Hardware.
I now have 5 flights on my Moki powered Sundowner.
Sparky

[mfuess]

Sparky69,

Thanks for the info! That is my break-in prop, an APC 20x12. I don't plan on flying with it. I will probably start off with a Biela 18x12 for the first few flights. Meanwhile, I ordered some really high pitch 16 inch props 13,14,15,16. One of these will launch that BME 50. I will most likely cover the inlets as you suggested, they aren't doing me any good anyway... My Sundowner balanced perfectly using the steel stab rods and moving my receiver pack to the rear. The aircraft came in at 13 pounds, 11 ounces. That's nearly a pound lighter than my DA-50 powered RV-4. I will probably leave the gear alone for now. I'm no stranger to F1 landings. I was speaking with a racer down in Houston yesterday and he's running a BME 50. He told me his BME will run all day long at 12,000 RPM and won't even get hot. He recommended a 16x14N APC. That calculates to 159.10 MPH. I will give it a try...

I will be taking the Sundowner out New Years Day for its maiden.

I also installed an on-board flight recorder.

Here is my Sundowner Ready To Fly, minus the spinner.

[Flatlandman]

I got the same answer from Da about the 50. That they have customers running it at 11,000 rpms with no issues.

[Sparky69]

I think your 16" props are way to small of a dia. I did the math and if you can spin a 16 " prop at 11 or 12k the prop tips will be supersonic. About .8 mach I think is were you want to be. I would be looking at something in the 18" dia at about 12 or 14 pitch.

What flight recorder are you using?

I now have the Moki Sundowner on a 16x14 and everything is going well in flight RPM around 9K.
My math says that should be about 123 MPH and prop tip speed of 628 FPS.
Sparky

[mfuess]

	Quote: Originally Posted by Sparky69
	I think your 16" props are way to small of a dia. I did the math and if you can spin a 16 " prop at 11 or 12k the prop tips will be supersonic. About .8 mach I think is were you want to be. I would be looking at something in the 18" dia at about 12 or 14 pitch. What flight recorder are you using? I now have the Moki Sundowner on a 16x14 and everything is going well in flight RPM around 9K. My math says that should be about 123 MPH and prop tip speed of 628 FPS. Sparky

Hi Sparky,

Happy New Year! I'm not getting that kind of RPM out of my BME. So far it's getting 9790 on an APC 16x14N which translates to 129.80 MPH. The recorder is made by Winged Shadow Systems. I'm not totally sold on the recorder yet. It "seems" to work OK but I'm still a bit aprehensive.

I covered the inlets yesterday, but not completely. I used metal speaker grille. This provides "some" flow. While I was at it, I black powder coated my muffler so it wouldn't look too bad hanging down.

I'm trying to locate a Tuned Pipe & header for a BME 50cc engine. Not much luck yet, but I know they are out there somewhere...

I

[Flatlandman]

Is that on the ground?

[mfuess]

No. It's no strapped to my run-up table.

[CRG]

Is it just me that thinks 50cc in this airplane is kinda nuts? Not that I don't encourage experimentation, but it's only 80" span. Have been flying mine on a Saito 1.80, weight is around 10.75 lbs. and it flies awesome. As fast or faster than the EVO 35 powered version and handles much better.

CG.

[Flatlandman]

I flew my buds with the da50 for every flight its had and it flew great there are no ill effects to flying this with a 50 as far as flight performance is concerned. Plus you can attain a lot more speed out of a 50; thats what I'm going for and i believe that maximizing speed is what Mfuess is going for also.

[mfuess]

	Quote: Originally Posted by Flatlandman
	I flew my buds with the da50 for every flight its had and it flew great there are no ill effects to flying this with a 50 as far as flight performance is concerned. Plus you can attain a lot more speed out of a 50; thats what I'm going for and i believe that maximizing speed is what Mfuess is going for also.

That would be correct Mr. Flatlandman. My BME-50 weighs 2 ounces LESS than an Evolution 35. I can sling a larger prop at a higher RPM. I like Moki engines especially the 2.10, but I also greatly prefer running gas. As far as the air frame goes, it's built to carry a heavy engine, like an Evolution 35. So those bigger displacement engines are right at home in this bird. A DA-50 was my first choice, but I didn't like the stand-off distance for the DA. Then I considered all other 50's as possible alternatives. Remembering how much I liked BME 50's in my other planes, I took a close look at it. It's a perfect match, even the H 9 engine mount works. I have a DA-50 in my RV-4 and it pylons with the best of them and lands like a trainer. So my thinking is, a Sundowner built for speed will do even better than my RV-4.

I like Saito engines very much and they have their place. But glow powered four strokes really take a beating at consistant and continual higher RPM. Plus everyone that owns one, knows they are glow fuel burning hogs. I have no doubt that the Sundowner flies well with a Saito 1.80. I would be surprized if it didn't. But the bushinged rod and bushinged cam will be history before too long at these higher speeds. Not to mention the mess that glow fuel makes.

[rcplane]

Hay CRG
How fast are you going with the Saito and what Nitro % are you using?
There are 6 guys here with 180s in their Sundowners and 2 or 3 are burning 60% Nitro! We clocked one @ 135 (with a Bushnell radar gun) but it wasn't really getting all it had I don't think.
I have to try to keep up with these guys with my Evo 35!
I cant remember where I read it but there is a guy who says he is getting 145mph with a Moki 210?

A DA-50, WOW!

PS; Get your pictures, this is Mike B

[mfuess]

	Quote: Originally Posted by rcplane
	Hay CRG How fast are you going with the Saito and what Nitro % are you using? There are 6 guys here with 180s in their Sundowners and 2 or 3 are burning 60% Nitro! We clocked one @ 135 (with a Bushnell radar gun) but it wasn't really getting all it had I don't think. I have to try to keep up with these guys with my Evo 35! I cant remember where I read it but there is a guy who says he is getting 145mph with a Moki 210? A DA-50, WOW! PS; Get your pictures, this is Mike B

It wouldn't totally surprize me IF the Saito 1.80's did get 135 MPH. However, it's not an every day occurance. In order to attain 135 MPH, a Saito 1.80 would have to turn a 15x13 prop at 11,000 RPM. In order to make this happen, the 1.80 would have to yield 6.257 horsepower. It is possible!

There seems to be an air (drag) barrier for this aircraft right at 135 MPH for most engines. In order to over-come it, you really need a lot of horsepower. A Moki 2.10 can barely pull beyond 135 MPH using a larger diameter and bigger pitch prop.

The only truly accurate way to clock this aircraft is using an on-board GPS. I have an on-board flight recorder and I doubt its data almost as much as I question a ground stationed radar. BUT what the hell, all of this is for fun anyway!

GO get em' SAITO GUYS...

[mfuess]

Just so you guys will understand:
IF you plan on racing your Sundowner, speed alone won't do you any favors. Your aircraft (and you) must be capable of turning a very SHARP left, recovering your top speed in short order, AND keeping a TIGHT line all at the same time... Smaller engines will provide a competitive top speed, but they cannot and will not recover from super high G turns as good as a bigger engine spinning a bigger prop. It's just a fact of life. That's why there are rules regarding engine size for any particular class. With all things being EQUAL, it's completely up to the pilot to fly a good line, and stay ahead of the pack (or catch up).

All the horespower in the world will NOT make up for crappy pylon skills. Don't take my work for it, put up some Pylon Poles and give it a try... you'll quickly see what I'm talking about.