H9's Sundowner

[mfuess]

I have a spinner on my Mejzlik, but not the Biela. I'm having a tough time finding an APC 18x17 prop... Where do I find one?

I did locate Pro Zinger Laminated Props: 18x16, 18x18, and 18x20... I couldn't find where APC even offers 18x17.

[Flatlandman]

I called apc and asked for the props.

[mfuess]

THANKS!

I will give that a shot. I'm not too sure what will be an ideal prop for the BME 50 on a Sundowner. I normally use 22x8 but that's not going to cut it for pylon. These props carry a heafty price tag... so I'm trying to plan this out a bit.

Here is a photo of my SUNDOWNER waiting for the engine to arrive...

[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.