Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

sundowner 50 engines?

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Old 11-08-2008, 09:00 PM
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Default sundowner 50 engines?

Decided to go with the sundowner 50 over the revolver...thinking about dropping a 55AX into it...any thoughts on how she should run with this engine up front?
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Old 11-09-2008, 11:17 AM
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Default RE: sundowner 50 engines?

I have 55AX with Weston Genesis Pusher pipe and APC 10x10 on my SD 50. Following picture is part of first flight logged with EagleTree eLogger... I had wrong setings on my logger so the last peak on speed graph was cut out. Real top speed should be around 200-205KPH thats 124-127MPH
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Old 11-09-2008, 02:59 PM
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Default RE: sundowner 50 engines?

Have you ever tried a 10X9 APC? In the air, you never got over 13K which is about right with that prop and air frame. I have found that engine loves to be about 14K on the ground and 15K in the air with stock, tuned muffler(Jett or Ultra Thrust) or tuned pipe.
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Old 11-09-2008, 03:17 PM
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Default RE: sundowner 50 engines?

I'm going to try first without the airfilter that was on on the first flight with 55AX... I think it is taking some rpm off. If I don't gain enough RPM with the airfilter removed. After that I'll try 10x9 or even 10x8. I also have APC11x12 cut to 9.5x12 and 11x11 cut to 10x11 that I want to try. The weather here hasn't been co-operative with this project... Forecast shows rain for the whole next week...
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Old 11-09-2008, 04:45 PM
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Default RE: sundowner 50 engines?

i think you over proping this engine alot. you need RPM. try a 11x7 i bet you would be suprised by the results.
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Old 11-09-2008, 05:12 PM
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Default RE: sundowner 50 engines?

But then again not! For this kind of airspeed you need allot of pitch on the prop. 55AX is not designed to rev 18k, that 14k-15k is about the max RPM 55AX can take for long term.


btw. I had this engine on a pusher plane before and it had 11x7 APC pusher on it and wasn't nearly as fast as this SD50 with 10x10APC...
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Old 11-09-2008, 05:28 PM
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Default RE: sundowner 50 engines?


ORIGINAL: Timbba

btw. I had this engine on a pusher plane before and it had 11x7 APC pusher on it and wasn't nearly as fast as this SD50 with 10x10APC...
Tractor and pushers are apples and oranges, you can’t compare planes and props.


Yes the engine will turn those props, but it will be well off its peak power. The 10X10 prop on a 55 has had some success with somewhat clean planes like quickie 500 pylons and such. A 10X8 will get you to the golden 14k static if your muffler is less than optimum (Pitts) but its too little for anything else(except break-in). On the Sundowner you are on the low end of disk area already with a 10" diameter prop. I'd start thinking more thrust. 10-1/2X8 (cut down), 11X7 Master Airscrew (S2!), 11X6 APC. The 11X7APC is a bit too much load for your plane.

If this engine is turning about 15K in the air, you are getting the most out of it. It flat out falls on its face not much over this point, pipe or no pipe.

The large prop recommendations in the manual sure have caused some confusion and disappointment in some cases. Perhaps they are in regards to prop noise.

I my opinion, upon receiving a OS 55AX the very first thing one should do is throw the manual away and don't dare look at the information, especially prop suggestions and brake-in.

This is a great engine if its run in its power band.
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Old 11-09-2008, 05:46 PM
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Default RE: sundowner 50 engines?

I bet you are seeing about 14K on the ground with the 10X10. The problem is the prop is stalled or slipping and when the plane is in flight the prop un-stalls/hooks up and the engine actually loads down. This is a common thing seen with square or over square props. The 10X9 may be the same rpm on the ground as the 10X10 but it may unload a tad in the air.
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Old 11-09-2008, 05:55 PM
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Default RE: sundowner 50 engines?

I just checked, I ran an 11X6 APC pusher with a 55AX on a bobcat clone and it was the best prop for it. The 11X7 was too much, stock or Jett muffler.
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Old 11-09-2008, 07:14 PM
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Default RE: sundowner 50 engines?

I'll try the APC 10x9 next when the weather permits. I don't have 11inch props other than 11x9 APC and [link=http://shop.lindinger.at/product_info.php?cPath=1130_1158&products_id=34317]Graupner CAM Speed 11x8[/link] and [link=http://shop.lindinger.at/product_info.php?cPath=1130_1158&products_id=49133]Maro 11x8 wood[/link]

I removed the airfilter so I think I get some RPM from there also.
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Old 11-09-2008, 07:27 PM
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Default RE: sundowner 50 engines?

freak is correct just like i was saying. you need lots of thrust on these "slow" planes to pull them thru the air. i believe that anything under 140 needs 7" or less pitch for 40-90 size planes. i have run 190 on a 7" pitch in a clean plane.
another example look at the 60 size GP toni. we have one with a gms 120 thats been juiced up some. we tried many props15x7, 15x8,15x9 15x10, 14x10, 13x12 16x8 and maybe a few others. can you guess which one was the fastest?....... the 15x7 this plane is in the 120-130 range no dive. when we put the 14x10 on we thought this thing was going to haul azz. well it just fell on its face. it was about 15 mph slower. i say most arf sport planes should perform best with 5,6,7" pitch props. just try to get the largest dia. you can to get the most thrust.
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Old 11-10-2008, 10:09 AM
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Default RE: sundowner 50 engines?

I put the 10x9 APC on and got same ground pitch speed as with 10x10 but on higher RPM... Now the RPM was 13992 on the ground. Now waiting for weather to change, today it was raining and 27MPH wind.
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Old 11-11-2008, 09:18 AM
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Default RE: sundowner 50 engines?

I got two flights on SD today. First with APC10x9, top speed 233KPH(144.8MPH) @ 14851RPM and second with APC11x7, flight top speed 228KPH(141,7MPH) @ 15690RPM. The 11x7 was more fun to fly with because of better climb rate and faster cornering, but the 10x9 was a little bit faster... I have to get some other make 11x7s to try, the engine sounded like APC11x7 was a little bit too much for it, but I don't want to go under 7 inch pitch.


oh and both top speeds were on bottom of a 45degree dive. I didn't dare to fly straight vertical dive because the plane sounded scry even on 45degree dive [&:]


here are partial graphs of those flights. The engine went lean with 11x7 on a dive, it was just before landing and I ran out of fuel while taxiing back to pits... Never happened before [:-]
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Old 11-11-2008, 09:20 AM
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Default RE: sundowner 50 engines?

geee... forgot to add the pictures...


First 10x9 second 11x7
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Old 11-11-2008, 09:28 AM
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Default RE: sundowner 50 engines?

BTW. I threw the Perry pump out of the plane and engine temperatures are now 40C lower than before...
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Old 11-11-2008, 09:58 PM
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Default RE: sundowner 50 engines?

I don't know if you have them there, try a Master Airscrew 11X7 but is must be the S-2 type (formally called Scimitar), this prop fits right between a 11X6 and 11X7 APC. It seems like it has greater thrust and speed in the lower 13-16k range (in flight) than the APC but the MA seems to be less efficient and noisier at higher tip speeds than the APC.

In both charts, it looked like the average RPM was 14k (not diving or turning). Im betting that 15k in the air would be the sweet spot, your real close to the optimum now with those last two props you tried.
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Old 11-11-2008, 10:14 PM
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Default RE: sundowner 50 engines?

I ordered today MA 11x7 S2 and MA 11x8 S2 and Graupner G-Sonic 11x7 and 11x8 to try with. I have to findout what caused that lean spike on the curve with I flew 11x7 with...

Those Graupner G-sonics are also lighter load and faster than APCs. Never tried these smaller ones though..
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Old 11-11-2008, 11:59 PM
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Default RE: sundowner 50 engines?

When your fuel is getting low and you are in a long dive, is the clunk still coverd? Hummm.
You may have had a bit of foaming. Higher rpms may have made the problem more pronounced as you hit the right note in harmonics.
Try to isolate the fuel tank or at least have REAL foam rubber in contact with the bottom of the tank. I now use the OS bubble-less clunks as standard equipment too.
Check the MAs for balance, most made latetly have been good.
Oh, and more power eats more fuel
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Old 11-12-2008, 06:27 AM
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Default RE: sundowner 50 engines?

Throw a Jett bladder type tank in it. Little more work to service it, but the engine will settle down a bunch.

Just got my Jett 60 last night. Today starts my little SD build. WOO HOO
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Old 11-12-2008, 06:53 AM
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Default RE: sundowner 50 engines?


ORIGINAL: freakingfast

When your fuel is getting low and you are in a long dive, is the clunk still coverd? Hummm.
If there was enough fuel to reach the hole on clunk, then yes... On my tank assembly the clunk goes freely to every single corner of the tank without kinking the clunk line... And the clunk cannot get stuck anywhere... And the tank has half incc thick foamrubber under it and tank is secured with velcrostraps instead of those zipties that came with the plane...

I just went through the whole EagleTree flight data, that lean spike was about in the middle of the flight... I may have tuned it couple of clicks too lean though...
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Old 11-12-2008, 08:21 AM
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Default RE: sundowner 50 engines?

Some of those real limp fuel lines that let the clunk go everywhere have a small inside diameter and may not let enough fuel though for a thirsty engine. The limp lines have been more prone to dissolving, pin holes, tears and eventually kinking so keep an eye out for that. All of my tanks are set up so the clunk gets to the four corners only at the rear of the tank, unless the plane stops suddenly
It's only when the fuel is REAL low on a long dive I may hear it want to shut down. I’ve not YET had the need to go to a bladder tank even with my 26k df engines.
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Old 11-12-2008, 11:21 AM
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Default RE: sundowner 50 engines?

I checked all fuel lines, filter, T-fittings and found the possible reason for that lean spike. I have smoke system onboard and the smoke oil injector was loose causing exhaust pressure to drop...
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Old 11-12-2008, 12:58 PM
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Default RE: sundowner 50 engines?

A guy at our field has a OS Hyper .50 Heli motor on one and it is screaming fast little snot!
A little higher priced but man tha little plane flys fast and straight too. I think he is running a 10X10 APC prop on it.

http://www3.towerhobbies.com/cgi-bin...&I=LXHGN9&P=SM





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Old 11-14-2008, 09:24 AM
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Default RE: sundowner 50 engines?

ORIGINAL: newflyer

A guy at our field has a OS Hyper .50 Heli motor on one and it is screaming fast little snot!
A little higher priced but man tha little plane flys fast and straight too. I think he is running a 10X10 APC prop on it.


Newflyer
Most likely he was running a 10X6 or 9X10 APC that's what works out on paper with that engine's power rating. A 55AX may actually out run it with a 10X9 APC or 11X7 MA S-2 because of the larger disk area, pitch combination and RPM that the 55AX can do. No doubt the .50 heli motor would be quicker on a cleaner plane.

The first size heli engine that would show worthwhile improvement on a SD 50 is the OS 70.
A 90 OS, YS or Webra heli engine would abso-freaking-lutely kick @$$!
But put a twice the stock size fuel tank in it for it will suck down a gallon of 30% on a nice day. The OS 70 on 30% will empty a 16oz tank at wide open in about 7 minutes, keep in mind when the engine is used in a heli it's not ran at full power all the time.

Kinda makes the 55AX+tuned muffler/header look pretty economical and reasonably quick huh?
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Old 11-14-2008, 12:44 PM
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Default RE: sundowner 50 engines?

picked up a sundowner kit yesterday at my local hobbytown....paid 179 for it...still looking at different engine options
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