Thrust Rating & Wing Loading
 

I don't know if this is the right chat room to ask this question. I just finished my first conversion and I want to make sure I have all the bases covered before I try to fly this plane. My plane has a wing loading of 25.2 sq in and the engine comes out with a 15.4 oz thrust at 7000 RPM using an 18x8 prop. Is this a good ratio to have good performance for doing casual flying(take offs, landing, loops & roles)?:eek:

Thanks

RE: Thrust Rating & Wing Loading
 

Go back in and edit your posts so we can help you. I'm sure you mean 15 lbs - 4 oz thrust?

Whats the weight of the plane? I hope it has more wing area than 25.2 square inches? I'm trying to figure what you are meaning here? Is it 25.2 oz/square foot?


Thanks,

Jim

RE: Thrust Rating & Wing Loading
 

Jim

Sorry for the confusion. I hope I am more clear this time around.

I have a wing span of 83" with 1276 sq. in. wing area. The plane weighs 14 lbs total with a Ryobi 31cc. According to ThrustHP I should get 15.4 lbs of thrust using a APC 18x8 prop at 7000 RPM. My wing loading is 25.2 oz per sq ft according to my wing loading Calculator. Do you think with a wing loading of 25.2 oz per sq. ft and a thrust of 15.4 lbs is a good enough to do casual flying?:eek:

Thanks

RE: Thrust Rating & Wing Loading
 

Jim

Yes it is 15lbs - 4 oz of Thrust.

Thanks again

RE: Thrust Rating & Wing Loading
 

Hi,

With those numbers, it should fly quite nicely. Don't worry, just go for it.

However, do not expect the performance that Thrust HP indicates. That is a very optimistic program for determining thrust, and you will not see 15.4 lbs. of thrust. If you are looking for 3D performance, it's just not going to happen with that combo, but it will do normal sport aerobatics just fine.

Hope this helps,
Good luck,
AV8TOR

RE: Thrust Rating & Wing Loading
 

AV8TOR

Thanks for the reply. I fell much better knowing that I can do casual flying with my plane( Touch n Go's, loops, & Rolls):D

Thanks

RE: Thrust Rating & Wing Loading
 

You're welcome! Please let us know how it works out.

Take care,
AV8TOR

RE: Thrust Rating & Wing Loading
 

You should have a nice flying airplane here.
You've built it nice and light for it's size, and that's the main thing. You will probably get about 13 pounds thrust, which sure as heck will fly a 14 pound airplane quite nicely. You'll probably be cruising around at 1/2 throttle most of the time. Your volumetric wing loading is about 12 pounds per cubic foot, which is just fine as well.
As av8tor said, don't expect 3D performance, but every airplane doesn't need to fly straight up!
Have fun!

RE: Thrust Rating & Wing Loading
 

Sortflier

Thanks for the reply. I am going to but an APC 81x8 prop this week and test it on my Ryobi. If hope to be getting 7000 rpm from my engine with that prop. I won't be able to fly this weekend, but I cannot wait until the next Saturday to go out an fly her.:D

Thanks again

RE: Thrust Rating & Wing Loading
 

lol@Jim/ your brain thinks faster than your fingers type. We cant wait till the 2nd weekend in Feb to hear a flight report. Call in sick and fly this weekend!:D Piper

RE: Thrust Rating & Wing Loading
 

Hey Jim! I am flying a Ryan's Rebel with a Ryobi 31 cc on it with an APC 16x8 prop it turns at 8700 rpm (read on a magnum tach) my plane has an 80 inch wing span, an area of 1120 square inches and weights about 12.5 lbs with an approximate wing loading of 25.7 oz/square foot and I am having a ball with it, this is my first conversion project and I like the results, the only mods I made to the Ryobi where enlarging the intake venturi to about 0.4 inch diameter, eliminating the exhaust exit tube and drilling a big hole on the inside plate of the muffler on the exhaust port side and in the bottom of the final exit and widening these holes with a dremmel routing bit, I can do all of the basic manuvers and almost unlimited vertical at slow speed but it will get up there. so I dont see you having any problems with that set up but try to use the smaller (16x8) prop and try to get the most rpm's that you can.

RE: Thrust Rating & Wing Loading
 

AeroNut

Thanks for your reply. I have used ThrustHP to help me determine my bust thrust to weight ratio and using an 18x8 prop seems to come out the best. If the plane flies really well with the 18x8 prop I my us the 16x8 prop to see if I can get anymore speed out of her. I am glad to here from someone who is flying a plane that has about the same wing loading as mine. I know for sure now that I well be able to fly the stingray 120 this weekend and not have ant trouble with her.:D

Thanks

RE: Thrust Rating & Wing Loading
 

Jim I can confirm that for you. I am currently flying a Hangar 9 PT-19 with the Ryobi. Mine is a newer two ring version and it turns a Master Airscrew 18x8 wood prop at 7200 rpm's tached. A buddy of mine has the same plane, same set up. We have expiremented with many props and this seems to be the best. I did not try APC's though as we were looking for a more scale looking prop. Don't be fooled by the high rpm's of the 16" props, they just don't pull. When we had the 16" props on you had to give the plane bursts of almost half throttle to get them up and moving to start taxiing. With the 18x8 you have to set the idle as low as possible just to keep them from rolling. I had no idea there was that much difference in prop performance. From level flight full throttle to a 45 degree climb my plane will climb 400-500 feet before powering out. I fly at 5200' elevation here in Utah as well.The two planes weigh 14 1/2 lbs. with a little over 1000 sq. in. They run beautifully as well and I have had mine up for almost a half hour and still had fuel left when landing. Have fun! I'll never see glow fuel again with this much cheap fun.

Later,

Maximus

RE: Thrust Rating & Wing Loading
 

Maximus

Thanks for the reply. I to have the MAS 18x8 prop that I have put on my Ryobi. I have not yet tached the engine to see what RPM I am getting, but with a MAS 16x8 prop it max's out at 7400. I hope to be around 7000 with the MAS 18x8 prop. I have notice a much larger pull with the 18x8 prop when I tested her. I just cannot wait for this weekend to fly this plane. I first must change my throttle linkage. I did like most other and have set it up the old way with a metal push rod for the throttle. I have read that this is a no no with a gasser. I am going to change the linkage out this week to a nylon push rod.:D

Thanks

RE: Thrust Rating & Wing Loading
 

Also be sure to do a range check of your radio, both with the engine off, then again with the engine running. Don't fly it if you get glitching or a range reduction of 10% or more with the engine running. You need to be sure you have a resistor plug in the engine, a shielded plug wire, radio equipment as far from the engine as possible, separate battery and switch for the engine ignition (if cdi), etc.

Good luck,
AV8TOR

RE: Thrust Rating & Wing Loading
 

Also, the APC props are expensive, but will generally give you considerably more rpm's and thrust for a given size. I had one model gain an honest two lbs. of thrust with nothing more than a change from MA to APC props.

AV8TOR

RE: Thrust Rating & Wing Loading
 

Av8tor1977

I have my receiver all the way on the tail section of the plane and the battery pack is up under the wing. The LHS did not have an APC 18x8 prop and I have one on order with him, but for this weekend I will use the MAS 18x8. I do not have a shielded plug wire, but I do have the resistor spark plug. I have seen others here at RC Universe and you are the first one who has mentioned a shielded plug wire. I am using the magneto that came with my Ryobi and I do not see any way to change it unless I just cut it and splice on another one. Will I be OK for this weekend or do I need th change to a shield plug wire. For my radio I am using an older JR PCM Radio and my LHS told my I should not have ant trouble with that system and my setup.:eek:

Thanks

RE: Thrust Rating & Wing Loading
 

Jim, Dont mess with that wire. Most all of us are using the stock coil too. The most I would do, and Ive never had to do it yet, would be to put foil aroung the plug wire. Some have gotten rid of problems that way but using a resistor plug should be all you need to do. Piper

RE: Thrust Rating & Wing Loading
 

Piper

Thanks for the reply. I'll leave the plug wire alone and see how it works with the setup I have. I have to change my throttle linkage before I fly this weekend. I have it setup the old standard way with a metal push rod and I here that is a no no with a gasser. I am going to get a nylon push rod tomorrow at my LHS and install it before I go flying. What type of linkage are you using on your Ryobi setup?:D

Thanks

RE: Thrust Rating & Wing Loading
 

good call....yep, metal is a big no-no. On my throtle pushrod I use weedeater line. Afterall, converting all these engines from trimmers leaves one with a lot of leftovers and the trimmer line makes great throttle pushrod. You can get the plastic tubing from the LHS thats ment to be used to run the rx antenna wire in it for r/c cars and boats and use it as the outer part of the pushrod and run the trimmer line inside that, use EZ conectors and both ends and, WHA-LA, you got it done for pennies. Piper

RE: Thrust Rating & Wing Loading
 

Piper

Isn't the weedeater line made of metal. My engines where given to me as engines only so I don't have any weekeater line. Can I get this at my local small engine shop?

RE: Thrust Rating & Wing Loading
 

Its the string that goes in the head of the weddie that does the cut'n Jim. Its plastic, buy it at wall mart for 2.00 for a ton of it.

RE: Thrust Rating & Wing Loading
 

Piper

Sorry I must be gotten brain damage! I had my mind thinking so much on the throttle linkage when you said weedeater cable I was thinking of the cable the weedeater was using for the throttle and not the plastic cable it uses to cut the grass. DA! I have this in medium grade strength at home know. I'll look at it when I get home. Thanks again for all of your help.:eek:

RE: Thrust Rating & Wing Loading
 

the size that fits the tube im talking about is .065 trimmer line I think. Anyway its the smallest stuff.

RE: Thrust Rating & Wing Loading
 

Piper

I used the medium trimmer line last night and I had to trim it down a little. I am going to Home Depot today and get the smaller stuff. Have you every had a problem with this breaking after it has been used for awhile?

Thanks