9" prop !! Wow ....

I used to fly the QB10 on a 7" when IC .... and the QB10H I built little while ago used a 7x5 on about 1400kv ... was more than enough ...

I reckon a 9" prop may give you torque problems .... I reckon max you should go is 8" and keep pitch down to ~4.5 to 5

My thoughts anyway ...

Nigel

I agree with Nigel; smaller prop and lower pitch - will make the battery last longer too. Even if you do go bigger, it's a good idea to start smaller and build up after each test flight.

I used to always put the biggest prop I could on my electrics when I first started but after buying a 'Watts Up' meter and doing a few tests I found I was over-propping them needlessly. They all fly just as well with an inch less in diameter and less pitch, plus the aforementioned increase in duration.

If in doubt, buy a few props and experiment, all part of the fun isn't it!

Regards
Harry

Even the 11" prop is not overpropping. In fact it is giving me just about my target power of 150 watts. The 9" props don't get over 100 watts.

Originally Posted by ripplewave

Even the 11" prop is not overpropping. In fact it is giving me just about my target power of 150 watts. The 9" props don't get over 100 watts.

For me - I go for THRUST ... watts are fine IF you are getting pitch speed / thrust as well.

Put a flat plate wood on a motor and have it put out a million watts - you aint going anywhere with it !

Only value I see in figures above is the run-time with the 9" will be better than the 11"...

But on a QB10 - originally designed in LitePly and balsa flew on an IC 10 engine.... that's small and could never swing a 9" prop well and certainly not an 11". Even when I converted my QB10 to a 'ballistic display' machine without wheels, swept back wings and an IC 20 motor - she still ran only a 8x6 .. and then it was very torquey !

A large diameter prop will have a serious flywheel effect and create a torque moment ... My foam QB10H now as i say is on a 7x5 ... and that climbs like a bat outta hell !

Only trying to help ....

Nigel

Alrighty! She is all dressed up and ready for the prom!

AUW is 20.5 oz or 690 grams. She came in under the specified weight range on the plan. The CG is just at the spar.

As far as props go. I am going to build a thrust meter and do some more testing. I do know for certain that it will not fly with a 7" prop or I should say, not fly well.

The motor is as stated in the test results post an 880 KV motor. If the battery is fully charged and for simplicity sake I have 12 V this means without a prop the motor RPM will be 10,560. My TT .10 can do closer to 12,000. One of the advantages of outrunner electric motors is their ability to swing a larger prop because of their torque. I am thinking that I would not go any smaller than a 9" prop. Even with the 9" props, some of them will give me a decent flight time of close to 10 minutes (not full throttle.)

Anyway I will update when I get a chance to further test props and fly her.

Thanks

Joe

Originally Posted by ripplewave

Alrighty! She is all dressed up and ready for the prom!

AUW is 20.5 oz or 690 grams. She came in under the specified weight range on the plan. The CG is just at the spar.

Very nice too !

[As far as props go. I am going to build a thrust meter and do some more testing.

Far more use than watts per lb in my view ... Watts / lb as guideline ... thrust meter for actual. Then Pitch speed from RPM ...

I do know for certain that it will not fly with a 7" prop or I should say, not fly well.

The motor is as stated in the test results post an 880 KV motor. If the battery is fully charged and for simplicity sake I have 12 V this means without a prop the motor RPM will be 10,560.

No wonder you want 9" prop !! 880kv motor ? I'm running an 1800kv ... much more suited to such a model IMHO.

I know I differ from some - but my idea is that low KV motors are more for slow-flyer jobs and not aerobatic / sport machines. With the QB10 series I would consider motors in the 1400kv and up range to keep more in line with original 10 FSR IC specs ...

Nigel

Looks great, like the finish - simple but very attractive.

White planes always seem to look bigger in the air somehow - or at least I think so.

Look forward to the flight report!

Regards
Harry