Need prop advice
 

My brother and I are building some HOB warbirds. We have an ME 109 done with a Cox .051 r/c motor in it. We are going electric with the P-47 and FW 190. The motors we are using are 1811-2900 with 25A esc. Both have wingspans of 36 inches. What props should we use on them? Batteries will be 2 to 4 S Lipos. I think the planes run around 30 ounces or so. Thanks.

well you have the wrong motor unless you put a gear box on it. 2900 KV is just to much. you will need a small prop so you wont burn up the motor and the small prop will not provide enough thrust to take off unless on a smooth paved runway. 30 ounces in that plane also is on the heavy side.to make that plane fly well you will need a motor with a 850-1200 Kv and around 300-500 watts of power. The motor should not weigh more than 4 ounces and you should use anything over a 2200 MaH pack or you will stall it on take off and crash it.

I thought I saw a description of the motor saying it was in the .049 to .09 range. Maybe I misread it. Time will tell. Keep the thoughts coming. Thanks.

I agree. 2900 KV is too much. Anything over 2000KV is usually best with a gearbox.

If you are set on trying anyway use the 2 cell lipo and a small prop like a 6 x 3 or 5 x 3. Be sure to check the draw with a watt meter to be sure you are not going above your max amp load at full power. If you get close to 25 amps before you get to full power try a smaller prop, less pitch or less voltage.

100 watts per pound is usually a good place to start test flying but given that this plane is a bit heavy a little more would be nice, so you will need at least 200 or better yet 250 watts on the watt meter. However, 250 watts at 7.4 volts is 33 amps which is too much for your 25 amp ESC. In fact you won't even get to 200 watts at 25 amps, at best you will probably get 180 watts or so, if you could find the right prop.

Your plane has about 216 square inches of wing area which is 1.5 sq feet. Therefore your wing loading is about 20 oz per square ft which is a bit high, but not unflyable.

Truthfully, I don't think that the combination you have chosen will work very well. Your ESC is undersized and your motor is over KV. If you could lighten the plane a few ounces it might work OK.

With the right amount of power and the right prop it should be fast and sporty. If it's a hand launcher it will likely take a good heave into a stiff wind to get going.

I find it funny how guys ask for a little bit of help and when advice is given dont listen lol. You cant go off what the MFG says its = to. I have experience with those kits and I have experience with electrics also. that motor with your esc maxed out at 35 amps will need a 4.2x4.2 prop to meet that amp draw. a 4" prop isnt going to do well on that overweight high drag plane. I am not trying to be a jerk but trying to help you out. now if you still insist on running that motor put what ever prop you think is best and the battery of your choice and film the first flight for me ok. Even a Eflight park 400 size motor will fly it well on a 9x9 prop and a 3 cell 1800 pack.

I think I will go with your suggestions. Heck, the motors are so cheap I don't want to ground pound it. I have a bunch of ESC's and I am sure one will meet your suggestions. Will the 25A ESC work on that motor? Thanks for the advice. We have ready the HOB ME 109 with a screaming Cox .051 R/C in it and I think it will pull it. We have pulled somewhat bigger aircraft with it so I am not worried. I will let you know what motor we get beforehand.

Airraptor........how does this motor look? What ESC and battery would recommend? http://www.hobbyking.com/hobbyking/s...ner_Motor.html

Yes that one looks much better. the good thing with a lower KV motor is that you can increase the cell count and go to a smaller prop and fly much faster. a small prop can get the plane in the and might be fast but it will not climb well and be a pain to fly. that HK motor is about the power and size of a Eflight Park 450 which is plenty of power. Now if prop clearance is an issue run a 4 cell battery and a 7x7 or 8x7 prop.

I'd be looking to run a 5-5 on two cells for a motor on your KV range. You can always prop up a little if the amp draw is low-going to three cells will likely be too much current.

A Speed 400 is about 2200KV if memory serves, and we ran 4.7-4.7's and 5-5's in pylon on 8.4V.

Dave did you read what type of plane is flying, the weight of it and the speed control he is running??

Yep. Sure did. A 6-6 on 2-3 cells is about right.

Dave he only has a 25 amp speed control. that 5x5 prop on that motor will draw close to 45-50 amps. a 6x6 will put it over 80 amps and the motor will burn up. dave nothing against you but have you ever seen a House of balsa 1/12 warbird?

OP what brand of motor is that that you have. if the 1811 is the size of your motor then way to small for this plane. can you post a picture of that motor? i really want to help you get a good set up.

I tried to find that motor but the one that came up the most is the turnegy one. if so way to small and you would need 4 of them to fly that plane. most of the time the numbers 1811 mean that it is a 18mm in diameter and 11mm motor width. this would put it in the eflight park 250 range.

A-Rap....can you give me the exact Turnigy motor I need? Also the correct ESC size, battery selection and the right prop? We are new to electrics and want the correct stuff. I like the Turnigy stuff because it is economical and has served me good in the past. I appreciate your help and am on a limited budget. Thank you very much.

Steve no worries. I will shoot you an email on here once I do some research to find what I would do if it was mine.
first though how do you plan to fly the plane?
Will you hand launch or take off ground?
do you care if has a larger than scale prop or do you want one close to the 6-8" range?
What kind of charger do you have or at least does it charge LiPo batteries?
and lastly do you want scale performance or are you looking for speed. scale speed would be in the 60-80 MPH average speeed is 80-95 and high speed would be 100-110.

I found two motors in eCalc that are Turnigy 1811-xxxx but not 2900kV. Hoped to pull out some rough numbers (if it helps) but don't have the rest of the specs.

29kv with a 6x6 and a 4s is a great combo....... to pack with you for early season hiking in case you get lost and need to start a fire quickly. Ask me how I know this. :D 30oz on a 36" wing puts that in 09 territory, maybe even a light norvel or fox 15. So you want something in the 10kv range swinging an 8x6 or 9x5 as you will need the thrust at that weight.

I ran a 6x6 prop on a Neu 1514 1.5y motor and pulled 1800 watts on 4s.

HK has the 1811 2900 and it is a tiny motor. Steven I will work on motors this weekend ok.
for all other lookingto help a motor in the 200-300 watt range with a KV of 1200-1800 will be what I will be looking for. also motor weight will be under 80 grams and a 35-40 amp speed control. 1200 KV looking to run a 10x7 prop and the 1800 kv looking to run a 7x6-8x5 prop. props are APC electric.

I will probably hand launch but maybe both ways(rog) Prop doesn't matter. I have the correct lipo charger. Want scale performance.....not too worried about big speed. Thanks my friend.

http://www.hobbyking.com/hobbyking/s...arehouse_.html 200-280 watt motor 17.71 or if wait a few minutes might get an offer for 15.50 dollars

http://www.hobbyking.com/hobbyking/s...dProduct=24527 2.09 dollars required for this motor. not sure why not included. HK...

you can use your 25 amp speed control if you like or get a bigger one. I think a 35 amp one would be best but up to you. they also give some prop and power suggestions. They list 3 and 4 cell set ups. So if you want to run a scale type set up run a 8x5 APC prop on a 4 cell pack of around 1500-1900 Mah. now once you fly it you can play around with props and cell count. if ground clearance permits can go up to a 9x5 on 3 cell and fly really well. now for some speed run a APC 7x6 or 7x7 E prop on 4 cell.

One last thing. if getting started in electrics there is one very important tool to own and that is a power/watt meter.
Now this one is a cheaper one and I dont have any experience with these from HK so I cant give great advice on these. I usually buy name brand on watt meters.

http://www.hobbyking.com/hobbyking/s...arehouse_.html this one is 19 bucks.

these really are a great tool keeps you from burning up a motor or speed control and lets you know if you can run more batteries or more prop.

A-Rap.......I think I will go with your recommendations. I need to check with my brother as to what ESC's we have. If we do not have a 35 A ESC I will buy one. They are all pretty much alike aren't they? Do you have a favorite? Also, with the hidden shaft on that motor, does the accessory pack take care of that? I really do appreciate your help. Keep it coming. I will check on our ESC's. I have a couple of 3S 2200 MaH batteries.....will they work? Thanks.

yes they will work. yes that accessory does fix that and i really like these style of prop adapters. If i was you just order two or three since only two bucks. run a 8x7-8x8 or a 9x5-9x7 on the 3 cell packs. once you get everything installed show some pics so we all can see. thanks

Thanks my friend. I appreciate your help tremendously. I will send pics when they are done. We have never flown any HOB warbirds but I have heard some pretty good reviews of them. Thanks again.

A-Rap.........if I were to pick up a couple of extra batteries what would recommend? I am going to buy a 35A ESC for these planes. Thanks for the advice.

Well i would try a couple of different sizes. this way you can see what fits best for you. a 4 cell 1350 might fit well into the flight performance your looking for. Look at batteries in the 1500-2400 for 3 cell packs and 1350-1800 in the 4 cell range. They are so many directions you can go in. try to shoot for around 200 watts in what ever direction you go.