• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Bushwacker Flight time length census?

Headbang

Master member
#21
For 3d you want a larger diameter, smaller pitch prop. 3d is all about static thrust. A fast plane is all about pitch speed.
For the same motor with different windings allowing for different kv. A higher kv works with less cells on the battery to make the same rpm. Sort of like high gear. Lower kv would mean more torque, allowing for a larger prop at the same amp draw.
Larger props cause more airflow at slow speeds over the control surfaces, this is what you want for 3d.
For 3d I measure to figure out the largest prop I can get on it and still have landing clearance. I take my all up flying wieght in lb and multiply that by 300 to get my target watts. Then I pick a motor with that wattage and a kv that allows the prop I want. That is over simplfling it, but gives a good base line. For a good example of charts look at subsonicplanes.com and the motrofly motors. Same motors with different kv and wattage and recommended cells, might help put it into perspective. Or I just confused it all to heck lol
 
#22
Or I just confused it all to heck lol
No xD I get it thank you so much.
While the larger prop is good for increasing airflow over the control surfaces, are there any reasons why I might not want use a larger/smaller pitch prop for non-3D planes?

Also correct me if I'm wrong: for 3D, a lower kv motor is better because it can allow us to use a larger prop and not draw too much current. But if I use a lower kv motor then I should probably move to a 4s to reach the same rpms.
 

Headbang

Master member
#23
No xD I get it thank you so much.
While the larger prop is good for increasing airflow over the control surfaces, are there any reasons why I might not want use a larger/smaller pitch prop for non-3D planes?

Also correct me if I'm wrong: for 3D, a lower kv motor is better because it can allow us to use a larger prop and not draw too much current. But if I use a lower kv motor then I should probably move to a 4s to reach the same rpms.
So here is the issue. I lot comes down to style of flight. Low and Slow would be lower kv, larger prop, same amps. If you up the cell count you have to lower the prop size to draw less amps to remain at the motors rated wattage. At some point it all comes down to math and testing.
For example. I have an E-Flite Beast 60e Pitts Model 12 biplane 3200W 425kv motor 9lb flying weight. It does amazing low and slow with a 18x8 prop, but my prop clearance was too tight for rough fields. So I put on a 16x12. Top speed went up, low and slow became less stable. I changed my flying style to suit and started doing all high energy 3D. With the speed up I got in the habit of a fast rolling full throttle dive, pulling up at the last second dragging my tail on the ground. The gasps from the crowd are as good as crack for me! The 16x12 makes for amazing blenders as well!
My Pilot Edge 67" 2700W 400kv motor 8lb flying weight. I fly low and slow, doing all sorts of seemingly impossible things. It does much better with a 19x7 prop then it does with a 18x8. The control while being in high alpha is night and day between the props. But the 19x7 does torque roll more.
Both are on 6S 60C batteries.
The edge would be even better with a 2700W 370KV motor on a 19x8 prop. Or a 20x7 if it had the clearance.
My latest pitts model 12 I am building is a 50cc sized plane. XPWR 60 motor 6000W 190kv 24x10 prop on 12S. In this case I am doubling the cell count to get the rpm I need, and proping up to get a peak of 120amp draw (120amps x 50.4V = 6048W). For low and slow I would go to a 25x8 if I had the clearance. For high energy I might push it a bit with a 24x12. Using a 160amp esc.
Once again, hope I am not confusing the issue. So much of it comes down to math and feel.
 
#24
So here is the issue. I lot comes down to style of flight. Low and Slow would be lower kv, larger prop, same amps. If you up the cell count you have to lower the prop size to draw less amps to remain at the motors rated wattage. At some point it all comes down to math and testing.
For example. I have an E-Flite Beast 60e Pitts Model 12 biplane 3200W 425kv motor 9lb flying weight. It does amazing low and slow with a 18x8 prop, but my prop clearance was too tight for rough fields. So I put on a 16x12. Top speed went up, low and slow became less stable. I changed my flying style to suit and started doing all high energy 3D. With the speed up I got in the habit of a fast rolling full throttle dive, pulling up at the last second dragging my tail on the ground. The gasps from the crowd are as good as crack for me! The 16x12 makes for amazing blenders as well!
My Pilot Edge 67" 2700W 400kv motor 8lb flying weight. I fly low and slow, doing all sorts of seemingly impossible things. It does much better with a 19x7 prop then it does with a 18x8. The control while being in high alpha is night and day between the props. But the 19x7 does torque roll more.
Both are on 6S 60C batteries.
The edge would be even better with a 2700W 370KV motor on a 19x8 prop. Or a 20x7 if it had the clearance.
My latest pitts model 12 I am building is a 50cc sized plane. XPWR 60 motor 6000W 190kv 24x10 prop on 12S. In this case I am doubling the cell count to get the rpm I need, and proping up to get a peak of 120amp draw (120amps x 50.4V = 6048W). For low and slow I would go to a 25x8 if I had the clearance. For high energy I might push it a bit with a 24x12. Using a 160amp esc.
Once again, hope I am not confusing the issue. So much of it comes down to math and feel.
Wow seems like you're very experienced, thanks for your response. It makes a lot of sense now.
I just have another question; How does the pitch of the prop play into all of this in terms of flying style and amp draw?
 

Headbang

Master member
#25
Wow seems like you're very experienced, thanks for your response. It makes a lot of sense now.
I just have another question; How does the pitch of the prop play into all of this in terms of flying style and amp draw?
Not sure how experienced I am, but I do hang out with a lot of very experienced people and it rubs off here and there 🙂
More pitch on the same size prop increases amp draw and and speed to the plane. So for fast high energy you want more pitch but have to reduce diameter to compensate for amp draw. Real tough rule is up one on pitch, down one on diameter.
 
#26
So I've finished the Build with the Bushwacker. It's has gone together really nice. My only concern was even after knowing that the plane has a difficult CG to correctly obtain and taking caution in gluing the back half of the plane together as carefully as can be in order NOT to add weight with excess glue, it still is tail heavy based on the 1.75 or 44mm recommended CG measurement. I placed an 1800mAh battery as far forward in the nose as possible making it a huge pain to remove because it's buried up there so far that I can hardly get my fingers in to remove it. basically have to remove the pod to get it out or use a popcicle stick and slide it inbetween the two velcro halves. I also dded a nose spinner to add weight to the front and I still had to add 1-ounce of weight to finally get it level. I used a CG balance machine to be more precise rather than fingers. Why is the CG so far off on this plane?... I feel like the nose should have been longer for it to be a better plane... I have not flown it yet so hopefully after a test flight maybe the CG recommendation of 1.75 is off and I can remove the weight... Guess I'll find out this weekend if the CG really is 1.75 or not.
 

Attachments

#27
So I've finished the Build with the Bushwacker. It's has gone together really nice. My only concern was even after knowing that the plane has a difficult CG to correctly obtain and taking caution in gluing the back half of the plane together as carefully as can be in order NOT to add weight with excess glue, it still is tail heavy based on the 1.75 or 44mm recommended CG measurement. I placed an 1800mAh battery as far forward in the nose as possible making it a huge pain to remove because it's buried up there so far that I can hardly get my fingers in to remove it. basically have to remove the pod to get it out or use a popcicle stick and slide it inbetween the two velcro halves. I also dded a nose spinner to add weight to the front and I still had to add 1-ounce of weight to finally get it level. I used a CG balance machine to be more precise rather than fingers. Why is the CG so far off on this plane?... I feel like the nose should have been longer for it to be a better plane... I have not flown it yet so hopefully after a test flight maybe the CG recommendation of 1.75 is off and I can remove the weight... Guess I'll find out this weekend if the CG really is 1.75 or not.

Wish I could speak experience for this model, but mine is still in shrinkwrap ready to be put together. First thing I would do, is up your battery to a 2200Mah. It's a common FT battery size, will give you more weight to help with balancing, a little more flight time (as long as you throttle manage well), with the same power. That looks like a plastic spinner...wonder if you could find a different material spinner that is heavier...I dunno, just another thought.
 

buzzbomb

I know nothing!
#28
That is one darn good looking build! But really? You couldn't find bigger wheels? :)

With my TT I had to push the battery completely behind the PowerPod to get it to balance. I used a skewer to hold it there. My TT is now done (more on that, elsewhere) but I never did figure out why that batt had to be so far back to balance.

But, balance she did! And she flew absolutely beautifully once the balance was achieved. A major pain in the backside to change batteries, but I'd say it's a big 'Ol "Whatever." So long as it balances, go fly it!
 
#29
Thanks for the complement Buzzbomb. ha, no I couldn't find bigger wheels... I love the oversized wheels for Bush planes. I found these wheels and had to have them.. they are a tad bigger than I wanted but they are made of extremely light foam, lighter than any of the Dubro wheels you could find. They are the E-Flight Timber wheels and would recommend them to anyone who wanted larger wheels with out added weight.
I fly in grassy areas in a park basin so it's nice to just be able to taxi out to take off or land and taxi back and not get stuck or do the nose tip from long grass after landing... I could land this ANYWHERE with those wheels and plane STOL attributes.

The Maiden flight went really well.. The plane has a ton of thrust and endless vertical. It's very sensitive with the full length ailerons so tone down the rates and up'd expo just a tad on that.. The plane flew level right off the bat, no trim needed in any direction. crazy.. the only problem I had which was totally my fault in overlooking was I didn't center my left aileron servo and when I set the radio I just subtrimmed it into position. Doing that wouldn't allow the flaperons to work correctly as it over rotated in the down position and would not stay even with right aileron.. Always do your flight checks before taking your plane up.. Duh...
Anyhow, I didn't realize this until I was up in the air and coming in for landing and put my flaps down and the plane would rotate while I was fighting to keep it level.. quickly just turned flaps off and landed with out them at speed... landed just fine that way too. just took up more space to do so.

My over all feeling of the plane is that it is just awesome. It has great authority in the air but flies subtle if you tone it down. I would recommend going with the bigger motor as I did as it provides a much larger flying envelope. I flew mostly at half throttle and easily accommodated my 10 minutes of flight. I decided not to use all the battery on my first couple flights as I wanted to end on a good flight and make my aileron adjustments at home and replace the tail wheel. The only other thing I would recommend is you will notice that the Rudder control wire is just long enough that if you fly it aggressively you could get blow-back, so I added a small dubro wire guide to the middle area of the wire to keep it steady in such flying.
I had to remove the "stick" tail skid as it was pretty awful to have... Unless you go full throttle to immediatly to get up in the air fast you have to endure the tail bouncing all over the plane while trying to take off or taxi around.. I replaced that with the smallest/lightest wheel I could put on there and still have it work.
It's ready for it's next flight this weekend.
 
#31
I really like the neon green color looks great.
Thanks! I was going for what I would be able to see in the sky best. The under site actually has the 3D checker board so I don't mix up top from bottom.. ha
The computer monitor makes it look brighter than real life... it's a bit of a Chartreuse color. it's sprayed lightly over metallic a base white and that just makes it pop. I stole the color scheme from a full scale plane manufacturer "just aircraft" that I saw online. looked doable... painting foam board has got to be one of the most difficult things ever... if you use traditional foam board.. .it warps.. use flite test and NOTHING sticks to it...not well anyway... just a big pain...I've done all the scuffing, priming, etc.. it just doesn't take well to that waxy stuff..
 
Last edited:
#32
Second flight went even better.. tail wheel is the way to go. I flied more aggressively this past weekend with the plane, pulling many verticals. Battery time was still pretty decent. may have been slightly less than 10 minutes but with how hard I made the motor work I'm okay with that. The STOL part was okay but with the flaperons it doesn't slow (float) as well as I think it would if I had gone with basic split flaps full down. Flaperons down too far of course just makes it stall out and want to drop a wing tip. I've toy'd around with the idea of adding SLATS to the leading edge but I don't want to use foam board. It's too bulky. I'm thinking maybe thin balsa shaped it to match up to the best angle and attached to front with skewers directly through leading edge. Maybe this will give me the effect I'm looking for.
Reason I haven't done the split flaps is I like having the more aggressive full ailerons for aerobatics and also less weight on the wing. Adding two more servos, wires, glue, control horns, and wire.. probable would add another 26 grams.... I'm already heaving than what I originally wanted just from trying to balance the CG out. Who knows, maybe I'll change my mind in future.
 
Last edited:

Bricks

Master member
#33
Depending on plane if I do split flaps I use 2 servos in each wing that way I set up a mix to a 3 way switch I can do full ailerons, flaps and ailerons, or crow.
 
#34
So I've finished the Build with the Bushwacker. It's has gone together really nice. My only concern was even after knowing that the plane has a difficult CG to correctly obtain and taking caution in gluing the back half of the plane together as carefully as can be in order NOT to add weight with excess glue, it still is tail heavy based on the 1.75 or 44mm recommended CG measurement. I placed an 1800mAh battery as far forward in the nose as possible making it a huge pain to remove because it's buried up there so far that I can hardly get my fingers in to remove it. basically have to remove the pod to get it out or use a popcicle stick and slide it inbetween the two velcro halves. I also dded a nose spinner to add weight to the front and I still had to add 1-ounce of weight to finally get it level. I used a CG balance machine to be more precise rather than fingers. Why is the CG so far off on this plane?... I feel like the nose should have been longer for it to be a better plane... I have not flown it yet so hopefully after a test flight maybe the CG recommendation of 1.75 is off and I can remove the weight... Guess I'll find out this weekend if the CG really is 1.75 or not.
Awesome build, love the color scheme! I wanted to ask what is the purpose of the tail fins? Are they merely cosmetic?
 
#35
Awesome build, love the color scheme! I wanted to ask what is the purpose of the tail fins? Are they merely cosmetic?
They are simply cosmetic I think. It's part of the build kit so I added them. I would imagine they offer to some degree stabilization in flight, but unfortunately also weight on the tail end of the plane. I like the way they look so decided to keep them.
 
#36
Depending on plane if I do split flaps I use 2 servos in each wing that way I set up a mix to a 3 way switch I can do full ailerons, flaps and ailerons, or crow.
I don't think my radio will do that... I was familiar with that method but it's not an option for me.
 
#40
Yes the DEVO 7 is a great radio, but it's interface is not easy by any means.... I've visited the Deviation website many times but it's not a site that supports the 7 model, only pretty much ALL the other models: Devo 6/8/9 and 7E/10 and 12E

There may be a way to make it work, but with reading the manual ENDLESSLY Iv'e not found a way to make it work.
thanks for the ideas and support though. I've not totally given up, just need to keep playing with radio until I've exhausted all avenues. The little V-Tail mixer device may be my solution though. at $3 it seems like it would be a cheap easy method to have best of all worlds.