Official Skynetic Bison XT STOL Discussion Thread

[Starck Mad]

Well my friend all I can do is throw a little logic your way. I read what you are writing, but I can't inspect your plane and look at your set up. All I can do is judge the one thing I can see...in your video you are not using rudder properly. There has to be something in your set up, your gear alignment (maybe something is bent?? Too much toe in or out), or your ground handling technique.

If it was the plane I couldn't do it, much less repeat it over and over again with no ground loops. We are doing a third video on the Bison next Monday where we fly it without slats to do a comparison. Another video with no ground loops and lots of take offs and landings. I get you let other people try...they may not be any better with rudder than you are. My plane doesn't have anything special that yours doesn't...stock rudder, tail wheel, main gear and even the stock tires...which are sometimes not equal in pressure. Still it will take off and land without a ground loop if I do my part. If I do my part. So many RC pilots get behind a taildragger and don't know it. It takes a lot of practice to get ahead of them...to anticipate a tendency. The Bison is demanding in this regard, and you won't get there (learn these techniques well) in one additional trip to the field. In your video...you are way behind it. By the way...the pavement isn't helping you. It is much harder to handle a taildragger on pavement than grass...even rough grass.

The saving grace...these skills can be learned and then repeated consistently.

[mea culpa]

I'll also mention I didn't check the installed tail linkages. The elevator was loose and sliding a good 1/8 inch on the servo causing that porpoise landing. This was a very short maiden.
Been out one more time with it since this post. I've been to an asphalt runway with no bumps trying to get past this. Full rudder on takeoff ends up with a left ground loop. Had two guys at the field say give it right rudder. I let them try. Ground loop. Let them land. Ground loop. The plane is a treat in the sky. 25° to 30° bank, rudder, and you get a nice scale turn. But the landings just ruins it. This time of year our weather sucks. When my schedule and weather let me go to the field I don't want to waste time with this. When nicer weather comes and more people are flying I may put it up as best offer.

[Starck Mad]

Help. Finally got a break in the northwest weather and managed to get a few flights in. Pulls real hard to the left on takeoff and landing. Landing always rolls over and scrapes the wing tip. I have to punch it and take off quick or it'll run off the runway. Both main wheels free spin - no binding. I used Dave Brown 6" foam tires so it isn't a low tire issue. The tail wheel was given lots of oil. I put zip ties in the springs so they can't stretch. Dead stick landings are the same so not P factor, torque, etc. This thing is great to fly - only a few clicks of right rudder trim and aileron. But landings are destroying the wingtips so until I have other things to try to fix it, it's grounded.

video below

Hey bud...watched your video several times. You need a lot of rudder throw and you need to use the rudder. You can't be shy with it...it takes a lot of rudder to counter P factor on takeoff (and your issue on takeoff is absolutely P factor...they all go left) and I'm not seeing you use any really. If it wants to turn left on landing then you now can anticipate that...that is what your plane does, and a lot of planes have a tendency to go one way or the other on roll out. My Corsair for instance goes the same way your Bison does...I know this so I start feeding in right rudder just as I touch down as the plane begins to roll out to correct it. I'm ahead of the tendency...not waiting until I see it go left...at that point I'm already behind it. It may take full deflection...that is fine, and normal in this case...you are slow so the rudder is less effective...so it takes all of it. Set up lots of throw...and use as much as it takes. Dial in as much expo as it takes not to be so sensitive around center stick so you can fly smooth, but remember you may have to move the gimbal a lot to get the deflection you need to correct on landing. As your plane begins to go left...I'm not seeing any rudder input on your video. Not trying to be critical or mean so please don't take this in a bad way, but I can't help you by BSing you. What I'm doing isn't magic in my videos...I just use a lot of rudder and you are not. Hope this helps you my friend.

Edit: A little more info...Some planes need more rudder than others. Some may seem almost automatic, some not that way at all. With models...depending on the design - the power, the amount of right thrust it has, the size of the rudder and throw, how long the tail moment is, what the angle of attack at rest is, how tall the gear is, how narrow the stance is, how high the center of mass is relative to the wheels, and where the main gear is relative to the center of gravity on a tail dragger can affect how easy/hard the ground handling will be. I have said before about the Bison...it is a rudder plane. It is relatively short coupled, has tall main gear, sits at a high angle of attack at rest, has a lot of power, and a high center of mass. It has enough rudder and throw if set up right...but you need all of it at times. There is nothing automatic with this plane...has to be flown all the time...including on the ground.

[mea culpa]

[mea culpa]

Help. Finally got a break in the northwest weather and managed to get a few flights in. Pulls real hard to the left on takeoff and landing. Landing always rolls over and scrapes the wing tip. I have to punch it and take off quick or it'll run off the runway. Both main wheels free spin - no binding. I used Dave Brown 6" foam tires so it isn't a low tire issue. The tail wheel was given lots of oil. I put zip ties in the springs so they can't stretch. Dead stick landings are the same so not P factor, torque, etc. This thing is great to fly - only a few clicks of right rudder trim and aileron. But landings are destroying the wingtips so until I have other things to try to fix it, it's grounded.

video below

[gerbilstrom]

Prop reamer…

https://www.amazon.com/Great-Planes-.../dp/B001KNGAXW

Thanks I bought one rite away, got it a few days ago and refitted that APC 15x6 for the Bison. Perfectly balanced, smooth and a lot more power ! Awesome!!

[Capt G]

How did you get the APC 15x8 to fit the 8mm motor shaft? I ordered one direct from APC but the inside hole diameter won't fit its too small...it comes with the adapter rings, but I'd have to drill it out for it to fit.. they all have 1/4 size hole and nothing I found any bigger or what am I missing here?

just drill it out

[Evan D]

Prop reamer…

https://www.amazon.com/Great-Planes-Precision-Metric-Propeller/dp/B001KNGAXW

[gerbilstrom]

Well today was beautiful and just the opportunity to try out my props and get some real numbers. ESC was recalibrated .All three flights were 8 mins and the results were:
1. 15x8 APC prop on 6s x 5000 measured 42 A and landed with 33%. Performance was good.
2. 16x10 APC prop on 4s x 5000 measured 32 A and landed with 50%. Performance was subdued but good for pattern work and touch and goes.
3. 16x10 APC prop on 6s x 5000 measured 62 A and landed with 35%. Performance was very lively.

My preference is the 16x10 on 6s for spirited performance . If you only have 4s that's fine as the plane will still fly ok.
(checked the motor after landing and was barely warm)

PS - the spinner would not fit with the 17x10 APC so i did not use that prop

How did you get the APC 15x8 to fit the 8mm motor shaft? I ordered one direct from APC but the inside hole diameter won't fit its too small...it comes with the adapter rings, but I'd have to drill it out for it to fit.. they all have 1/4 size hole and nothing I found any bigger or what am I missing here?

[Starck Mad]

After watching many, and especially AV8R's videos, I want to go 4s and fly scale. Even at 4s, on the bench, the light controller is too hot to touch. I put in a BEC and things are much cooler. This is something they really need to address.

I'll put the slats/spoilers fixed in the retracted position.

Other than these issues if it flies as well as it does in Adam's videos I'll be happy.

Thanks for watching my friend. Just remember...it takes power to get the nose up and ride the slats so to speak...and use the rudder. Use the rudder a lot. I hope you find yours as much fun as I do mine. It is challenging to fly really slow, but very gratifying when you get it right. You can also choose to use power to land it normally...you'll flare using both elevator and power. You don't have to get the nose at as high of an angle of attack as I do unless you want to. Happy flying!

[mea culpa]

After watching many, and especially AV8R's videos, I want to go 4s and fly scale. Even at 4s, on the bench, the light controller is too hot to touch. I put in a BEC and things are much cooler. This is something they really need to address.

I'll put the slats/spoilers fixed in the retracted position.

Other than these issues if it flies as well as it does in Adam's videos I'll be happy.

[Nutz4flying]

Landing Gear Bracket Replacement

One of the features of the Skynetic Bison XT model is the unique metal articulating undercarriage. This design features breakaway parts that can be repaired or replaced while limiting risk of damage to internal parts of the model. Two of the breakaway parts are the brackets which attach the undercarriage to the bottom of the fuselage. The brackets that are supplied with the mLodel kit are made of molded metal, which when put under stress, will break at the attachment point to the bracket base or elsewhere. A replacement bracket from the model manufacturer is not available, except as one of the parts included in the undercarriage replacement package.


Big A Tools, an Ohio-based small business, has designed a replacement bracket specifically to fit the Bison XT. The replacement bracket will fit the fuselage’s recesses and the screw holes align with the fuselage attachment points as well as the undercarriage attachment points.


There is a quantity of 4 brackets shipped with each order. Keep two brackets in your field box for an on the spot repair if needed after your next hard landing. Use the original screws included with the kit.


Order the brackets directly from Big A Tools. https://www.etsy.com/listing/1110617...r-brackets-for

[Narly]

@ebrahimijohn:

The 6 mo. old Cavalier KCS that I was doggie sitting f/ 3 days ate it, along w/ 1 hearing aid & the ear & nose pieces off my glasses ....... while I was concentrating on Bison mod 🙄
Xpensive lesson learned ..... 'bout 2 Bison's worth ......

[ebrahimijohn]

Can you post a picture without your slats?

[ebrahimijohn]

Have noticed in many of the posted videos lots of wing tip strikes in less than perfect landings; and since I do lotta that I came up with this mod:

Thought the exposed wing tips could be improved with drop tip "winglits" to protect the exposed wing tips and ailerons. Found carbon fiber sheet/plate 2mmx200x300 on ebay; made a template 1/2" larger than the airfoil top and bottom. Counter sink 6-32 blind nuts and epoxy into wing tips; but the trick is getting that done with no epoxy in the threads! Could also use screw in threaded inserts in 6-32 or small M sizes. Next I foam tacked on the stock black winglets in the recess. I cut the carbon fiber with a Jig saw with fine tooth metal cutting blade just outside the line and final sanded to shape with just sand paper on a block. Do use a good respirator since you don't want to breathe the fine carbon fiber dust. The cut out for the wing tip lights was with me old Dremel jigsaw with fine thread blade and a hand jigsaw. And the finished look:

Looks great and might even help knife edge flight (like I can even do dat). I haven't flown it yet 'cause it's 34* F outside and I don't have a suitable 6S batr'y because I spent all this months
budgit on a 48v. 17.5Ah Li-ion batr'y that is attached to a new e-bike !! 😎

This is a great mod, but I have a question regarding the pictures you uploaded. What happened to your other Crock?

[ebrahimijohn]

I will take a better pic and upload to the forum.

[SEWERFLY]

I have put a dozen flights since removing the slats and this is what I have observed. #1. Lower speed take off and landings with dramatically improved handling. #2. No more left pitch at low speed. The amount of throttle needed to maintain flight at low speed is reduced therefore the torque of the motor no longer affects low speed flight. #3. Increased laminar flow reduces need for increased throttle in turns and at low speed flight which extends battery life giving me more flight time on same battery. One of the deciding factors for purchasing this plane was the slats, I had never had an RC with them and I thought they looked pretty bad ass on this plane. I could get the plane to fly decent with lots of rudder input and using the ailerons to counter pitch, but I could never get it to fly slow enough to be considered a STOL aircraft. A much more advanced pilot then myself may enjoy this type of flying, but for me it was not a fun plane to fly until I removed the slats. It is now one of my favorite planes to fly in almost any condition!

Can you post a picture without your slats?

[SEWERFLY]

That's a great mod

[Narly]

Have noticed in many of the posted videos lots of wing tip strikes in less than perfect landings; and since I do lotta that I came up with this mod:

Thought the exposed wing tips could be improved with drop tip "winglits" to protect the exposed wing tips and ailerons. Found carbon fiber sheet/plate 2mmx200x300 on ebay; made a template 1/2" larger than the airfoil top and bottom. Counter sink 6-32 blind nuts and epoxy into wing tips; but the trick is getting that done with no epoxy in the threads! Could also use screw in threaded inserts in 6-32 or small M sizes. Next I foam tacked on the stock black winglets in the recess. I cut the carbon fiber with a Jig saw with fine tooth metal cutting blade just outside the line and final sanded to shape with just sand paper on a block. Do use a good respirator since you don't want to breathe the fine carbon fiber dust. The cut out for the wing tip lights was with me old Dremel jigsaw with fine thread blade and a hand jigsaw. And the finished look:

Looks great and might even help knife edge flight (like I can even do dat). I haven't flown it yet 'cause it's 34* F outside and I don't have a suitable 6S batr'y because I spent all this months
budgit on a 48v. 17.5Ah Li-ion batr'y that is attached to a new e-bike !! 😎

[ebrahimijohn]

I have put a dozen flights since removing the slats and this is what I have observed. #1. Lower speed take off and landings with dramatically improved handling. #2. No more left pitch at low speed. The amount of throttle needed to maintain flight at low speed is reduced therefore the torque of the motor no longer affects low speed flight. #3. Increased laminar flow reduces need for increased throttle in turns and at low speed flight which extends battery life giving me more flight time on same battery. One of the deciding factors for purchasing this plane was the slats, I had never had an RC with them and I thought they looked pretty bad ass on this plane. I could get the plane to fly decent with lots of rudder input and using the ailerons to counter pitch, but I could never get it to fly slow enough to be considered a STOL aircraft. A much more advanced pilot then myself may enjoy this type of flying, but for me it was not a fun plane to fly until I removed the slats. It is now one of my favorite planes to fly in almost any condition!