F22trainer

I could not help it...
https://www.motionrc.com/collections...lite-pt-17-bnf

They marked them down and I was always hypnotized by one club members model, that I just had to have one.
With AS3X it's a real jewel.

Don Sims

Looks like a nice plane. Hope it flies as nice as it looks.

F22trainer

I've seen one fly flawlessly at our club, and I've seen the nose heavy issues some have had. AMA had a great review and correction without adding weight. Our member said he had easily 200 flights on his and flies it nearly everyday, so I'll pick his brain a little more on the balance. His flies super smooth and he does agree the gyro is probably the only reason he can fly it so well.

F22trainer

I did get the opportunity to ask more info from Ken on his PT-17. His is PNP, not a Spektrum AS3X / SAFE but does have an Eagle Gyro stabilizer. His comments - make sure battery is ALL the way forward and check CG and it shouldn't be any problem.
I plan to enable the SAFE select to keep the set up similar to the Cub using the DXe 6 channel tx.

F22trainer

A little scale like realism...

F22trainer

Got 2 landings and 1 takeoff, two batteries worth of fun in the pattern getting used to it. Got a little short video, but it was not worth posting as there was only a little yellow speck against a blue sky, and then Dave saying "...ok, you ready to fly it?"
I did have to add 2 oz. into the hollow cylinders even with the battery all the way forward. Still need to adjust the rudder a tish too.
Wind kicked up shortly after the last flight, so I was happy to load up with both nearly ready to go next trip.

F22trainer

A few more flights - still flying with the SAFE mode and avoiding the x-winds. It seems to fight me on takeoff and landing with SAFE tempering use of rudder.

F22trainer

Now I probably have close to a hundred flights on this bird. She is a favorite of mine and the club. She has a little rash and I found the barrier fence when Xwinds got the best of me, but nothing high speed or real hard impact with a post. I did apply Polycryllic over the whole thing - 2 coats and it is still turning the same 11x7 prop she came with. Wind slammed it into the pavement today, about foot off the deck on landing - struts did their job. Taxi over to the pit, check her over good and the take her around the pattern one more time for a greaser landing with 7-10 knot headwind.
She has some company now -another looker moved into the hangar.

F22trainer

https://youtu.be/1cwMOndmNvk

CreativeRC

Fly it as a monoplane. Flies even much better, faster and much more aerobatic. A hidden gem. I put the battery, 2200 3s, 1800 4s or 2200 4s, in the pocket behind the receiver so as to balance the plane. The low dihedral lower wing is not an issue and in fact helps in its aerobatic abilities. With landing gear well ahead of the wing, tipping over on grass is rare.

Whizzer

Curious how you managed to support lower wing to give it strength. I have a PT-17 and like the idea of flying it as a monoplane but the way the wing attaches to the fuselage it seems loose. Wondering how you managed to get strength to the lower wing.

CreativeRC

Thank you for your interest in this modification. I first flew it as is without issue but recognized, like you, there is a potential weakness with the foam tab and socket at the front of the bottom wing. I flew it at least a dozen times but after a couple of bumpy landings where the wing tips caught the ground (due to pilot error), I noticed a bit of slack in the wing much like I would get with some Parkzone planes. The foam was not cracked or damaged, just a little compressed such that the foam tab now had slack. I could have kept flying it as is but preferred to address that. I cored the foam with a sharpened 1/4 inch brass tube and installed two 1/4 inch x 2.5 inch long nylon bolts with no. 2643 flat washers at each end. You will notice I added small brass washers to help with the oversized holes of the flat washers. In the fuselage are two nuts to lock each nylon bolt. See the attached photographs. The location of the bolts is perfect and there are no obstructions in the foam where I cored the foam. Very secure now.

If you do this modification, remember to put the 2200 mah battery in the pocket behind the receiver. I installed two carbon rods (visible in the photos) to which I could attach a hold down strap. These carbon rods were also used to support the control rods. Under the battery, I cut out a small wedge of foam to allow the battery to pass though all the way to the back of the pocket.

A really fun modification. Put the left aileron in Rx channel 6. You will still get AS3X on one aileron which is better for flying it as a monoplane and you can even add flaperon with a programmable Transmitter. I did try it with the AS3X operating on both ailerons (as programmed for the biplane) but it was too sensitive and needs the gains to be reduced something I have not yet learned how to do. The short cut is to have it operating on one aileron only as I have done.

I removed the dummy engine and streamlined the front end buy cutting an old large spinner and painting and taping it in place (but not necessary). Using an APC 11 x 8.5 propeller with both 3s and 4s. Very pleased with this relatively easy monoplane conversion.

Good luck.

Whizzer

Thank you for the explanation. I bought one of these at a swap meet but the plane has been crashed and repaired. It needs going over to make corrections and improve strength where needed but once completed figured it might be interesting to try it as a monoplane. I noticed the lower wing was loose and to repair it, did an nearly identical repair using a 1/4 inch drill and slowly drilled through the same location you indicated and inserted two bolts with smaller washers but intend to replace them with larger ones. To give needed support to the wing, placed a small section of 1/16 inch plywood and put the bolts through that but think it might give greater support if I ran the plywood from behind the landing gear attachment past the plastic used to anchor the rear section of the wing by drilling for those to pass through the plywood.

One thing I don't understand is the CG issue. As is, the plane had 2 3/4 ounces of weight added to the dummy cylinders to balance properly. Does removing the top wing change the weight so drastically the battery can be placed behind the receiver? I'm still a beginner but having fun.

CreativeRC

The simple answer is "yes". Note the top wing is more forward than the bottom wing and for the monoplane conversion you are now balancing the plane on the bottom wing. Removing weight that is forward of the bottom wing allows you to put weight behind it and for this model it even allows you to remove any extra weight that was added in the dummy engine cylinders by the previous owner.

As a monoplane, you do not need the extra weight that was placed in the dummy engine as that will likely make the plane nose heavy even with the 2200 mah 3s battery placed behind the receiver. The balance goal for the monoplane conversion is for the plane to balance at 1/3 of the bottom wing width (known as the wing chord) measured from the leading edge of the wing next to the fuselage. We measure next to the fuselage because some wings are tapered but not on this plane. Note, I even removed the dummy engine itself, but compensated that weight loss somewhat with the install of a red spinner and makeshift plastic cowl.

With regard to the biplane setup, there appears to be a design error in the plane. There is simply not enough weight up front or the rear stabilizer is at the wrong angle or maybe even a combination of both. As you know a tail heavy plane is difficult to impossible to fly. The manufacturer did install a cube of steel embedded in the foam just behind the top of the dummy engine but it was not enough. The plane will be tail heavy even with the 2200 3s battery placed all the way forward and the elevator trim available on the transmitter will not address the problem as it normally should. This is the reason model pilots have been adding lead nose weight in the dummy engine to get the plane to fly and land properly. The balance point shown on the top wing in the manual is not correct. In all honesty, the plane should not have been on the market with that problem.

I read in RC groups where one pilot resolved the problem by changing the entire angle of the whole rear stabilizer a few degrees upwards (equating to a built in down elevator) and did not need to add extra weight to the dummy engine for the plane to fly well. This suggests the design error could also be that the rear stabilizer with elevator in neutral position is at the wrong angle for a plane with two wings where the top wing adds a drag moment to the entire plane with the effect of wanting to pull or push the tail downwards. A rear stabilizer angle change as was done by this pilot can correct for that.

After first flying it successfully as a monoplane, I did assemble the top wing to fly it as a biplane using a heavier 3,300 mah 3s battery thinking that would resolve the balance issue without needed to add weight to the dummy engine. The plane balanced exactly per the manual. But I was wrong and the tail was dragging low in the air and all it wanted to do is climb. I clicked in all the down elevator trim available in the receiver but that was not enough. I needed to keep some down elevator on the stick to land and luckily without mishap.. In order to fly well enough, I still had to attach about 4.5 ounces of lead to the dummy engine. First thing I did when I got home is take off the top wing and leave it as a monoplane.

Note: For the bottom wing monoplane modification, the rear stabilizer with elevator in the neutral position is at the correct angle. The drag moment of the top wing which pushes the tail down is gone. With the plane correctly balanced, at 1/3 of the wing width, it takes little elevator trim on the transmitter for the first flight.

Bottom line, its is fun especially when you get these things right.