Hello fellow RC'ers...I am about to finish the wing halves. I have heard pro and con about how much dihedral. I am building the "B" wing and it calls for 5 inches total dihedral. Do I want less, say 4 inches, or maybe more? I will be flying where we have some wind at times. I have a simulator so I hope some practice will help. Thanks in advance for your opinions. Dave BTW it is the first PT-40 not the MKII

If you are installing the ailerons, then I would use the least amount of dihedral. I found the plane flew better.

My PT-60 has 3.5" total on a 71" wing.
The book called for 4" on the sport wing and 6" on the trainer wing.
Since the 40 size has about 10" less wingspan, 5" seems huge.
If were doing it again, and I might, I'd probably reduce it to around 2" or so.
The PTs are so stable and forgiving they don't need a lot if you're using ailerons.

I run an RC Airplane Club at the school where I teach and we finished and flew our PT40 that we built. I substantially reduced the amount of dihedral on the plane to about 2" total. The plane handles much better, especially in the wind. Young people catch on to RC very quickly and as well, we have been using Realflight G2 in the classroom too. Just waiting for the weather to warm up a bit to get back at it. If the student was an older person perhaps the extra stability might be useful, but in general, I believe the PT series use too much dihedral in the design.

Cheers!

Jollidude

Thanks for the info.....hey jollidude, are you insinuating that because I'm old that I suffer from dementia, senileity, bad eyesight, slow reflexes, poor co-ordination, tired aching muscles, I am grumpy and sinical. Just kidding.....I'm probably all of the above. Thanks again. Dave Please do not take offense, it was not meant that way.

Hi Tucker,

I have no idea how old you are, or if you are senile, demented, or any of the above mentioned ailments . When I say "young" people I'm talking Grade 8 students, 13 or 14 years old. These guys are part of the Nintendo Generation and latch on to anything computer-like or electronic. Of course when flying the Realflight sim, they have more fun crashing than flying and then razzing each other about their piloting skills. Much like it is out at the flying field I might add! I used to have the old Dave Brown Simulator that told you how much the repair would cost. They loved that! Each one trying to out-crash the others! Seriously though, they do catch on quick and can't wait to get a chance to fly the real plane. Rock on Tucker, if you eyesight is bad just build a bigger airplane!

Cheers!

Jollidude

I have had the chance to build a lot of different trainers and the PT-40 just begs to have some of that dihedral removed. If I were doing another one I would take at least 50% out.

I know this will catch some flack, but, build it flat, and don't look back. at the most put 1"under one wing. It will handel the wind much better.
plus it will turn better too.

I just finished a PT-40. They give you two dihedral gauges. One for the trainer version and one for the sport version. I built mine using the sport version. Seems ok to me and using the gauges, it makes it less easy to screw something up.

I built the PT-40 with the trainer wing. It had to much dihedral in my opinion. I purchased another wing kit and built the sport wing. I think it flys and handles much better.

Hey Art.....I see that you changed your logo....did you read Hackworth's book..."About Face" Dave USMC 1957-58
Jollidude....I'm 65 but I'm starting to leak a little oil. Thanks guys

The intent of the Great Planes PT-series of models is to be a series of Primary Trainers.

They were initially designed to be super stable with a strong self-correcting tendency. To correct a bank when you let go of the controls, you need the dihedral. To correct a nose-down attitude, you need the positive incidence in the wing relative to the horizontal stabilizer. The PT-series achieved those design goals.

If you build the Trainer wing, the ailerons won't be that effective. You may as well just make it a rudder-elevator-motor airplane. It flies very nicely that way.

Again, please realize that the PTs are for absolute novices. They weren't originally intended to be for experienced fliers...at least as they were designed.

They don't have "too much" dihedral...at least not for their intended purposes.

One more question....Washout, put it in or leave it out.....I have heard that it is easier to just raise the ailerons 1/8 inch when the servos are set at neutral. Dave

On a tangent to this thread, I'd like to ask about suggestions for an engine for a PT-40, built with the add'l dihedral.

I have an Aero-Star 40 kit, which flies beautifully, and I'll be working with my 10-year old daughter this summer, teaching her how to fly it. The PT-40 I'm working on is for my son, who was born with some significant neurological problems, which impact his coordination and reflexes, not to mention his reaction time. The more stable and self-correcting, the better. I'm hoping the PT-40 will work as a huge confidence builder for him, as he is always wanting to fly with me, but the A-Star is a little too aerobatic. If you've never worked with a special-needs child, I encourage each of you to try it, and I almost guarantee that the reward you'll feel as a result will just about take your breath away.

But on to my question: Can anyone give me some suggestions on an engine to put on the PT-40, which will pull it around the sky, but won't make it anything approaching a high (or even close to high) performance aircraft? I have an Evo 46 on my bench, but I am thinking that is way too much engine for this airframe, given that I want this to be a docile, and gentle aircraft. (I suppose I could let him fly my Gentle Lady, but I think he'd enjoy a powered airplane more [8D] ). I thought maybe an OS LA-40 might be appropriate, or maybe a TT or SuperTigre 40, or even a GMS 40.

Any suggestions you have would be welcome, and most appreciated. Thanks so much, in advance, for your help with this. Blue Skies!

Mitchell Schaff
Williston, North Dakota

The O.S. .40 LA or O.S. .46 LA will both work well. The airplane will have plenty of power with either engine. For most training flights, even on the .40 LA, you'll be flying at a much-reduced power setting. That airplane will easily "putt-putt" around the sky at 50%-70% power. Trimmed for level flight at that power setting, you just have to add a few clicks of throttle and the model will gently climb. A few clicks off the throttle and the model will gently descend. Hit the power to full and the model will nose up and climb very nicely, thank you.

Took a saw to mine after 11 year old lost interest, now he loves it!!!!

Hey All
I too built the PT-40 kit, in hindsight, I would have removed half of the dihedral. The airplane is very forgiving and stable for the novice the way it is designed. I will convert mine this fall to less dihedral and to a conventional gear set-up. The engines that have been installed on mine are a K&B 40, OS LA 40, and currently a pre China tower 40. Plenty of power for this airplane, however, I just got a K&B screamin' 48 that is going in it next. As I see it the airplane is built strong enough to hang a 60 sized engine on it.
-Tom

I learned to fly on the pt40 markII. and i used the trainer type wing with ailerons. there was another learning at the same time as i did he used the sport wing and it handled the wind a little better. But i put over three hundred flights on it before it was time to strip it down and retire the airframe. for an engine i used a thunder tiger GP42 and that was plenty of engine for it. i would'nt go any smaller than a OS 40la on a grass runway depending on how tall the grass is at your runway. i forget now but i used three and a quarter inch wheels due to the thick grass and cracks from the clay opening in the summer. It was a nice plane pretty sturdy also i put it into a tree once into the plowed soy bean field i don't no how many times. probably broke fifty props on it. and i never remember having to fix the wing. knocked the firewall out a couple of times though and bent the nose gear up numerous times. i'm glad i don't break props like that anymore. i'd go to the hobby store on a friday night and buy six props and i would come home on sunday with all six broken. thinking man i'm never going to learn to land. but yet the plane survived all that and yes i finally learned how to land. Good Luck on your plane.