Hi,

I'm very new to R/C. I've seen a couple of video clips on line and I read a lot of the posts in this forum, big help. I'm building a Great Planes PT-40 kit because I could download the manual from their web site. Read it before buying the kit to see what I was getting myself into. Wish all manufacturers posted all their manuals on line.

I'm at the join the wing halves part, two choices 8" dihedral trainer or 5" dihedral sport wing. It has a 60" wingspan. I thought 8" was the way to go, sanded the spars the LE and TE to the specified angle and did the test fit. 8" of dihedral is a lot, it just looks like too much, kinda ugly. First thought I had was, are these wings supposed to flap up and down, it would save on fuel. So is the 5" dihedral enough? I think it looks a little better. Think worst-case scenario here, like worst pilot ever. Will the plane be able to self-recover? If I fly it I think I may need that feature. And yes if I do I will get an instructor to help me but I want it to be as easy on him/her as possible.
Also does anybody have a better method of securing the hatch cover, I’m not real happy with the three little screws.

Thanks for your time and advise,

Dennis

Stick with the 8" trainer dihedral....this will enable
the plane to "self-right", and will add greatly to the
stability, and ease of flying for a new flyer.

Dave.

DenJ,

My 2002 "Avistar 40" has approx. 1 1/2" to 1 3/4" of dihedral, measured from wing tip to wing tip on a wing that spans 59.5".

It does have less than the "SuperStar 40", but 8" is just too much (in my opinion)... but the wider the wing span, the greater the dihedral - equaling the same.

I'm new and haven't had a problem with it. It tracks well, and is stable. It does, however, have a semi-symmetrical wing design.

MacAir

Do a search for PT-40, and I'm sure you'll find quite a few mentions of the dihedral. That plane is designed to be able to fly on 3 channels (no ailerons), which is part of why there's an 8" option. If a plane uses the rudder to induce a bank, it needs quite a bit of dihedral. If you've got ailerons, you don't need to worry about having that much. From what I've read, the 8" is excessive and makes the plane more difficult to fly.

For what it's worth, a friend has a PT-40. He built it with the 5" option, and it's proved to be both stable and able to recover. He doesn't fly often, and it works out very well for him.

Looked at joining any of the local clubs? Which part of the Cities are you in?

Leave the 8" dihedral in the wing,makes recovery easy and faster,turns are faster,inverted is harder ,been many years since flying 3c pt 40,but training on 8" seemed easier,yes you'll get a few coments on the high dihedral,my Lil Bull combat has 8" dihedral,it will out loop and out torn most at the combat events I've been.

I disagree. If you are using ailerons (which you should) go woth the 5" dihedral. I have built and trained several people on PT 40's and only the first one had the 8" dihedral. IT WAS TOO MUCH!!!!!!

While it gave the plane good recovery characteristics, it also made it "too stable". It took an ape with an air hammer to get the thing to do what YOU wanted it to do.

My first plane was a PT, the dihedral is ridiculous. There is such a thing as too much of a good thing. Self-righting capability and is one of the main reasons to get a trainer but you shouldn't have to fight the plane to fly it.

Even the "sport" version has enough. (IMO the "sport" version is too much…)

I would agree with Minnflyer, less dihedral and ailerons.

As far as self righting and stability goes. its a trianner and will have these characterics to a degree with either amount of dihedral in the wing.

One other thing since you will be learning with an instructor its their job to save the plane for you when you get out of control.

If you're going to use 4c then less dihedral,if using 3c then 8",add:to post # 5

8" (you could cheat a little and go with 6-1/2") with 3 channels for training ....... And once you've learned to fly, you can always build another wing with less dihedral and turn it into a sport flyer !

I have to agree with some of the others. 8 inches is way too much. Might be ok for one or two flights, but then you will know how to right it. If you use less, you can enjoy the plane a lot longer. Personally, if you were my student, I would have you put in less, 3 to 4 inches and teach you to fly it so you can have fun with it later and it would fly better. Might be a little harder at first, but later you would be very thankfull. It will not be that much harder to fly and will be a better airplane with less.

I am a newbie. Can someone define what dimension we are talking about when diehedral is mentioned. Is it the distance from surface to last rib when one wing side is sitting flat on surface or is it when wing is level so that the distance would be half of that.

lay one half of wing flat,measure from wing bottom tip to surface wing is on,diehedral.

Maybe MinnFlyer could post up a picture? That'd clear it up quite quickly.

Dihedral keeps a plane level in the roll axis. If it's in a bank, and the controls are neutral the plane will roll back to level. With a sport plane you have less dihedral generally, so that it will stay in the bank with neutral controls. Most trainers have a fair amount of dihedral to make level flight easier to achieve.

The planes with the most dihedral are generally 3-channel designs that use rudder, elevator, and throttle. There's no aileron. The dihedral translates the yaw that the rudder applies into a bank, allowing the airplane to turn. Without dihedral, a rudder-only design won't turn. It also levels the plane when the rudder goes to neutral. If you've got ailerons, you don't need as much dihedral.

I am building the 4ch version and most think the 5” dihedral is plenty. Would have built it either way but I like the 5” better. Any methods of securing a hatch other than 3 tiny screws into the top edge of the firewall? Or do the screw holes hold up ok after repeatedly taking them out and putting them back in?

I’ve was keeping an eye out for people in MN. Minnflyer is hard to miss the name was my first clue. I live in Brooklyn Park just off 94.

And no I knowingly broke what seems to be the first rule of getting into this hobby. I did not check out any local flying fields or clubs to see what equipment to buy. I’m a C5-6 quadriplegic and I was looking for a challenging hobby. My neighbor told me about rc planes he seen a nascar guy flying on tv. I got the bug to build instantly. I was 90% sure I could build without any help (too much help takes the fun out of it for me). Now that the fuse and wing halves are built I know that I can finish it. I’m just not sure about flying it. I’m sure I could fly it but the part between building and flying I will not be able to do myself (that fun thing). Or I might really like flying and only be able to when it fits into someone else’s busy schedule. I thought that if I had all the equipment and a trainer that was ready to fly I’d be more inclined to give it a try. For now I’m having fun building, can’t put off a Tiger II or a sig 4* much longer.

Just curious does anyone have any quadriplegics that fly at their field? Paraplegics don’t count too much function.

Thanks again

Dennis

If you are new, use the trainer dihedral.
If you want, build a second wing with the sport dihedral for when you are ready.

hwflyer,

I hope this helps to "illustrate" it.

MacAir

Macair,
Thankyou for illustrating that for me. The drawing clears it all up for me.

Nice drawing MacAir, I was just about to do one when I saw yours LOL

hwflyer & MinnFlyer,

Thanks! It was quick and had to keep making it smaller and smaller and smaller, just to get it to upload.

MacAir,
AMA# 762723 (big new number)

I just built and am training on the PT40 with max dihedral.

It gets alot of comments at the field, but it is very easy to fly.

I thought I might build a second 'sport' wing, but have decided to move on to a complete new kit.

Re the three screws for the hatch cover, harden the holes with a little thin CA. They are working fine for me.


fever

hello,
here is my two cents worth.i have been building and flying since 1965 started r/c in 1970 ans designing in 1971,back when i was researching dihedral i learned that alot of the trainers using 3 channels used 1 inch of dihedral for every 10 inches of span,so a 60 inch wing would be 6 inches.if using 4 channels dihedral is reduced 50 to 75% on a low wing pattern type dihedral runs about 0 to 1 inch on a 60 inch wing,mostly to keep the wing from looking droopy.remember that this design has been around a long while and if changes needed to be made for flight performance it would have been done by now.the ecessive dihedral was used to help make this particular kit return to straight and normal flight with release of the control sticks back to neutral.this plane was designed for those learning to fly WITHOUT an instructor.if you are flying with an instructer and using buddy box you can use the less amount.hope this helps all