Tomcat_AL200

Hello, I was wondering if anyone knew how many G's a PT-60 on high rates, or a similar trainer, would pull? I need to know how much stress the center wing joint will be stress, I'm making a two piece wing. Thanks.

Flypaper 2

If you think your going to put a lot of stress on it, before you cover it put a 4 in. wide strip of 6 oz. fibre glass cloth around the centre section. Not a bad idea anyway in case of a panic pullout It will more than double the strength of the joint.

Fastsky

I think what flypaper means is that you glue down the fiberglass down with 15 or 30 minute thinned epoxy. I have planes made from plans that have no dihedral brace between the 2 wing halves. They are just glued together at the centre and the gap is filled in with epoxy. Then the fiberglass is added from 4 to 6" wide depending on the model. The fiberglass is where the wing joint gets its strengh from. [8D]

jaka

Hi!
Around 20-40 G!
Regards!
Jan K
Sweden

Flypaper 2

Thanks Fastsky, think I had an old age brainfart. I use epoxy or thin CA.

GRANT ED

I very much doub't a trainer would be capable of pulling 20-40 G. The wing would stall before it could produce enough lift to support 40 times its own weight. I have read on a website that said the wing for a large scale extra (I think it was Composite aircraft) was rated to 30G max and that is for a fully 3D TOC model. My friend designed a .10 pylon racer for competion. He really knows what he is doing as he wins pretty much every race he enters. When designing the wing he calculated his model would pull 20G max in a race. Remember that is for a model traveling around 120MPH and turning sharply around a course.
I think 10G is a more realistic figure for a trainer.

ICE_MAN

I doubt if the wing would hold even 10g.. Maybe some one with an old wing can stack some weight on it and see.. I may be wrong.

Tomcat_AL200

btw a PT-40 wing could hold 20gs and only bend a pt-60's pretty much the same, but since I split it in two I will reinforce the slots with FG and then add my nylon netting over the wing root just in case.

Fastsky

The nylon netting isn't needed if you do a good job with the fiberglass and the netting may create unwanted problems. I have some fairly fast and responsive low wing planes with wings that stay together just fine with the fiberglass joint. The PT is a trainer so its not going to be building up a lot of speed or high speed turning stresses turning compared to low wing sport planes I wouldn't worry about it.[8D]

jaka

Hi!
Well mayby not 40G ...that was a bit too much for a high winged trainer ...but in the eighties I heard some American Formula 1pylon airplanes that had been measured at 40 G in a tight turn.That was in the early eighties....with todays Dutch and Russian engines speed is much higher in international pylonracing....around 375-400km/h.
I would imagine that a trainer with a rear C of G traveling at around 100km/h , in a dive, pulling up sharply, could reach really high G forces.
Whether or not 20G or 25G it is vital that you reinforce the wing enough.
Having a wingspar is nice to have but 3-5 layers of 25g glasfiber cloth is also going to work.
I once flew off a wing during a sharp pylon turn at the nr 1 pylon with one of my P-51 F3D racers going around 300km/h ...the wing just broke in half ! That wing did not have a wingspar through the middle of the wing ...just 6 layers (different sizes) of 25g glass fiber cloth were used and some carbon fiber strings.

Regards !
Jan K

Dukester

My Feedback: (31)

Grant, You just misunderstood Jan, those were Metric G's....

Tomcat,

On two wings that I did, I used a 1/4" carbon fiber arrow shaft fitted into carboard tubes for reinforcement. Since you say you want a two piece wing, fiberglassing the joint is not a solution. I drill a hole big enough for the cardboard tube in each rib going out to 3rd rib, then I cut pieces of 1/4" balsa sheet about 1" square (assuming rib is large enough for that) and drill them to receive the tubes. Then slide the tube through the ribs with one 1/4" reinforcement square per rib and epoxy it all in. Once you get each wing half fitted like that, put a pin or wire through the tubes at the end so the CF tube can't slide out the ends and cut the CF tube to fit (or not, I left mine stock length and just left some extra cardboard tube past the third rib) then you can join the wings together using the CF tube as the strength member. I did the same thing but only out to second rib on the back of the wing to keep them aligned.

This requires careful work to liine up if the wings are going to have dihedral, but if you get the hole in the rib pretty close and cut it a little large, you can use the 1/4" block to carry the load and just epoxy it well to the rib to transfer the load to the wing structure. I've been happy with the strength and its not too much weight. I don't Pylon race, but I do some high stress maneuvers and never had a problem.

PS, the CF arrow tubes are available from Academy, hunting stores, Walmart sometimes, etc. They also make great leading edges for thin wings.

Duke