Trainer type plane - Page 3 - RC Groups
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Aug 18, 2010, 10:16 AM
Kevlar's Avatar
Originally Posted by cpc625
Can someone point me to an explanation of the forming process?


Using a piece of paper as an example (11" running left to right, 8" vertically). Draw the line where you want to fold, say 3" from the top, flip it over and run packing tape the entire length of that line and it should be in the center. So 2" packing tape, line would split it the full length.

Now turn it over and cut a groove along that line about 1/8" wide and half-way deep - don't go all the way through. You can run the tip of a #11 x-acto, making two parallel cuts about 1/8" apart and then gouge it out with a flat eye-glass sized screw driver.

Now begin your fold, evenly - little at a time...groove will allow it to bend on itself, and the tape will keep it from ripping, tearing. I will sometimes use yellow packing tape, gives the leading edge a nice look. IMO

That's how I do it....I'm sure there are other techniques.
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Aug 18, 2010, 10:18 AM
Registered User
Thanks gentlemen

Aug 18, 2010, 02:17 PM
Registered User
I use the edge fold of the FFF like The Flying Farmer said. If I don't have that I just glue the two LE pices together and sand it round then tape it.
Aug 18, 2010, 02:35 PM
Registered User

Did you use hot glue for the foam joints and epoxy for the shaft to foam & wood joints?

I have parts for two cut and hope to do the assembly this evening.


Aug 18, 2010, 04:33 PM
^Its what I do^ - FPVholic
The Flying Farmer's Avatar
I use hg for everything but the motor mount, and I'm pretty sure Russ does the same.
Aug 19, 2010, 07:50 AM
Registered User

Thanks for the info. I need to cut the motor mounts and start assembly. If not today then tomorrow.

Aug 19, 2010, 02:31 PM
Registered User
TFF is correct. I used epoxy on the motor mount and hg on the rest.
Aug 22, 2010, 02:03 PM
Registered User
Potshot wipped up some plans for a 75% version. It looks great and I am going to build one as soon as I can get the gear together.
Aug 22, 2010, 06:43 PM
Vertical approach specialist
potshot's Avatar
I had somewhere mentioned to Russ40 that this drawing was scaled to 75%. My bad. It is actually 2/3 original size, which makes the original 6mm foam become 4mm. I had figured on using 3mm Depron for everything except the tail group, for which I might use some 5mm Cellfoam I have laying around. I guess a 3mm tail group would be OK for indoor, which is where I will most likely fly mine.
Aug 23, 2010, 03:44 PM
Registered User
Originally Posted by Russ40
Thanks potshot. pm sent.

The motor mount to the front of the wing is 5" and 26 1/4" to the leading edge of the hor stab. The cg is around 3 1/4 to 3 1/2" from the leading edge.
I can only put my CG at 4", I use the folowing materials:

Foam Core 10mm Wing, Rudder and Elevator
Foam Core 5mm KFm parts
10mm wood Main body

It is a bit heavy, first try to fly the wood broke, and the tail was too heavy, the plane was always climbing.

The total height is about 800g with battery.

Now, the CG is better 4", I'm using a 10x6 DD propeller, 1400Kv motor and a 11.1V battery, lets see if it flyes.

My main problem is the Foam Core, the paper and plastic that covers the depron on both sides is heavy (I have many problems to find depron in Portugal , only two places and both are on vacations).

Aug 23, 2010, 05:02 PM
Registered User

fishing rod

garage sale fishing rod works great for shaft and tip of(2) rods works great for landing struts
Aug 24, 2010, 08:50 AM
High Altitude Flyer
viking60's Avatar

You wrote: " Wing is a Kfm3 airfoil 50" span. The center is 36" with 7" tips. The tips have a 2 1/2" rise. The first step is 3" and the second is 2" back from the first. Cord is 9" total. "

I like the way your KF'ed wing is handling in the videos. You've built a nice trainer!

I'm curious as to your ideas & comments on using the KF steps farther forward (33% & 55%) than the 'classic' approach of having the first step on a KFm3 at around 50% of chord, and the secondary step at around 70% to 75% of chord. (I've also more recently built some aircraft which used the steps farther forward, so I've built them 'both ways' with varying placements, and with good results, too. )

Aug 24, 2010, 09:12 PM
Registered User
Rui... Keep us posted on how it flies.

Viking... I thought that the steps farther foward looked more like a regular airfoil. I thought I would give it a try and it worked very well. I was thinking that the steps being farther back would interfere with the airflow over the ailerons. This is the third plane I have done like this. On the other ones I can double the weight of the plane and it still flies good.

Aug 25, 2010, 08:49 AM
High Altitude Flyer
viking60's Avatar

Thanks for the thoughts on this- I like how you think, & then put your thoughts into a foamie design to verify it!

I have my own similar thoughts about steps too far back & too tall messing with airflow over ailerons and producing far too much drag.

I just finished up this new 48" span wing to this point yesterday. It started at 10" chord in the center, and 8" at the wing tips. That's about 3 square feet of wing area. The hot melt glue did the trick for a fast build-up. I also used balsa aileron stock that I had on hand.

The forward / primary step is at about 38% of chord, while the rear / secondary step is at 64% in the center, tapering to 56% of chord at the wing tips. Ailerons start just outside of the prop arc in the center, and end 1-5/8" in from the wing tips. I'll set the aileron servo today & start test flying it.

I laid out this wing so that I could temporarily add and remove filler strips behind each of the steps to see how they affect the handling / performance of this wing. I can also mount a variety of wing tip plates / structures to see how they affect the handling. It's very interesting, & all fun!

Aug 25, 2010, 02:06 PM
Registered User
Viking... I like that wing design. I am looking foward to the flight reports to see if how much the addons change it.


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