Foam Board Jenny

[Tench745]

Shot of the cabane struts in place. I added some wire to them in an attempt to fight the last plane's tendency to shed it's upper wing on hard landings.

Here she is after paint. With battery but sans prop and landing gear she weighs in at exactly 22oz. Tomorrow I cogitate on gear, etc.

 

[jamboree1]

Now Jenny is looking sweet, good luck on the maiden. One thing i noticed about bipes is the tendency to nose up under throttle with all the lift the wings create, keep this in mind on the maiden or even add a bit of nose weight if in doubt of the CoG. Remember that a nose heavy plane can fly but a tail heavy plane only flies once.

 

[Tench745]

Maidened the rebuilt Jenny today. AUW ~28oz Wing area 505sqin.


It was a rather windy day, not great for first flights, but I said, eh, what the heck, I'll try it.
I tried some taxi tests, but the wind would blow her up onto a wingtip every time it shifted. So I decided to hand launch. I tossed her into the wind at full throttle and in twenty feet she was pointed straight up and climbing vertically. Not what I was expecting. For about a minute I did a series of turns, etc. trying to keep her pointing into the wind but there was too much of it for my skill.
Jenny seemed a bit pitch sensitive, so I think she's tail heavy. I tried a landing or two but mostly smeared the wingtips in the mud. I think on a windless day or indoors she would be a great flier once the cg is adjusted.
I'll get some footage next time I go out. Hat-cam works.

 

[Tench745]

Video as promised. Less wind today, so I have a better idea of how she handles, but I need to either 1, fly better or 2, get a bigger space. I like to perform takeoffs rather than hand launch, which is only possible from the road at the moment. Soggy grass. Next time I'll start in the field and give myself some room.

 

[jamboree1]

Yup, still tail heavy, add about 2oz weight on nose

 

[Tench745]

I don't think it's all that tail heavy actually. She glided alright when I chopped power, so I put a little down thrust on the motor. Seemed to fly better the next day, at least for the ten seconds before I flew it into a grill and ripped the top wing off. She's fixed and waiting for another calm day.

 

[desert wings]

Beautiful plane. Once you have it "dialed in" it is going to be awesome.

 

[Tench745]

The journey of the Jenny has been long and hard. She was just too flimsy and too squirrely to fly. Every time you gave power she'd nose up hard, and the wings flexed with every turn. The wing loading is so light and the surfaces so large any breeze made it almost impossible to fly.
I've downgraded from a 3s 2200 to a 2s 2250 and that has made a large difference. She's no longer so over-powered that an application of throttle pulls her vertical, she just kind of lopes along like a Jenny should. Extra nose weight was needed to make up for the loss of battery weight. I've also added some spider-wire bracing on the wings, but have not had a chance to fly her since doing so.
The low wing loading and large tail still means it really has to be calm for her to fly.
A bigger field would be nice for this one.
I'm slowly completing a few finishing touches:
Dummy Engine

Spoked Wheels
This one was a first attempt. I think the spider-wire spokes are too thin to look right and they're not entirely tight. The next one will be laced with black thread to see if I like that a bit better.

 

[Tench745]

Flew the Jenny again today, it was way too windy. My ipod says it was gusting to 15mph. Flying was tricky, a controlled landing was impossible. I'm having a hard time figuring out how to land her even on a still day. You have to keep power on because of all the drag, but she just floats if you have too much on and the difference between too much and not enough seems like about one detent on the throttle.
I'm having difficulty keeping the top wing from coming loose as well. Maybe if I can figure out how to land it will become less of an issue. Flights on a 2S are much more scale and it's fun to watch the massive rudder skid her around in the air. I'm still amazed by how quickly she'll take off. At full throttle she can be airborne in six to eight feet with enough speed for a climbout.

Climbs are pretty scale as well, and by that I mean, I've never gotten her higher than 40 feet. Jennys were never climbing fools, about 200ft/min for an OX-5 powered Jenny. In scale (approximately 1:10 scale) that's about 20ft per minute for this model.

Anyway, now I have some fixing to do on top of my Cafe Racer build and Searey build.

 

[Tench745]

I finally got two successful flights in on the Jenny. Very light wind is a necessity, and I had to reinforce the cabane struts with skewers to steady the upper wing. But, with a 9x4.5 prop on 2S she flies rather nicely. I also removed a large portion of foam from beneath the turtledeck to reduce the amount of lead needed in the nose.

 

[Ron B]

I had a chance to see a full sized Jenny flying beside me about 1 mi. away and had to slow my semi down to a crawl to stay with her. I got to do this for about 20 min. before traffic showed up and I had to leave her behind.

 

[Tench745]

Heya Ron. Im pretty jealous; I've yet to see a full scale Jenny fly. Where were you driving when saw it? There are so few real Jennies flying anymore, I only know of three, maybe four. I'm amazed she could keep up with you at all. Top speed was about 70mph wide open.

 

[Ron B]

I was in colorado on hwy 50 between Grand Jucntion and Delta and I had to slow down to near 30 so I wouldn't out run it.

 

[Ironmannc750x]

Well I got my Jenny up in the air today. Took off from the grass, a little trim and it flew perfect. I used Flying Penguin plans and with a 2200 battery, it flew like a dream.

 

[Userofmuchtape&glue]

Lovely looking plane and welcome to FT!

 

[Ron B]

very nice
I got to drive along side of a real Jenny yrs. ago and it was a thrill

 

[docque]

Can this be built as a 3 channel? I am still new to building and flying.

 

[Tench745]

I never shared these, but this is a MK2 version of my DTFB Jenny plans.
View attachment DTFB Jenny.pdf
As it is there are little circles where bbq skewers should go through the wings and fuse to reinforce everything. Foamboard struts get glued to the back of these skewers for a more scale shape. In future I would make a double surface wing top and bottom, with struts like the FT DR1 or SE5.
With scale dihedral it really needs both ailerons. If you put in 10 degrees or so of dihedral you might be able to get away with 3ch.

 

[Daniel Kezar]

what electronics are recommended for this build?

 

[Tench745]

I just designed it around whatever I had at the time. It used a 3007, 1100Kv Hobbyking Donkey motor turning a 9x4.7 Slowfly prop. A 3s battery was a bit too powerful but it flew nice on a 2450ma 2s running a 30Amp ESC. Servos were 5 gram but 9 gram might be a better idea. To sum up:

Motor: 1100KV Brushless Motor
ESC: 30A Brushless
Prop: 9x4.7 Slow Fly
Battery: ~2500ma 25-30c 2s
Servos: (4) 5 or 9Gram servos

I stole all the electronics from this plane for another project I'm working on, but someday I'd like to build an improved Jenny 2.0 so I can add a step-by-step build log for it.