My aerodynamic experiment

[EAS]

I came up with this idea in 1994, but had only built a small mock-up based on pusher props....still getting a counter-rotating setup back then was problematic. These two EDFs are built and sold as a matched set so I finally got around to building it. Hard, mostly because at 33" EDF nose cone to nose cone is still pretty small. Getting the linkage and 6, 10 awg wires thru the rudder wasn't easy....and I insist on not having ANY control surface linkage on the outside

 

[EAS]

This is just too small. The first fuselage rib on the back end. At least there'll only be a few this size, at the front and back. At the back I'm going from this one to a perfect 4.5" circle in 10.75". Balsa carved blocks on both ends. The back end and some of the middle of the fuselage will be sheeted with 1/32 Plywood. So I don't have to make anymore cuts for stringers. I can glue in short pieces for the top....just in the back end section. The rest will have more stringers.

 

[EAS]

Sometimes a little force IS required. I couldn't find landing struts that were sized for my model, mostly because everything is either huge or made for giant wheels, or pathetically flemsy. My little model is still going to weigh 5-6 Lbs. My wheels are 33mm because there's a really good runway about 30 miles from my house......so I ordered some T6061 and bent my own for the main landing gear.

7" wide and 3" high with 33 degree angles on the struts. The T6061 bar is .5" x .125". I've used T6 extensively for many projects. It's maybe, my favorite material. Even this small size bar requires a sledge to bend.

 

[Pieliker96]

Man those JP Hobby fans look beautiful, and man is that a unique-looking aircraft.

 

[cyclone3350]

I am making progress, however slowly. ....some time working on my Ranger's transmission. This being my first RC, it's heavier than I wanted. I'm coming out at 23.5 oz. per sq.ft. of wing. But there's a second version in the planning too. I think I need to repaint my windshield a little.

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Good to back back from U. I luv that Corporate Jet theme. If U have enough power for the total weight, I think it should fly just fine. I built this thing years ago, and came in @ 28oz pr. sq. ft, I thought that it would either not get off the ground or fly @ an unmanageable airspeed. It was one of my best flyers with very good slow flight characteristics. I can't wait to see it done.

 

[EAS]

Good to back back from U. I luv that Corporate Jet theme. If U have enough power for the total weight, I think it should fly just fine. I built this thing years ago, and came in @ 28oz pr. sq. ft, I thought that it would either not get off the ground or fly @ an unmanageable airspeed. It was one of my best flyers with very good slow flight characteristics. I can't wait to see it done.

Suprised it was that high. JP Hobby says these EDFs have 5.2 lbs of thrust each...part of the reason I bought them. Expensive too.

 

[cyclone3350]

Suprised it was that high. JP Hobby says these EDFs have 5.2 lbs of thrust each...part of the reason I bought them. Expensive too.

That is why I can't wait to see your project fly. I am working on a twin 70mm sport jet and was seriously considering the JP hobbies. They R a bit on the pricy side. I am not sure if my contraption will fly or fly very well when done, so I went with the less expensive FMS 6s 70mm EDF and will go from there.

 

[EAS]

That is why I can't wait to see your project fly. I am working on a twin 70mm sport jet and was seriously considering the JP hobbies. They R a bit on the pricy side. I am not sure if my contraption will fly or fly very well when done, so I went with the less expensive FMS 6s 70mm EDF and will go from there.

In the one high wing above, 28oz......what battery did you use and how long would it fly?

 

[cyclone3350]

It was a 78" WS and weighed in a little under 7lbs. I used an E-flte .46, a 13x8 prop, and a 5000mah 5s. I was getting 6 min of sport flying and around 8 1/2 for lazy touch and goes.

 

[EAS]

It was a 78" WS and weighed in a little under 7lbs. I used an E-flte .46, a 13x8 prop, and a 5000mah 5s. I was getting 6 min of sport flying and around 8 1/2 for lazy touch and goes.

Those are good numbers. When I purchased the EDFs I picked up a cheap 3300/6s just to test them upon arrival. 5500 is all I've got room for.

 

[L Edge]

Why didn't you run the 6 wires from the fans to the fuse thru the lower wing rather than the upper? Save quite a bit of wire weight that way and improve power . Were are your ESC's located?

 

[EAS]

Why didn't you run the 6 wires from the fans to the fuse thru the lower wing rather than the upper? Save quite a bit of wire weight that way and improve power . Were are your ESC's located?

That wing-tip is attached in a completely different manner, no room. I still have some aerodynamic trim to put on that tip, which sets in front of the inlet to the EDF....but the size of the model meant I couldn't without messing up the aerodynamics.....I want the air coming off the forward wing-tip going directly into the fan, not around the outside of the winglet.

If you look carefully, you can see the ESCs on the side....inside, the fuse where the four blind nuts are gluded to the outside (close to each other).

 

[EAS]

This is how I mounted the forward wing-tip to the winglet. I made four to get two that were right. I've handled the model a lot, upside down, on end. You can hang the model by the winglets. It's very strong. If it were larger I would do it a bit differently.

There are still some other aerodynamic trim pieces needed for the wing-tip....haven't made them yet.

 

[EAS]

That is why I can't wait to see your project fly.

It will be some time till then. I'm going to do some substancial testing first, including building a small wind tunnel (in my living room). I want smoke it look at the air.....get photos and/or video. That's my real purpose for building it. The testing and documentation will come first.

 

[EAS]

My first RC build, rookie mistakes? Yes, in truth, a Whopper!

It really is just the size. When I designed it, I sized considering the proportions between the motors and wings...not much other consideration. I really needed to stretch the distance between the wings by about 3 or 4"...and made everything bigger according to that difference. The result is that in order to make my calculated CG, I'd have to add 6 to 8 ounces on top of the nose gear. I can do that, I made all that removable, but it would also mean bigger nose gear wire and a bigger wheels. I knew this before I put on the main landing gear, but I intended to finish it regardless. I would've had to start over from scratch, right then with nothing to show. I can fix it with added weight in the nose, but I see that as unexceptable. Otherwise everything fits and works. My purpose from the beginning was to smoke this model in a living room sized wind tunnel. Still gonna, haha.

First RC build, quite a learning process. Version 2 on the board, but this one will be finished first.

 

[Piotrsko]

Just an observation but it looks like you have enough room to shuffle stuff around so the heavy stuff is forward assuming it is mostly sitting on the CG now. With a tandem wing you may be able to deal with a slightly aft of calculated CG if there is enough rear authority.

 

[EAS]

Yes, I've looked at that carefully. It would mean moving and rebuilding most of the center section, and I'd still only be able to move the battery 3" forward, plus the ESCs and extending the motor wires....etc. From what I've done so far, I've figured out a number of improvements that will make a big difference (including 25 to 40% larger). This model is still good for testing many things, including the living room sized wind tunnel I want smoke it in and document. I feel I should move on to the next version....sooner than later. Still going to finish this one soon, but only for testing. One in particular, torsional stress of the wing-tips and winglets. Running the motors at full and looking for vibration and twisting.

To me, documenting what my winglet configuration does to the air is more important than flying it.

 

[EAS]

I'm still working on putting my transmission back in my truck...a couple more weeks.

I'm getting close to finishing the fuselage foam. Everything else is done, except covering the wings. I chose to use tissue because I've done it before. I didn't want to try something new. The only process I've used is typical dope, but I'm concerned it'll dry too fast, plus I'd like to use a paint that's not compatible with the old fashioned dope. I've got nitrite, which may also dry too fast. So I'm studying different tissue processes including doing it wet. I haven't decided which way to do it and I'm quite apprehensive about it. Anybody with tissue experience... advice is appreciated.

 

[Matthewdupreez]

I'm still working on putting my transmission back in my truck...a couple more weeks.

I'm getting close to finishing the fuselage foam. Everything else is done, except covering the wings. I chose to use tissue because I've done it before. I didn't want to try something new. The only process I've used is typical dope, but I'm concerned it'll dry too fast, plus I'd like to use a paint that's not compatible with the old fashioned dope. I've got nitrite, which may also dry too fast. So I'm studying different tissue processes including doing it wet. I haven't decided which way to do it and I'm quite apprehensive about it. Anybody with tissue experience... advice is appreciated.

why not use monokote? or some other type of plastic covering? they come in all colours, so you won't need to paint it

 

[EAS]

why not use monokote? or some other type of plastic covering? they come in all colours, so you won't need to paint it

I appreciate all responses, but I did explain that in the post you quoted.
Thanks