Ladder21

Here is my latest creation...

It is a Sig LT-25 kit that I modified into a twin. I removed all dihedral, so the wing is flat. I installed one servo for each aileron, and converted the wing to attach with bolts instead of rubber bands. I am using two O.S. LA-.15's, with Master Airscrew 8 X 4 props, and two 6 oz. tanks as well as two mini servos for throttles. It balances perfectly with an 1100 mah NiCd Rx battery all the forward in the nose. All up dry weight is 5 lbs., 2 oz.
It flies like a trainer with two engines...duh? I have 7 flights on it without any engine out situations yet. It will easily take off at half throttle.
Thanks for looking.

w8ye

My Feedback: (16)

Good job and a neat plane

Enjoy,

Jim

eastkurt

diegoconsafos, beautiful!!!!
I am having some wings without fuselage and have been considering using them for a twin, so if you have some pics from the building it would be very much appreciated.
Thanks
/Kurt

teufelhund

My Feedback: (2)

Diego, Nice twin! I like the covering scheme also. Got any in flight pics?

Ben

Ladder21

Thanks to all of you for the kind words. I am sorry to say that I don't have any construction photos. If you want, I will try to upload my "plans" for the engine nacelles, when I have more time. Also, I don't have any flight pics right now, but next time I go flying, I will see if I can get my "photographer" (wife or daughter) to go with me to take a few pics.
Thanks again.

Jay

IWC

any word on the nacelles

Ladder21

Here are my very crude hand-drawn "plans" for the nacelles. There are two views: side view and top view. Each view has two parts that need to be printed and joined together. Also a few more pics. Let me know if you have any questions.

Jay

w8ye

My Feedback: (16)

What about thrust angles?

I would think as high as the thrust line is that you would have no down thrust?

Do you have out thrust on both engines?

Enjoy,

Jim

Ladder21

w8ye,

Out thrust: 4 degrees each engine. (Right engine has right thrust & left has left thrust)
Down thrust: 4 degrees each engine. Original plans show 6 degrees of down thrust with one engine.
I believe mine should have more down thrust. If I trim it for level flight at half throttle, then go to 3/4 throttle, it wants to climb quite a bit. As I understand it, this is characteristic of a flat bottom airfoil and can be somewhat corrected by using more down thrust. Anyone disagree with this?
Also, next time I fly I intend on partially filling one tank only, so I can see how it will fly with one engine. I will let you know what happens...
Yikes!

Jay

BillS

The airplane is pretty and appears carefully constructed.

If your radio has enough capabilities it will be safer to shut one engine back to idle with the radio.

Bill

Ladder21

Bill,

Thanks. I will try to figure out if it is possible to use my radio to set one engine at idle in flight. Presently, I am using a wye to the throttle servos, and have flaperon/spoilerons activated on the ailerons. My radio is a 7CHF Futaba. (I also have a Century Hawk Sport Whirlybird)

Jay

w8ye

My Feedback: (16)

diegoconsafos

There are ways to determine your engine thrust angle needs and your wing incidence requirements.

To trim the plane and run it wide open throttle, trim it out, then chop the throttle.... See what it does? If the plane tries to immediately climb, you had too much down thrust. And, naturally, the reverse of this is true.

If you get your engine thrust correct and it tries to climb at higher speeds, you may have too much positive wing incidence.

Looks like you've done some homework already to have the outward thrust on the engines.

Enjoy,

Jim

eastkurt

diego,
thanks for the nice pics and drawings. Will assist immensely when I get around to bash my wreck.
/kurt

BillS

Jay,

For what it is worth. After shutting one engine back to idle it takes about two circuits to become disoriented. The ability to throttle up the dead one is mighty handy. Actually it allows the airplane to live while you learn dead engine characteristics. But shut down is a bunch of fun and will cause other flyers to pay attention and sometimes hide under the closest bench.

Bill

Ladder21

Bill,
The more I think about your suggestion, the more it appeals to me. Not only from the saving the plane perspective, but also from the "fun" standpoint. Thanks for the suggestion.

Jay

BillS

Jay,

Your pictures of the twin were an inspiration to continue a Cherokee bash. Thanks.

Bill

Ladder21

Bill,
Thanks, you big teaser. Now how about some pics! You can't say that and not show pics...
I have been pondering the best way to rig up my throttles so I have independent control on demand. I am thinking the best way would be to use my helicopter transmitter in helicopter mode and connect one engine to throttle and the other to collective. That way, I would be able to have "normal mode" both engines
"idle up 1" left engine off
"idle up 2" right engine off.
I've just been to busy to fly or even tinker...
If I figure it out and test fly it I'll let you know
Jay

BillS

Jay,

My workmanship is nowhere close to your skills. Must have been standing in the wrong line when building skills were being passed out. I will take some pictures over the weekend.

If you fly Futaba I might have some suggestions. I use the knobs to sync the engines and switches to drop to idle (5000 RPM). The engines idle at less than 5000 RPM but on simulated shutdown mine need to be at fast idle to prevent real shutdown.

Bill

Ladder21

Bill,
Thanks again for the kind words...
My wife often says I'm a pain-in-the-***** anal-retentive perfectionist...

10-4, I do fly Futaba so I will do some more thinking (dangerous for me) and keep in touch with the outcome.

Jay

BillS

Jay,

The beat up, banged up and broken Cherokee seemed like a candidate for another twin experiment. Had two 25’s that were previously on the Kadet Senior but inadequate to fly with any reserve power (10.5 pounds). The Cherokee center engine mount was left in place just in case more oomph is needed. The engines are snug against the wing. Stability is better if the engines are further forward but alas a lack of building skills interfered with construction of nacelles. Your nacelles look good and a ideas will be borrowed next time. Four-ounce oval tanks (glue bottles) fit inside the tank covers behind the spar. The plain bearing engines are reasonably thrifty but I should make a timed full throttle run.

Looks like it is going to balance OK.

The Kadet is being flown with 45’s and the center engine has not been cranked in 30 flights.

Bill

Ladder21

Bill,
Awesome projects. Is that red and white wing on the bottom right from the Kadet? And do you have two tanks for each engine? Or are the two tanks in the center for the center engine in the fuselage? What engines do you have on the Cherokee? The Kadet? Have you test flown the Cherokee yet? Do I ask too many questions?
Later.

Jay

BillS

Jay,

I have not flown the Cherokee. Someone else crashed it while single engine. I started making it a twin. Your inspiration helped finish building the firewalls, tank covers and repairing crash damage. The Cherokee has OS 25 plain bearing engines. Now that I know it will balance without center engine I am looking for a cowl to cover the front end. Didn’t weight it but it feels light.

The red wing is from the Kadet with three engines. The tanks service the outboard engines. Started with 25 size outboard engines and now have 45’s. It will barely fly on 25 outboards only and is a beast with one 25 outboard only. Flies well with one 45 outboard. Took off the driveway once with 45’s and a switch set to simulated engine shutdown by mistake. Have asphalt rash on the right wing and almost got a driveway light. Will get more pictures soon.

Bill

JustPlaneSweet

Ladder21,

I have an LT-25 and a couple of OS 15CV-A engines for a twin conversion. Any recommendations after two years with your setup?

Thanks,

Stan

somegeek

My Feedback: (2)

Wow - nice build!

How much does that 1100mah pack weigh?

somegeek