A few years ago I designed a twin electric Stunt model that has a 530 square inch wing, a built-up fuselage, and profile nacelles. It was much the same in aesthetics as my big test bed twin, but with no retracts. It was reasoned that a small electric twin might be attractive to those who might wish to try an electric twin Stunt model, but with much reduced building time and much reduced cost. As for overall size, think of a Nobler with a longer tail moment.

As with the original big test bed twin, the smaller ship (name will either be "Double Take" or "Two Small") features a "Lost-Sheeting" wing. That's the name I gave to my adaptation of the Combat world's treatment of foam cores. They cover them with a low-temp plastic material, while I chose to apply .2 carbon mat using water thinned Titebond II glue. In either case the strength of the wing mainly comes from two imbedded 1/8 x 3/8-inch basswood spars - one on top and one on the bottom - that run full span and have a couple of 1/8-inch balsa shear webs installed between them. The basswood spars are glued into a slot in the top and bottom of the foam panels and are also glued to the shear webs, preventing "racking." This yields an incredibly strong wing at very low cost and very little building/assembly time.

The new small twin will be powered by E-Flite Park 450 motors (with the option to go to Park 480 motors if needed).
My question is: Would the readers/contributors here be interested in a photo essay of the build, and if so would they also be interested in plans and foam parts for this model?

Thanks - Bob

PS: Attached are a couple of photos of the original big twin test bed for reference as to what the new small twin will look like, and also a couple of photos of the Lost-Sheeting wing construction on one of the Joe Nall Cadets. - Bob

   



 

Oh yeah Bob! 
(But you already knew I would be very interested!)

Bob,
What is the motor/ESC/Timer/Battery set up for this ship? For the ESC how is it sized for amps?

Best,   DennisT

You've got me on the edge of my seat now

Bob,
So are you using two Castle Talon 25 ESCs (one for each motor) and a single 4S 2,800 mAh battery with Y harness and single timer with a Y harness? Just trying to understand how these twins are set up.

Best,   DennisT

Bob,
I think this is a very interesting thread. It would be great if you could go through the process for the Twins of initially selecting motors, props, ESC size, Timer options (with and without retracts) and battery size so it could be applied to different size ships. Would also be good to layout the wiring arrangements (like a one line diagram) and component hook-up arrangements (like the "Y" harnesses needed). Then the build pictures for the actual ship which you do a great job on always.

Best,   DennisT

I think I could see myself flying something like this. The more I look, and read through this... the more excited I get to see it develop. I'm a big fan of a "smaller" plane. Not that it's small, but I don't fly a lot of 60 sized ships. I stay around the sig twister size.

I always enjoy your builds!

Rob

Can't drive two motors with a KR timer. So you need ESCs that have RPM control and a Hubin timer.   In an earlier post it was mentioned that some one makes a twin motor timer.  Is that true?  How does it work?

I ran three motors with my KR. Worked fine.

Bob,
Can you post the layout sketch of the twin so we can understand the dimensions and how you arrived at the location for the nacelle. What wing airfoil did you select? Why?

Best,    DennisT

Of course, Bob.  Glad you like the syrup.
I'm looking forward to the rest of this thread,

Rick

You are a master Bob.  Everybody, pay attention on how Bob does things.  It will serve you well!

 IMO, what Bob is trying to do here really should motivate guys who wish to experience a twin , but desire minimal work and cost.
I built a full fuse twin," TURNING POINT", that Bob designed a few years back.
It's full house ; retracts and all.
 A treat to fly.
 In the hands of someone like Bob, it's a weapon !

wow Bob. Cool!

Two Park 480's???

I flew the first B-17 with 4 Park 480's at 120 ounces, and power was NOT the issue!
I suspect you will have "ample" power!

Good luck.

Bob, the old DOC gets a lot of info from your construction posts and I've borrowed a lot of them on different planes.  Thanks for all you do here.

Sweeeet!

Nice!

That is so cool. I like the process.

I'm pretty sure the Igor timer system has that feature as well, but I'm not certain of that. Someone enlighten me...

I see I again missed great thread here, sorry Bob I did not see it before. I like that building, I see I must show it to our kids, I am sure they will make milion of different models this way :- ))))

But to your question -

Yes and no  . My timer does not do anything only controlls motor. I always concentrate to make the function fully implemented tested and well working and not to give other side fancy functions. So no, my standard timer does not have any buttons, landing gears lights and similar things. However my timers are modular, so in case that model needs another function there is no problem to add any other specialized gadget. In this case I have specialized timer for landing gears synchronized with main timer. Of course it is programmable by Jetibox and beside its normal function it has also input for RPM sensor with adjustable rpm. It can be any standard R/C device, so it will work with sensor for standard motor, or also magnet sensor for IC engines etc. That means it can be used also without my timer with accelerometer. Optionally it can be also connected to speed sensor or centrifugal sensor, but that is not good solution because it needs very good ajusting (so that does not extend when model slows in fugures, but act safely when it is really needed, does not react to whipping etc.) and I think it is not good idea to test landing gears with risk of landing to belly. Setting RPM is much simpler, exact and repeatable even on ground. Timer has many settings, beside RPM for emergency gear down with adjustable servo angle, it has slow motion retracting to look better (but emergency gear down function is quick). Unfortunately speed setting has no effect with electronic LGs. And of course it has "go home" button/jumper.

It also works with normal servos and standard hardware with lock arm, also servos without lock arm (so that it make hardware much simpler) and it is also tested with servo-less electronic landing gears which has little bit tricky controlls. Chris can tell stories about it :- ))

Here is picture how to connect it with my normal timer.

Hi Bob, very, very interesting project! What are the dimensions of the model - wing span, wing area? What is the expected takeoff weight ?

Welcome aboard Maksim. 

Hey Bob, where are you getting you're carbon veil?

projected weight with battery is in the 45 to 47 ounce range.

Wow, It seems that this will not be easy to do, given that the moto setup will weigh about 20 ounces, an empty plane should weigh no more than 26 Oz. What density foam are you using? And how much does a wing weigh without flaps now? And another question: will the model be painted?

How's it going Bob, are you still working on this build?
Thanks

Wow! Thats BA!

Ditto!

Looks awesome Bob!! Can’t wait to see it!!