Twin-Air .20 - Anyone here scratch build one before?  
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All Forums >> RC Airplanes >> Twin & Multi Engine RC Aircraft >> Twin-Air .20 - Anyone here scratch build one before?
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Twin-Air .20 - Anyone here scratch build one before? - 7/25/2003 9:39:54 PM   
Don T. - NN4S



Posts: 59
Joined: 7/2/2003
From: Toney, AL, USA
Status: offline 		Well, after all of the threads about how good a first twin the Twin-Air series planes make, I decided to get one to train on & get acqainted with twins while working on my OV-10 kit (HH). I wanted the .20 size version so that I can use the same engines that the Bronco will be using (Saito .30s). Problem with this idea is that I couldn't get that kit anymore & the .15 size kit isn't available yet! Anyway, the plans for the .20 were available and I ordered a set of them so that I can scratch-build one. It's going to take time away from the Bronco but I figure better prepared than picking up pieces!

So my question stands: Has anyone here scratch built one of these from the plans or only the kits? Are there any plane-specific weak areas that I should be made aware of? Since I'll be cutting all of my parts I figure it's beter to know ahead of time; that way I can beef them up with stronger materials in the first place! On the other hand, if it's perfect as designed then I'd like that feedback as well so that I won't go second guessing the designer & just end up adding weight. It'll be a grass field plane as well as my first experience flying a twin so keep that in mind as you respond. Thanks!

_____________________________

Don T. NN4S NN4SatARRLdotNET
Building again & loving it!
       Post #: 1

Twin-Air .20 - Anyone here scratch build one before? - 7/25/2003 11:09:44 PM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Don T:

Is that short (long?) for Dante? Just curiosity.

The Twin-Air series is a solid design, neither too heavy not roo light, and strong enough to last a long time.

Some minor things to alter:

Flying from grass you might want to go with a taildragger configuration, doing this you can eliminate the heavy front fuselage former, and some of the reinforcments in the nose area.

The wing is a solid design, no weak spots, provided you are careful about the gear mountig blocks. And flying from grass, use all three rib reinforcements on each block instead of staying with just two.

You will like the plane. I just got a pair of HB 21 engines for mine.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to Don T. - NN4S)
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Twin-Air .20 - Anyone here scratch build one before? - 7/26/2003 7:48:35 AM   
Don T. - NN4S



Posts: 59
Joined: 7/2/2003
From: Toney, AL, USA
Status: offline 		Nope, just my name! There are a lot of Dons around here so the initial for the last name works to differentiate & it's become habit. Nothing so deep & sneaky behind it...

I like the idea of it being a tail dragger since that's what all of my other planes are. The Bronco obviously won't be one, but why force myself to deal with trike gear any sooner than I have to? It'll let me get away with being more comfortable flying it & I also intend to use a yaw gyro to aid in the transition. I use the rudder frequently and am not likely to forget to use it since I still fly single-stick but I don't wish to take any unnecessary risks with the twin. I have a buddy who's been flying for years who got bit badly on his first twin and he's got much more experience than I. Learn from other's mistakes, that's the plan!

HB.21s? Not the .21 Gran Prix perchance? That's a hot combo for sure! Mine will have the Saitos & three-blade props that will end up on the OV-10 so that I can get even more familiar with them before flying them on it. I've currently got one of them on a Mud Duck and the other on a Kadet LT-25 to break them in and get a bit of time on them before the twin. They should be a well known quantity by the time they end up on the twin; one less thing to worry about!

_____________________________

Don T. NN4S NN4SatARRLdotNET
Building again & loving it!

(in reply to Don T. - NN4S)
       Post #: 3

Twin-Air .20 - Anyone here scratch build one before? - 7/26/2003 8:41:28 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Don:

As I said, the Twin-Air is an easy build, and an easy flyer.

One bit of advice you're liable to get is to build it with out thrust on the engines. DO NOT DO IT.

The T-A, with either engine out, is no problem to fly. VMC is seemingly below stall speed, so if the plane has enough speed to fly, it has enough speed to fly with one dead and the other at full throttle.

Out thrust is not a safety measure on this plane, it's merely an unneeded crutch that decreases its twin engined performance.

Going taildragger, if you're lazy, can be done easily. I mentioned the wire legs angle about 45 degrees down and out from the gear blocks. The wires look long enough to bring the angle closer to 90 and bend them forward without getting the wheels too close together. You also could bend new gear and keep the wide track. You could also remount the gear blocks further forward. I'm lazy, I look for the easy way.

Another good thing about going taildragger. The Twin-Air is developed from a single that used a 60-90 engine, and the front fuselage former is a big thick slab of plywood. Toss it, replace it with 1/8" balsa, and cut the center out. All it has to hold, as a taildragger, is the shape of the forward fuselage. And you have a block that mounts on it to form the nose. Hollow the block too. And the plywood doubler for the side of the fuselage isn't needed forward of the wing's LE either. Save some more weight. Trim it.

Those are just a few points, when you start to build come on back and we'll discuss some more points.

Or build it completely stock. It's still an excellent flyer.

Enough for now.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to Don T. - NN4S)
       Post #: 4

Twin-Air .20 - Anyone here scratch build one before? - 7/26/2003 9:17:57 PM   
Don T. - NN4S



Posts: 59
Joined: 7/2/2003
From: Toney, AL, USA
Status: offline 		Bill,

Since I'll be making all of the parts to build it myself, it won't be a problem just to make them the way I want them in the first place. I'll build the front end of the fuse as you say; no point in adding unneeded weight! As far as the gear legs are concered, I'll be bending them from scratch as well so no point in compromises! I prefer forward angled gear since it allows me to tailor the tracking of the plane. No reason to end up stuck with a plane that ground loops or noses over when you can adjust the position relative to the CG without any major effort!

Thanks for all th info, this is exactly the type of stuff I'm looking to find out before starting the project.

_____________________________

Don T. NN4S NN4SatARRLdotNET
Building again & loving it!

(in reply to Don T. - NN4S)
       Post #: 5

Twin-Air .20 - Anyone here scratch build one before? - 7/26/2003 9:40:36 PM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Don:

I made an error in my last post. When I said "Developed from a 60-90 design" I was talking about the Twin-Air 45.

The Twin-Air 20 is the reworking of a 40-46 single.

Other comments are correct.

Bill.

< Message edited by William Robison -- Jul 26 2003 4:49PM >

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to Don T. - NN4S)
       Post #: 6

Twin-Air .20 - Anyone here scratch build one before? - 7/26/2003 11:13:09 PM   
acobra



Posts: 161
Joined: 7/5/2002
From: Vincennes, IN, USA
Status: offline 		Don:
I've flown the twin Air and it flys good, just a comment on the engines you want to run. In my opinion the Saito .30 is by far and away a terrific engine...so go for them. Also being a single stick flyer myself I think this mode of flying is a definite plus for multi engine flying ( it's more natural if you need to get on the rudder). You can check out a picture of my latest twin a PBY-3) on the thread on 3-blade props

_____________________________

Bild to fly NOT to crash

(in reply to Don T. - NN4S)
       Post #: 7

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