Chevelle

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Hi,

I am getting back into R/C after a 25 year absence. (Man! The gear has changed!!)

While I am relearning, I will be working on my dream project which is an R/C version of an AVRO Triplane IV. I have already "mic'ed" a SolidWorks 3D model 1:1 from the R/N kit that I build 25 years ago. I will be purchasing the kit again and remodel it in SolidWorks from those plans to an R/C scale.

My question is a "chicken vs. egg" kid of thing. Do I select the motor and scale the model around that or scale the model and then pick an appropriate motor for it's size & weight?

More about the motor.... The AVRO had an inline motor that sat out in the open in a "V" shaped forward fuselage. This can't be a megabuck project so is there a motor that would not look too out of place for a 1910 vintage plane?

Right now I'm leaning to 1:6 scale but I might go to 1:4. (There is a lot of open framing in that plane. I may need the larger size to hide the rcvr, servos, etc.)

Any thoughts and suggestions would be greatly appreciated. If anyone has a set of the R/N plans, that would save me the trouble of getting the kit just for the plans. I would be happy to provide the 3D model in return.

Thanks!

BMatthews

Obviously you'll want a 4 stroke engine for starters.

Secondly, you're going to want to build this very much faithfully to the original R&N free flight style of construction. This means it'l be very large and light compared to most of our P51 Mustang or F18 like power to weight ratio style models. Think SAM old timer set up for sport flying rather than contest climbs.

For example if you use an OS 48 Surpass or a Saito 56 to 60 I don't think an 800 to 900 sq inch wing area would be at all out of the question as long as you can keep the weight down to around 6 or7 lbs ready to fly. This is NOT going to be a model for windy days obviously. But when it does fly it would look SO nice as it floats by.

Functional rigging using Proctor turnbuckles and control line steel cable would help keep the structural wood sizes down and add to the mystery. I can see this model being built entirely out of skinny spruce sticks that are close to the original scale sized wood. Or a spruce and balsa mix. Spruce edges, longerons and spars with balsa cross peices, ribs, formers, etc.

Am I close to what you want here? To add some credance to what I'm suggesting I have a OT Flamingo on radio assist that is 84 inch span, about 1000 sq inches, weighs 5 1/2 lbs and flies with fine authourity on an old OS loop scavenged stunt 35 two stroke. If I throttle back to about 1/2 revs it flies pretty much as I would want to see your Avro doing. Gentle climbs and definetly flying on the wing rather than the prop. At full throttle it gets up to about 600 feet in less than one minute.

Chevelle

My Feedback: (2)

You've given me a place to start. I'll look into those engines and get a feel for where the model should end up in size and weight.

Yes, this plane will definitely fly from wing lift, not prop spinning. It would look pretty odd to see it hovering on its prop, snap rolling or hammerheading!!!

Right now, I am contemplating one concession and that is ailerons. I don't think I'm up to a complete wing warping setup. I don't know if I'll put them in the wing or possibly interwing as in the Curtiss pusher. The latter would be more period but certainly historically inaccurate.

I will have the opportunity to visit the Shuttleworth Collection in England some time in the next six months. (I just returned from a UK business trip and visited the Duxford museum.) Hopefully I will be able to gain some first-hand information that will help with the project.

I dug up the SolidWorks model that I did a few years back. It isn't as accurate as it should be for building purposes. (It did it just as a test.) Here is a rendering of the incomplete model...

BMatthews

Yes, that would look a little odd wouldn't it...

COWARD Actually with a couple of the 1/4 scale servos and if you kept the wing construction and design as per the original there's no reason why the wing would not be flexible enough to react very nicely to the power of the 1/4 scale servos. I suggest two as then you could use a computer radio with the pair programed for extreme differential in their respective throws so only the up bending trailing edge would move. Mind you I suspect it wouldn't be the end of the world if you warped them in a symetrical fashion but if you try that I'd use some thumb or computer coupled rudder to offset any adverse yaw from the down warping wing. Extreme warping commands at low airspeed may want to stall the up warping wingtip so it's important to keep your speed up above that point. That's why I suggest the two servos and extreme differential.

Of course all that would only work if you use the scale rigging.

Hmmmm perhaps ailerons WOULD be easier... but I'd just use regular strip ones that are easier to "hide" and make the model look as scale as possible. A smooth upper suface hinge using the iron on covering with an inverted V on the lower side for movement allowance would be all but invisible from more than a few feet away. It would certainly look nicer than the Curtiss types.

Chevelle

My Feedback: (2)

My thoughts exactly regarding the ailerons with just one exception. I thought I'd put them in the middle wing. They would be even less noticable and the control linkage could be all internal to the middle wing from the fuselage. There would be no need to have control rods or even rigging to control upper wing ailerons. There is just no way that a servo would fit in such a thin wing.

BMatthews

Oh, did the original warp the top wing?

I was sort of assuming that the strip ailerons would go on the middle wing just to make things easier.

Chevelle

My Feedback: (2)

My assumption is that the whole wing assembly (at least the middle and upper anyway) warped. From the look of the model and from the pictures that I have of the one at Shuttleworth, there doesn't look to be any isolation between one wing and another. I don't see how one could be warped and the other(s) remain stationary.

wrbirch

My Feedback: (1)

Guys, A question from a newbee, how do you warp a wing, Is it just twisting the ends of the wing for more or less incedance? or what ?
thanks
Bill

BMatthews

Got it in one....

Of course the wing structure has to be made flexible in torsion to some extent to accomadate that. So the forward set of bracing wires (all the warpers I've ever seen use wire braced wings) are fixed and structural and the rear set is run through a bunch of pulleys to the stick for warping control. The lower rear wires handle the lift loads by being fixed to the two wings and running through a set of pulleys somewhere down low. the pulleys lets the wire shift from side to side during the warping but still takes the flight loads. The Fokker Eindecker is a fairly easy to understand example of all this.

wrbirch

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thanks for the explanation

Chevelle

My Feedback: (2)

The design work progresses... and surprisingly well.

I have completed the first pass at all three wings, including the ailerons for the middle wing. I am sure that I will have to add more stuff to the wing models when I have done some of the rest of the plane.

By the way, I would be happy to share the information that I have with anyone that is also considering this plane. Maybe we could share some of the material cost when it comes time to get some of this made. There are about 120 ribs. I figure I will have them cut for me, most out of balsa, some spruce and a few that are double thick.

You can email me at [email protected] if you are interested.

Chevelle

My Feedback: (2)

Here is a close up of the ailerons. The wing span is 64". The cord is 7". The ailerons are 10.5" long by 2.6".

The edge of the wing where they attach is vertical. The leading edge of the ailerons are angled back at 22.5° from the top to the bottom. This should look better when the plane is viewed from the top with no aileron applied.

(I increased the spar from .5" by .25" shown in the picture to .75" by .25". I was uneasy with such a small spar in those long wings. I don't want a wing warper! This will also reduce the workload on the rigging.)

Any suggestions are welcome.