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Old Dec 09, 2012, 11:05 AM
MICROACES's Avatar
Joined Sep 2012
378 Posts
Help!
Designing & Building the Curtiss P-6E Bipe

As many of you will know Red Flyer won the Microaces poll and I have now cleared the bench to start the process of bringing the fantastic Curtiss P-6E Hawk together as a Microaces kit.



It is certainly a challenging aircraft to design and more-so to produce it in kit form so as to make it relatively straightforward to assemble and of course, cost effective to manufacture.

I thought it might be interesting if the design and build was laid out in this thread so everyone whose interested can see how it progresses and have the opportunity to input ideas and thoughts along the way if you wish.

The first subject I wanted to tackle was SCALE.

In some preliminary research I've tried to get a feel for how the aircraft behaves in the air, it's speed and agility. I've watched a few vids on line of larger RC Hawks and it would appear, unsurprisingly that its characteristics seem pretty docile.

With a top speed of less than 200mph the full scale aircraft was slow when compared to the WWII fighter aircraft already available as Microaces kits, but the hawk also appears fairly agile in the air as you would expect from an advanced biplane of it's era.

At 1/24th scale, that of the other Microaces kits, the resulting wingspan of this aircraft is going to be 368mm or 14.5 inches (if not profile scale the wingspan would be 8% larger to take into consideration the fuselage width) and I estimate weight would be 55-60g using the sticker method of construction.

Now that, to my mind, is too heavy and it would have to fly relatively quickly to keep airborne. Not scale like and not much fun!

Also if I want to stick to the same power train as the other kits (which ideally I would), the Hawk needs more frontage hanging out in the breeze to increase drag and not having it hurtling round the skies like a P51.

This all leads me on to consider the option of increasing the scale to 1/22nd or even 1/20th. I always expected that this would be necessary when considering WWI aircraft as potential subjects for kitting so I'm not surprised that I'm considering this on the Hawk too.

At 1/22nd scale the wingspan is a hairs breadth over 400mm or just under 16 inches with an estimated flying weight of 60 - 65g and at 1/20th the wingspan is 442mm (17.5 inches) with an estimated flying weight of 65 - 70g.

Both scales can be squeezed into the existing box so that's not a problem and the current power setup provides 90g thrust which would work for both.

My gut feeling says go 1/20th but I would like to get some other opinions on this as I know there are many out there with much more bipe experience than me.

I can always prototype both and see what feels best I s'pose!

Either way, any words of wisdom and helpful opinion would be most appreciated at this stage.

Jon
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Old Dec 09, 2012, 02:13 PM
miataman
miatamama's Avatar
Erie Pa.
Joined Oct 2007
635 Posts
Jon, Great looking and flying models, I love them all but I really like biplanes. I have built SE5a's in 10 12 14 16 20 24 and 32 inch using the same plan and every one was a great flyers. You could go from one size to another with only a few clicks of trim. I think any size you decide on would be good flying. Just my opinion

JCS
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Old Dec 09, 2012, 02:37 PM
Gravity is a harsh mistress.
Tim Wolff's Avatar
United States, MI, Temperance
Joined Sep 2002
6,518 Posts
Quote:
Originally Posted by MICROACES View Post
As many of you will know Red Flyer won the Microaces poll and I have now cleared the bench to start the process of bringing the fantastic Curtiss P-6E Hawk together as a Microaces kit.

It is certainly a challenging aircraft to design and more-so to produce it in kit form so as to make it relatively straightforward to assemble and of course, cost effective to manufacture.

I thought it might be interesting if the design and build was laid out in this thread so everyone whose interested can see how it progresses and have the opportunity to input ideas and thoughts along the way if you wish.

The first subject I wanted to tackle was SCALE.

In some preliminary research I've tried to get a feel for how the aircraft behaves in the air, it's speed and agility. I've watched a few vids on line of larger RC Hawks and it would appear, unsurprisingly that its characteristics seem pretty docile.

With a top speed of less than 200mph the full scale aircraft was slow when compared to the WWII fighter aircraft already available as Microaces kits, but the hawk also appears fairly agile in the air as you would expect from an advanced biplane of it's era.

At 1/24th scale, that of the other Microaces kits, the resulting wingspan of this aircraft is going to be 368mm or 14.5 inches (if not profile scale the wingspan would be 8% larger to take into consideration the fuselage width) and I estimate weight would be 55-60g using the sticker method of construction.

Now that, to my mind, is too heavy and it would have to fly relatively quickly to keep airborne. Not scale like and not much fun!

Also if I want to stick to the same power train as the other kits (which ideally I would), the Hawk needs more frontage hanging out in the breeze to increase drag and not having it hurtling round the skies like a P51.
Increasing drag (all other factors unchanged) will only increase your power requirements and inhibit the ability to glide. Lowering the wing loading does more than anything to decrease a plane's min. flight speed. Airfoil choice being another important factor.

This all leads me on to consider the option of increasing the scale to 1/22nd or even 1/20th. I always expected that this would be necessary when considering WWI aircraft as potential subjects for kitting so I'm not surprised that I'm considering this on the Hawk too.

At 1/22nd scale the wingspan is a hairs breadth over 400mm or just under 16 inches with an estimated flying weight of 60 - 65g and at 1/20th the wingspan is 442mm (17.5 inches) with an estimated flying weight of 65 - 70g.
If your shooting for a indoor/gym flyable plane, all the estimated weights are nearly twice what they need to be IMHO.

Both scales can be squeezed into the existing box so that's not a problem and the current power setup provides 90g thrust which would work for both.

My gut feeling says go 1/20th but I would like to get some other opinions on this as I know there are many out there with much more bipe experience than me.

I can always prototype both and see what feels best I s'pose!

Either way, any words of wisdom and helpful opinion would be most appreciated at this stage.

Jon
Feel free to accept/reject/ignore my observations. I'm posing only in an attempt to be helpful. Profile scale planes don't float my boat.
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Old Dec 09, 2012, 04:51 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
130 Posts
Watching with interest...

As above, how does wing area (and hence loading) compare to you previous efforts? At the weights you're talking, I'd be leaning to the larger scale. Small, heavy and fast is no fun, and with a biplane subject you might have some customer expectation of slow and floaty flight characteristics.I don't see any reason why you have to keep the same scale. It's quite a different subject to the ww2 fighters (first of a series of thirties biplanes, perhaps?).

Why not knock out a few prototypes? I suspect you're going to go through more than two to get this one sorted. Any chance of forming an undercambered aerofoil instead of going with a flat plate?
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Old Dec 10, 2012, 12:17 PM
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Paris (France)
Joined Jan 2006
839 Posts
To have a decent wing loading, you should choose a wing span around 20" and the weight should be less than 80g.
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Old Dec 10, 2012, 01:31 PM
MICROACES's Avatar
Joined Sep 2012
378 Posts
Thank you chaps for your time and wise words.

I should have mentioned I'm working with several restrictions. The size of the box restricts wingspans to a max of 18.5", the covering material, as wondrous as it is for the graphics and ruggedness it brings to the airframe, it also loves to lay flat, so cambered surfaces, especially the 'under' part will be troublesome.

I am with Jim_the_Sane on this one. I'm going to produce several prototypes of various sizes and get them airborne to see how they do. I will try the 1/24th scale too as I have a few 'tricks' I have in mind for this build to get things slow but working with the materials & techniques we've developed.

Having that AP05 with its relatively high thrust capability gives quite a bit of room for movement if you know what I mean

Right, time to design up the airframe!

Jon
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Old Dec 10, 2012, 07:40 PM
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Joined May 2012
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Quote:
Originally Posted by MICROACES View Post

Now that, to my mind, is too heavy and it would have to fly relatively quickly to keep airborne. Not scale like and not much fun!

Also if I want to stick to the same power train as the other kits (which ideally I would), the Hawk needs more frontage hanging out in the breeze to increase drag and not having it hurtling round the skies like a P51.

You want to increase drag in the front?

Easy!!!

Drop the "P" and add an "F" and build it as the F6C USN/USMC version with the P&W 1430 radial out front.

If you do, please build it in 1/22 scale and do an extra nice job on the engine. I need it for the F6C I'm building.
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Old Dec 12, 2012, 09:02 AM
MICROACES's Avatar
Joined Sep 2012
378 Posts
Alphabetical suicide!

Now that would be hard to do as a profile scale model. Open radials like that are a little tricky and weird looking as a profile flat surface. Looks like you'll have to get the fettlin' & whittlin' tools and make it from scratch

However I think 1/22nd would be an interesting scale. I've just printed off the Depron templates for the 1/20th scale aircraft and it look massive! But then again I am used to the little fellas.

Jon
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Last edited by MICROACES; Dec 13, 2012 at 09:07 AM.
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Old Dec 13, 2012, 04:47 AM
MICROACES's Avatar
Joined Sep 2012
378 Posts
Got the profiles down on computer then cut out the outlines of the main airframe components.

Still got to cut the cavities into the parts. This is the 1/20th scale airframe. Wingspan is about 17.5" - about the same as the 1/24th scale Mustang.

It 'feels' about right for this biplane; all the spaces for the electronics are ample and there's plenty of wing surface. Should build up quite quick over Christmas.

Jon
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Old Dec 14, 2012, 08:48 AM
Fly Low - Hit Hard
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Canada, ON
Joined Oct 2010
858 Posts
Hello Jon and all,

I have been on vacation for a bit and I am very interested in this project !

Incredible progress!

RF
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Old Dec 14, 2012, 09:51 AM
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Joined Nov 2012
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Volunteer

Okay, I'm gonna stick my neck out and volunteer.

The National Museum of the US Air Force (aka the Air Force Museum) is just about an hour up the road from where I live. They have a P-6E Hawk on display, and it's done up in the 'owl' paint scheme that everyone likes so much. I need an excuse to visit there again, so . . .

If you need any technical data, measurements, detail photos, etc., that a trip to the museum might answer, just let me know, and I'll try to get it for you. I can't promise what the turnaround time might be, but I'll make every effort to be prompt.

So let me know if I can help. It should be an interesting project. If you're interested, I'll contact you thru the Microaces web site.

And, for the record, I vote for the largest scale and lowest wing loading you can do for this bird. Is it possible to turn the wing diagonally in the box, and get a bit more span? Probably not significant but, hey, I had to ask.

Enjoy!
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Old Dec 14, 2012, 11:44 AM
MICROACES's Avatar
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Originally Posted by Hatman View Post
Okay, I'm gonna stick my neck out and volunteer.

The National Museum of the US Air Force (aka the Air Force Museum) is just about an hour up the road from where I live. They have a P-6E Hawk on display, and it's done up in the 'owl' paint scheme that everyone likes so much. I need an excuse to visit there again, so . . .

If you need any technical data, measurements, detail photos, etc., that a trip to the museum might answer, just let me know, and I'll try to get it for you. I can't promise what the turnaround time might be, but I'll make every effort to be prompt.

So let me know if I can help. It should be an interesting project. If you're interested, I'll contact you thru the Microaces web site.

And, for the record, I vote for the largest scale and lowest wing loading you can do for this bird. Is it possible to turn the wing diagonally in the box, and get a bit more span? Probably not significant but, hey, I had to ask.

Enjoy!
Hatman that is fantastic stuff. Thank you so much for your offer. I would love to pay a visit myself but I don't think the budget can stretch that far just yet

I've been able to reference quite a few photos of the aircraft so far but none really have too much detail. What I would particularly be interested in is those areas that go un-photographed normally.

That is to say upper and lower flight & control surfaces (although I realise it might be a bit difficult to get the top of the wing).

Inner surfaces of the wheel spats and legs, any panel and hatch detail, cockpit edging, surfaces and details around wing spars and aileron control strut, armament, rivet detail etc.

Basically all the stuff that people are normally not that interested in but when you have to illustrating every surface of the aircraft you need to know to ensure good detail.

Oh - also any stencil work on the aircraft as well and other markings, both port & starboard. Aircraft can be quite asymmetric in both structure and livery so it's important to get both sides.

And believe me your efforts will not go unrewarded!

I've attached a sample of the images I've found on t'internet. As you can see they're OK but when your illustrating fairly fine detail they lack something - apart from the closeup of the Owl - that's perfect!

As for squeezing more span, I'm afraid that 1/20th scale is about it. The boxes for the kits are long but narrow. But I have to also balance the power aspect as well, with a maximum of 90g thrust. With a 5030 prop and all that surface area I think it should be a good match.

Jon
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Old Dec 14, 2012, 01:35 PM
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Charlottesville, Virginia, USA
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Very interesting!

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Old Dec 14, 2012, 04:28 PM
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deadbird's Avatar
UK. Dorset
Joined Jun 2009
375 Posts
Instead of going to the pub this evening I decided to crack on with the Hawk. All cavities now cut out. Next job is to cut out the channels for the carbon fibre bracing in wings and fuselage and for the aileron control rods, cut the 45 degree bevel into the LE of the ailerons, rudder and elevator and start work on the strut system and undercarriage.

Sure is thirsty work! Cup of tea I think

Oops, logged in as my previous incarnation. Deadbird - AKA MICROACES
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Old Dec 16, 2012, 11:28 AM
Registered User
Carbondale PA
Joined Aug 2005
513 Posts
Jon,

This should be a great flying plane, and perfect for your new covering technique! The extra drag of the biplane will require more power, but the extra wing area with also give you a slower flying model. I would love to see it fly at 14.5 inches, but it will be a winner at any scale.

Joe.
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