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Peter Miller24/01/2019 16:00:05
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10152 forum posts
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I love the odd ball aircraft. Recently I found this video on You Tube showing Frad Knapp's Li'l Cub breaking the Worl Stol record in Valdez, Alaska.

**LINK**

Here is a still just to tempt you

lil cub 2.jpg

I just had to build it.

Model is going to be 54" Span for electric power

Plans drawn. Building has started.

Peter Miller24/01/2019 16:07:55
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10152 forum posts
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l.cub 1.jpgI spent a lot of time working out the best way to build it.

The cabin sides are 1/32" ply on the outside with an inner lamination of 3/32 balsa. THis is so I can make good round grooves to take the balsa dowel for the rear fuselage. Stucture.

Lightness is vital. Electric power is the only way togo with this model because pacticing STOL will almost certainly result in nose overs, Starting an engine a dozen time flight is not fun.

The first step is to make the joint between the dowel and side. This needs a half round groove. Fortunately I have a 1/4" Abrafile but a good 1/4" round file will do or you can gouge it out with a sharpened 1/4" sharpened brass tube

 

Edited By Peter Miller on 24/01/2019 16:08:51

Nigel R24/01/2019 16:20:55
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That is certainly short!

A lot of slats, some big flaps, and looks like every bit has been lightened as much as feasible.

What AUW are you aiming at? I would think at 54" you need to be down in the 2lb - 2-1/2lb region?

Peter Miller24/01/2019 16:29:40
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10152 forum posts
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Yes, Hoping to be in the 2 lb area. Well those 1/4" balsa dowels only weigh 7 grams each!!

Former Member24/01/2019 17:21:40
1322 forum posts

[This posting has been removed]

ken anderson.24/01/2019 17:38:30
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eyes down here as well peter......

ken anderson....ne...1.peter miller dept.

Former Member24/01/2019 17:52:26

[This posting has been removed]

Peter Miller25/01/2019 08:25:36
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10152 forum posts
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Well another bit further.

Buildong thye sides over the plan. Because the sheet parts are on the side of the tubular parts I had a mirror image printed off so I can build both at once. Also tryingto build the second side over the first would have been tricky with round member this was a good idea.

l.cub3.jpg

Here the longerons have been glued into the grooves in the sides.

 

l.cub 4.jpg

Shaping the joints is a lot harder with round stock. Not only do you have to get the angles right, the hollows have to be at the same angle

l.cub 6.jpg

The side has been built. The vertical member at the tail end is not fitted because when they are joined the fin post will go down and form that member.

Not sure if I should make that out of birch dowel in case the fin gets knocked but then hinging might be a bit of a problem. We shall see

My drawing shows the diagonals as being 3/16" however I found that the joints would have been much weaker so kept them the same as the longerons

Edited By Peter Miller on 25/01/2019 08:27:34

Edited By Peter Miller on 25/01/2019 08:28:07

Ron Gray25/01/2019 09:42:26
1441 forum posts
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Brilliant Peter, just what I want but at about twice the size with carbon tube for fuse.

Peter Miller25/01/2019 10:32:57
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10152 forum posts
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Well You can always enlarge my plans.

There is some curvature on the plan view. Not sure how well carbon fibre tube will do that.

Former Member25/01/2019 11:04:50
724 forum posts

[This posting has been removed]

Peter Miller25/01/2019 11:16:03
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10152 forum posts
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I am using the scale Piper Cup section USA35B but with the bottom flat instead of very slight undercamber.

At the size I am building it the undercamber is barely visible.

I am not using the slotted flaps. In fact the flaps are acurally curved down and I am making them flat like the ailerons.

Just for added interest. I found this You Tube video of a walk round which shows some morfe detail in close up.

https://www.youtube.com/watch?v=UZLH_2tMoGo&t=88s

I am also simplifying the tail mounting and have reduced the extreme longitudinal dihedral.

Edited By Peter Miller on 25/01/2019 11:16:51

Nigel R25/01/2019 11:57:31
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3040 forum posts
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Looks almost identical to the infamous Clark Y.

Are you putting LE slats on?

Thinking about wing loading, the full size Cub is 7:1 aspect ratio, I think. At 54" that's looking like 400 (ish) sq in, giving a loading of around 12oz / sq ft with a 2lb AUW, which certainly works for a slow flyer. At 2-1/2lb, it's14oz /sq ft.

WCL for both AUWs is 6 and 7.6.

A slightly challenging weight target with a wood build at this size I think, but certainly not impossible. I got 3lb dead on with a 500sq in wing of 52" span, using all sheet construction. Lots of open framework would knock that down a good bit and lighter drivetrain and radio gear could be used.

Speaking of which, what sort of batter / motor / servos are you using?

Dave M

What was your J60 AUW?

Former Member25/01/2019 12:37:09
1322 forum posts

[This posting has been removed]

Peter Miller25/01/2019 12:39:01
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10152 forum posts
1192 photos
10 articles

It is very similar to Clark Y.

Yes, I am fitting slats. I used them on my scale Legrande Simon and they really worked.A pain to make but...

As fpor the area, the Li'l Cub has had its wings cropped where the tip curvature starts.the model is in fact just under 1/6" scale so the chord is 9 1/2 " which will give it a bit more area

Martian25/01/2019 13:45:23
2217 forum posts
1091 photos

Looks great I'm following Peter

Ron Gray25/01/2019 15:10:45
1441 forum posts
363 photos

This is what I’ve really lusted after **LINK**

Peter Miller25/01/2019 18:12:43
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10152 forum posts
1192 photos
10 articles

Well not the same but it might be a lot cheaper to buildlaugh

Nigel R25/01/2019 19:00:50
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3040 forum posts
474 photos
Great stuff. More wing than I'd guessed. It'll work out quite close to daves j60 I should think. Wing loading that is. What are the slat going to be made from?

Edited By Nigel R on 25/01/2019 19:01:07

Peter Miller25/01/2019 19:25:47
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10152 forum posts
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The slats will be laminated from 1/32 and 1/16" sheet balsa.

On the Legrande Simon I shaped a piece of hardwood to lamintae them, This time I ma just use the wing leading edge if I can't find the old pattern

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