Slingsby Skylark 2

[Alan_Perse]

At smaller scales full size airfoils don't usually work. it's all to do with Reynolds numbers.

As Alan says Chris Wiliams advocates the Quabeck sections even in his 1/3 scale aircraft

Ah, you got there before me Bill    

[Ron]

Ah yes, Reynolds Numbers.

Wikipedia:
If an airplane wing needs testing, one can make a scaled down model of the wing and test it in a wind tunnel using the same Reynolds number that the actual airplane is subjected to. If for example the scale model has linear dimensions one quarter of full size, the flow velocity of the model would have to be multiplied by a factor of 4 to obtain similar flow behaviour.

Ron

[billscottni]

One of our club members is a real airfoil buff. Right in to the whole mathematics of the things, which is how I know it.

If anybody is looking for good, SIMPLE, explanations try:

Understanding Aerofoil Date for RCSoareres, by Denis Oglesby. Available from Traplet

and/or

Understanding Polars without Math by Bill & Bunny Kuhlman available from
B2 Streamlines, http://www.b2streamlines.com/

[Ron]

Thanks for that Bill.
I shall certainly look into those books.

B2streamlines also has a good few links to aerofoil plotting apps for Mac. :clap:

Ron

[Alan_Perse]

Finally started some construction. I'm starting with the fuselage. According to the RC Model World magazine article on this plan, the Fuselage is supposed to be built on a jig in one piece (e.g. using whole formers not half formers), not sure if you understand what I mean. But there was no information in the article or the plan as to how the formers were to be attached to this jig or how they were to be aligned. So after much head scratching I decided to build the fuselage in two half's.    

[Ron]

Hi Alan,

Nice job.
Can't think how you could do that fuselage on a jig.
Wonder how they did the full size one in the factory :?:

If it was a boat the keel would have been set up first and the frames fitted to that at the appropriate angles.
I guess the keel could have 'legs' down to the baseboard to keep it at the right height, and maybe even fit the legs into slots in a jig to hold it all up.
Bit of a procedure I would have thought.

Great work though. :clap:

Ron

PS. What's that glue?

[Alan_Perse]

Happy New Year All.
Finally warmed up enough to get some work done. Photos below.
Ron: The glue I'm using is some sort of French white wood glue that I got at Retroplane. It's called Pattex I think, I'm sure Fred will know exactly what's it's called. It seems pity good.

[Fred]

Very good Alan!
Sheeting in plywood ?  :?:

Retroplane glue, very good stuff indeed !  :clap:

[Alan_Perse]

Hi Fred.
No I'm sheeting it in balsa. The area around the cockpit and where you hold the fuselage when launching will be reinforced with extra sheeting on the inside to stop it getting crushed, at least thats what the plan says.

[Alan_Perse]

Another update. I have built the tailplane. Again I have deviated from the plan. The plan called for a solid balsa tailplane. But to try and keep the weight down at the rear I decided to make a built up tailplane sheeted with balsa. Hopefully that will reduce the weight at the rear-end a bit meaning less lead in the nose. Photos below.

 

[Alan_Perse]

Hi All.
I have started work on the wing center section. It's built in two half's and joined together later as there is a dihedral angle built into it.




Here are the dihedral brace's

 

[billscottni]

Nice Alan, Wish my KA-3 was progressing as quickly.  :x

Suffering alack of enthusiasm at the moment, probably as a aresult of too little flying.  :cry:

You need some return from your building efforts

[andrew wallace]

looking good alan  :clap:
it's coming along nicely

bill it's hard to get motivated sometimes maybe we'll get out next sunday  [-o<

[Alan_Perse]

Thanks Lads.

Suffering alack of enthusiasm at the moment, probably as a aresult of too little flying.  :cry:

You need some return from your building efforts

I know how you feel. But what I do is look at the pictures from Retroplane and the Retroplane DVD and that gives some enthusiasm to get going. I'm dying to get some flying done myself. I think the last time I few was in September or October. The last time I few the K8 was at Retroplane in July.

[billscottni]

Thanks Alan, tried the DVD's, flown the sim, still no good. Last time I flew was 12th Dec 2010. Not just the flyig that's bugging me, few probs in my personal life too, like an ex-wife! :x