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Old Dec 12, 2012, 09:26 AM
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Skyhawk 120

Sleger Int. Skyhawk 120

I have purchased this model from the classifieds section and it is here now.
http://www.rcgroups.com/forums/showthread.php?t=1751320
I am excited and a bit confused about some things that may need clarifications and for sure I can use a lot of advice.
What do I want to do with this kit? I want to have a model that flies comfortably that I can take out and have fun with. I do not intend to have a competition plane but I want to have the best performance I can muster out of it. If it means modifications I say yes I will do them. Maybe we can talk and see what would be a good direction to go with this model.
Also I am thinking to redo the tail surfaces (which I may end up doing anywise to save weight) and a second pair of wings to make it legal in the Woodie class.
Some decisions that I am thinking about right now. The Vertical stab built in the fuse is large and the rudder small. The idea here is to have a full flying stab, cut the ruder (back of the fuselage) and make a larger rudder. If I go this direction then I will make a Woodie legal stab and ruder construction with the idea that in the future I will make a Woodie wing. For fun fly I will use with the stock wings.
I do not have a lot of technical data on this model other than it has a 120in Wingspan.
First does anyone have complete data for this model? Airfoils Wing area etc?
Second based on the above data, what is a good target weight for this model.
Meanwhile I will put the components on the scale and see where I stand so far and get some projections.
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Old Dec 12, 2012, 05:24 PM
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Ok Traian this should help, I too have a SH fuse that I bought from Brian Agnew who used to work for Mark Allen and Slegers as well. If brian see's this post he may chime in and help you. Ok I can't read the spec's so here they are span 116", area 900sqin's choice of airfoils SD-7037-S-7012 root and the same at the tip with the 7012 at 8%. Wing loading 9.5-10.5 oz/sq. ft. Price $359.00 Michael Lachowski win's the 1995 Eastern Soaring League Championship series.
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Last edited by prodjx; Dec 12, 2012 at 05:30 PM.
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Old Dec 12, 2012, 06:43 PM
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Thanks for the information
If my grammar is correct at exactly 80miles per hour we wills send it back to the future…….
Ok on a serious note I crunched some #
Weight between 59.3-65.6oz or 1.7-1.86Kg
I will get some weights when I go home.

Thanks Traian
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Old Dec 12, 2012, 06:49 PM
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I am missing the Basswood LE and I am thinking to go with balsa to cap the LE and TE.
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Old Dec 12, 2012, 10:06 PM
Kurt Zimmerman ≡LSF 4461≡
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Quote:
Originally Posted by Traian View Post
I am missing the Basswood LE and I am thinking to go with balsa to cap the LE and TE.
You can use Balsa for the LE/TE. You just have to be careful that you don't hit anyting with the wing with the balsa leading edge. You can splice spruce stock since the LE is going to be 2 pieces anyway. The TE will be 2 pieces but you can use balsa there if so desired. FYI I had a Skyhawk. I loved that plane. I sold it here a few years ago and am having some regrets selling it. The most common airfoil configuration was the SD7037. Ed's later runs offered the S7012. I brought home lots of wood with my Skyhawk. You will find it to be a great flying plane. It is a real easy plane to fly.

Good luck on your build.

Kurt
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Old Dec 12, 2012, 10:10 PM
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Skyhawk

I found the Skyhawk a bit too sensitve with the T tail.

I converted it to full flying cross tail and made no other changes, other than a balsa cap on top of the fin. It was a pleasure to fly and much less sensitive. I would not change anything else.

I lost it in the sun on a launch and destroyed it, a sad day.
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Old Dec 12, 2012, 11:36 PM
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Oldokie , Brian did the same thing with the tail on his and the one he sold me.
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Old Dec 12, 2012, 11:38 PM
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Ok the instructions say that the model i have id the one with the SD7037 airfoil. So it must be the older one.
I will reinforce the LE. Balsa on the rest.
Weights:
Wing 340g x 2=680g
Horizontal 51g
Vertical 25g ???? we will see.
Fuse bare 260g

In the tail section 60g for the stab 10g servo 25g vertical total aprox 95g
Nose balance for the tail section: 95 x 5= 475
Other bits and pieces 200g

Grand total 1710g plus finish. It souds like it will be FAT.

If I go full flying I can make it light and perhaps in the 40g for the elevator finished. That will save 20g.
No servo in the tail 10g for full flying stab hardware. That will shave another 15g. Vertical perhaps the same weight. That will save me 35g in the tail. If i trim the glass fin vertical I can shave another 5g that totals 40g lighter tail.
maybe abit too optimistic but that means 40x5 equals 200g lighter nose 240g total svings.

1710-240=1470 that would get me the budget for finish.
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Old Dec 12, 2012, 11:55 PM
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It looke like I am heading to a full flying stab.
Should I keep the same surface area or get it a litle smaller? It looks like a shovel right now at 110 sq in.
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Old Dec 13, 2012, 09:53 AM
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I have a question.
Is carbon allowed in the horizontal stab spar of a Woodie ship?
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Old Dec 13, 2012, 10:15 AM
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I remember that model......

Actually the model ended up in the National Soaring Museum as part of an R/C soaring display for a while.


Quote:
Originally Posted by prodjx View Post
Ok Traian this should help, I too have a SH fuse that I bought from Brian Agnew who used to work for Mark Allen and Slegers as well. If brian see's this post he may chime in and help you. Ok I can't read the spec's so here they are span 116", area 900sqin's choice of airfoils SD-7037-S-7012 root and the same at the tip with the 7012 at 8%. Wing loading 9.5-10.5 oz/sq. ft. Price $359.00 Michael Lachowski win's the 1995 Eastern Soaring League Championship series.
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Old Dec 13, 2012, 10:48 AM
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Best bet for rebuilding the tail would be to get a copy of Curtis' design spreadsheet and enter the measurements from your plans. That way you will have known good dimensions, and a good recommendation for a safe starting CG. http://www.tailwindgliders.com/Files.html
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Old Dec 13, 2012, 10:55 PM
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Ok I have some numbers here.
Can you double check.
The stab will be 24in span 5.5 at the root and 2.75 at the tip.
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Last edited by Traian; Dec 13, 2012 at 11:10 PM.
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Old Dec 13, 2012, 11:15 PM
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I need to research how to make a full flying stab. Are there any good links?
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Old Dec 14, 2012, 06:52 AM
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Check your tail length numbers. It looks like you have a 9" difference between the TE to horizontal and TE to veritcal stabilizer measurements. For the all flying tail, you will want to put the pivot point at the red triangle (aerodynamic center). That way your servo load will be essentially zero. Keep the hinge and control linkage as slop free as possible. A good way to mount it is use hard brass tube, or CF tube for the tail mount through the rudder and use styrene tube bushings in the rudder to support it. I have some pictures on another computer and will post tonight if no one else jumps in here first.
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