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Super 60 Wing Spars


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Hi All,

         Very quick question! I’m just about to start building the super 60 three channel version wing, I’ve read many articles, that the wing spars should be replaced with spruce, I do intend to use spruce on the front top and bottom spars, but was just wondering about the single rear bottom spar, can that be left balsa or should I replace all three spars to spruce.

your comments much appreciated 

mark 

Edited by Hunter
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There's nothing wrong with the wing strength as designed, however the wing attachment method was designed with FF only stresses in mind. The long stretch the rubber bands have from the front dowel to the wing LE is prone to allowing the LE to lift off it's seat in even moderately high G manoeuvers leading to possible wing failure. It's really the front cabin area of the fuselage that needs to be slightly modified to allow the front wing dowel to be fixed at a higher position or peg & screw wing fixing employed.

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Thanks all, using struts is anew one on me! But makes sense, I also will add strength to front cabin and move dowel position, even might go for the peg n screw fixing which was something I was proposing earlier, but will finalise later

thank you

 

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I’ve had several but the last one built as plan except that I added good thick dihedral braces on each joint ( le, te, spars) and the centre section was strengthened with bandage and pva.  I used to aerobatic the day lights out of it and it never once let me down. Had a .40 glow in it. 

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8 hours ago, PatMc said:

There's nothing wrong with the wing strength as designed, however the wing attachment method was designed with FF only stresses in mind. The long stretch the rubber bands have from the front dowel to the wing LE is prone to allowing the LE to lift off it's seat in even moderately high G manoeuvers leading to possible wing failure. It's really the front cabin area of the fuselage that needs to be slightly modified to allow the front wing dowel to be fixed at a higher position or peg & screw wing fixing employed.

Many years ago a fellow club member had a Super 60 with a 60 glow 2 stroke in it. A fast low pass resulted in the leading edge of the wing lifting. The wing didn't break but the rest of the model did as it performed a very tight loop into the ground. 

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I've had three Super 60s, built two and bought the other. All three had balsa spars. These proved adequate for training and sports flying. However, if you intend to fit an engine bigger than say a 40, Ben Buckle recommends a 35 as a maximum size engine, then perhaps using spruce spars would be appropriate. 

 

 

14th August 2024.jpg

Super 60 Merco 35 up.JPG

RIMG0008.JPG

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Thank you for your replies, as it will be only training model, no acrobatics! And as David mentioned, if powered with a small ic engine, and using hard balsa, with some strength added to centre section, moving dowel position closer to le, or peg n screw fixing, I shouldn’t have a problem, still I’m tempted to replace spars if material below par with spruce.

would I be correct David, that you have cap strips on that wing? I know the four channel version does, was wondering if it’s possible to add them to three version wing, I guess it would mean trimming 1/16” around rib to allow for cap strip fitting. 

thanks All 

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1 hour ago, Hunter said:

Thank you for your replies, as it will be only training model, no acrobatics! And as David mentioned, if powered with a small ic engine, and using hard balsa, with some strength added to centre section, moving dowel position closer to le, or peg n screw fixing, I shouldn’t have a problem, still I’m tempted to replace spars if material below par with spruce.

would I be correct David, that you have cap strips on that wing? I know the four channel version does, was wondering if it’s possible to add them to three version wing, I guess it would mean trimming 1/16” around rib to allow for cap strip fitting. 

thanks All 

 

 You have me there Hunter!

 

The red and yellow model is the only one I didn't build so I can't answer your question! I bought it off a bloke in Wolverhampton. If you look closely you'll see that the wing has ailerons. What I do know about the model is that it is a Penn Models Super 60 built to order. An ARTF before ARTFs were thought of if you like! AFAIK they were all finished with Cub Yellow Solartex fuselages and red wings.

Edited by David Davis
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21 hours ago, Hunter said:

Hi All,

         Very quick question! I’m just about to start building the super 60 three channel version wing, I’ve read many articles, that the wing spars should be replaced with spruce, I do intend to use spruce on the front top and bottom spars, but was just wondering about the single rear bottom spar, can that be left balsa or should I replace all three spars to spruce.

your comments much appreciated 

mark 

 

Balsa is fine but you need the right grade (i.e. rock hard). If you build from a kit, you might get something soft and soggy instead of the hard grade that you need. Whereas, spruce is a safe choice.

 

I had a Junior 60 (the predecessor) for ages, with a small four stroke in. It had much the same construction (which always made me a touch nervous in tight loops) it had more flights than I can remember and was then passed on to several further owners after me.

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Hi Hunter, I have been thinking of building one of these for quite a while now. The days of my fast AcroWot and Wot 4’s seemed to be behind me now, and the Super 60 looks more inviting these days.

so are you building from the plan on Outerzone, or another version.

I can’t believe I was given one of these approx 30 years ago, complete and ready to fly and I donated it to the club as I felt it wasn’t my thing at the time. How age changes one’s mind.

I’ll be following to see how your build goes, I have a lovely OS 35 to fit as well.

 

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I haven't built one but I do have a Ben Buckel Kit. Personally I don't think it is the spars that are the problem but the wing joiners when using larger engines. The joiners look pathetic and when I do get around to building it, it will be replaced with full-depth ply joiners. I remember seeing a Super Sixty clapping wings over Epsom Downs many years ago. Such a same to witness the demise of such a fine model. Yes, use several rubber bands to secure the wing to avoid tears too!

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Hi Tom,

            Apologies for delay, but up to my neck in re-skimming my house!

    The model I’m building is the Ben buckle version, and from what I’ve read, seems most are saying replace the spars with spruce as well as the centre section, but some say just beef up the centre section as it’s not that good, so I’m still pondering over it still!

nice engine that is 35 fs? I’m going to be installing a four stroke something in the region of a 35 as yourself

once I’ve sorted house out, I will be making a start!

cheers

mark

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I'd suggest that you don't overthink it. They have been flying in their thousands, if not tens of thousands, without problems for the last 64 years - see the launch below. So they are well proven. Whilst there may well have been the odd failure in that time I expect the standard of building, and the odd material selection, has also been, let's just say, variable.  I'd just build to plan. Mine was bought second hand about 10 years ago, has balsa spars and is still going strong.

 

image.thumb.png.89f36eafcb8713848c60d9c1fc79afe0.png

 

IMG_3331.thumb.jpeg.c5eceaeda49698a644d8b631bf3d4507.jpeg

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On 13/01/2025 at 13:54, Hunter said:

it will be only training model, no acrobatics!

Of course a training plane will on the odd occasion be highly stressed if a wrong signal is given or someone panics! 

So use spruce if in any doubt.   Spruce will probably make the wing more likely to be repairable when the inevitable prang occurs in training. 

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55 minutes ago, kc said:

Of course a training plane will on the odd occasion be highly stressed if a wrong signal is given or someone panics! 

So use spruce if in any doubt.   Spruce will probably make the wing more likely to be repairable when the inevitable prang occurs in training. 

That of course says, build heavier, cos it’s stronger, and ignoring the bit of physics, heavier= more energy carried, therefore faster to support the weight, and when the faster, heavier weight hits the ground, it has no consequences under Professor Newtons Laws.
Build light. 
History lesson, can anyone show me a wing that failed in the outer panels, trod on by a cow excepted. The stress goes through the middle, reinforce that if needed. Note, full size does tapered main spars. 
Also being brutal now, trainers have been known to break up if the pilot over stresses it, perhaps, perhaps, perhaps. Too much power, excessive stick throws, poor build, are not involved? Also, being nasty, part of a learning curve?

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I agree - always build as light as is practical, - crashes are lighter!  However spruce spars are the only extra weight I add and I think it's worth just the slight extra weight to have a wing that is repairable.

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44 minutes ago, kc said:

I agree - always build as light as is practical, - crashes are lighter!  However spruce spars are the only extra weight I add and I think it's worth just the slight extra weight to have a wing that is repairable.

Don't build to survive crashes, build to reduce the chance of them happening.

And prangs are not inevitable during the training stage !! 

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Super 60s have a fairly lightweight structure to start with. Lots of air, occasionally punctuated by balsa sticks.

 

I note the Colin Usher redraw of the plan shows 2 dihedral braces per spar, for a total of 8 braces:

 

https://outerzone.co.uk/plan_details.asp?ID=4059

 

This would be plenty strong, I think.

 

Whereas the Ben Buckle version has fewer braces. 5, according to:

 

https://outerzone.co.uk/plan_details.asp?ID=552

 

 

As a quick fix in this area only, I would either do what Piers suggests, and put a full depth brace at the front, or add the extra braces at the rear.

 

(mind you, I'd probably not build the thing that much like the plan in any number of places, I'm more of a fan of D-box wings and slab sided fuselage construction)

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Thanks everyone for your views and input.

All very interesting and constructive.

i am leaning in the direction of fitting full depth ply bracing, that does seem a good option and plenty of strength added to centre section, as well as doubling up rear brace. But still mulling over balsa or spruce spars, but spruce does offer alittle more crash resistance and easier repair! Well that’s what I’m lead to believe!

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I wouldn't suggest spruce for crash resistance - "no such animal". Spruce is simply a consistent wood.

 

If you're happy that you have good hard balsa spars then just use them. If you're not happy grading them or you bought a kit and the supplied spars are soggy soft, then replace them.

 

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Well Don & PatMc are of course right - we should build light and not build to withstand a crash.   However the one item I would err on the side of strength is wing spars,   hence the suggestion of spruce instead of balsa.   The weight difference is slight - a  3ft piece of 1/4 sq balsa weighs about 1/8 of an ounce ( balsa is of course very variable - this piece is fairly hard ) while a 3ft piece of 1/4 sq spruce weighed 1/4 ounce.   So one would use less than 4 lengths for spars ( upper and lower spars ) in a 63 inch wing and the weight difference would be less than half an ounce- for 1/4 sq spars.   But have a stronger wing for half an ounce.   You might save that half ounce by not putting stickers on the model or by wiping away all excess glue etc etc.  Moving the gear well forward might be an easy way to save half ounce of ballast!

 

Note that spruce is not easier to repair than balsa ( spruce doesn't glue as as easily as balsa - depends on type of glue )- its the wing spars might remain intact in a crash which makes repair easier!   Broken spar might well cause wing to be scrapped.

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Hi All, well I’ve been reading these links and as I said earlier something a bit more sedate is now more in my line of flying.

So my drawings turned up today, so why not, let’s have ago.

Ive got the Outerzone version, so as soon as I’ve finished refurbishing my DB Mascot, this is my next project.

just starting to workout what wood I need.

 

Edited by Tom Flynn 1
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