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Old Jul 21, 2008, 05:31 PM
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Joined Jan 2008
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60" EPP sport wing?

I am about to build this plane and I was wondering if anyone has built the 60" sport wing out of EPP? I have some 9mm and I was wondering if it would work or not.

Thanks,

Joe
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Old Jul 21, 2008, 05:40 PM
In Rc for a LONG TIME FFAA#1
laserman's Avatar
Canada, ON, Ottawa
Joined Jun 2004
1,375 Posts
Quote:
Originally Posted by Jmcdonald870
I am about to build this plane and I was wondering if anyone has built the 60" sport wing out of EPP? I have some 9mm and I was wondering if it would work or not.

Thanks,

Joe
Hmm epp you would definately need spars !! a very boucey wing that would be hehehe
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Old Jul 21, 2008, 05:50 PM
In Rc for a LONG TIME FFAA#1
laserman's Avatar
Canada, ON, Ottawa
Joined Jun 2004
1,375 Posts
hmm the bb 24 edf did not survive the motors went boomies oh well, so on went a tp 2409-18 think that is enough power!! grunt grunt more power!! a binford more power bb 24
like this
http://www.hobbycity.com/hobbycity/s...3.8_Prop_Combo
laser
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Old Jul 21, 2008, 09:05 PM
I'm not flying backwards!
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Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by jackerbes
Tony,

Thanks for sharing your genius with us. I'm getting started on building the BB 33 and also want to build the KFm3 sport wing for it too. My plan is to have a plane that I can use either wing on or maybe even to have two planes.

I have a question, is there a single sheet or full parts plan available for the "Blu Baby 32 inch KFm3 sport wing.pdf" file in the downloads area? I see you have them for the BB 33 and BB 24.

I had some trouble getting started on the BB 33 because I was having trouble making the cutting templates for the parts from the download with the tiled parts drawings. But Bill Seagraves and his ScaleAndTile3 applet got me off and running on the BB 33, I just had to tile the full drawing to get tiles that work with my printer. Now I'd like to do the same thing on the 32" KFm3 wing but the only drawing is the previously tiled nine page plan.

My issue is that the nine page KFm3 plans have a part of each page missing and don't join up when I print them so I'd like to tile them from a one page drawing like I did for the BB 33.

Thanks for your time,

Jack
OK Jack, it is posted on page one.

Tony
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Old Jul 21, 2008, 10:06 PM
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Washington MO
Joined Jul 2008
567 Posts
Thanks Hopalong. that was exactly what I was looking for. I figured someone had put it up somewhere just hadn't found it yet.
heres some pics of my progress so far. dont mind the mess small drafting table I use for everything. I think its coming along good so far let me know what you think.
Thanks
Jon
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Old Jul 21, 2008, 11:52 PM
BEC
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Auburn, Washington USA
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Been reading back pages of this thread.....and came across a discussion on dihedral:

Quote:
Originally Posted by springer
LarryR: I can't remember what real J3's look like for dihedral, but it's clear from the 150's, 152's at my local airport, on the ground they look like no dihedral, but in the air, they seem to have plenty. Cub might be the same, flex in wing produces dihedral once airborne. seems wierd, but it might be safer. I also recall being told about the flex in commercial airliner wings and remember watching it from a window seat in rough air - was a little disconcerting to see it flex but obviously designed to do that.
mike
If the wings on a Cub (or a 150/152) are flexing noticeably then I'd be worried about the lift struts.....alot!

I haven't been able to find a definitive J-3 three-view but the Taylorcraft A/B series (and related Austers) have 1 degree of dihedral, and since the Piper Cub is from the same designer I wouldn't be surprised if it, too, has a degree or so.

Now wing flex on an airliner, especially a big one - you bet - and that's by design.
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Old Jul 22, 2008, 12:50 AM
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Carmichael, CA
Joined Feb 2007
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all wings are designed to flex. big and small wings have similarly shaped aluminum structure, which is basically scaled up and down depending on size. for example, if you scale a j3 wing to fit a 747, the shape and thickness of the spars will be about the same with respect to span, so they go through roughly the same amount of strain. strain is an engineers way of saying "tip deflection per foot of wingspan".

that's why you'd notice the overall deflection more on a larger plane. same reason a 100 story skyscraper can get away with swaying 10' at the top and not break, while my single story house cannot.

hope this helps explain what you guys are observing out there.

kev
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Old Jul 22, 2008, 01:11 AM
BEC
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Well, sort of.....there is quite a bit more to it than that. Bear in mind that the spars in a J-3 or a Taylorcraft are spruce, not metal, and the wings are externally braced via the lift struts of which I spoke - which are steel tubes loaded in tension (when the plane is in positive-G flight).

Agreed even on a lightplane the wings flex some....but to say it just scales up to a 747 or 777 or now the 787 - when completely different materials (various aluminums on 747 or 777 and carbon fiber composites on 787 - all with different stress/strain curves) and load alleviation schemes are involved is rather oversimplifying things.

For one thing, any jetliner wing does not have a constant thickness to chord ratio in part to tailor the aeroelastics. They typically have a greater t/c at the root where the bending moments are higher (this reduces overall structural weight as well).

I'm sure one of our Structures guys (say Don Bailey who is d_gliderguy on here and a Boeing colleague of mine - who also writes for Sport RC Flyer) could explain it in much more detail. Or I could reach down to the Structures volume of the Roskam design books and start quoting, since they're stacked on the floor nearby - but it's better to talk Blu-Babies in this thread, I think.
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Old Jul 22, 2008, 01:17 AM
BEC
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More on the Willard/Stevens gear

Tony asked for more details on what I called the Willard/Stevens gear in this post yesterday. I linked to some other details in an earlier post of mine , but here is some more. The picture shows the dimensions of the gear I have on my BB 32 KF. It is formed in one piece from about 12 1/2 inches of 0.078 inch music wire.

As shown there's prop clearance for a 9 incher when using the 52mm GWS wheels I'm using. That means on moderate grass an 8 inch prop gets green tips, but the airplane gets up and down easily enough.

The gear weighs 0.6 ounces, evenly divided between the wire and the wheels.
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Old Jul 22, 2008, 05:46 AM
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Hopalong X's Avatar
Grafton, Il
Joined Nov 2007
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Quote:
Originally Posted by jhtitan
Thanks Hopalong. that was exactly what I was looking for. I figured someone had put it up somewhere just hadn't found it yet.
heres some pics of my progress so far. dont mind the mess small drafting table I use for everything. I think its coming along good so far let me know what you think.
Thanks
Jon
You start with a sheet of foam and out pops a BB!

Your welcome!
If your like me I read that lipo post about a dozen times before it soaked in.
You'll still have questions but some basics always helps.

Mike
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Old Jul 22, 2008, 06:03 AM
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Attica, MI
Joined Dec 2006
10,541 Posts
BEC,

When I look at the WS gear, it looks like a no weight penalty for this configuration. In fact, I would say there is slightly less wire, and probably the same amount of wood with the exception of the additional dowel. That is likely offset by less glue required. Do you add any reifrcement on the side of the fuselage between the dowel and ply plate on the bottom?

As I remember, the Roaring 20's, Rascals, Schoolboys, etc... You had to wind up the rubber bands really tight to keep the gear from flexing too much. Otherwise the gear would flex on the landing and nose over anyway. Then again, I did not have elevator control to flair the landing either.

Ken
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Old Jul 22, 2008, 06:25 AM
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blxpy's Avatar
Adelaide, Australia
Joined Apr 2008
813 Posts
Quick question Tony or anyone else that can advise. My AP BB Kfm3 wing is coming along nicely. I'm up to gluing the second step from the smaller strip of balsa down to the wing surface. I'm thinking I might cut a 45 deg into the end that will glue to the wing surface to make a nice neat join. Will removing the 5mm step at this point and replacing it with a smooth transition from the second step to wing have any detrimental effects on the wings performance?

Cheers for any help!

Ben

(Also posted on KF thread)
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Old Jul 22, 2008, 06:34 AM
I'm not flying backwards!
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Oshawa, Canada
Joined Sep 2004
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Quote:
Originally Posted by blxpy
Quick question Tony or anyone else that can advise. My AP BB Kfm3 wing is coming along nicely. I'm up to gluing the second step from the smaller strip of balsa down to the wing surface. I'm thinking I might cut a 45 deg into the end that will glue to the wing surface to make a nice neat join. Will removing the 5mm step at this point and replacing it with a smooth transition from the second step to wing have any detrimental effects on the wings performance?

Cheers for any help!

Ben

(Also posted on KF thread)
Yes! The steps are what give the wing its performance. Build to the plan and you will be happy...honest.

Tony
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Old Jul 22, 2008, 06:47 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by dz1sfb
BEC,

When I look at the WS gear, it looks like a no weight penalty for this configuration. In fact, I would say there is slightly less wire, and probably the same amount of wood with the exception of the additional dowel. That is likely offset by less glue required. Do you add any reifrcement on the side of the fuselage between the dowel and ply plate on the bottom?

As I remember, the Roaring 20's, Rascals, Schoolboys, etc... You had to wind up the rubber bands really tight to keep the gear from flexing too much. Otherwise the gear would flex on the landing and nose over anyway. Then again, I did not have elevator control to flair the landing either.

Ken
I totally agree. If there is any weight penalty, which I doubt, it is minimal. Nice system. It would go very well on the larger BBs especially. The camera planes can be rough on landing gear fully loaded.

Tony
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Old Jul 22, 2008, 07:14 AM
Glue-it-again-Ben!
blxpy's Avatar
Adelaide, Australia
Joined Apr 2008
813 Posts
Quote:
Originally Posted by Tony65x55
Yes! The steps are what give the wing its performance. Build to the plan and you will be happy...honest.

Tony
Thanks for the speedy reply Tony. Glad I asked before buggering it up!

Very happy with how the wing is coming together. I love the way the LE is formed - looks nice and strong and should put up with a few knocks.

I had to shape the top step a bit before bending it down to the spar so that I didn't end up with a symmetrical airfoil. Doing that, I managed to keep the bottom surface perfectly flat. LE is probably a little more 'blunt' than on the diagram - can always squish it down a bit I guess. Will post a pic of the profile when it's done to get your opinion.
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