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Old Oct 23, 2008, 05:01 PM
Put a bigger motor on it!
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Costa Mesa, CA
Joined Feb 2007
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Yes you are right; I did cut the spar for the retracts. This is something I did not want to do, but I planned for it. The wing has an upper and lower spar, with a shear web between the two. I only cut the lower spar. I installed plywood rails that span 4 ribs and bridge where I cut out the spar. I planned on fiberglassing the area too, but after I push and pulled on the wing I decided it was not necessary. I applied more force with my hands than I think the plane will ever see in flight, and I heard no sounds like wood crackling and the wing still felt quite rigid and strong. The plane is quite fast. I'd guess it does at least 60 MPH. I've done tight turns, snap rolls, high G stuff, full throttle inverted passes, etc., and the plane is still flying strong
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Old Oct 25, 2008, 03:06 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Costa Mesa, CA
Joined Feb 2007
1,339 Posts
I take back what I said!

Your comment made me curious and I decided to investigate inside the wing. I took off some covering and noticed MANY cracks starting to form. I almost would like to say that the wing would have come off on the next flight! I'm going to have to do some major reinforcements in this area. Originally, the wing would have withstood high forces, but the weakness comes from a fatigue standpoint. The cracks probably grew more and more after each flight. I also fly off a dirt field, so high speed takeoffs and landings probably do a good job breaking my wing too. I hope you didn't cut into your spar just yet!
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Old Oct 27, 2008, 06:09 AM
a.k.a Alex Desilets
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wakefield, RI
Joined Jun 2008
79 Posts
at least he said something or you may have been in for much more "modifications"
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Old Oct 27, 2008, 07:38 AM
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Nah, I never cut my spars. I sent the retract servo and retracts back to Tower Hobbies the following day for a refund.

Never cut spars! The spars ARE the wing.
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Old Nov 05, 2008, 08:32 AM
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Quote:
Originally Posted by gtfreeflyer
I take back what I said!

Your comment made me curious and I decided to investigate inside the wing. I took off some covering and noticed MANY cracks starting to form. I almost would like to say that the wing would have come off on the next flight! I'm going to have to do some major reinforcements in this area. Originally, the wing would have withstood high forces, but the weakness comes from a fatigue standpoint. The cracks probably grew more and more after each flight. I also fly off a dirt field, so high speed takeoffs and landings probably do a good job breaking my wing too. I hope you didn't cut into your spar just yet!
So how is it coming? Did you repair the wing? Did you keep the retracts?
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Old Nov 05, 2008, 11:14 AM
Put a bigger motor on it!
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Costa Mesa, CA
Joined Feb 2007
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I haven't had a chance to get around to it yet. Been pretty busy with something else and have a 2 week vacation coming up. I'll probably get back to flying in December. I'm going to lay fiberglass over the weak areas. I'm keeping the retracts.
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Old Nov 10, 2008, 01:32 PM
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It seems like, in order to properly strengthen the weak areas, that you would have to lay fiberglass over the retract cut-outs (particularly over the cut spar area). I don't understand how you will strengthen the wing AND keep the retracts?
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Old Nov 10, 2008, 06:33 PM
Put a bigger motor on it!
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Costa Mesa, CA
Joined Feb 2007
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Neither do I

I'll have to think about it and come up with something when I have time to look at it.
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Old Nov 13, 2008, 09:59 AM
zup
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United States, PA, Oakdale
Joined Jan 2008
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how bout glueing a carbonfiber rod further back behind the retracts.
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Old Nov 17, 2008, 09:27 AM
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It would have to span wingtip-to-wingtip to be of any structural importance.
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Old Jan 25, 2009, 07:14 PM
Put a bigger motor on it!
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Costa Mesa, CA
Joined Feb 2007
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So I had decided to retire this plane a little while back. I was shopping around for a new plane to transfer all the electronics into and then decided it was too sad to retire an rc plane. Over the weekend, I tore up the wing, put in a new solid spar, and then layed fiberglass strips across both sides of the new spar. The fiberglass continues onto the exisiting spars as well. I took it out to the field today and had some fun high speed passes before a near perfect landing in the strong turbulent winds today. 4 minutes total flight time before I got too annoyed by the winds. A post-flight check of the wing and I see no cracks or anything to be concerned about. It looks the the new spar is working out great.
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Old May 02, 2009, 11:11 AM
Put a bigger motor on it!
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Costa Mesa, CA
Joined Feb 2007
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Rip

Unfortunately, my Sportster flew its very last flight yesterday. I had been flying the hell out of this plane since my last post in January. Lots of flights, lots of aerobatics, and lots of high-G manuevers. It was a great flying plane indeed.

Yesterday I took the Sportster out during my lunch break. On the second flight of the day I executed a nice 3/4 loop followed by a 4 point axial roll (in the dive). This was nothing new for this plane. It was the final manuever (the 1/4 loop to bring it back level) where things went wrong. As soon as I touched the elevator to pull out of the dive, a loud pop was heard and I saw the right wing snap over the top of the fuselage and "clapped" the left wing. Not more than .5 second later, another loud balsa crushing sound as the plane met the ground. There was a lot of energy built up from the dive, so the crash was quite spectacular.

Examining the wreckage, I was not able to determine the exact point of failure on the wing. It was for sure somewhere around the retract area near the wing root. That area was reinforced quite well. I think I just overstressed the aircraft a little more than usual during that last manuever and it was inevitable that the wing would have snapped whether or not I had ever modified the wing. A combination between a high wing loading and high-G manuever is never a good idea

See the photos...
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Old May 02, 2009, 10:33 PM
a.k.a Alex Desilets
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wakefield, RI
Joined Jun 2008
79 Posts
sorry to here about you sportster, a similar fate met mine. I had come out of a dive and, with the huge wing loading from a .28 on a mini ep, the wings folded (and removed the throttle servo from the reciever) causing a full throttle, 3 agonizing second dive straight into the ground. The only part of the plane still existant it the wings and the fuse from about 2/3 back to the tail, the rest is fire kindling!
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