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Post by wingedgecko on Jul 9, 2011 19:01:12 GMT 1
So, I took my super cub out on 7/7/11 to work on my flying skills, and test a new 8 cell battery. I was really doing quite well considering it was only my 7th time going out to fly. Although it was windy, I handled it quite well. The new 8 cell 1500mah nimh pack from cheapbatterypacks.com worked awesome! I even tried doing a few loops for the first time in real life, and not on the sim. Made several very soft landings, flew without the ACT, changed the control horns to an inner hole...all was good. But then I tried a third loop, and wanted it to be bigger than the rest. Well, I had way too much speed, was too close to the ground, and I think the wind was too strong. The pictures say it all.      |
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Post by renard80 on Jul 9, 2011 23:52:21 GMT 1
Ouch! I share your pain.  At least the nose section should mend with epoxy (?). Are those landing gear skirts aluminium? The wires appear to be tied strongly to the skirts. A number of people do this. I tried it recently - tied the wires on with dental floss. First hard landing ripped the bottom out, just like yours. Made me wonder whether it's not best to keep the stock rubber band set-up which flexes under impact, absorbing the stress? |
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Post by wingedgecko on Jul 10, 2011 3:25:10 GMT 1
Was just thinking the same thing!!!  When I unscrewed the metal skirts, the landing gear actually sprung back almost to normal. I got the metal ones to help reduce the gear bending on harder landings, and cracking those plastic skirts. Now, I'm thinking I'm going to switch back, and maybe glue two skirts together...they seem thin enough. That way they will be a bit more durable, but will give on a really hard landing. Although this was only my 7th time out flying since 2007, it is my second cub...it had 5 flights under its belt. I think the nose came off because the adhesive was 4 years old. They seem to use the same stuff on the servos, which I had to replace when it caused a couple of rough landings when my control was really sluggish. |
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Post by wingedgecko on Jul 10, 2011 18:17:23 GMT 1
Some afterthoughts about my HZ Super Cub crash. Or as my wife calls it, the eulogy. LOL Also, there is a "lurking" boxer in the video named Maximus. (Max)  |
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Post by renard80 on Jul 11, 2011 1:09:57 GMT 1
That is a very useful video!
Having watched it, I must amend my earlier advice to mend the nose section with epoxy.
I wrongly assumed that the foam had severed. In fact, the video shows that only your firewall has come adrift. Do NOT epoxy this back on! Use only silicone sealant (caulk). Using anything stronger will make the firewall much more difficult to remove without damaging the foam next time you have a bad crash.
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Post by flydiver on Jul 11, 2011 2:16:52 GMT 1
While you are in repair mode consider changing out the Tamiya connectors. They are notorious for giving up complete connection sometime during repeated use as the prongs get loose.
FWIW bendy landing gear is often needlessly vilified. A bent LG can absorb a LOT of shock and often be easily straightened as in the Cub. Rigid LG will send that force somewhere else, the battery box in the Cub's case. In your particular crash I doubt anything could have helped much.
I also seriously doubt you lost the tip to the rubber band holder during the flight. It most likely ripped off during the crash force when everything unloaded.
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Post by renard80 on Jul 11, 2011 23:25:06 GMT 1
FWIW bendy landing gear is often needlessly vilified. A bent LG can absorb a LOT of shock and often be easily straightened as in the Cub. Rigid LG will send that force somewhere else, the battery box in the Cub's case. In your particular crash I doubt anything could have helped much. I was very interested to read this opinion from someone of your experience. There is much advice - notably by neflyer in his excellent YouTube videos - to secure landing gear wires tightly to the skirts. The intention apparently is to avoid bending the wires in heavy landings. Well, as I said above, after taking that advice, my first heavy landing was a disaster. Despite being reinforced with wood, the battery box and considerable amounts of surrounding foam were ripped out. Such was the carnage that my best option was to buy a complete new fuselage. Like you, my conclusion is that the apparently flimsy landing gear absorbs the impact stress. Far easier to straighten the wires than to repair a great gash in the foam. |
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Post by flydiver on Jul 12, 2011 1:39:19 GMT 1
Yep, as I've said over and over, newbies seldom fully appreciate the forces involved in a crash.
Even a series of poor landings can create some nasty accumulated damage. The Cub appears to shrug it off but physics will not be denied. I had a friend bring me a Cub for some soldering work and it took well over 2 hours to repair a mess of damage he wasn't even aware of. He did know his Cub didn't fly so well anymore but couldn't figure out what was wrong. Every time I read one of those accounts of a bad crash that the pilot walked away from I thing to myself, 'they only think so....'
I didn't get this knowledge by reading on the forums alone. I did it like everyone else....the hard way.
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Post by geoff2474 on Jul 12, 2011 9:33:15 GMT 1
[quote author=renard80 board=crash thread=4122 post=29437 . In your particular crash I doubt anything could have helped much. [/quote]
Hi
I always fly at home and my grass is about 8" long, so no chance of a ground take off.
Also when landing the undercarriage just gets hooked up and causes the plane to nose over.
So I have removed the undercarriage plus the small plastic bomb drop bracket.
Hand launches are no problem and landing is a breeze, just skim across the grass and let her down.
Geoff
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Post by wingedgecko on Jul 26, 2011 18:23:24 GMT 1
That is a very useful video! Having watched it, I must amend my earlier advice to mend the nose section with epoxy. I wrongly assumed that the foam had severed. In fact, the video shows that only your firewall has come adrift. Do NOT epoxy this back on! Use only silicone sealant (caulk). Using anything stronger will make the firewall much more difficult to remove without damaging the foam next time you have a bad crash. OK, so I just got my new firewall in...and do not epoxy it on??? I thought that is what it was put on with. Where do I get this silicone sealant /caulk from? Is it just for hobby, or is it the same stuff for home from Home Depot? Can I use CA glue? I repaired the foam, and now I'm going to strengthen the battery box using the popsicle technique. |
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Post by wingedgecko on Jul 26, 2011 18:30:16 GMT 1
While you are in repair mode consider changing out the Tamiya connectors. They are notorious for giving up complete connection sometime during repeated use as the prongs get loose. I also seriously doubt you lost the tip to the rubber band holder during the flight. It most likely ripped off during the crash force when everything unloaded. What I am going to do now is use loctite on those caps to keep them from coming apart. As far as those Tamiya connectors...are they really that bad? Couldn't I just pop them out, use pliers to make them tight again, and then pop them back in? I do that all day long on molex connectors for computers. Thing is, I don't know how to solder. My dad never taught me, and these videos on line have not been much help. Could I just cut the wires and use crimp connectors? |
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Post by flydiver on Jul 26, 2011 18:43:48 GMT 1
If you know how to re-tighten the connectors that will do OK.
But, they are low draw/low amp. Once you step up to higher levels of power they will not be suitable.
Learning to solder - watch the videos, get some DECENT tools and learn. No one starts out knowing how. You learn by screwing it up. Practice on wires, dead batteries, junk connectors, etc until you figure it out.
Firewall is just silicone/bathroom caulk. If you CA or epoxy it in the next time you break it you will regret having done that.
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Post by renard80 on Jul 26, 2011 23:43:13 GMT 1
OK, so I just got my new firewall in...and do not epoxy it on??? I thought that is what it was put on with. Where do I get this silicone sealant /caulk from? Is it just for hobby, or is it the same stuff for home from Home Depot? Can I use CA glue? As I said in my earlier post (now confirmed by flydiver), use nothing stronger than silicone. Do NOT use CA, it is far too strong for this purpose. In UK, and doubtless over there also, you can buy small tubes of silicone from the hobby shop. Much cheaper is the stuff sold in larger tubes for sealing baths, window frames etc (again, as flydiver says). Downside is that you buy a huge tube for a small job. Incidentally, also use silicone to secure servos if necessary. As with the firewall, do not be tempted to use anything stronger - your servos will be a pig to remove next time. |
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Post by wingedgecko on Jul 27, 2011 8:01:56 GMT 1
OK, so I just got my new firewall in...and do not epoxy it on??? I thought that is what it was put on with. Where do I get this silicone sealant /caulk from? Is it just for hobby, or is it the same stuff for home from Home Depot? Can I use CA glue? As I said in my earlier post (now confirmed by flydiver), use nothing stronger than silicone. Do NOT use CA, it is far too strong for this purpose. In UK, and doubtless over there also, you can buy small tubes of silicone from the hobby shop. Much cheaper is the stuff sold in larger tubes for sealing baths, window frames etc (again, as flydiver says). Downside is that you buy a huge tube for a small job. Incidentally, also use silicone to secure servos if necessary. As with the firewall, do not be tempted to use anything stronger - your servos will be a pig to remove next time. I actually used double stick foam tape. I put it along the sides and bottom in a one piece strip. The friction alone keeps it steady, yet I can still take them out with ease...tested that already. |
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Post by flydiver on Jul 27, 2011 14:58:36 GMT 1
Double sided tape....for a motor?
Good luck with THAT!
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When I unscrewed the metal skirts, the landing gear actually sprung back almost to normal. I got the metal ones to help reduce the gear bending on harder landings, and cracking those plastic skirts. Now, I'm thinking I'm going to switch back, and maybe glue two skirts together...they seem thin enough. That way they will be a bit more durable, but will give on a really hard landing. Although this was only my 7th time out flying since 2007, it is my second cub...it had 5 flights under its belt. I think the nose came off because the adhesive was 4 years old. They seem to use the same stuff on the servos, which I had to replace when it caused a couple of rough landings when my control was really sluggish.
