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Jun 04, 2017, 12:58 AM
Registered User
I finished one of the super cubs around three months ago and I have been enjoying it thoughly. That said, I have had a wing strut wiggle its way out from the fuze during a high G spin (The wing twisted and pushed the strut out). The airframe is not modified at all with the exeption of carbon rods versus brass in for the wing joiner tubes to save weight. After the strut came loose, there was notable flex (7ish degrees) on my approach to landing. The plane, however, was fine with no damage whatsoever. So Bleu, I am confused as to why you had a wing rip from the fuze. My flying weight for the cub is about 750g.

On the subject of loosing scratchbuilt planes, Last summer, I built a Tritle 50" Champ while I had a broken collarbone. Stupidly, I did not add the struts because I was impatient and I told myself that I would maiden it and not try any high G manuvers. Well, after a beautiful maiden and about 15 minutes of flight, I forgot about the struts and tried a loop. The wing folded with a loud snap, and one detached and slowly floated down while the rest of the plane spiraled into the ground. It ended up hitting a concrete drain. To be honest, while I was upset (who wouldn't be), I accepted the crash and made sure never to repeat the mistake. I converted it into a glider as much of it apart from the front end was salvagable. As a glider, it was great for very light wind slope soaring. It makes me want to kitbash a Tritle 60" cub into a Tg 8 glider
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Jun 04, 2017, 08:57 AM
Neophyte hacker
portablevcb's Avatar
Strut failures

I probably have hacked Pat's designs the most. The Dumas Birddog with flaps and ailerons (and triple the power, 50% increase in weight). His Agwagon with a beefed up LG and a dusting 'pod' that almost doubled the weight of the plane.

The Agwagon was the most fun. It already had flaps. I had to go from a small 2s to a larger 3s battery for the extra power to drag it around. Unfortunately I did not change the struts. They were the original balsa. I did MANY crop dusting runs complete with high G pullouts, stall turns WITH a partially full pod. One morning I did not drop as much 'dust' as usual and pulled out hard. Strut broke (they are in compression on a low wing plane) and the wing folded. Very dramatic end to a great design and build.

My fault entirely. The design was sound. I just overloaded it.

I've watched Pat fly his Cub many, many times. Two friends also built them and, despite not being near as good a pilot as Pat, theirs have held up over many flights as well.

Secure the struts, fly within the envelope and the original design is beefy enough for years of flying pleasure.

charlie

PS Because of the light design I choose to not build very many of Pat's designs. I tend to build heavier so I lean toward stuff like Peter Rake's. Needless to say, at our field I was known as the guy who flies 'tanks' cause they are so heavy. Or, in the case of a few of my planes, they are the 'rocket ships' cause they fly so fast.
Jun 04, 2017, 10:14 PM
Registered User
Ojimy's Avatar
Quote:
Originally Posted by Bleu
If we look at the design of the Super Cub and the design of the DH Beaver. It can be seen that the mounting tubes are shorter on the SC. The Beaver has three ribs of support, the SC only two. That's an error. Then the tubes are larger in the Super Cub, cutting more meat off the ribs. That's an error. The weight was never supposed to be on the ribs, that's another error. Sorry, I wouldn't recommend this kit.
Bleu, have you ever seen the wing root attach fittings on a full-scale aircraft with semi-cantilever or strut-braced wings? They're about the size of the fork ends that hold a bicycle wheel to the frame. The bolts that run for-and-aft through those fittings (there are usually two per side, one for the forward and one for the rear spar) are little larger than a pencil. And yet, failure of those fittings and/or their associated bolts is extremely rare. In fact, if one were to employ a professional aerobatic pilot to cause failure of those fittings, I doubt he could do it. There is actually very little upwards force on them in flight. Many of Pat's models, including this particular Cub are set up with similar force and stress arrangements as their full-size counterparts. It's an arrangement that works, and one of the things I most admire about his designs.

Failure of the struts, usually at an end fitting, is far more common. And as you have become recently aware, usually catastrophic.

I have not built this particular kit, although it is percolating to to the top of a very short list. (maybe this summer?) When I do, I will make a few mods to suit my style of building and flying. But the mods you suggest, I.E., bonding longer tubes and whatnot, will not be one of them. In fact, if anything, I'll shorten them to a couple dowel nubs and a rubber band to hold them to the fuse.

Build them light, don't overpower them, and make sure your strut ends are securely fastened, and a Trittle design will survive anything but dumb thumbs or an attack by the family pet.
Jun 05, 2017, 07:31 PM
Registered User
I'm moving on. I'll do what I have to do, to ease my mind. I'm building the Beaver now, it has a beefier design, but I'll make it bullet proof. The modified wing will carry the plane without the struts, if the spar holds. I won't add much weight, grams, but real load bearing strength. As a mod. I'm not trying to hurt anybody especially the master. I'm just trying not to hurt myself
Jun 05, 2017, 07:39 PM
Registered User
Oh, I see. We show off pictures now to prove integrity. These are my Pat collection. I've built since 1962, scatch built Bob Owen Zephyrs and the Airdrome Albatross Dll in the seventy's. I'm not Willy Lump Lump. Don't make me get my film out.
Jun 06, 2017, 10:46 AM
confused poet
HanksGB's Avatar
Blue,

Nice collection of models. I like the Rapide on floats. Good luck on the Beaver, you might consider your own thread on that plane showing how you plan to re work it. Or not , you'll probably get a bunch of people telling you you're wasting your time fixing Pat's design.

Hank
Jun 06, 2017, 10:51 AM
confused poet
HanksGB's Avatar
Pat,
That’s great! So do all you modern designs have a link to this design philosophy of yours? Do you state on your plans or in your instructions what are the design limitations, weight, power and speed?
What kind of "change control" do you as the designer use to convey lessoned learned about a design, Addendum or Service Bulletins?

Yes it is incumbent on the builder to understand the changes he/she is making to your designs. But it is disingenuous to not stated what constraints are in your design and have the public suffer your learning curve.
In the past I recall that the strongest charge leveled against your designs has been the lack of documentation. You are at the forefront in these ultra light builds as such you are responsible for educating your customers as to their limits with proper documentation (plans and instructions). These are far from the industry standard 40 sized trainers that are the default standard to which RC aircraft are understood to be. You have brought the build standard of the stick and tissue Free Flight to the scale RC model. And as such it is incumbent on you to make this philosophy of yours known.

As you have a web site, lesson learned with older designs should be easily posted for all the benefit from.

Hank
Jun 06, 2017, 07:31 PM
Retired and Lovin' it!
TPfingston's Avatar
I suppose it takes a lot of reading but I've been following Pat's designs for 7 or 8 years now and I guess I have just absorbed his philosophy by osmosis. I really love his designs because they look great and more importantly, they fly very well. I do have trouble occasionally with the light structure (I tend to be somewhat ham handed). As far as the lack of documentation, I personally rather enjoy mostly figuring out what Pat's thinking was about a particular bit of structure. I also read the construction threads and study the photos that he posts. And I think perhaps on occasion I have commented on the appropriate build thread and gotten all kinds of help and advice (some of which I heeded and some that I totally ignored).

I really believe that more folks should study the threads and the photos and when the kit arrives, study the plans thoroughly. Personally, I have bought many sets of plans just for the purpose of studying them and seeing how the designer approached a given problem. I truly miss the days when model airplane magazines mostly printed articles and pictures and plans about airplanes meant to be built be the modeller. For many years, a monthly issue of RCM or Flying Models would give me hours and hours of entertainment just studying the plans printed in them.

I am not sure just how much responsibility for more info and addenda, etc. are due from a model designer but I feel sure that if we go too far, the designers will finally just say 'forget it, I'm done'.

Tony
Jun 06, 2017, 07:44 PM
Neophyte hacker
portablevcb's Avatar
I guess I consider it common sense. If you build a plane this light you just should not expect it to do spirited acrobatics or other high G maneuvers. Keeping to the power level specified on the plans will help that. From what I have seen of Pat's designs, they will do everything the full size could do.

After all, if you build a Cub then expect it to fly like a full scale cub, not like a pattern plane. But, then again, I am one of those guys who does not watch if a pilot starts doing loops and rolls with something like a PBY or DC3. It completely removes all the desire of flying a scale plane for me.

chsarlie
Jun 07, 2017, 10:28 AM
Registered User
I found in my junk box a spool of bead stringing wire. It is nylon coated stainless steel. It is .018" (.46mm) diameter. I set up a test using a 9 gram servo and a temporary rudder and it worked just fine.

Ed
Jun 07, 2017, 01:45 PM
Veni Vidi Volavi
Brian Allen's Avatar
Ed

I have used that beading wire for pull pull systems in the past and it works fine.

Brian

Veni Vidi Volavi

I came I saw I flew
Jun 07, 2017, 04:58 PM
Neophyte hacker
portablevcb's Avatar
I have also used it for controls and rigging, but usually for larger/heavier/faster planes like my 1/6 scale SPAD (5lb) and WACO YMF (7lb).

For the smaller stuff I like the thread better.
Dec 01, 2017, 09:02 PM
Registered User
Is anyone familiar with SolarTex, I understand it may not be as light as some of the plastic coverings, but I am wondering how it shrinks? Would it damage this model? Thanks for any input!
Dec 01, 2017, 09:12 PM
Veni Vidi Volavi
Brian Allen's Avatar
Solartex would be way too heavy and shrink too much for any of Pats designs. You are far better off using Solite/Microlite/Nelson Litefilm (all the same product) or perhaps something like Parklite.

I usually use World Models Lightex. It is a bit heavier than the Solite films but comes in a larger color palette and you can control the shrink. I also use it as our field tends to play havoc with Solite and I get tired of patching all the small holes and tears.

Lightex is available from Airborne Model in California or from Sig as Aerokote Lite.

Hope this helps.

Brian

Veni Vidi Volavi

I came I saw I flew
Dec 01, 2017, 09:26 PM
Registered User
Quote:
Originally Posted by Brian Allen
Solartex would be way too heavy and shrink too much for any of Pats designs. You are far better off using Solite/Microlite/Nelson Litefilm (all the same product) or perhaps something like Parklite.

I usually use World Models Lightex. It is a bit heavier than the Solite films but comes in a larger color palette and you can control the shrink. I also use it as our field tends to play havoc with Solite and I get tired of patching all the small holes and tears.

Lightex is available from Airborne Model in California or from Sig as Aerokote Lite.

Hope this helps.

Brian

Veni Vidi Volavi

I came I saw I flew
Thank you! I will look at those!


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