CBX24V

A couple of photos of Nick's Herr Cub, covering material is Litespan...

Martin.

encan

Here is my Cub all finished and ready to fly. I will do my first flight on saturday. I will try to make a video if i can bring my friend to the club with me. I dont know how accurate this scale i have (from ebay) is but with the larger batery it is around 157 grams and with the smaller battery it is 149 grams. Both way it balances right on the CG shown on plans.

It is very fragile tough. I already cracked one of the balsa sticks on the fuselage.

CBX24V, Thanks for all the halp and info you given me. I charge my batteries to 8.1 volts on purpose because if i charge them fully to 8.4 then the ESC recognizes them as a 3 cell battery (3 beeps and motor is having trobles to run properly). This happens with both of the battery packs i have. I will ask on electric forums why this happens and if there is a way to override it.

B. Matthews, Thanks for the advise. I really like slowflyers. Very relaxing to fly and easier i guess And i would really like to experience some thermals. If you remember (lonng time ago) i had question about free flight too. I keep building free flight models every now and then. But i get discouraged when i dont get satisfactory results. For some reason i didnt have one that flew very good. I guess its hard to learn free flight without 1-1 help. I hope i can find these thermals that want to carry my cub away you mention.

Here are some pictures.

CBX24V

Hi Encan, She looks very nice! Good luck with the first flight!

Rgds,

Martin.

BMatthews

Wow.... 5.3 oz.... Yeah, that's thermal material.

To catch one treat it as a glider. Get it up decently but not overly high and cut back the throttle until you're descending. Then fly S turns back and forth upwind of you and set the turns such that your model is crabbing back and forth without moving upwind or downwind. Always turn gently into the wind to reverse your track. Watch the model carefully for signs of turbulence. Typically turn into the lifting wing and watch the model carefully. If it seems to be going up then continue the turn and maintain it for a circle or two. If it's going up then hold the turn. If it was just a momentary bobble then come out of the turn and go back to tracking back and forth.

A lot of it is learning to read how the air affects your model. Try to study the failures as well as the successes to get a handle on finding and riding thermals.

Thermalling is sort of like fishing. Sometimes they bite hard, sometimes they just kick the hook to fool you and other times if you play them right you'll set the hook and then play them for a free ride. The hook being your model.

Best of luck with the test flights on a sweet looking model.

Your weak longeron is likely a rather punky length of balsa that came in the kit. This is why I always test snap a short bit off each end of my longeron stock. If I see lots of fiber content in the break I use it. If it snaps off easily with little or no fiber content then it gets set aside. I'll bet you got a length of the non fiberous sort. Hopefully it won't come back to haunt you. If it does it's not out of the question to replace that piece but it would be a messy bit of work and obviously involve recovering of at least two sides of the fuselage.

combatpigg

My Feedback: (3)

Looks great Encan! My wife even likes it and she isn't very easy to please. That is a weird sounding problem with the ESC, all this time I thought there was nothing to that electric stuff.

encan

Thnx combatpigg. Compared to troubleshooting norvels and especially cox engines electric stuff has really nothing.

encan

Hi, i was able to fly my plane and unfortunately it didnt survive the day.

First flight was a little scary and i figured out that it was tail heavy. So i added some weight to nose (thats why i have the ugly electric tape) and it was flying real nicely altough It was snapping real bad if i get too slow.

I was doing some loops. I thing too greedy and the wing snapped on me during one.

Here is a video shows some flying and the crash.

http://www.youtube.com/watch?v=T2HB--pc03o

Andrew

Encan --

That's terrible luck. You had a great looking plane and the build thread was really enjoyable reading. It would take some effort, but unless you have some other structural damage, it's repairable.

The plane was flying nicely - sorry the maiden didn't finish well.

digital_trucker

Two words; wing struts. Install some when you repair it and no more worries about wings folding on ya.

Half-A-Hec

Encan,

That stinks! Your plane looked so good in that flight too. There is no doubt that you can repair it. Sorry that the maiden went so wrong.

Hec

hogflyer

Encan,

Bummer - sorry to see that happen. It looked like a good flyer.

I agree with Andrew about being rebuildable. When you get into the repair, the damage is probably not as bad is it initially looks. I also think DT is right on the mark - it needs struts to support the wing in flight just like the full scale Cub.

You did a great build thread, now lets see the rebuild thread.

Hogflyer

combatpigg

My Feedback: (3)

It really is a fine line between too heavy and too light. For a real light frame work like that, I'll bet bamboo spars would work good.

BMatthews

Sorry to see the wings fail like that. Spars are one place where it's not a good idea to save that extra gram or two.

CBX24V

Hi Encan,

Very sorry to see your mishap. As others have said, it does look very repairable and the fact that it looks so nice and flies well will definitely make the effort worth while!

I have not attempted a loop - most of my flying has been indoors in a fairly low roofed shed, the outdoor flight was very gentle. In the light of your experience and the advice from others, I will fit wing struts - probably 1mm carbon fibre rod faired with balsa strip. I did intend to fit plain balsa strip struts to add scale detail, now I'll make sure they're functional, thanks for sharing your experience.


Martin

BMatthews

Keep in mind that structural struts require structurally sound attachment points and that the stretching tension across the bottom of the fuselage will be high since most of the wing's loading will now be located in that small spot. And the tensile load in the struts and across that lower strut joiner is multiplied by the ratio of the distance out to the strut attachment and the angle of the struts where they meet the wing so the tensile load in the lower joining element is many times more than what the wings are generating. A 6 oz model like this could easily be generating an 8 to 10 lb tensile load in that link between the strut ends when in a high G maneuver.

combatpigg

My Feedback: (3)

I think it is possible to work some pre-preg carbon strip a few rib bays into each wing panel to reenforce the existing spars, then use a carbon or FG strand joiner [dihedral brace] in the middle. I think it could be done without disturbing the unharmed side of the wing. The strut idea would be more invasive.

encan

Thank you all for your help through out this experience and encouraging me after. Unfortunately after the crash i have decided that it would be so hard to repair it and disposed the remainings. I tought building a new one would even be easier and i could do a better job next time.

Digital Trucker, i really tought about putting struts for the looks but i didnt think that i would need them for their function.

B. Matthews,
The spars were all already cut parts and they are pretty thick actually (you can see it in the pictures) so i didnt think about replacing them. There were two spars that are as tall as the ribs themselves plus the sheeting at the leading edge made me think its pretty strong already. It just failed at the joint...

The pictures show where the wings were folded. I think the joint was not strong enough. I used woodglue to join them. This is one thing i dont like about using wood glue because it sticks to surface of the wood only. When i looked at the broken joint i saw the wood fibers still stuck on the glue. I wish i used thin CA. I dont know if it would have survive but i think the wood aound the joint would be stronger as it absorbs thin CA really good.

I am thinking to build another of herr rubber powered planes. I really liked the way this one flied. I am thinking about the Bonanza, or the corsair.

BMatthews

It's too bad you did that. I've had models that suffered just as much damage but once I've peeled off the covering and got started on the repairs I always found that it went pretty fast. One time I even went dumpster diving at a SAM champs and pulled out the remians of a Dynamoe rubber model that someone had exploded the motor in which had ripped away a part of the fuselage. In disgust they had folded the wings and tail and dumped the whole works in the trash. I went by and thought "that wouldn't be so hard to fix" and a minute later I was back in my finest imitation of a skid row bottle hunter fishing the bits out of the can. I flew that model for a few years after and loved it. A sticky DT timer finally saw it fly out and away OOS and thus ended my time with my "borrowed" model.

RocketRob

My Feedback: (1)

after a crash...gather up every little piece....put it on a shelf.....and every time you look at it, the repair gets easier!

combatpigg

My Feedback: (3)

Those balsa spars that have been deeply notched for all those ribs are junk.....they've been chopped in half already by Herr. Even if those spars carried through the wing full span without any notches, they are questionable unless you know how to select balsa for that job. An example of good engineering for 1/2A powered wings in this size range is a design called "The Nickle"

Mr67Stang

I just got a chance to see your video of the fatal flight. You sure did an outstanding job putting together a very atractive airplane. I certainly hope you rebuild or replace as you have discussed (and of course post the build/rebuild details here). The wing struts idea sounds ike a winner and it does not look like the added weight would hurt this plane.

peteapilot

I WISH I COULD GET THIS SITE FIGURED OUT ANY HELP PLEASE

hallagon

Sorry to see your plane go the way it did. I am glad I got to see it in action before I glue mine together it will arrive in the mail tuesday. I have planned the transparent green for the wings and white for the fuselog

skaliwag

My Feedback: (1)

Cubbies don't do loops, certainly not tight loops. Try a Citabria or Decathalon.

hallagon

Not sure what consistutes a real plane but I like the other two as well. It does explain why no one ever does any loops with them