Here are a few pics of the damage on my trainer after I lost it and my instructor couldn't catch it in time to save it.

Most of the damage came from the rubber bands crushing the wing on impact. The fuse cracked and broke, but the repair was simple and straight forward. Repairing the wing is taking a bit of time and I will use wingbolts from here on out. I am also going to fiberglass the center section of the wing for added strength.

The interesting part of all this is I was testing the Flight Data recorder, from Eagle systems and I have a complete replay of the flight & crash. The damage sustained was from a 1 point spinner landing at 54 mph.

I learned three lessons:

1. Don't let your instructor think you know what you are doing, cause you don't.

2. Wing bolts are better than rubber bands.

3. The Flight Data Recorder is really a neat tool.

Do you like wing bolts over rubber bands?

Will get her back in the air soon.

Al

Here is the wing pic.

Al

Here is the Flight Data Recorder, Battery & Receiver.

Here is also some info on the Flight Data Recorder.

Eagle Tree Systems, LLC
4957 Lakemont Blvd SE
Suite C-4 PMB 235
Bellevue, WA 98006
425-614-0450
Fax: 425-614-0706

http://www.eagletreesystems.com/

Al

Did you cross your rubber bands? If so, the damage can be exagerated considerably. I've seen wings separate cleanly with very little damage when the bands are laid fore-aft, but cross 'em, or cross the last two, and you might as well have epoxied the wing on. Lots of the old-timers at my field are horrified at the thought of no crossed bands. I think the reason they're worried about it is because the dowels supplied with most kits are on the short side, and they worry about the bands popping off in flight. I cut my own if I don't like the length. I think that bolts look better, but I'll go with bands for minimizing crash damage.

Yes, I crossed the rubber bands. I was following the destructions from the kit.

Live and learn.

Al

Bands vs bolts? Just different fastening techniques, in my opinion.

I've used both, and crashed both. I've had bolts shear off, and I've had them
not shear off, and twist the block out of the fuse, demolishing it, in the process.
Same with bands... sometimes they pop, sometimes they don't. Crossed or otherwise.
Same with using nylon versus steel bolts, for bolting on the landing gear.
I've seen fuse bottoms ripped completely out, using either method.

The amount of crash damage is "luck of the draw", generally speaking.
I've seen crashes where one method may have been better than the other, for that
particular crash, but it all depends on the plane, weight, speed, angle of impact, etc...
There's no way to tell which way you're going to crash, next time, so use what you like.
At 54mph, straight into the dirt, you expect total destruction, except perhaps tailfeathers.
(Must agree with you on the flight data recorder... nice gadget )

Build them to fly, not to crash.
I do prefer bolts (nylon OR steel), personally... purely from a simplicity standpoint.
I have no illusions that they will decrease my chances of crash damage. I know better

in my experience i much prefer bands to bolts for training with

once when i crashed with a wing bolt planes, it ripped out all the area that held the wings onto the planes, instead of having to cut open the fuselage and spend ages repairing it, i just cut slots in for dowels and changed it to elastic band wing arrangement

i suppose once you get to a good solo stage, bolts won't be much of a problem as you won't crash as much as you are a better pilot but for trainer planes, i think elastic bands are the best way

but i have heard that the bands should theoretically snap off and release the wings in a crash...never seen this actually happen in a crash though

I think overall, bands are better than bolts for trainers.
My first major crash was when I put my Superstar 60 through a tree. The tail came off but the wings popped off with no damage.
Unfortunately, I landed the plane 50ft up in another tree shortly after. This time, the wings were pretty much trashed by the time I got it out of the tree. It wouldn't have mattered how the wings were held on.
I crashed my Hobbistar on its 2nd flight shortly after take off. I found the plane stuck vertically in the ground. The wings had seperated back into their two respective halves, and are probably repairable. I think the damage would have been greater had the wings been bolted on.

My current trainer, an LT-40, has bolt on wings. I haven't crashed it yet so I can't comment on the damage the bolts will cause...

Overall, I think we put too many bands on wings to prevent damage in the event of a crash. I know I've been told to keep putting bands on until the wing will not lift. By this time, the wings are so secure that they are held on too tightly to come off easily in a crash....

Bands almost invaribly come out a bit better for any given crash and now doubt in my mind damage could have been worse with bolts.

There was a time when all designed for RC aircraft had banded wings and in many cases the stabilizer too. There was one big differance from the modern banding method. The front dowels were oriented fore and aft. This one simple change drastically reduced crash damage. In recent years I have done a few modern trainers this way for folks and it is 'the best method' for minimizing crash damage with trainers, far superior to bolts and conventional banding.

John

Alstack,

Rubber bands are the preferred method for holding wing on trainers. The mistake comes from putting to many on the wing. It all depends on the weight of your bird, but for a forty sized trainer, I would only use 8. For a sixty sized trainer, use 10 bands. I fly a combat bird with 8 and I have never come apart in the air because of the rubber bands breaking. Most of the guys at my field will tell you to use more than this for strength, but I routinely have 160 mph mid-air collisions that result in no damage. When you hit the ground, something has to give because the ground will not.

Bob

Properly done, nylon bolts are far superior to rubber bands. Notice the word--proper--which entails quite a few items. Use proper size bolts. Have no play between the wing and the material the bolts go into, i.e. flush with the wing so that, in case of a side load, the wing and the mount act like scissors to sheer the bolt. Adequate strength in the wing where the bolts go through and adequate attachment of the blocks the bolts go into in the fuselage. As to size, for 6 lbs or less; use 6X32 , for 6+ to 9 lbs, use 8X32 and for 20 to 15 lbs, use 10-32 nylon. If you try to use the 1/4X20 all you get is a removable wing with no crash protection; it will either tear out the wing or the fuse or both on a crash.

Sorry, but rubber bands for holding on the wing is far superior on a trainer. AND, 54 mph straight into the ground? I'd say you got off REAL easy! I'm also willing to bet that if that wing had been bolted on, it wouldn't have survived any better, but your fuselage would have looked a LOT worse. Sure you're not stretching the truth a BIT Bob?
Dennis-

Dennis,

I have been known to stretch the truth every now and again. but in this case it is "mostly" the truth. If you get a chance to see combat you will know that it is not uncommon to see a mid air in which one or both of the planes come flying out. Most of the planes scoot along at 80 to 90mph and will flat spin when hit in the wing. Most of the time there is some damage but usually it is minimal. I have flown one wing in two contests with 20 mid airs with the last one retiring the wing. Most love taps happen at about 85 mph but we have survived head on crashes also. The point is that we use rubber bands to allow the wing to move out of the way during the impact and the move back where it should be after the impact. These birds are tough and I have seen a great many fly away from a head on collision.

Bob

I HAVE seen combat events, which is why I asked the question. While surviving 160mph midairs IS possible, doing so "routinely" with "no damage" is quite a bit less than common.

Last event I attended, 3rd heat, 7 planes went up, 1 & 1/2 minutes later, one plane left flying. But that's the other end of the spectrum.
Dennis-

You are correct, it is uncommon, I did stretch the truth a little bit by saying it was common. I have survived three head to head wing hits and flew out. I would like to think that by attaching the wings so that they move out of the way, this will be the norm for us. The sad part is, I will have to keep crashing them in order to find that out. The good news is we flew 16 rounds of combat and only lost one wing and 4 props.

Bob

I prefer bolts, but both will do damage if you crash. People say that if you band them, you can save the wing, but if you put enough on it to keep the wing from coming off in the air under a lot of Gs, then it will do the same damage. Bolts are cleaner. They tend to cause more damage in a crash though, generally speaking.

One thing to watch out for when modifying wings for bolts... espically the tower trainers. I recentally had a student that did the same thing, modified his tower trainer .60 for wing bolts. First flight it was flying around fine until the section of the wing where the bolts went through ripped away from the rest of the wing. He was lucky, since tower replaced the plane for free, even though he modified it. However, he now uses the bands on it and other planes that he modified in the same manner.

This is like asking "which is better, a tricycle or a motorcycle?"

Bolts are by far a better means of securing a wing, But I would no more put bolts on a trainer than I would put a 750cc engine on a kids tricycle and tell him to go learn how to ride it.

Rubber bands for trainers.
Bolts for more advanced planes.

Did he modify the wing for the bolts?? Certainly doesn't sound like it.

You can't just drill some holes through that trailing edge and expect it to hold up; it needs to be rebuilt to tolerate the new loads.
Dennis-

Al,
That looks like the Tower 60 trainer- same one I have. Cartwheeled it a few times and plowed it in in a landing and all I'll say is that I love rubber bands. The wing twists sideways and pops off and no damage.
I sometimes plow my sailplanes 2-4" into the earth (someday I'll learn to not make "one last turn" before landing). Rubber bands save them every time.

I use about 8 to 10 bands. I want enough tension where the wing won't change incidence under load, but not so much where I can't get some criss-cross movement when I push.

I bet at a 54mph spinner landing, it would crack-up anyway. The rubberbands just held the scraps together for you.

Yes indeed like everything in aviation there are always compromises and this is just one. To suggest that just one structural technique is superior for every mission is just silly. banding is usefull for some of those missions.

You seldom see it any more because it is a little more difficult to install but if your truly want to minimise damage to a trainer in a crash try the 'fore and aft oriented front dowells pins' that I mentioned earlier in this thread. The improvement in protection to the wing and cabin area is dramatic over conventional banding or bolted installations.

John

I've got an LT-40 ARF which I bought a couple of months ago. SIG have apparently changed the design from rubber bands to a bolt on wing. This has not caused me any inconvenience as I've not crashed it - yet
I can't believe that bolt-ons are cheaper to produce than banded wings and they certainly wouldn't have redesigned the wing (just added plywood plates). So what do you think SIG were thinking? Increased replacement sales perhaps from less crash resistance?

Again, if you use the proper size screws, nylon bolts will cause less damage than rubber bands. If you do like John buckner said, use dowels in front and bolts in the back, they will usually cause less damage in a crash than rubber bands do. Two 6-32 nylon bolts in the aft end will hold to 100 pounds (10 G's on a 10 pound model) yet will shear with a 30 pound side load. Try to do that well with rubber bands in any combination. Now, that is 10 G's at the bolts but you have a big leverage advantage besides, would no doubt hold to at least 20 G's. Now, if you are using 1/4X20, you will get damage, they shear at 200 pounds yet only have 150 pounds tensile strength. However, as mentioned above, you must design this into the airframe, both at the wing and at the fuselage to properly take the loads. You can not just put holes in a wing designed for rubber bands and expect bolts to hold.

Rodney forgive me for my poor comunication skills. That is not what I was describing. What I was suggesting was rubber banding the wing but the difference is the front dowell. The rear dowell is tranverse across the fuselage as normal however the front dowell is now replaced with two dowells, one on each side oriented fore and aft. Now in any sudden deceleration the wing will simply push the bands straight forward and off far easier than a conventional banded wing. Yes its a bit harder to do than just drilling holes across the front of the cabin and sticking a dowell across but is far superior to any other method.

I have converted a large number of trainers over for other people and the results in the invarible 'Dings' have been most gratifying. The so called good old days of the fiftys while in reality not so good, this is one of the old fogotten techniques that modern trainees can certainly benefit from.

Trigger
What Sig is in fact responding to is not neccessarily better or more effective but just what the market wants, a fact evidenced by this pole. Of course if they did not do this they would not have lasted all these years. But that in no way negates the fact that for trainers used as trainers with the banded wing (particularly if the forward and aft oriented front dowells are used) will cause less emotional trauma for the trainee during the course of his training at some point.

John

Gonna have to agree with MinnFlyer on this one.