Do most guys just make their own hold down for wings or are there kits one could purchase. Talking about rubber bands versus bolt hold the wing on . My plane in question is the Avistar trainer and I despise the putting on the rubber bands to hold the wing. Not a biggie but seems like a pin a hole and nut plate and all would be well. Alignment of the front hole could be tricky. Ok that is the subject your for commentiing on. Thanks gphil

Most trainers use the rubber band method. Actually, it's probably the best way to hold the wings down.

The purpose is to have a quick break-away method of the wing in case of a bad landing. The rubber bands will allow the wing to break away with minimum damage.

Bolt-down wings may look better, but they may take more of the fuselage with them in a bad landing, thus causing more damage than would a rubber-band held-down wing arrangement.

CGr.

For the Avistar, I would stick with rubber bands. I would suggest waiting until you get into kit building or have a lot of experience before trying to modify a RB mount wing into a bolt down. That takes a lot of thought/experience and if not done correctly, things can go wrong besides wing failure. Your wing can end up crooked, not square with the fuse and stab and fly really bad.

gphil I don't like rubber bands either but for the ARF designer they are fast and easy. You can convert most planes to a bolt on wing by cutting through the bottom sheeting and adding a couple of pieces of plywood epoxyed to the spar and the leading edge and then drilling for a hold down dowl to go through the forward bulkhead. Then add and bolt hold down plate at the rear of thefuselage and drill through the rear edge of the wing and add bolts. This assumes you are an experienced builder and since we are talking about an ARF I am guessing you are a newbe with little building experience. If thats the case stick to the rubber bands. My newest plane has a rubber band on wing because it was fast and simple. Plus this will be a beater plane that will be flown close to the ground and having a pop off wing is a plus. Here are a couple of pics of the plane.

This is a coroplast plastic plane called a S.P.A.D. There is a section here dealing with these planes if you have never heard of them.

Well once again RCU will not let me load a photo. Maybe later.

Here is a link to the SPAD forum and my newest plane.

http://www.rcuniverse.com/forum/m_11094335/tm.htm

GP its a common modification and many folks have do it and as you surmise its not really that big a deal.

Without going into the pro and con arguments which always seem to go on forever, I will say I have done many such conversion both for myself and sometimes others. Heck I have even done some conversions of returning an 'oldtimer'ish' airplane back to a banded wing.

No there are no really practical kits for such conversion the best way for you to get going is to connect with one of your clubs known builders Every club has a few or more who for a consideration or a hot cup of coffee will spend time with you and guide through the process.

One down side of the conventional method of using a plate at the rear top rails of the fuselage in the wing compartment works great but makes working with your pushrods a bit more crowded.

When using this type of plate I beleve its best not to use tee nuts for the nylon wing bolts but drill, tap and harden with thin CA. This is my preferred method.

John

Converting your Avistar from a banded system to a bolt down system is not as easy as it sounds. First, is your version a straight Avistar or is it an Avistar Select? The difference is that the original Avistar used a plywood wing joiner to hold the wing halves together while the Avistar Select uses a metal rod for this purpose. To do this job you MUST have plywood or hardwood pieces epoxied to both the rear of the leading edge of the wing and at the main spar. The plywood wing joiner in the original Avistar can be used for this purpose meaning you would only have to cut into the wing sheeting at the leading edge. If you have the Avistar Select, you would have to remove sheeting at the leading edge in order to insert your hardwood piece as well as at the main spar. Then you would need to drill a 1/4 or 5/16 hole through the leading edge, through the hardwood piece you just glued to the back of the leading edge and into the plywood or hardwood piece you just installed at the main spar. Now you have to epoxy a hardwood dowel through the leading edge hole and through the hole in the piece at the spar. This is all necessary because there will be times when several times the weight of your plane will be hanging on that dowel and you don't want it to rip out of the wing. If installed through only balsa, it would eventually rip through the wing. This is all assuming that the wing sits low enough in its wing saddle for that dowel to go into a hole you are going to drill in the former just in front of the wing. In other words, the front of your wing must butt up against a plywood former that extends upwards past the center of the leading edge or this job becomes almost impossible.

This is just for the leading edge of the wing. Now you have to deal with the trailing edge of the wing. Is the section of the trailing edge that is inside the fuselage solid or is it hollow? If solid, you can drill through it and run you bolts, no problem. If it is hollow, you must remove some wood, either top or bottom, insert some balsa wedges, and replace the sheeting. This being done, now you have to epoxy some hardwood blocks inside the fuselage and the trailing edge. These have to clear your torque rods and aileron push rods. In other words, you will have only an inch or so (probably less) space between your aileron push rods and the inside of the fuselage to place your hardwood blocks. Once you get the hardwood blocks glued into the fuselage and make sure they clear the aileron push rods, you will have to drill down through the trailing edge of the wing and through the hardwood blocks you just installed. Once these holes are drilled you must thread them with a tap. These will probably be 1/4 inch bolts, so drill with a 1/4 inch drill bit. Here, you must keep in mind that in order for the bolts to snug up flat against the wing, the holes will have to be drilled at the same angle as the trailing edge. You will have to drill at a 90 degree angle to the trailing edge, not straight down. If you were to drill straight down, when you thread the bolts in they would snug up with the front of the bolt digging into the wing and the back of the bolt standing clear of the wing. Not good. OK, you have your holes drilled and tapped. Now harden the holes with CA. That is, just apply a couple drops of CA in several places around the holes and let it run down into the threads you just tapped into the hardwood blocks. This will tend to keep the threads from stripping out when you run the bolts in unless you really crank down on them. It is not necessary to get them more than just reasonably snug to keep that wing down. Remember that when you harden these threads with CA, let them sit for an hour or so to cure before running your bolts in. If you run your bolts in before the CA cures completely, you will never get them out. And CA in the open like that does not cure instantly.

Except for the CA you used to harden the threads in the hardwood blocks, everything else is 30 to 45 minute epoxy. CA won't stand the vibration, aliphatic resins will not penetrate the hardwood pieces well enough, Gorilla Glue expands and pushes the pieces apart. Only epoxy is effective when you are going to have several times the weight of the plane depending on the glue joints.

Like many conversions and modifications on these airplanes, this one can be done, but it ain't easy. An experienced builder will know immediately what I am talking about. Only you know if you are capable of doing this mod. If you are, you might want to think about removing that servo in the center of the wing, removing those push rods, cutting off the torque rods where they make that last 90 degree bend inside the fuselage, and installing a servo in each wing half directly in front of the horn. You have a semi symetrical wing, a bolt on wing and servos for each aileron now. This would be a fun performer for a long time.

Can't say I'm a fan of rubber bands, although they really do reduce damage in a crash.

Once you stop crashing (Hang on, none of us have achieved that yet ... Once you crash less often ) Bolt or glue on is the ticket. Just make sure everything is straight, you don't change the wing incidence, you recheck cg, and the bolts are very well anchored to the chassis - and you'll be fine.

All very interesting for sure. Probably just leave it. I have crashed three times really bad the last hit so hard the rubber bands cut all the way into the leading edge to the spar. Wing did not pop off. Needless to say the thing is now flying once more. I have soloed but still have to be thinking every moment but getting easier. Love this sport and I am a old guy. Keeping the trainer Avistar, long as I can. Can not say enough about the strength of this plane. Fellow members may know t his name I have given it, Scarface like the watch takes a licking and keeps on ticking. Thanks guys. gphil

Set it up using Velcro straps -Dont laugh we use them on Sr Teles for rc skydiving and have never had one come loose -I use one on a 40 Super Star trainer all the time and never had a wing come loose or damaged from all the tension on using rubber bands or binders as they call them in Mn

dmowery, I've been wondering about another system of retaining the wing. Would it be possible for you to expand a bit on the velcro strap system, maybe even a couple pictures? I'm really interested.

I'm interested in the velcro strap method myself.

, when I first started flying my trainer I showed up and told my instructor the plane was ready.
He almost die laughing, I have put 2 rubber bands on the wings, one on each side.
Stick to them my man, but more than two OK??

That's funny.

More info please? I have a Hobbistar 60 on the way andI'mnot looking forward to using rubberbands. Velcro sounds like it would work but some instruction and pics would be a big help. Thanks.

Randy

Nope I am not laughing. While I beleve I still tend to be a traditionalist about using a banded wing for trainers at least trainers that are being used as trainers but a working utility airplane is an entirely different matter.

Yes, if possible please post a picture of your set up. For this type of use the velcro idea is indeed interesting. I am thinking it would most usefull for some of the activities I am involved with such as glider towing towing and cross country flights. The very quick and easy wing removal with no tools could be quite an asset.

Excellent idea.

John

A thought on rubber bands if you use too few but enough to hold the wing on, the plane will tend to zoom with positive G, because the wing will actually lift off the mount causing large positive incidence momentarily (top winged models). I've actually seen daylight between wing and mount during flight on rubber band mounted wings on trainers. Easy fix.

After learning how to fly, I did that on purpose to play around with zooming of the plane at its own whim an not mine

One thing I've found with velcro straps is they need replacing after about 100 uses. Turns out the hooks apparently get straighter over time and yarn loop ends frey, and they don't hold as well. It's a simple replacement.

On plastic bolts used as hold downs, I did a strength test on a single 1/4 -20 nylon bolt many years ago. This was a standard test using an Instron Extensometer. I was surprised to determine that one 1/4-20 nylon bolt starts deforming at around 80 lbs load, stretches threads at 120 lbs load, but doesn't break the bolt until about 150 lbs. A single bolt is strong enough for many wings, but I'd use 2 anyway. Have also used a pair of smaller bolts such as 10-24 and these work fine too

If you definitely want the wing to come off on hard landing, forget about rubber bands. The easiest way to do that is with a snap on spring loaded set-up. A spring loaded wing installation takes two seconds to put the wing on or take it off. Set up the springs so that dowels are pushed in as the wing is pushed forward, and then let the wing slide back into its rear dowel socket. It's actually a very simple set-up and its great on trainers

Hi
Rubber bands will work well-,number 11
I still use them on a trainer i love to fly and flying RC 21 years-,24 planes to fly
Change them after a days flying or wrap them in a paper towel if glo fuel is on them,they break ,if they are going break ,when putting them on if they are bad
I ALWAYS use 8 pair and four that cris cross pattern over them-,to hold those on
My first plane was an Avistar
IF or when your wing lifts off its seat it feels like a radio glitch ,-not a good thing
We need to keep the wings on the plane-as much as is possible-LOL ! ! !
When you get good at building and flyingyou could consider building wing mounts
Unlike most guys I like metal bolts and blind nuts ( through hardwood blocks ) to hold my wings on
Some like the nylon snap off kind of an idea
I just never liked that idea
Best Regards Tony

I use inner tube rubber bands on my 3D.

Just kidding. When I first got into R/C I was told two rubber bands (I used #64) per pound would suffice. It's worked for me, no problems.

One of the old timers in our club had a problem with his aircraft zooming up after coming down the chute (he doesn't need a throttle, he only has two positions, full and off). One look at it, and it was found to have the leading edge starting to point up and pull away resulting from an insufficient amount of rubber bands.

Another member was flying his large warbird and suddenly his wing separated and fluttered down while the fuselage became a lawn dart. It seems he never glued the dowels securing the leading edge in and they eventually worked their way out. And this occurred after a number of flights.

Bob

I've never heard of someone saving a wing in a crash by using nylon bolts. I use them because they don't vibrate loose, but I once nicked a tree with a Cessna that had nylon wing bolts and when I picked plane up off the ground the bolts were still tight to the fuselage mount... minus the fuselage!

But on the rubber band topic, it's really not a big deal. It may take 20 seconds longer to put rubber bands on than it does to secure 2 wing bolts. You can invest the 2-3 hours to do a conversion on a lot better things in this hobby, but fly the trainer as designed and look forward to screwing in the bolts on the sport plane you'll soon graduate to.

One note concerning metal bolts. The very fine threaded bolts that commonly come with many arfs make marvelous berings!

A large diameter course thead bolt will resist self removal in flight far better. And the nylon bolts especially 1/4 20's are the least likely to 'self remove in flight'.

Don,t laugh I have seen far to many arf's loose a wing in flight due to the fine threaded metal metric bolts.

Dmowery

Please do come back with a picture of your 'working' airplanes and the Velcro set up. This does promise additional utility for certain types of airplanes and I seriously want to know how you have set this up.

Thank you

John

If using 1/4-inch bolts, the tap drill is appreciably smaller, about .195. A 1/4-inch (.250) drill won't leave much material for threads.

Rubber bands are just fine for wing hold-downs. Let's not forget early sport and even pattern planes used rubber bands on the wings, and sometimes even landing gear, Not a bad idea to put a couple extra on each side in case of a failure.

eddiec, you're right. I saw that a few minutes after posting but did not bother to try to correct it. My bad.

The tap drill for one-quarter inch threads is a #10 @ .193"

Bob

TBH, close is good enuff when finding a tap drill for wood.