Rubber Bands

[David Davis]

Like many of us who learned to fly before the age of foamies, I learned on a model with the wing attached to the fuselage with elastic bands. I still have three vintage models whose wings are fixed this way. I recall being told to attach the band to the front dowel first then stretch the band diagonally across the wing to the opposite rear dowel. Then to do the same with the dowels on the other side of the fuselage. Whenever I tried running the band from the rear dowel to the front dowel I was told that I was doing it wrong!

 

Why is it so important to start at the front, stretch it over the wing and attach it to the rear dowel and not the other way round?

[PatMc]

It isn't. 😉

[kevin b]

16 minutes ago, PatMc said:

It isn't. 😉

But the logic was that the dowel you hooked on first took the greatest strain and that the leading edge was stronger than the trailing edge, so that when you fitted the band to the rear dowel some tension was released and thus less pressure on the trailing edge (more difficult to explain than show !).

Many old vintage designs didn't have sheeting to support the bands.

[leccyflyer]

Like Pat said, it really isn't important.

[Martin Harris - Moderator]

I like Kevin’s theory - although I’m not sure how much load would actually be transmitted to the trailing edge.  Those older models were designed for positive G operation so the trailing edge (and rear fixing) wouldn’t have needed as much strength to resist flight loads. Therefore it’s entirely feasible that the front fixing could have been designed more substantially in some of the designs of the time, leading to such a convention. 

[Steve Dunne]

Just my 2p worth...

I have used rubber bands on many lively aircraft over the past fifty years or so, and I agree with the advice to fit to the front dowels first.

The latest banded model is the 102" KK Falcon, which although designed as free-flight and built as a tame rudder-elevator model, is occasionally persuaded to loop and roll 😬.

During these manoeuvres the wing definitely lifts off the fuz to an "interesting" degree, primarily at the leading edge.

When fitting the wing bands, 8" x 1/2", fitting them from the front dowel allows them to be stretched very tightly over the leading edge, minimising the wing lift. The slacker part of the band is over the trailing edge, which does not have as much lifting tendency.

I have observed the same on previous aircraft, such as the Andrews Aeromaster.

So - I agree with KD, front dowels first every time!

 

Steve

 

 

 

[leccyflyer]

How many bands have you got on the Falcon Steve? The wing shouldn't be lifting at all in flight - isn't that just indicating that you don't have enough bands on there?

[J D 8]

Wing lifting is just not enough bands.

Had only two bands on my Limbo Dancer once and heard a strange slap sound when I turned just after take off, happened a couple more times before I realized what was happening. Gentle return to safe landing.

Classic case of being distracted setting up.

[Steve Dunne]

8 bands, very strong 8" x 1/2", fitted very tightly.

I can't lift the wing LE by hand, but a loop definitely lifts it at least 1/4" to put the wing off its location points!

[Steve Dunne]

Unless I attach the bands front peg first, and stretched very tight...

[kc]

Maybe you all missed David's point?-  I think the advice was to put the bands diagonally which spreads the load a bit instead of concentrating it by running bands right along fuselage edge.      

[Steve Dunne]

I agree - On the Falcon, all eight bands are fitted diagonally, alternating from left to right.

[PatMc]

3 hours ago, David Davis said:

 

 

Why is it so important to start at the front, stretch it over the wing and attach it to the rear dowel and not the other way round?

 

1 hour ago, kc said:

Maybe you all missed David's point?-  I think the advice was to put the bands diagonally which spreads the load a bit instead of concentrating it by running bands right along fuselage edge.      

 

That's not the question he asked.

[Steve Dunne]

OK, point taken.

In my view, the importance of starting the rubber band stretch at the front dowels, is to ensure that the maximum tension is at the front (Leading edge) of the wing, so as to minimise the possibility of LE wing lift when the LE is raised relative to the air flow.

😶

[PatMc]

I agree that it's undesirable for the LE to lift from it's seat under flying but I doubt whether stretching from the front or rear makes any difference.

OTOH the distance from dowel to LE has a significant effect on the tension which can cause the LE to lift especially through loops & other strong positive G manoeuvres.

IMO this is why KK Junior 60s & Super 60s have a mis-identified reputation for weak wing spar construction when in fact the models were designed originally for free flight & S/C rudder/motor control only. Instead of beefing up the wing spar they really need the dowels re-positioned (& a small redesign to the cabin front) or, better still, peg & screw wing retention. The Falcon also looks as if it would benefit from the same treatment.

[Brian Cooper]

By fitting the bands to the front dowel first, there is (hopefully) more pressure applied to the leading edge. 

In any case, the bands can be "shuffled" to create more force at the front if required. 

 

If anyone is in any doubt about the lifting force of a wing with insufficient bands holding it down, they ALWAYS lift at the front. 

[Martin Harris - Moderator]

1 hour ago, Steve Dunne said:

OK, point taken.

In my view, the importance of starting the rubber band stretch at the front dowels, is to ensure that the maximum tension is at the front (Leading edge) of the wing, so as to minimise the possibility of LE wing lift when the LE is raised relative to the air flow.

😶

How long does friction hold the unequal distribution of tension in the band, especially once flight loads and vibration have had a little time to do their work I wonder?  I think Pat has hit the nail on the head - however you fit them there is a long run between the LE and the dowel on the Falcon and similar models, allowing considerable potential for elongation and subsequent lifting.

[Nigel Sharp]

Not having enough bands certainly leads to interesting behaviour. My Wayfarer was initially a bit of a mystery in the handling department until I upped the number of bands on the top wing from six to eight. After that it became perfect. Wing lifting was the culprit.

 

However... due to a moment of poor piloting on my part  a re assembly was due... now changed to wire cabane struts and bolts.

 

Still flys superbly.

 

Ps I fit bands from the strongest edge... once had the front dowel ripped out of a veron cardinal. What a right mess that made!

[John Stainforth]

I usually start with a pair of diagonals (from the leading edge), then 2 pairs of straights, then 1 or 2 more pairs of diagonals, i.e., 8 to 10 bands in all. The final diagonals keep the underlying bands pulled inwards on the dowels.

[Nick Cripps]

I'm right-handed. I stretch each band from the left-hand side of the fuselage (as I look at it) to the right. That means on one side the band is fitted front to back and opposite on the other side.

 

I've never had a wing lift in flight but I watched one of our club members win our looping competition when he accidentally fitted only 2 bands to his Wot4 and the wing lifted on every loop, tightening the radius. He won by a country mile!

[john stones 1 - Moderator]

By fitting at the front first, it reduces the chance of it smacking you in the face if it slips off. 😉

[Robin Colbourne]

Getting the maximum tension on the band at the front dowel to prevent leading edge lift makes sense.

This will be contentious, but in my view is all bands should be fore/aft and not diagonal.  The reason we band wings on is to allow the wing to move or come off in the event of a cartwheel (wingtip/nose/other wingtip/tail - type of arrival).  If the bands are diagonal then the bands are very unlikely to come off when the wing twists in an 'arrival' and the bands are more likely to cut into the leading and trailing edges.  
If the dowels are short and there is a risk of the bands slipping off (particularly on an engine powered model on which the bands can get oily) then having the last bands diagonally works, as the diagonal bands will pop off when the wing twists.

The ARC (later Thunder Tiger) Ready, seen below, had a single wing bolt holding the wing on, with the bolt just behind the thickest part of the wing.  It allowed the wing to twist either way, snapping the nylon bolt in a really heavy arrival.   This, perhaps with the addition of some magnets for consistent wing alignment, particularly with flat bottom aerofoils, seems a far better way of doing things than large numbers of bands that take ages to fit and remove.

Edited November 27, 2023 by Robin Colbourne