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Aug 20, 2019, 04:19 PM
'Douglas' to his friends.
Thread OP
Question

Rubber motors à la française..?


A question, basically aimed at the Continental European community but feel free for anyone to add something, of course...

I'm finishing the VLC SE5a, a free-flight, rubber motor 'plane. I've been looking at sources of strip rubber suitable for models of this sort, not for competition or the like, but just to get some decent flights from 'planes I'll build for Our Littl'Un (or myself, of course...). There is a rubber band supplied in this present kit, but what do I replace it with if/when it busts..? I've seen the offers from a couple of UK sites (Sam, Free Flight...), and the Easy Built Models stuff, but can't help thinking that it's extraordinarily expensive, and doubly so when shipping is factored in. So, my question is...
Can anyone recommend a decent source for elastic or rubber, suitable for free-flight 'planes in the 16"-30" category..? I've read that 1/8" (3mm..?) is a suitable width, so that would be my starting point, but am willing to learn from the experience of others if there's anyhting else that'll do the trick.
Any thoughts, please, folks..? Thanks in advance.
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Aug 20, 2019, 05:17 PM
ffkiwi
Well you need to understand that there is only ONE manufacturer of rubber for model aircraft use in the entire world-and they are US based. They produce two grades-'Sport' and 'super sport'...the latter being the contest grade (which is essentially determined by the energy storage capacity of the rubber)-there is no significant component difference between 'sport' and 'supersport'-they come out of the same factory by the same process-but manufacture is a batch process, and rubber is a variable beast! Most of the 'sport' grade is purchased by kit manufacturers for inclusion in kits, actual flyers use supersport almost exclusively.

...the upshot of this is that you really have no choice-you buy from a retailer (who may have had it in stock a long time), or from one of the 'cottage' FF suppliers, or direct from the factory supplier-which is FAI rubber in the US....either way you'll be paying postage-unless you happen to live in Ohio within easy driving distance of FAI Model Supply!

Suck it up-because there's no alternative...'rubber bands' are simply not in the same league-and are a complete waste of time for propelling a rubber powered model. Rubber is available ex factory in 1/4", 3/16", 1/8" 3/32" and 1/16" widths-anything outside of those sizes has been specially stripped (usually for indoor use) by a third party-various retail suppliers will sell you rubber by the yard or in packets-but the factory options are 1/4-lb, 1-lb and 10-lb boxes, depending on usage. A quarter pound box of 1/8"(or smaller) will see you right for quite a bit of flying. Other than vintage model fliers(and the occasional Open/Mulvihill flyer) most people use 1/8", 3/32" or 1/16" strip. 1/16" allows you to fine tune the strandage a bit-but can be a bit challenging to deal with when making up larger motors with many strands.

One final point-rubber weight-relative to the overall model weight, determines flying performance-the model itself does not especially care whether it is fed 1/8", 3/32" or 1/16" strip....obviously for a rubber motor weighing 'x' there will be more strands of rubber in the motor if you use 1/16" than if you use 1/8"....the skill is in determining how much is appropriate for a particular model (assuming it is not specified by the rules for a particular class such as P-30, Coupe or Wakefield). Rubber motor cross section determines power, rubber motor length determines duration-and between these two you have plenty of room for experimentation...in terms of motor weight, cross section and length. A reasonable rule of thumb for a scale model is a motor weight of at least 15% the weight of the model as a good starting point [you may well find with many plans and/or kits the designer/manufacturer recommending a suitable motor makeup either on the plan or in the accompanying instructions]

ChrisM
'ffkiwi'
Aug 20, 2019, 05:30 PM
'Douglas' to his friends.
Thread OP
Wow..! That's unexpected expertise if you like..! Thanks for that. So there's little mileage in unwinding the insides of a golfball, then..?
In France, there is a supplier of 'SIG' rubber (although, ironically, stock is 'ruptured' presently...); is that stuff any good..? Is it the same stuff but re-badged..? Still expensive, mind, but no transatlantic postage, which is really, really high. It seems that it's less costly to cross the Pacific, to judge from many Oriental offerings.
Thanks for the educative contribution.
Do all European modellers use this sole source, or is there a secret 'rubber mine' somewhere behind the Causasian hills..?
Aug 20, 2019, 09:16 PM
B for Bruce
BMatthews's Avatar
Free flight still exists in Europe. So I'm sure there's an online source. And being located within the EU the shipping SHOULD be less than boxing it in solid gold wrapping paper and throwing it across the pond to you.

Don't mind that the same rubber that is used by the contest types is also what we use for sport flying. Just don't wind it up so tightly and enjoy the MUCH longer lifespan to be had from using something less than 80% of the maximum possible. Kept down to around 75 to 80% of max turns I've found it's not at all unusual for a motor to last for a good 3 dozen or more flights before noticing bad nicks along the edges. When you see those retire the motor as the risk of bursting it near your last turn of the winder rises dramatically. And where one edge tear has led to a bad nick another is close to occurring.
Aug 20, 2019, 10:06 PM
ffkiwi
Quote:
Originally Posted by Dad3353
Wow..! That's unexpected expertise if you like..! Thanks for that. So there's little mileage in unwinding the insides of a golfball, then..?
In France, there is a supplier of 'SIG' rubber (although, ironically, stock is 'ruptured' presently...); is that stuff any good..? Is it the same stuff but re-badged..? Still expensive, mind, but no transatlantic postage, which is really, really high. It seems that it's less costly to cross the Pacific, to judge from many Oriental offerings.
Thanks for the educative contribution.
Do all European modellers use this sole source, or is there a secret 'rubber mine' somewhere behind the Causasian hills..?

Rubber has a finite life-even if reasonably well stored-cool, dark and kept away from UV light [not conditions you generally find in a model shop!] SIG of course is a major supplier of all sorts of things aeromodelling-across all disciplines-but if the SIG rubber is recent then it will be FAI rubber rebranded. Note that earlier SIG DID sell their own line of rubber-but that was when there were multiple manufacturers in the game-and by multiple I mean 3 or 4 tops! Now there is only one-period! People have come and gone in the interval-there was for a time two US manufacturers-one the current FAI, the other being 'Champion rubber'-the Chinese produced some stuff in the 80s called "Panda rubber"-it was hopeless stuff-about a decade or so past Tim Goldstein had 'Tru torque' rubber made for him somewhere-but the market steered well clear of it generally. There may be stocks of these older rubbers hanging out in model shops around the globe-but their quality will be highly suspect-and in any case their energy storage was not a patch on the current product-and it too varies from batch to batch [batches are of the order of 3000 pounds]

As I said earlier-suck it up-this is a one stop option-you either use FAI, very old 'other brand rubber (in the unlikely event you can still buy some in usable condition 30 years after it was last made!)...or you stick with rubber bands....which is like trying to run a car engine on fish oil and turpentine instead of petrol.....if it works at all..

ChrisM
'ffkiwi'
Aug 21, 2019, 01:19 AM
Registered User
Gluehand's Avatar
Not too far away....?
FREEFLIGHT SUPPLIES

-----------------------------------------------------------------------------

BTW
Just a couple of weeks ago, at one of our tuesday club evenings, we put the proverbial "golfball myth" to a test...!
Golfballs stuffed with rubber bands were a reality in the past (however despite my age, I'd never opened one up before),
Under curious and encouraging cheerings, we put an "ordiunary" golf ball on the surgeon's bench........just to find said object.....solid...!
The ball consisted, throughout, of a white, pretty hard (or "semi-hard") synthetic material..
What a dissapointment...!
Modern production methods seem to have found its way even into the otherwise conservative golf world...!
Ore are there "vintage golf balls"....?

Aug 21, 2019, 02:36 AM
Sticks, Tissue & old Diesels
brokenenglish's Avatar
Douglas, Chris just about said it all.
I wouldn't mind betting that "Sig rubber" is simply the FAI supplies product.
The only really excellent local supply is here:
https://www.freeflightsupplies.co.uk...roducts/rubber
Aug 21, 2019, 03:13 AM
I like real wooden aeroplanes!
Sundancer's Avatar
What Brian said - Mike Woodhouse. For the small amount you will need to make several motors for the SE you could buy 1/8" by the yard, postage for such a small amount won't break the bank, I have bought from Mike plenty of times for delivery here in France and (unlike some UK suppliers) he doesn't rip you off for postage. And everything Chris said about the supply situation and the uselessness of "rubber bands" is of course also spot on.

Edit: Better get it done before Boris drags us off the cliff though, 'cos who knows what may happen then!
Aug 21, 2019, 04:12 AM
'Douglas' to his friends.
Thread OP
OK, then, Mike Woodhouse it'll be. For the small amounts I'll be using, and in light of the aging of rubber, there's not much scope for a bulk order of any kind. I'll do as George suggests and order a few yards (metres..?) of 1/8th (3mm..?) FAI stuff which will suffice for the SE5a, and The Littl'un's Topaz. I'll order a medium bottle of silicon rubber lube, whilst I'm at it, which should last a lifetime or so at current rate.
As for the golf balls: I did cut one in half, many decades ago, and watched mesmorised for many minutes as a writhing mass of baby snakes sprang out, twisting and turning frantically all over the table. It was amazing the volume of cut rubber that was produced, far more than the size of the original ball, such was the compression of the stuff. Good Fun.
Thanks for the info so far; if there's any more to come, I'm still listening.

Aug 21, 2019, 05:43 AM
ffkiwi
Quote:
Originally Posted by Dad3353
OK, then, Mike Woodhouse it'll be. For the small amounts I'll be using, and in light of the aging of rubber, there's not much scope for a bulk order of any kind. I'll do as George suggests and order a few yards (metres..?) of 1/8th (3mm..?) FAI stuff which will suffice for the SE5a, and The Littl'un's Topaz. I'll order a medium bottle of silicon rubber lube, whilst I'm at it, which should last a lifetime or so at current rate.
As for the golf balls: I did cut one in half, many decades ago, and watched mesmorised for many minutes as a writhing mass of baby snakes sprang out, twisting and turning frantically all over the table. It was amazing the volume of cut rubber that was produced, far more than the size of the original ball, such was the compression of the stuff. Good Fun.
Thanks for the info so far; if there's any more to come, I'm still listening.

funny you should mention golf balls.....the actual company that makes FAI rubber is a small family firm located somewhere in the US whose primary product was rubber for golf balls....whether this is still the case I could not rightly say...but to clarify the situation-this firm manufactures the rubber strip for FAI Model Supplies-under an exclusive contract. No one else can get similar or identical rubber from this firm due to this exclusive arrangement and the proprietary nature of the process. I earlier mentioned 3000lb batches....well that is because that is the smallest size production batch they can cope with at the plant...and in practice, that means a run of FAI rubber every couple of months....the annual world wide supply for everything is of the order of 20,000lbs-ie less than 10 tons a year....in the overall scheme of rubber manufacture that is a drop in the ocean.

You may well read about 'Tan-2' rubber-which was produced from the early 90s (ca 1993 until into the early 2000s-and was the best rubber ever manufactured for aeromodelling use-some batches exceeding 4000 ft/lb per pound in energy*....well the key to tan-2 was a special additive required for golf ball ....which is no longer economically available...as a result of which both the structure and makeup of golf balls has changed....and as our product piggybacks on that production technology and chemistry....so has our rubber....the good thing is that fortunately the current production tan super sport has energy roughly equivalent to the best batches of Tan-2, thanks to thorough R&D and the willingness of the firm to continue to improve their product.

* and currently small quantities of the very best batch, May 1999-sell for more than their weight in gold on Ebay...

In case you're wondering-my source for this information was first hand: Mr FAI model supplies himself-John Clapp [he's since retired and onsold the business to its current owners] who visited NZ and flew in our Omarama and Kotuku cup world cup events-we persuaded him to give us a lecture on the full story behind FAI rubber, and he regaled a large number of us with about a two hour lecture on the manufacture, the issues and the development of FAI rubber from the early 90s when he took over the business until the the success story of Tan-2

ChrisM
'ffkiwi'
Aug 21, 2019, 06:21 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Fascinating stuff, Chris - thanks! I still have a box of (I think) FAI rubber I bought for my first KK Gypsy, but as it is 30 years old and has just been kept in a cardboard box in the loft, I don't think I'll be using it to power any models now! For the same reasons, it's probably not a good idea to offer any foc to Douglas - I can still remember watching the Gypsy fuselage exploding when the poorly-maintained kit rubber gave out when nearly wound, and it thrashed around inside the balsa and tissue framework.....

I'll maybe use it to make a bungee.........one day!
Aug 21, 2019, 06:28 AM
Thermals, Tom
RyanNX211's Avatar
Volarè is nice to deal with.

https://volareproducts.com/index.php...facturers_id=8
Latest blog entry: Steak and Old Timers
Aug 21, 2019, 08:37 AM
'Douglas' to his friends.
Thread OP
Quote:
Originally Posted by RyanNX211
No doubt about that, but three items ordered : 25$. Postage to France : 26$. Hmm... That's a lot of bullet to bite.

I've just asked Mike for the cost of similar items from FreeFlight, totaling £16.60; we'll see what the postage costs work out to; I'll report back here with the result...

Edit: reply from Mike to say that they're on holiday; he'll get back to me on their return.
To be continued...
Last edited by Dad3353; Aug 21, 2019 at 09:53 AM.
Aug 21, 2019, 04:59 PM
ffkiwi
Quote:
Originally Posted by Colonel Blink
Fascinating stuff, Chris - thanks! I still have a box of (I think) FAI rubber I bought for my first KK Gypsy, but as it is 30 years old and has just been kept in a cardboard box in the loft, I don't think I'll be using it to power any models now! For the same reasons, it's probably not a good idea to offer any foc to Douglas - I can still remember watching the Gypsy fuselage exploding when the poorly-maintained kit rubber gave out when nearly wound, and it thrashed around inside the balsa and tissue framework.....

I'll maybe use it to make a bungee.........one day!
Depends on what it is Colonel-the early FAI was black-the 'tan' varieties only appeared ca 1990-first 'Tan' then 'Tan-2' [I was at the 93 FF WCs-and there was just about only one subject of conversation.."have you heard about this new Tan-II...where can I get some'']-anyway early black FAI was quite 'vicious' in output-ie it delivered a fair proportion of its energy in the first burst of power after launch and didn't leave much for the cruise phase....so you had to design and trim models to deal with it-which meant things like VIT and AR-whether it was a coupe a wakefield or just an open model (though the latter you could get a bit creative with the stranding to get a suitable run length...)....The Tan rubber when it came out had a much milder burst phase and a much longer cruise-and was far closer to the Pirelli rubber of the 60s and 70s-but lacking the latter's explosive tendencies.....

George Schroeders 'Champion' rubber was likewise black-not quite so bursty as FAI, but didn't have as good energy storage as the FAI equivalent....the appalling (and short lived) Panda rubber that came out of China (I still have half a pound box of the smelly stuff!) was just hand grenade material and would let go violently at about 1/4 of the turns you'd previously proven by testing to be safe-or any other rather percentage of full turns it felt like...it was like playing Russian roulette with 5 chambers loaded and one empty....! I never did get to the bottom of WHO exactly made the Champion rubber for George-he was understandably a bit cagey with that sort of information...

Funnily enough though-that 'bursty' FAI black is just what you want for catapult glider-and I keep my dwindling stock of 1/4" FAI black for that exact purpose-though I cheerfully admit that its feeling its age by now-30+ years on-and breaks fairly easily.

If your FAI rubber is a tan variety it is probably still usable-though how fragile it is now probably depends on how hot your loft gets....or not, as the case may be. The serious afficionados store their rubber stocks in a beer fridge....us lesser mortals make do simply with a cool garage...

ChrisM
'ffkiwi'
Aug 22, 2019, 02:03 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Well, if memory serves me correct it is certainly not black, and if your date of 1993 is correct, it will be 'Tan' rather than 'Tan 2'. As for the loft temperature, I would suggest that it will have varied from probably -10°C to +40°C in that time, so not a good environment.... perhaps I'll just use it for binding wet 1/16" sheet around plastic pipes.....


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