David Ingham

Does anyone know where forums on rubber power are?
I have a Peanut Scale Jetco Dayton Wright Racer that I hope to repair. But I will need support to fly it up to its potential. Long ago when I flew it, I never dared wind it up more than a fraction of the breaking strength of the rubber.
I also have plans for the big Draft Dodger endurance model and a smaller version of it; they look like they would be great for RC rubber. Maybe with less or no dihedral and ailerons. Maybe add a cockpit-like bulge on top for the electrics.
I read some German.

NormF

Try Small Flying Arts (SFA)
http://www.smallflyingarts.com/cgi-bin/yabb2/YaBB.pl

- Norm

ffkiwi

Do a google check on 'ffml' -the free flight mailing list [I used to be on it, until they changed their ISP and I never got around to converting across]-this covers all aspects of Free flight, including rubber. Also check out the NFFS site at www.freeflight.org-this has numerous sub forums.

Over the years I've built several Draft Dodgers-they are a good design and fly well. What do you actually want to achieve with rubber powered R/C? just to show it can be done? It has been done in the past on odd occasions-Tony Naccarrato of T&A Hobby Lobby was quite an exponent. Whether it is practical is another story altogether. You will need something of the size of the Draft Dodger to be decent flights-and these will only be of about 3-5 minutes duration. My Draft Dodgers run 80-90g motors-and these give prop runs of 1:20-1:30-so only at best a minute and a half of flight is actually rubber powered-the rest is glide. As well you need to consider operating costs-rubber motors will not last long if wound hard-and they need to be wound hard to give top performance-to at least 90% of maximum possible turns. modern rubber has good energy storage, but is quite soft and prone to fraying-you will need to make up multiple motors-and at 90g you won't get many to the pound!
Yes it can be done-but it is a lot of work for relatively short flight times-and quite expensive compared to ic power. If you go smaller, your payload capacity diminishes rapidly and so does the prop run on the rubber. Gearing is an option, but adds another level of complexity.

'ffkiwi'

BMatthews

David SFA is a great resource for your intrest as well as there's a free flight forum over at RCGroups.com . Most of same folks frequent both places but each has their own separate members as well.

What's this Draft Dodger model? I can't say I'm familiar with that one but to take an 80 to 90 gram motor that runs so long it's got to be quite big. The only Draft Dodger I know of was a spark ignition OT model with a very short nose.

ffkiwi

Draft Dodger is quite a famous Unlimited rubber model design, by Robert Dunham. It was NFFS Large Rubber Model of the year ca late 1980's IIRC. About 50" span and 48" long. The plan was by Carstens (CF-366) so it would have apeared as an article in Flying Models.
The plan quotes 2.8 oz of rubber, which is 80g-and the motor section is ca 36"-so about 12 strands of 1/4 or 16 strands of 3/16" is a typical motor. The Naccarato model I mentioned in my previous post was a similar size-possibly larger, and featured in Model Builder. IIRC it was flown indoors under R/C at one of the big trade shows-Toledo I think.

It should be possible to fly something of P-30 size under R/C control-but you would have to use very specialised R/C gear to do it-the kind used for ultra lightweight indoor R/C-magnetic actuators or muscle wire, not servos. Indoors it ought to feasible with a large enough venue-outdoors might be a different story. As before flights would be very short-only a couple of minutes. Remember that after the motor is unwound, all you have is a very flimsy R/C glider thats carrying deadweight ballast.

'ffkiwi'

rainedave

My Feedback: (1)

David, if you do find a good online source for rubber info, please post it here.

I have an Embryo model by Jetco called the Eaglet. It always flew great. In fact, I remember there was a picture of the Dayton Wright racer on the box.

As for P-30 there was a man in Asheville, NC named Phil Hartman who kitted an almost foolproof model called the Square Eagle. I'll never forget watching my first one max on a test hop with only around 300 winds on a still summer evening. That got me hooked on rubber power. I may have to build another one this winter. I understand Tan II is no longer available, but that there's something called Tan Super Sport that everyone's now using.

David

flyinrog

My Feedback: (1)

I am slowly working on a Herr Fairchild..but heres more,,the aaz? section where models are purchased is a bit hard to follow but there are lots of planes on it

http://www.peck-polymers.com/


.....Rog

Yuu

Try www.parmodels.com ... they have a 'techniques' section... which shows how to build a 'blast tube' which goes inside a rubber powered plane to prevent the rubber motor from exploding and destroying the fuse. They also show how to build a rubber motor "torque meter" which you wind up to 95% of the breaking strength number of winds... [there's a chart somewhere to show rubber size vs. number of turns]. This means you'll have to wind up a motor until it breaks. The torque meter is a piece of music wire in a brass tube that takes the torque and turns a little pin [needle] on a dial. Don't try to go over about 80% of the "one revolution" of the wire or it deforms. If you need to go higher, make another one with a slightly larger diameter music wire. I made one and it works great. There are a lot of plans there too, but some require legal size paper.

Raymond LeFlyr

My Feedback: (2)

I had two Square Eagles. Both fly-aways. Don't know if the DT fuse went out or they were just in boomers. P-30 was a great idea for breaking into rubber FF. The Sig One-Night Specials work good too. The only peanut I'm embarassed to admit that flew really well was the Fike that was published in Flying Models. I actually had pistachois that flew better than my WWII peanuts.

I can vividly remember the first model of mine that Hung took! And the mixed feeling of "aw heck" and "woo hoo" that I felt (it was a HGL wo/DT).

Alas, aging knees (and my ever-increasing AUW) preclude any 'real' FF these days. But once in a while a catapult/HLG will emerge from my toy room - and I have some Rapier pellets that I want to touch off one of these days.

rainedave

My Feedback: (1)

Raymond, I'll bring this HLG the next time we get together. I glued on those black thread turbulators at some point, but I don't remember when. Brian and his kids have been building them, too.

David

build light

Dave, that's a nice hlg. I see the DT fuse but what does it do? I do not see any moveable parts such as a pop up stab.

Robert

Raymond LeFlyr

My Feedback: (2)

Dave, I have a couple I'll bring too - if I can get Nathan to retrieve.

rainedave

My Feedback: (1)

It's a Pepsi can DT. You cut a horizontal section from an aluminum can and lash it to the fuselage. It curves outward away from the fuselage in the front (because of the curve of the can). You then hold it flat against the fuselage with the fuse and a rubber band.

Edited to add a photo of the finger notch and sandpaper grip.

David

build light

So, the bit of can that sticks out is the key? This is to provide drag to DT the model?

Robert

BMatthews

It actually acts as a drag rudder to tighten and steepen the turn. Hopefully not TOO tight or TOO steep or it's lawn dart time. Ideally you'll cut it down until it produces a tightening of the regular circle enough to steepen it into a 30 or so degree dive angle. Much steeper and it'll really be moving when it hits and could suffer damage or harm whoever it hits.

build light

Thanks Bruce, I have seen lots of DTs but not onne like this one!
I now understand.

Robert

David Ingham

I did not suppose that rubber RC had not been done. My problem is that the nearby place to fly RC does not allow combustion engines, and electric seems a bit boring, because everyone else uses it now and because I have spent so much time working on electric things, most of them more interesting than motors or radio control gear.
I guess you must be right that it is not practical, even basing it on an unlimited endurance airplane. I was thinking a longer thinner motor than one would use in competition to get more endurance under power. But if those who have flown Draft Dodger say it is not practical, I suppose it is not. I don't have a place to fly large indoor models. Something like the radio gear leftover from a dead Cox Warbird, which I was using on my 020 Puss Up, seems as though it would be fine. It might really need aerodynamic compensation, mass balance and good hinges for such little servos to work such large control surfaces, thought.
By the way, does everyone realize that rubber gets cold instead of hot when it runs, like carbon dioxide does? In both cases, thermal heat energy is converted into work, while entropy increases in spite of the decrease in temperature. The relaxed rubber has more degrees of freedom because the shapes of the long molecules are less constrained. CO2 gas has more possible places for the molecules to be than the liquid does.

jessiej

Very interesting thread. It is a lot of fun to fly a Coupe/ Mulvihill, or other high performance rubber model among RC modelers who have never seen such a thing. Folding props and DTs seem to be magic.

jess

Hueydriver

Exactly....but there is merit in giving it a whirl. I think there was an R/C Wakefield in one of the Zaic annuals (64-65?) that used an Elmic escapement for rudder only control. On any given day, you might hit that thermal and get more than a few minutes out of the flight, as long as you have enough rudder authority to fly out of the boomer when required. The interest here is the challenge of doing it, even if it has been before, especially in this day and age of ARFs and such. As true Free Flight fields disappear with suburban sprawl, it is time to reign those designs of old into smaller fields, perhaps with radio control.

David Ingham

Yes, if you consider it a way of launching a glider, then flight times are not limited. My local RC field is hilly. Maybe one could hill soar.
An easier possibility to try it would be a Gwillows Arrow kit I got on eBay.

David Ingham

Yes, there probably is nowhere within 50 miles where I could fly a free flight Draft Dodger, at least I don't know where and skaliwag, who knows the area, did not suggest such a place when he saw my free flight Daniel Boom 020.

BMatthews

If you're considering it as a way to get a soaring model into the skies then it'll work just fine. And you'll totally confuse any other modelers at the field as you stretch wind a 12 strand gumband. I'd love to be there to see the perplexed look in their faces....

Guillows Arrow is just way too small for rubber RC even with the super small and light stuff. The radio gear would almost double the weight of the model. I really think the right size is the 40 and over inch span range with models in the 3.5 to 4 oz range then add 3 to 4 oz of rubber and maybe 1 to 1.5 more of radio gear. Unless you doubled the size. If you tried that then it would be a fine choice. But forget the landing gear and shoot for a folding prop.

May I suggest an old Easybuilt Taylorcraft rubber model? Or perhaps a Paratrooper? Or a double size of any of the Jimmy allen 24 to 25 inchers? With care they can be made light but still be able to soar in lift. I'd go for a lightly undercambered airfoil rather than their usual low camber semi symetrical shapes though.

Something to consider if you're doing this is that you have no rules at all to follow. As such I'd seriously suggest an insertable power stick made from a couple of larger but thin walled carbon tubes with the motor between them. This would let you wind the motor outside of the delicate fuselage and prepare the motor module and insert the wound assembly into the model, lock it in place and then fly.

Forget about "throttle" brake. Even on a larger motor model of this sort you'll need to use the power a little more quickly than a dawn event unlimited which has more of an uphill shallow glide than a climb once the initial power "burst" (snort, chuckle) wears off. With radio aboard you'll want a little more oomph in the climb and that means reduced run time. That'll reduce your run time to more like 40 or at best 50 seconds. Just get the thing up there and then go thermal hunting.

David Ingham

The Ecoman RC electric dragon fly I just bought my grown son for Xmas is a lot smaller and looks a lot lighter than a Gwillows Arrow, and the box says it has "two channel digital proportional control". I don't know the range, but at worst one could use a directional antenna on the transmitter. It was about $30, a little less than the hover craft I bought. I don't think it has servos, looks like the channels control motors.

jessiej

I expect I have had a pretty interesting look on my own face when a big motor blew[X(]

jess

BMatthews

That's why it would be nice to have an extracting power "stick" so you can wind and prepare the motor for insertion. It's a little heavier overall but it avoids that look of pain when you see the shreds of fuselage hanging from the stooge.