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Author Topic: Unlimited Rubber circa late 1970s  (Read 1220 times)
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Sundance12
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MAAC #25680, VE4BDF (amateur radio callsign)

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« on: June 23, 2018, 10:09:35 AM »

I have been fortunate to receive a resurrection project that has its origins in Canada. I was informed that the original builder was Duncan McRae of Winnipeg, Manitoba and that it was a design that was developed by a Phil Ball around the 1970's. I have plans for the wing and stab from Duncan before his passing.
Prop is 24 inches with a montreal stop front end. 59 inch overall length. 58 inch span. 16 to 18 strands of 6mm rubber, 43 in long.

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Unlimited Rubber circa late 1970s
Unlimited Rubber circa late 1970s
« Last Edit: June 23, 2018, 10:30:29 AM by Sundance12 » Logged

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MAAC #25680, VE4BDF (amateur radio callsign)

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« Reply #1 on: June 23, 2018, 10:31:59 AM »

Wing construction is underway. Simple construction but the plan is incomplete and I am trying to decide what to do about top and bottom spars. I think I will add 2 more to the bottom. Makes front and main on top  and front main and submain on the bottom.
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Re: Unlimited Rubber circa late 1970s
« Last Edit: June 23, 2018, 02:18:47 PM by Sundance12 » Logged

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MAAC #25680, VE4BDF (amateur radio callsign)

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« Reply #2 on: June 23, 2018, 02:20:10 PM »

Anybody know what its like to fly one of these?

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« Reply #3 on: June 23, 2018, 04:22:46 PM »

It doesn´t look like any Phil Ball design I´ve seen, certainly from the late 70s. Usually diamond fuselages and angular surfaces. Models that size (and much bigger) were fairly common as fly-off models, and 10 plus going off together was quite a sight.
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« Reply #4 on: June 23, 2018, 06:11:03 PM »

Now THAT'S a rubber job.
Lucky you to have it and are able to repair it ready to fly.
Please keep us informed.
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« Reply #5 on: June 23, 2018, 08:18:55 PM »

Anybody know what its like to fly one of these?

Exhilarating....once launched !   for the flyer.....trepidation whilst winding, stressful whilst unhooking the winder and reattaching the prop assembly.....challenging for the timekeeper (unless its dead calm-in which case he/she gets a stiff neck!)-considering these models could do 15 mins+ on full turns-and believe me-by that stage your eyes are watering-binos or no binos!   I timed Phil Ball in the flyoff at the 1st Centralised area event of Feb 2003 at RAF Church Fenton-he did in excess of 15 minutes, and despite my best efforts I still lost him oos in the binos downwind. That was with a much later design than this one though-but about the same sized prop....

 ChrisM
 'ffkiwi'

PS Having checked the photos-posted by sundance-I have to agree with Bill Dennis-the prop assembly is not a Phil Ball style-he prefers Montreal stops and a high tensile alloy arrowshaft tubular hub assembly....
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Sundance12
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MAAC #25680, VE4BDF (amateur radio callsign)

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« Reply #6 on: June 23, 2018, 08:53:22 PM »

I think my friend Duncan was influenced by Phil Ball deigns alot. Duncan is a SK now so I am on my own to work up some wings and stab. Regardless of the origin of the design, I am intrigued by the prospect of flying it when I get it to a stage where flight is possible. I am going to need a field support helper for sure, by the sounds of things. The prop is a Montreal Stop folder or a design similar.
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Re: Unlimited Rubber circa late 1970s
Re: Unlimited Rubber circa late 1970s
« Last Edit: June 24, 2018, 09:16:10 AM by Sundance12 » Logged

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« Reply #7 on: June 24, 2018, 12:31:10 PM »

Sundance,

I agree with Gossie and Chris, THAT'S a rubber job! If it is your first it would pay dividends to make up a motor, lube it and run it in a fixture with the prop connected to get some practice with the whole set up before you take the chance of muffing it with a wound motor that gets loose and tears up your treasure. You can make a winding fixture fairly easily with a 2x4 cut somewhat longer than your fuselage with ply or aluminum plates at the front and rear to mimic your nose and rear hook-up positions. I mount mine in my bench vice with lots or room behind it in case the motor gets loose. Then go through a series of winds just like you were testing the real thing. Trust us, you don't know scared until you've got a quivering, slippery mess of rubber at 900 turns trying to break your grip while you are trying to hook up a prop with your model in a stooge, unprotected by your having just removed the blast tube. It's time to take a breath only when that monster is safely stowed in the fuselage and you have control of the prop. It's GREAT!

RB
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« Reply #8 on: June 24, 2018, 01:43:44 PM »

Well described, RB  !!
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Sundance12
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« Reply #9 on: June 24, 2018, 01:53:59 PM »

I am intrigued and forewarned at the same time. I will take these directions to heart. I am getting the feeling that these rubber motors are not for the faint of heart. I thought that IC engines were to be respected.
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« Reply #10 on: June 24, 2018, 03:02:51 PM »

Sun,

One of the things that opened my eyes was comparing the torque of a large rubber motor to an IC engine. Take a look at some of the torque figures in engine tests and compare them to something like 50 - 80 inch ounces which I have seen on motors of 24 to 28 strands at 70 - 85 grams. Guys like Gossie and Applehoney have flown stuff in the 100 gram range that are even more fun. Then think of holding that IC engine in your hand while it runs, gets slippery and tries (probably successfully) to escape your grasp.

None of us would try to dissuade you from flying your old hand. In fact I'm a little jealous...We would all like to see you fly it a whole bunch of times at full winds!

Bill
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« Reply #11 on: June 24, 2018, 04:01:41 PM »

These types of models were still being flown in the UK in 2004 (and maybe later) in contests known as OPEN RUBBER.
They could be any size and weight up to the general limits for model aircraft as set out by the governing body.  
The pics show "rounds models" that only needed to fly for two and a half minutes for a max. The "fly off" models were about
half as big again and typical fly-off times were 10 minutes plus.

From my notes, the rubber motors for my rounds models were 12 strands of 1/4" weighing 90 grams wound to 900 turns.  
The fly-off model motors were 16 strands of 1/4" weighing 120 grams wound to a similar 900 turns.

I wasn't too keen on these large models as I preferred to retrieve my model on the same day as the contest. For me 10 grams has always been an adequate motor size.

At the fly-off of one Open Rubber Area Team Event, when I was included in the club team of three fliers, I did 6 and a bit minutes.
One team mate did 12 minutes plus and the third member did well over an hour in a strange weather event over an adjoining
large reservoir.  His time was the third highest as two others recorded longer flights - with the models still in sight without binoculars.  The longest flight was by non other than Phill Ball.

These models were magnificent fliers.  Pity that there are fewer places available to fly them.  

Enjoy your model Sundance but make sure the D/T works.
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Re: Unlimited Rubber circa late 1970s
Re: Unlimited Rubber circa late 1970s
Re: Unlimited Rubber circa late 1970s
« Last Edit: June 24, 2018, 04:21:46 PM by Sundance12 » Logged
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« Reply #12 on: June 24, 2018, 04:28:50 PM »

Thanks for the words of encouragement, I am suitably motivated as this is new territory for me. RalphS, thanks for the great images, that prop in the launch image is working very hard. Thanks for the flight reports of your experiences and the images of same. I will be looking into a suitable DT for this airplane. I have to investigate the acquisition of some rubber as I have none at this time. I am open to some advising in what rubber to get. I will have more construction images to come.

Sundance12

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« Reply #13 on: June 24, 2018, 10:43:12 PM »

I continue to work on this wing, it's nothing special. just traditional rib and spar construction. What is different is that I have not built much of anything for a very long time and this level of building is easy for me to work with. I have a habit of not finishing builds. However, the motivation to try something new is strong and I am committed to making this a proper resurrection in remembrance of model builders that "Elmered" me through some early years of my hobby of aviation. Some who were members of the forum that are not with us today.

I don't have a name for this airplane, but I think that will come.

Thanks for those who made opinions to this current project, all suggestions are honored.

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Re: Unlimited Rubber circa late 1970s
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« Reply #14 on: June 25, 2018, 03:31:10 AM »

You'll get a lot of enjoyment out of it-but take heed of the warnings that those of us who fly the class have posted-these models fly superbly when correctly trimmed and wound-implicit in that is you need a decent size site to fly them on-no sports field stuff here-and equally be aware-that if things go wrong when you're winding-they can go catastrophically wrong!   If 80g of rubber lets go unexpectedly on 900 turns whilst winding-or slips when you're in the process of reattaching the prop-then you can kiss goodbye to the model-what will be left won't even be worth repairing. Conversely-the sheer size of these-if you're only used to small cabin models or P-30s-can also catch out the unwary or unprepared-snag the tailplane as you launch, get a hand in the prop likewise-and it will be over so fast you won't even have time to swear!
   So take it slowly and carefully as you progress-and accept that these big beasties are always somewhat vulnerable-even under ideal conditions-they are always a bit fragile-and easily damaged, so ongoing repairs are a fairly routine event-a typical O/R is built down to a minimum strength to cope with the motor, rather than for extended durability. In later years Phil Ball pioneered the use of C/F longerons-which added a significant strength improvement-but required a jig to build the fuselage! I campaigned....until our last Nats-where I lost it at 15+ minutes-a modified 'Draft Dodger' which used 1/8" spruce longerons rather than balsa-that proved to be an inspired choice nearly 30 years ago-and saved some otherwise disastrous fuselage collapses over the years-albeit at a bit of a weight penalty.
   You would be well advised to: (i) build or acquire a solid winding stooge
                                               (ii)acquire a good winder-one capable of handling 16 strands of 1/4"....the John Morrill 'sidewinder' is a good one-and fit it with an extended winding handle
                                               (iii) make sure you have the requisite accessories-winding tubes, winding rods, prop hook holding wires etc....short cuts or jury rig setups will come back to bite you with these big motors
                                                    -and as I advised earlier one bad mistake winding or hooking up the prop to a fully wound motor can destroy the model.

A couple of final points-these models use big motors-80g or more-you don't get many of those to the pound-but if you only wind to about 80% of max turns-the motors will last quite well-providing you're careful winding, and lubing them! I usually run three motors for each model-ie two spares. You'll quite often break a strand winding or unwinding-sometimes it's easier to simply swap out the motor rather than trying to tie a broken strand on a slippery lubed motor.

Torque meters are very useful-but not essential-but once you have one you'll never go back to winding without one-just for the consistency benefits if nothing else!

  ChrisM
  'ffkiwi'
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« Reply #15 on: June 30, 2018, 02:31:20 PM »

Progress is creeping along, but I have a wing almost complete ready for covering. Stab to be made next. The wing pylon will need to be designed. I am not sure if these pilos are fasened to the fuselage or able to slide longitudinally. Directions are needed here.

Thanks

Sundance12
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« Reply #16 on: June 30, 2018, 06:35:01 PM »

If it is feasible, I'd attach them temporarily, as it is rare (unless you've flown a fleet of the same design  previously and only made incremental improvements) to get the CG location and incidences spot on with these  models on the bench. Often they turn out tail heavy-despite generally rearward CGs.....being able to move the wing mount fore and aft a bit as a trimming aid is invaluable-and saves adding lead to the nose....which is a sin worthy of excommunication...in this particular class !    How much leeway of movement you have in this respect of course is totally dependent on the size of the model-but on a biggish one like this I'd suggest at least an inch either way of the plan location as being acceptable.....it doesn't help of course that there is a huge variation in CG location for this class of rubber model-anywhere from 50% (fairly rare) to 100% (not uncommon) of wing chord-with CGs in the range of 70-85% being probably the most common....likewise there is no real consensus on moment arms versus tailplane areas-which also impact the CG location (or rather the lack of consensus LEADS to the big variation in CG location....!)

Once you've establish an acceptable trim, then it pays to glue the wing mount pylon firmly in location-though I will confess to having several models where it is still 'rubber banded on'.....I also have 'witness marks' on the fuselage to ensure that it remains in the right location....about the only advantage (except for the initial trimming phase) of a rubber banded on wing mount I can claim over a fixed one-is that should you be unfortunately enough to 'tree' the model irrecoverably-the rubber bands will eventually perish-releasing the wing and pylon-you at least get the tracker beacon and DT timer back (if fitted) that way.....and my experience of nearly 40 years flying the class is that wings and tails once released will often work their way down from a tree-whereas fuselages tend to snag and stay firmly where they are.....unfortunately all the expensive and time consuming bits are on the fuselage....

 ChrisM
 'ffkiwi'
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« Reply #17 on: June 30, 2018, 06:53:08 PM »

Ok Chris, that pretty much answers my questions. I will design away and be prepared to have a banded on pylon. I am a duck on dry land in this class and working almost from scratch. I got some good tissue for the wing and finish with dope.  All i need to work up is a rubber motor jig, blast tube, winding extension and a stooge of some type.

I am realizing that there is a number of trade craft items needed to be successful.

Thanks

Bruce

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« Reply #18 on: July 01, 2018, 10:26:58 AM »

One other item would be a torque meter.  Easily made following the recent posts on that subject.  The Kothe type meter plan available on the Volare web site is very easy to make.  Calibration accuracy isn't absolutely neccessary.  I made mine using an aluminum arrow shaft.  The torque wire which is good for 80 lbs @ 270 degrees twist is anchored part way down the shaft, and an insert at the end anchors the hook.  The meter also acts as a winding shaft on which the winding tube is after winding and before attaching the prop assembly. 

Wire and hook anchors are held with small diameter steel split roll pins.

Winding to torque is much more accurate than counting turns.  Allows repeatability between flights--an absolute necessity when trimming rubber models of any size.

Using a  torque meter, I discovered that about all my fumble fingers could safely handle was 40 oz/in (on my meter at least)!  I tremble at the thought of 100!!!
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« Reply #19 on: July 01, 2018, 01:03:32 PM »

Hi Bruce,

On my Hornisse and Lefever Wakes the original designs used a built-up pylon (lightweight framework inside a sheet balsa wrap) with a fore and aft backbone of light plywood to anchor the rubber bands. If you extend this anchor a bit you can attach the wing with bands then attach the pylon to the fuselage with more bands. Then the whole unit slides fore and aft to adjust CG. A good place to start for the approximate CG is the mid-point of the motor. Then put 75% of the chord over this point, assemble the whole thing and give it a toss. Tall grass is good. When you are happy, glue it down, cut off the excess rubber band anchors and away you go. Don't try to set it too close to stall initially, or you will be wearing a bunch of nose weight when the wind comes up.

Bill
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« Reply #20 on: July 01, 2018, 02:05:01 PM »

I have used meters before but fot indoor class models and do very much appreciate the improvement in my consistency with flying. I have made them befor but not for 80 lbs of torque. I will have to research this...
Thanks for your
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« Reply #21 on: July 03, 2018, 09:48:07 AM »

I have had the privilege of flying with Herb Kothe a number of times. He is a real gentleman and one of the legends of free flight.  

I am attaching a picture of Herb taken at Eloy, Arizona, a few years ago.  He is launching his Taylorcraft model.

Herb is nearly unbeatable in any free flight event he chooses to enter.  I learned a lot from Herb. He is patient and generous with his advice.  

The Kothe torque meter design is well proven and his drawing gives all the details that you need.  I made one following Herb's instructions.  Mine used a carbon fiber composite arrow shaft to enclose the length of wire that is twisted as you wind.  You can buy one at Walmart or a sporting goods store for about $4 US.  The carbon fiber composite shaft is light weight and very stiff.  I believe it to be more durable than an Aluminum tube.  I used epoxy to affix the rear Copper end cap and the forward wooden disc to the opposite ends of the carbon fiber composite shaft. Epoxy "likes" to adhere to carbon fiber composite material.

If you can find one for sale on this web site, or on eBay, you might want to purchase a Morrill winder.  It is well suited for winding large rubber motors.  As shown in the attached picture, I retro-fitted mine with a helical spring torque meter purchased from Volare Products. The quality of the torque meter is superb.  The scale goes from 1 to 10.  I wind my Gollywock rubber motors to about 2 and that is plenty of torque.  I am confident that this torque meter would take 80 inch-ounces of torque although you should check with George Bredehoft at Volare Products to confirm this.  It is easier to wind with a combination winder and torque meter. Use of a combination winder and torque meter makes it safer to get the prop assembly connected to a "fully" wound large rubber motor.


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Re: Unlimited Rubber circa late 1970s
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« Reply #22 on: July 03, 2018, 11:16:55 PM »

I agree with Cal and use a combo winder and torque meter. I use the counter to help "pace" myself as I move in from my starting, stretch point. I start coming in toward the model at 60% of the approximate number of turns I will use. Then as I get pretty close I begin to monitor the torque meter. If I've done my job the torque will be there when I get to the nose of the airplane. If you muff it you will wind up with quite a gob of turns right behind the Crockett hook which can make the hook-up to the prop a bit of a wrestling match. Pace it right and you'll wind up with a much better distribution of turns.

I am pretty conservative with my initial stretch using 4X the motor length - and yes I do actually measure it with a tape. Others really stretch the poor thing to get the absolute most winds and torque. Another topic...

Bill
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« Reply #23 on: July 05, 2018, 08:33:14 PM »

Completed wing for this aircraft. I was pleased with the use of EzEDope product from the UK.

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Re: Unlimited Rubber circa late 1970s
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