cox 049 endurance record?

I can't find the thread here.. but a while back I pitched the idea of a CEF "Lindbergh-event".. for a single Cox .049 engine to fly a control-line model for a duration-record using one non-restricted size fuel tank for a single flight. That would obviously be just one class of duration.. but would be a fairly simple thing to try for anyone interested.

How many minutes of sustained flight could be achievable...? Anyone care to make a S.W.A.G.? Sure would be interesting to see what types/sizes of airframes people came up with.

I remember that discussion Roddie. I was wondering if the goal would be to fly as long a time as possible or to cover as much distance as possible. Either way, it would be an interesting competition.

For an R/C duration, I would look at Texaco engines and their run-time. Maybe a texaco-tuned bee-engine with a needle-throttle and an external tank?

We flew two Little Traveler Flights as a charity benefit for St. Jude Hospital---one successful and the other suffering the loss of the plane when it's wing failed over the Mississippi River.  Both flights benefited the hospital though, so not a real failure.

I searched for a while, but could never find a clear record that applied to specifically Cox-powered airplanes.

https://www.coxengineforum.com/t4660-little-traveler-revisited?highlight=Little+Traveler

Another Little Traveler is drawn up, but not seeing much work toward finishing it (typical).

The first two were based on light trainers...the Minnie Mambo and Q-Tee.  Little Traveler III will be a more heavily loaded scratch-built, using Ace foam core wings...if it gets built...

KariFS wrote:I remember that discussion Roddie. I was wondering if the goal would be to fly as long a time as possible or to cover as much distance as possible. Either way, it would be an interesting competition.

For an R/C duration, I would look at Texaco engines and their run-time. Maybe a texaco-tuned bee-engine with a needle-throttle and an external tank?

Well Kari.. IMO.. "Free-Flight" would be the ultimate test as far as the entire models' endurance is concerned.. but then; it's not an engine-endurance test.. and most modelers don't have local access to the size area needed to fly in. I'm curious as to what the current Free-Flight "Texaco-class" record is..

Then there's RC... which has the advantages of controlling for an actual distance-record using a chase vehicle.. but at the expense of liability-consequences. RC Pylon-racing is a different story. Distance can be somewhat measured.. but endurance is a non-factor. As far as an RC models' "duration" is concerned, a glider with .049 Cox-engine assist could be flown in a controlled-area.. (max ceiling) and have the advantage to catch thermals like a free-flight model might. Ultimate conditions could yield a flight of hours... but not under actual engine-power.

A control-line endurance model's performance can be accurately documented for distance; via the number of completed laps at a given line-length.. or endurance, at "any" given line-length. When the engine runs out of fuel.. the model comes down immediately. The clock starts when the wheels leave the ground.. and stops if/when the wheels touch the ground again; whether the flight is over or not.

This thread is a pretty cool place for discussion.. where it concerns our Cox engines.. and what they're actually capable of.. when it comes to flying any type of model airplane.

I'm curious as to how much of a payload that "any-type" Cox .049 engine can lift and sustain-flight when being flown on lines.

A powerful engine/prop-combo will be more capable to lift a heavier-load.. but at the expense of fuel-economy.. whereas an engine that "sips" fuel won't have as much power.. but will have a much-extended run-time. The key I think.. would be to build a super-lightweight airframe having a low-drag coefficient. It would be fragile.. but it would be purpose-built to only fly level-laps. R.O.G. would just be a cooler mandate.. like a "real" airplane. The fuel-load would best be placed directly over the C of G. A stream-lined "bay" in which differing sizes of balloon-tanks could be experimented with. Balloon-tanks would seem to be the obvious choice for weight and reliability of draw when used for level-flight.

A Clark-Y wing-rib airfoil IMO, would be another obvious choice for such a model. The wing-span/chord/tip-profile would all be variables.. as well as the lead-out guide placement. Line-length would depend on how calm the air is on flight-test. Shorter lines will reduce drag and help with keeping the model level. It's not a stunt-model.. and it's not a trainer either. I'm guessing that wing-span/area would exceed that of any 1/2A control-line sport model.. and might approach 30"/200-250 square inches. I'm babbling as usual.. but I really enjoy thinking about the possibilities!

Endurance with CL would be taxing on a pilot, very taxing. Short lines would be even worse. I suppose it's possible, if you could put enough fuel in a plane coupled with an engine powerful enough to pull the weight, lines etc.

Thanks guys, a lot of ideas here!

I'm aiming for something like what Kim have done back in 2009.

According to Google map, the small town next to ours are around 30miles. I plan to use lower nitro fuel, or maybe 0% fuel. Some of my Cox engines run happily without nitro, in Texaco mode.
Using a modified Cox SS turning a big prop, install a muffler to feed pressure into the tank if the big tank need to be pressurised.
If I'm using a glider for this , low wing loading means I can carry more fuel. I need to find the sweet spot between wing loading vs speed, most gliders are cruising very slowly. GPS waypoint controller and FPV equipments are optional, weight is my enemy here, but I will put a small keychain video camera.
I've seen some of Texaco plane weights up to 26 Oz ++, and small Texaco engine still can power it without much problem. Old designs are using heavy radio equipments, by using the lightest servos and receiver, I can save a lot of weights from there.
I need more than an hour flight time for this, sounds a bit too ambitious but I'm willing to try, and the charity event will be funded even I can't complete it, but hope I can make it a success event.

any suggestions and ideas are welcome

Cribbs74 wrote:Endurance with CL would be taxing on a pilot, very taxing. Short lines would be even worse. I suppose it's possible, if you could put enough fuel in a plane coupled with an engine powerful enough to pull the weight, lines etc.

Sounds a lot like the things Lindy's team had to work on, except for the line length of course

KariFS wrote:

Cribbs74 wrote:Endurance with CL would be taxing on a pilot, very taxing. Short lines would be even worse. I suppose it's possible, if you could put enough fuel in a plane coupled with an engine powerful enough to pull the weight, lines etc.

Sounds a lot like the things Lindy's team had to work on, except for the line length of course

... C'mon now fella's.. I'm talking about a "single" .049 engine here.. powering a control-line model. Do you think that a flight could actually go more than 10 minutes?

Well, 10 minutes is not much of an endurance flight. The full PAMPA pattern is done in 8 mins. On bad lean runs I have probably gone just over 10 mins at times. Mark mentioned spinning in circles for 10 mins. Without stopping in place to stunt it would be tough after a while.

I think it's possible if you can build a 1-2oz plane.

I was thinking like a 6oz fuel tank.

Yikes! A 1 -2 ounce plane and 6 ounces of fuel. Start Friday after dinner and stop sometime Saturday? A midnight flight!

NEW222 wrote:Yikes! A 1 -2 ounce plane and 6 ounces of fuel. Start Friday after dinner and stop sometime Saturday? A midnight flight!

A TD at full wail gets about 8 minutes per oz. so less than an hour for 6oz.

You could probably get the weight of the airframe up to 4oz and still be ok. It's doable, but a long time to spin around in a circle.

Keep in mind 1oz of fuel doesn't always weigh 1oz.

I think I could create a styro-wing and box-fuselage model of the Spirit of St. Louis and keep it under 5 oz. My "American Boy" weighs 5.5oz complete with the metal-backplate engine, tip weight and some ballast to get the CoG right. I didn't watch the weight while I built it, it has a lot of paint on it, long&heavy landing gear, steel pushrod and so on.

A Finnish company makes and sells styro wing cores of suitable size (24" span, 4 1/2" chord). Its profile is for gliders mostly but has been adapted to many other uses too:



The wing core weighs about 22 grams. It needs to be reinforced, but the Spirit has wing struts anyway. Those and some carbon fibre strips placed strategigally should make a strong enough wing. The wing profile is for slow flight, so the propeller diameter and pitch need to be selected properly. With a lightweight basic box fuselage made of light 1/16 sheet, plywood wheels and such, the rest would not weigh a lot. The tip weight might be eliminated with a slight asymmetry of the wing and maybe a LH prop.

The engine would be either a Texaco with the small venturi and a tank drilled for external supply -or- a sure-start type engine with the adjustable throttle. MAYBE even a throttle with a simple timer that would let the engine run at full power for a minute or so for take off and then slow it down to more economical cruise speed

The biggest questions that remain are:
1. What is the maximum total take off weight of the model described? That minus the dry weight equals the max amount of fuel carried at take off.
2. How long can the lines be for such an underpowered, slow and floaty model? Long lines would be nice so that the pilot would not have to spin fast. On the other hand, the rudder and engine offsets should be kept minimal to reduce drag.

An R/C application would be nice too. As a teenager I built an oldtimer that had about 42" wingspan, and it was designed for a Babe Bee. I only glide-tested it, and found out that the tissue I used to cover it with was not good. Got plenty of tears and punctures by just landing to grass so I did not even try it with the engine running as I didn't want to ruin it completely. Anyway, this model glided well with the 4xAA battery pack and heavy '80s radio gear onboard. A similar plane with a little bit less "draggy" wing profile and the weight of the battery pack replaced with extra fuel would have a pretty good flight time.

EDIT: I read Kim's story, great information! And coming from actual real-world experience too

CL one of these beast from the 70s .... http://www.ebay.com/itm/Carl-goldberg-eagle-2-kit-/282203732868

An .049 reedy will pull up a porky 2m+ glider. Probably a whole 32 oz easy. Vertical performance is non-existent, but not necessary.

I am pretty confident that a single Cox reed .049 will haul it to altitude. There are numerous videos of a single Medallion, or RR1, or TeeDee hauling Kim's 2m BOT to altitude.

Phil

pkrankow wrote:An .049 reedy will pull up a porky 2m+ glider.

Not sure this was the intention of the OP. We want a Cox endurance test, not a soaring endurance test- nothing new about that. It's common to see .049s, usually a Texaco, haul a glider to altitude, then stay aloft for a long, long time, as gliders do. That doesn't test the engine, just the aircraft & the pilot's skill. I think the real measurement needs to be from launch to engine quit. Round & round would be a real test. If a decent endurance could be obtained, no reason you couldn't have a relay of pilots taking over after every five minutes or so.

Oldenginerod wrote:

pkrankow wrote:An .049 reedy will pull up a porky 2m+ glider.

Not sure this was the intention of the OP.  We want a Cox endurance test, not a soaring endurance test- nothing new about that.  It's common to see .049s, usually a Texaco, haul a glider to altitude, then stay aloft for a long, long time, as gliders do.  That doesn't test the engine, just the aircraft & the pilot's skill.  I think the real measurement needs to be from launch to engine quit.  Round & round would be a real test.  If a decent endurance could be obtained, no reason you couldn't have a relay of pilots taking over after every five minutes or so.

That's kind of what I was implying Rod! This thread (IMO) is about the engine's ability to sustain flight under-power... however that is achieved. Relay-pilots would just be a given; for testing endurance. A co-pilot could easily take-over the handle for control-line record-attempts. If 8-10 minutes of flight seems well within normal limits.. then maybe 12-15 or more minutes should be the target?

Granted.. it would be a long boring time to turn level-laps... but it would be for bragging-rights!

There could also be a control-line RTP endurance class. This would involve an RC assisted elevator, controlled by a pilot having a transmitter. The weight of such a system would be minimal; given the current availability of the nano RC components available today.

Rod and Roddie, that was my general idea too. Except that I have no doubts about a Cox engine's ability to run for several hours continuously.

I think the limiting factor is the model's fuel capacity and possibly the pilot's endurance. And, of course about finding the balance between the model's drag, necessary thrust and fuel economy. I see this as an engineering excercise, and I keep bringing The Spirit of StL up because I recall it had something to do with Roddie's earlier thread that I have not yet dug up

The question of how heavy was also included. This does bring in the value of small engines taking models up for soaring as those can be very heavy.


Now RTP brings up a possibility:
Fuel line to the center for in-flight refueling.

Not quite sure how it would work out as the fuel system will have some weird pressures on it from centripetal force. The possibility of kinking is real too.

At least the remote fuel system will remove changing weight from fuel and allow much more fuel to be used in a flight - more than can be carried.

Phil

I smell the next CEF contest brewing....

Longest time aloft for a cox .049 powered control line model, rise off ground, all fuel carried onboard.

Any takers?

The competitive Jim

JPvelo wrote:I smell the next CEF contest brewing....

Longest time aloft for a cox .049 powered control line model, rise off ground, all fuel carried onboard.

Any takers?

The competitive Jim

To add to the challenge, I suggest that the model should look like a real-life endurance or distance record (or record attempt) airplane. I mean just about any record breaker, be it Wright brothers plane, the Spirit of StL, Hughes racer, Amelia Earhart's Lockheed or even one of Burt Rutan's planes. Just a suggestion

The CEF thread that I originally pitched a "Lindebergh-contest" in; was one that Kim Stricker posted. It addressed a previous endurance-thread by Ron Cribbs.  

https://www.coxengineforum.com/t4827-yo-ron-please-bump-your-endurance-run-thread-to-the-top-again?highlight=endurance

As with some contests.. "participation" can be sketchy. Many people will "like" the idea.. but when it comes down to building an actual model.. well.. the crowd can thin-out.

The 1/2A C/L proto speed-contest was well-participated.. the first year. There were also prizes to be had.. and a LOT of excitement! Many contestants experienced "challenges".. in the way of launching, and models that crashed before they got a single lap in. That may well have affected the attendance in the following year(s). Some WICKED models were built though.. Unique/one-off creations built to fly on the ragged-edge!

An endurance contest would be a bit less pressure I think. The Speed contest had rules that closely mirrored the AMA 1/2A profile/proto rules.. which was the best approach for that type of event.

An endurance-event/contest could be much simpler. The model need-not be scale.. but extra points/prizes could be awarded for that. No min/max line-length, no fuel-restrictions, no model-size restrictions.. only that a single Cox .049 engine power the model. There wouldn't be the need to regulate engine-configuration.. because a "hopped-up" engine will likely burn more fuel.. which would be counter-productive. Maybe there could be a separate class for compression-ignition (diesel). "Lindy's" highly modified Ryan was referred to as a "flying fuel tank"! That's basically how you'd want to wrap your head around designing a model.