View Full Version : 24" Sopwith Pup

10-23-2009, 11:10 PM
I want to build this Pup (although the official name was Scout) to use the scale "outrunner" Monosoupape I have already made.
At 24" span it is rather on the small side for 3 or 4 channel so weight will be at a premium but nevertheless I intend to follow scale construction as far as possible.
I found a nice 4 view line drawing which shows quite a bit of the detail so I just enlarged it and stuck individual A4 sheet together.

As a start I thought I had better built a "test" wing panel to try out construction methods and check the weight.
This test wing uses solid hard balsa 3/32 spars, 1/16 LE and everything else 1/32.
In this state it weighs 3.6 gm or 0.127 oz. This may not sound much but it will weigh quite a bit more when covered and of course there will be 4 of them.
As the RAF 15 section is so thin this test wing will also be used to develop a scale "closed loop" control system to move the 4 ailerons from a single servo in the fuselage. The elevator and rudder are a bit easier as the cables run straight down the fuselage.
I am aiming for an airframe weight, less motor, battery and servos, of 112 gm or 4 oz.

10-23-2009, 11:19 PM
Cool,, I'm Sub'ed! bubsteve

10-24-2009, 03:51 AM
24 inch Sopwith Pup , wow , when I read that I thought , oh my Parkzone has come out with a Sopwith Pup BNF ::o
Horizon Hobbies , Parkzone and E-Flite have been comeing out with so many new planes , I just thought they had done a WW1 BNF or RTF , biplane even , wishfull thinking :)
Sorry for the off subject , please continue the 24 inch wingspan build of a Sopwith Pup :)
I really do enjoy my Electrifly Sopwith Pup a lot ! :D

10-26-2009, 04:35 PM
The solid hard balsa spars of the "test" wing although admirably strong felt rather heavy compared to the rest of the wing structure.
For bending the best strength to weight ratio is achieved with a flanged beam so I have built another test wing but this time using a channel section spar made up from 1/32 sheet.
With the front and rear channels facing each other the rib middle sections are carefully slotted to support the flanges, where as the front and rear rib sections are simply glued to the flat face.
This wing weighs 2.7 gm. Yes, rather a lot of trouble just to save 1 gm but then that is a reduction of 27%.

Hopefully this wing will actually end up being used!

10-27-2009, 07:55 PM
Here's a picture of a kit (22" WS) I bought off of ebay. It is my intention to use a BNF 2.4G brick from a Vapor or Ember along with a small 1 or 2 cell lipoly. Should be an interesting build. Maybe a project for the winter building season? What do you Guys think? PS Q keep at it. Looks like a worthy project. Marty



10-28-2009, 07:44 PM
The second "test" wing aileron. The LE of the aileron is in the form of a 120 degree V to allow 30 degrees up/down travel with a centre line hinge.

I am hoping to create a true scale cable system using a fine mono filament fishing line with small metal eyes where the cable turns through a right angle. Of course all this has to tested before any covering can go on.

If it works ok for the ailerons the elevator and rudder will be quite a bit simpler as the cables run straight down the fuselage.

10-28-2009, 08:23 PM
I am hoping to create a true scale cable system using a fine mono filament fishing line with small metal eyes where the cable turns through a right angle. Of course all this has to tested before any covering can go on.

I would not use mono filament fishing line, it will streach.

10-29-2009, 12:23 AM
Yes I know its pretty stretchy but the Pup is pretty small so the control forces will be very low and a bit of "give" may be a good thing to absorb any problems with the geometry of the system. This is why I want to test it all before adding the covering.

10-29-2009, 12:58 AM
Use 10 pound test Spiderwire. The stuff is super light and thin and does not stretch much at all. I used it to rig 3 biplanes. Marty

10-29-2009, 01:05 AM

11-01-2009, 11:32 PM
This is not a quick build!
The top wing structurally complete. It weighs 7gm (1/4oz) along with a modest start to the fuselage.
Hopefully it will end up looking something like this.

11-01-2009, 11:52 PM
great progress!!

capn chaos
11-02-2009, 12:05 AM
I like your approach and willingness to experiment. Great progress on this.
I'm "all in".

11-02-2009, 05:23 PM
What an ambitious project quo! ;-) I don't have enough patience or time to devote to a build like yours although I prefer to build (scratch or otherwise). ;) I think sometime towards the end of this month I will start on my Pup. Should be a fun build (wish me luck!). Keep us posted of the progress. I'm sure I'll pick up a building trick or two by the time you're done. :) Marty

11-05-2009, 07:46 PM
As I now have some "hair like" 1.9lb mono filament for the control runs I thought I would attempt to scale brace the fuselage with it as well.
This fine line actually glues quite well with balsa glue so with a pin angled outwards at each joint a single strand is simply "weaved" around them, down the fuselage and back.
A drop of glue at the base of each pin and at each cross over completes the job.
It weighs practically nothing and it really does stiffens the structure quite a bit.
Scale? yes. Practical? not really and in any case it will be almost completely hidden by the covering!

11-05-2009, 10:06 PM
Good job. You must have a lot of patience!!

11-06-2009, 09:01 AM
The basic fully braced fuselage structure. It weighs 3.6gm.
With a scale electric rotary completely ahead of the firewall, the LiPo will go in place of the fuel tank with the servos & ESC underneath and, if I can get the radio in behind the instrument panel, everything will be virtually hidden so I should be able to have a scale cockpit as well.
But all that is some way off yet.

11-09-2009, 05:38 PM
The fuselage fairing structure.
The top deck stringers were unbelievably just 1/4 by 1/8 spruce on the full size so my 1/16 by 1/32 are actually 3 times too big. The cockpit decking is 1/64 sheet but again should be 1/96 for scale, however using balsa instead of birch ply means about scale weight.
Note the side "intermediate" formers, just like the full size, have to be curved to clear the fuselage bracing and for reasons I have not yet discovered there were 5 formers on the left but 6 on the right.
It now weighs 5.2 gm.

11-13-2009, 10:12 PM
The next problem to solve is how to actually thread a fine mono filament line from one aileron lead out to the other, negotiating two right angle bends and 18 ribs, and all after the wing has been covered?
One solution is bendy drinking straws!
This is a trial installation on my initial "test" wing panel.
With a suitable drinking straw channel I intend to blow the aileron line through once the plane is fully assembled.
Well that's the plan at the moment!

11-14-2009, 01:41 AM
Great project, it'll fly a treat. I once had a 16" span free flight Pup with a CO2 motor in it. When the motor behaved, it would take off, fly around in circles and eventually come back down to land. That's indoors!

Unfortunately, it didn't make it across the Atlantic when I moved to the US :(

It had somewhat more dihedral than 'scale' being FF, plus I aren't really a good enough builder for that sort of model. Pups are just inherently good fliers though, so yours should do fine. WW1 biplane structures were very light indeed, as you note about the top decking stringers - we all tend to over-engineer models, but you're on the right track.

You might find yourself wishing you'd painted the ailerons on! The Pup will turn on rudder, and often you get lots of adverse yaw off the ailerons. The only way around that is massive differential - say 10% throw down, 90% up - and/or accepting you have to use either the rudder as primary steering or couple ailerons/rudder either electronically or use your thumbs.

Good luck


11-14-2009, 02:54 AM

this is simply amazing...

its people like you that keep balsa scratch building alive...

I am just amazed at how you just took a 4 view drawing and just built the plane around it! no plans at all!

and the detail... its just awesome... defiantly keep up the good work!

I might have to attempt this after I finish up my Spit... are you planning on making plans? :D

anywho... keep up the AMAZING work... SPIT.

11-14-2009, 03:09 AM
Plans would be nice. Then you can be added to The Best Full Fuse Plans and Build Guides.;-)

11-14-2009, 03:25 AM
Plans would be nice. Then you can be added to The Best Full Fuse Plans and Build Guides.;-)

yeah... it would defiantly be one of the best...

but heck, at this point, I will probably just do what he is doing!

P.S. I thanked your post because I agreed... like it was thumbs up or something... man, I have been on youtube to long :D

11-17-2009, 11:36 AM
Although light at 4.5 mm diam a drinking straw requires such a large hole it rather weakens rib which is only 8mm deep so I am using 3mm diam ball point pen inners.
A 90 degree bend is steamed in and the sections joined with heat shrink sleeving.
To test it the fine mono filament line has been pushed through.
The aileron has a slot to mount the horn after is has been covered and a pad with a very small hole to take the line through to the other aileron. I hope to be able to rig the complete 4 aileron circuit with one continuous thread.

11-23-2009, 01:43 AM
With the guide tubes installed, along with the mountings for the struts and aileron horns, the wings are ready to be covered.
They weigh 17.4 gm

11-24-2009, 11:47 AM
The tail plane and elevator. Although the spar is solid the rest of the construction is similar to the main planes.
The final problem is how best to emulate the aluminium sheet sections. My intention is to use ally foil stuck on 1/64 sheet balsa.

11-24-2009, 08:34 PM
I think that it will look good no matter what you do. It looks amazing already.

11-25-2009, 12:34 AM
Love the pup. Your idea for running the cables for a pull pull setup thru a conduit is pretty good. You might try 1/8" soft aluminum tubing. If you cant find it at the hardware store, go to your local propane retailer. We use 1/8" tubing for the pilot tubing on blue flame heaters, ventless fireplaces and the like. Its dead soft,and can be bent to a 1/2" radius bend with just your fingers with out kinking.


11-26-2009, 04:15 PM
Well the Monosoupape fits!
This is actually my "test" Mono which will be rebuilt with a lighter Emax 2805 inside instead of the 2812.
Not exactly a true scale engine mounting but I do need the space directly behind the firewall (which is 1/16 2ply balsa) for the battery, servo and ESC.

11-29-2009, 01:10 AM
Started the tissue covering.
The lower RH wing.
The structure is really too lightweight to be doped so the tissue has been "filled" with Extra Hold hair spray. The tissue and spray adds 1.1 gm. It now weighs 4.9 gm.

11-29-2009, 01:55 AM
Its looking great! I am really looking forward to the final product.

11-29-2009, 05:30 PM
The first test run of the rebuilt "light weight" Monosoupape.
The rather noticeable "hum" is due to the building board it is sitting on.
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Not quite full power, the glue needs to fully harden.
It is slightly over propped so I will try a 7x3 but I am not sure it will all hold together at 10000+ rpm.

11-30-2009, 09:47 PM
Well it is 24" Span - the first layout of the fuselage and wings.
The fuselage has ally foil covered firewall and side panels.
Still a long way to go!

11-30-2009, 10:47 PM
Very nice! You progress so quickly!

11-30-2009, 11:51 PM
Q you're gonna rip the wings off with that much power! Excellent build BTW. MArty

12-01-2009, 12:42 AM
I estimate that the Pup will actually fly on just 15 Watts which about 2 amps on a 2s LiPo. This should be achieved at rather less than half throttle. Full power will certainly not be used for the first flight!

12-06-2009, 12:17 PM
The U/C with the trade mark Sopwith split axle.
It will use elastic cotton bungee cords, as does the tail skid.
The lightweight (1.8 gm) balsa wheels run on 20 swg (19 awg) axles. Its gloss because the paint was still wet!

12-10-2009, 05:15 PM
The 3.7 gm servo "block". Top for the elevator, bottom aileron. They are installed just ahead of the lower front wing spar.
This allows the fuselage sides to be covered and the tail feathers installed followed by the elevator control runs.
As in the origianl the fin is mounted clear of the tailplane (thus the characteristic fin gap) and relies entirely on the tail bracing.
The first elevator test. There is rather too much "down" so it will have to be redone! <object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/RxGOOEM-IxY&hl=en_GB&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/RxGOOEM-IxY&hl=en_GB&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

12-10-2009, 11:21 PM
Very nice! I like the servo block idea!

You make beautiful airplanes!

12-11-2009, 10:05 AM
The servo block is a neat touch agreed, the builds a work of art.

12-11-2009, 11:48 AM
The elevator has been re-rigged with thicker 7 lb mono line and the fuselage covering completed. Now for the wings.
This photo rather nicely shows of all the tail wires.

12-22-2009, 09:49 PM
Started to fix the lower wings.
There are in effect pin jointed so all the loads will be carried by the wires.
Actually they are fixed with small strips of acetate glued with cyno.
All the struts will be done the same way.
I know it looks crazy but it light and strong enough and if the worst comes to the worst hopefully they will pull out before breaking the structure.
The battery, ESC and radio must be installed before I can fix the top wing.

12-25-2009, 10:14 PM
wow, very nice. truly inspiring. thank you for sharing this project.
you lost me on the acetate joints though?

I'm going to tom stafford air and space museum tomorrow. they have an actual sopwith pup there. rotary and all. shall I post some pics?
they actually have a ton of cool stuff there.

12-26-2009, 12:13 AM
All the struts on my Pup are only 1/16 thick balsa so it is very important that they are flexibly mounted so they only see simple compression loads with no bending forces, just as in the full size. The thin plastic strip joint allows the strut a degree of flexibility but ensures it is still properly located.
I think I have all the pics I need but if you can get a nice shot of the inside of the cockpit........

12-26-2009, 03:55 AM
now I get it. thank you for taking the time to explain.

yeah, I'll see what I can do. they are pretty nice people who run the place.

01-03-2010, 01:34 PM
At last the radio arrived! Quite small (that's a one pound coin) but no case so it has a balsa 'slide in' mount which will be glued directly to the back of the firewall.
The Monosoupape and ESC fitted. To get the CofG about right it all has to squeezed in right at the front. The only access will be a hatch underneath to insert the 500mAh LiPo made up of two single cells, one each side of the servos.
It should weigh just under 4.5 ounces all up.

01-03-2010, 02:16 PM
Excellent build Q! That radio is indeed small. I'm amazed! Marty

01-05-2010, 09:02 PM
The last unsolved problem (apart from will it fly!) is the Monosoupape engine cowl.
Unlike the elegant full circle one used on the 80hp Le Rhone, the Mono had a rather angular "horse shoe" type so I decided to try and make one out of 1/32 balsa and cover it with ally foil to match the rest of the fairings.
The front and sides are sheet but the radius bit is made up of 40 wedge shaped 1/8 balsa blocks arranged in two rings and carefully sanded to profile inside and out.
It works ok and only weighs 2.1 gm however this will rise to 3 (still only 1/10 oz!) when covered in foil and the 4 little air scoops added.
However, a bit like the rest of the plane, this cowl is more an exercise in light weight carpentry than a practical way to make a cowling!

01-05-2010, 10:12 PM
That is some impressive work there. The curved part that looks like it is made out of 50 pieces all fit together perfectly would be beyond my patience.

01-10-2010, 09:48 PM
The cowling foil covered with its external stiffening ribs and air slots. Not quite as neat as I would have liked but the weight had to be kept to a minimum.
The top wing is now fitted to the cabane struts so at long last its beginning to look like a Pup.

01-10-2010, 10:11 PM
man that look great!. the cowl is very nice.

did get some pictures, but they are probably not going to do you much good. there was a pilot (manakin) in the cockpit that no one was interested in moving and I was already pushing my luck by climbing up on the plane. all of the parts in the cockpit had been removed, except for the stick.

I did get some pictures of the tailwheel, the engine, and overall.

thanks for sharing the build, it's looking great.

01-12-2010, 11:09 PM
Nearly there!
The 7lb mono line rigging. It is virtually qall done with a single thread threaded around each strut in turn and secured with a smear of glue. The main flying wire is doubled.
None of the lines go slack when its lifted by its wing tips which is my rough and ready test to simulated a 4g flying load.

The aileron horns have tiny holes in their ends allowing a single line to be threaded right round the system from the aileron servo and back. This allowed the line to be tightened and secured whilst the ailerons are still free to move. Each aileron was then accurately lined up and secured with a blob of glue and it works!
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01-12-2010, 11:50 PM
OH BABY!! :eek::D:cool: Marty

01-13-2010, 03:56 AM
LOOKING great~! Nice job on the cowl !! can't wait to see her airborne.

01-13-2010, 12:43 PM
A better view of the wires. I have painted them grey so at least you can see them.
A this size its amazing what you can get away with. There are no mechanical fixings on the rigging apart from where the lines that are tied to the servo arms. Everywhere else its just glue.

01-13-2010, 04:38 PM
Looking really good! I like the cowl. I'm surprised that they thought they needed vents considering the motor is spinning - seems it would cool down nicely on it's own as it swings thru the lower open section.

Anyway, it's a lot stronger than foam, and you probably aren't going to be hurt by weight that far forward anyway.

Have you weighed it lately?

btw, the landing gear is top notch too.

01-14-2010, 06:29 PM
The cowling weight was not really a problem as even covered in ally foil it only weighs 0.1oz!

I was a bit puzzled at first by the extra slots as they were only on the Monosoupape engined version, but the clue is in the name, the engine only has one valve so most of its combustion air had to go in through the exhaust valve.

This explains why the extra slots were so specifically arranged to ensure there was sufficient fresh air in that part of the cowling where the induction took place.

The normal 80hp Le Rhone was a conventional 2 valve engine and drew all its mixture from the carburettor behind the engine through the crankcase and out to each inlet valve through its trade mark copper pipes. Exhaust gas in the cowling would not effect engine power.

01-15-2010, 03:39 PM
Thanks for that bit of info! Cool to know that.

01-16-2010, 12:08 AM
Now close to being finished, just the roundels and fin strips to do.
Not quite the correct shades but to keep the weight down the Humbrol enamel was thinned 2:1 and applied sparingly.
Thinking about it I should have left the roundel areas unpainted as the olive particularly will tend to show through the white.
It weighs 5oz all up.

01-16-2010, 12:28 AM
SWEET! Very nice job. Have you ever seen cheverons (white) on the fuse sides? slightly forward of the elev? I had seen a picture of one years ago, that I can no longer find, it was suppose to be an original plane. Most original photos always seem to depict the Sopwiths very plain. I was going to put some on mine, but want to find out if that even existed. I love your paint color!!

01-16-2010, 02:31 AM
SWEET! Very nice job. Have you ever seen cheverons (white) on the fuse sides? slightly forward of the elev? I had seen a picture of one years ago, that I can no longer find, it was suppose to be an original plane. Most original photos always seem to depict the Sopwiths very plain. I was going to put some on mine, but want to find out if that even existed. I love your paint color!!

Here is a Sopwith Pup training plane that is not plain. I have found some training planes painted up more that planes on the line.

01-22-2010, 12:10 AM
The maiden for the Pup is going to be a bit of a nightmare as it really needs no wind and a super smooth surface to take off from to perform some test hops. A big hall would be nice!

So how to find out what it is likely to fly like and where exactly should the CofG be?
Answer: build another one, quick and cheap but as aerodynamically similar as possible so here we go with a 24" Depron Pup!
No plans just a dimensioned sketch with each piece then drawn directly on the Depron.
Obviously the wings are the most important so they have the most detail but the fuselage can be a simple box structure.
Each wing has a 3mm skin over ribs with the same thickness and sharp leading edge profile.
With a 2" wide fuselage and a 2" top wing centre section the top and bottom wing panels are the same size.
The tail plane in simply 4mm sheet & the fin 3mm. All the control surfaces have clear tape hinges.
It will have the same servos and closed loop mono filament control runs but for simplicity everything will be run outside the airframe.
I got this far in just 3 evenings work. The same stage in the balsa/tissue version took 5 weeks of evenings!

01-22-2010, 12:29 AM
It appears that a 'good' Pup was likely to be grabbed by the CO of the training squadrons as their 'personal' transport. These were the more highly decorated ones.

The UK authorities banned anything but the most modest squadron markings on front line aircraft unlike the gaudy colours of Richthofen's crack "Jagdgeschwader" group.

01-23-2010, 10:39 PM
The Depron Pup glued together. Nothing sophisticated the 1/16 balsa struts are glued into slots cut into the depron. The cabane struts and lower wings are simply glued to the side of the fuselage.
The wires for both wing bays were done with a single strand thread through pin holes in the end of the struts. Both ends were then attached to a weight (the pliers) and the sections were carefully tweeked to the same tension and secured with a dab of glue.
It is remarkably light only just heavier than the balsa & tissue version at that stage.

01-24-2010, 02:28 AM
qu you are the master (Marty bows to you). I am impressed! :cool: You must hang on to those plans for the depron pup. :) I might need them (after you work out the bugs of course!). :eek::D Marty

01-24-2010, 04:40 PM
Thanks scalercflyer.
This is of course just a "test" plane so apart from the flying surfaces accurate detail is not important,as a result the Depron Pup does not have any plans just a fully dimensioned sketch. The only full size drawing I made was for the wing rib profile.
If it flies as well as it went together I will redraw and post the sketch "as built".
The 1500kv Blue Wonder motor with its all Depron mounting.
Note the fuselage has been cut back to the cabane struts and the battery compartment rebuilt as tests suggested the CofG was going to be too far forward!

01-24-2010, 05:43 PM
You can use these files to make a foam pup.

02-02-2010, 11:18 PM
Not much progress - waiting for the servos but at least the ESC has been delivered allowing the motor to be tested.
The 7x4 prop is a bit too big as the current draw is uncomfortably close to the ESC limit of 10A.
As the all up weight looks like it is going to be just under 5 ounces I can easily afford a bit less power. Even 5A (35watts) gives 110watts/lb so I will try a 6x3.

02-06-2010, 12:55 AM
The servos mounted by my usual "stick them in" method. The elevator servo horn sticks out of the side of the fuselage so it can be simply connected up to the elevator. Not elegant but simple and very light.
A short video testing the elevators.
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02-07-2010, 01:46 PM
These show the ailerons connected up. I painted the line black so it was visible.
The aileron servo and cables rather get in the way but at least there is some distance between the radio and the ESC.
The CofG is 12mm from the lower LE.
If it flies well I will add a simple U/C.
A short video of the aileron test
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02-09-2010, 05:29 PM
Just a comparison shot, they do look about the same, aerodynamically speaking.

So far 2 attempts to maiden but even a gentle 5 to 8 knots breeze just about equals the expected flying speed! Dare not risk it.

02-25-2010, 07:29 PM
First two attempts to fly the Depron Pup were singularly unsuccessful because I had the ailerons reversed!!!!
I set them up using a spare TX and it never occurred to me that the two were set up differently.

The heavy landings broke the wing rigging so I removed it as the Depron structure is plenty strong enough without. Fortunately the basic Depron bits were undamaged.
I also reduced the stagger to move the top wing back and thus effectively move the CofG forward.

Third attempt and it does indeed fly however it is ridiculously slow and is mighty twitchy but two flights completed and no further damage.
It has plenty of power but turning into wind (it was only 2-3 knots!) on approach and closing the throttle it just 'parachuted' down landing well short of the chosen spot.

So first reduce the elevator travel by moving the lines in one hole on the servo.
I have also revised the motor mounting as the heavy landing had taken their toll.

Once I have it flying well I will replace the rigging to see what effect it has on the performance and then, and only then, try the scale Pup.
All I need now is some really calm weather.

03-01-2010, 10:12 PM
The cabane and wing strut bracing has been restored to stiffen up the wing mounting a bit.
The elevator wires have been moved in one hole on the servo to reduce the travel.
The much more rigid motor mounting highlighted the prop slightly out of balance. The blades were further thinned and carefully matched.
The LE of the tail plane was raised by 1mm to reduce the 'down' trim in normal flight.

The result is it now quite flies quite well, albeit still pretty slowly. It performs very tight loops but cannot roll as by the time it has rotated 90 degrees, it is pointing at the ground.

The 500mAh battery seems good for about 10 minutes.
I suspect the CofG could do with going just a bit further forward so I may try a slightly bigger heavier battery.

03-05-2010, 12:00 AM
The aileron cable guides have been moved to better mimic the original geometry at re rigged with thicker 7 lb line but with a lower pretension. The result is the ailerons centre better and there is less load on the servo at full deflection and the rather "open" motor mounting has been covered by a very non-scale square Depron cowling.

With its light weight and generous wing area it is spectacularly manoeuvrable with almost instantaneous changes in direction.
It will now perform consecutive loops with very little loss in height and can be made to roll - just.
It will fly inverted but so far only for short periods as it desperately tries to right itself!
It even glides quite well.

The little 500mAh battery gives 15 to 20 minutes duration however the testing so far has convinced me that the heavier and more 'draggy' scale Pup will need a bigger prop which will require a larger battery to provide the extra amps. Space limitations mean it will have to be a 4s2p800mAh set up.

03-05-2010, 12:19 AM
When you get through with the Depron Pup don't throw it away, ship it to me. I think it is like the old maid, just needs a little power and paint to look good. Well maybe a little more than that. At least a round cowl. LOL

03-06-2010, 12:30 AM
If you looked in my roof space you would see that I have rarely thrown a plane away, they just get retired! The oldest dates to 1959.

03-06-2010, 01:37 AM
If you looked in my roof space you would see that I have rarely thrown a plane away, they just get retired! The oldest dates to 1959.

Understand, mine date back to the mid 60s. One of them I better never throw away, I scratch built it when dating my wife, the name on it is Linda Lou. It is a .02 Taylor Cub. I guess I should put a brushless in it and fly it again.

03-09-2010, 07:17 PM
Replaced the 6x4 by a scale diameter 7x4. As this prop draws more amps a bigger & heavier 800mAh battery was also installed. This in turn required the firewall to be moved forward 3mm and the fuselage locally deepened by the same amount. The result is the CofG is now slightly forward so the scale stagger has been restored.
The odd shapes on the front of the cowling are to prevent the prop blades folding between the wings.
The performance is now quite spectacular but fly too close to the stall and the torque from the big prop results in what can be described as a 'snap' left turn.
Fortunately recovery from this and almost anything else is pretty rapid so '3 mistakes high' on the Depron Pup is still quite low.

03-10-2010, 02:18 AM
De, I still have an old MidWest Tri Squire that I converted to 3 channel and flew when my oldest boy was little (he's now 29). The plane say's Lil Chris on it. I plan to install some new radio gear and go electric some day. She'll fly again! Marty

08-04-2010, 08:28 AM
Nice build, Q. I'd like to hear how she flys.

08-04-2010, 11:27 AM
I have briefly flown the scale Pup.
It has more than sufficient power but as I feared the scale thin under-cambered wing section actually requires the tail plane to be set at an apparently positive angle of incidence so I was struggling to keep level flight even with full down trim.
The full size Pup was notorious for being very sensitive longitudinally. "Sneeze and you loop" being a period comment.
The Depron Pup has a Clark Y type wing section and is a bit less sensitive.

The final flight damaged the U/C so some repairs and adjustments and wait for the next absolutely calm day to try again - unless I can find a suitable indoor venue!

Light weight 24" biplanes planes are always likely to be a challenge to fly so I am already dreaming of a bigger 36" version that might actually be heavy enough to fly in a gentle breeze.