Dumas Dragon Rapide

[Chris Walby]

I still haven't finished mine and as my late wife bought it for me, well its at the end of the build list at the moment. I have bought film for it, but am now seriously considering dope and tissue and whether it just becomes a hanger queen once its complete.

 

Please keep posting Rapide and it will help me when I get back around to it, 

[Rapide]

2 hours ago, Chris Walby said:

I still haven't finished mine and as my late wife bought it for me, well its at the end of the build list at the moment. I have bought film for it, but am now seriously considering dope and tissue and whether it just becomes a hanger queen once its complete.

 

Please keep posting Rapide and it will help me when I get back around to it, 

Chris

Forgive going off topic for a moment but I keep looking at your Mosquito avatar - my dad flew them - and last year I had the coveted seat in the one at East Kirkby for taxi trials and testing the engines for their Lancaster - A MERLIN IN EACH YEAR.

 

Yes,  am finding it hard to get back to finishing the Rapide. Here's a few things that held up the re-start (intending to be helpful - not to discourage you) 

 

I had a similar problem to that mentioned earlier in this thread with the motor Xcross mount supplied with the motors sent by George4Max. Having struggled to build the alternative outrider motor mount extension demonstrated in the RC Groups Forum (also previously mentioned) it was only then that I found the black X mounts were too big to screw to the recommended ply "firewall", so I snipped off the holes at the end of each X mount arm and redrilled as close as I dare to the new ends. Then I found the screw heads were too close to the motor base and resorted to bolts with smaller heads. Fiddly but they are firmly in place now. 

 

Next I found a lot of conflicting advice on washout on the RC Groups Forum so on Christmas Eve  I PM'd Pat Tritle who got back to me immediately to say to build the wings flat on the plan then, when ready to cover, pin to the board with a 1/16" shim under the training edge of Rib 10 and shrink the covering to hold the washout angle. He stressed that the angle is not critical so long as it is the same on each of the 4 wings.

 

Then a simple thing held me up as I wondered how to stop the tube through which the rod from servo to elevator flopping around in side the fuselage but was given a very simple answer from Engine Doctor (see above)

 

So as the silver lightweight Solite had arrived, I wanted to cover something so started with the rudder. The shrinkage immediately pulled down the fragile top balsa so I stripped it and strengthened the top curve. Having received a super covering iron from my grandson for Christmas, I have just successfully covered the rudder and am very pleased with the result. 

 

Right now I am looking at the instruction for using the hinge material supplied with the kit but, more importantly, how to fix them to the control surfaces  and WHERE as the locations are not shown on the plan.  I have of course done this on other kits but used the heavier plastic ones with the tiny metal rod. Whilst cutting a slot in the wing spars where they meet the aileron would be fine but the angle of the aileron spar where it meets the wing would seem to prevent their use. 

As usual, Any advise welcome.

Ian, Rugby UK 

[Rapide]

On 27/12/2023 at 14:52, Rapide said:

a 1/16" shim under the training edge of Rib 10

That should read "Rib 12"

[Rapide]

This is a beautiful model and the kit is great but oooooooh I am getting frustrated with it.  There are now a lot of fiddly bits/detail towards the end of the build and I am spending hours of happy time working on each of them.  I have covered all but the lower wings using Ripmax Aerofilm in silver which is a joy to use and does look good. The rudder and elevator are attached to the servos and they work well.  I have spent today carefully trimming and fitting the plastic access hatch cover and the nose and cockpit cover mouldings.  Held it up to admire and noticed in horror that the heatshrink covering has warped the tailplanes due to their fragile structure - I do hope I can gently heat them straight again.  Just as well the weather is not great for flying.........................

[Chris Walby]

Any photos would be welcomed, cheers

 

[Rapide]

Auto focus on my camera decided not to work but I offer the pics anyway to show progress on my build.  This is a great kit but I admit that my skills are not quite up to is demands.  Don’t let that put off anyone buying it as with trial, error and running repairs, I am on the last lap and so far, so good.  The all-up weight is just under 22ozs, mostly due to the beefed up motor mounts and some strengthening on fin and wing trailing edge to fight the iron on covering shrinkage.  All radio gear is in and working, including the wing tip servos location.  I made the nose removeable with magnets to access the battery, and am about to tackle the plastic fairings.  I am leaving the main worry until the end which is the warping of the very fragile tailplanes which I have failed to correct with reheat.    Any tips on that would be welcome.

Edited January 17 by Rapide

[Rapide]

DISASTER ........... 

I was just getting keen on finishing and wired up the motors - I am sure I wired it correctly - even remembered to detach one of the ESC red wires - Powered it up and all seemed great - responded to throttle stick - then I pushed it to full revs and smoke appeared from both motors - One even melted the three wires coming from the motor.  I used the pack of recommended items (motors/ESCs/Lipo)  from George at 4-Max as apparently supplied to you Chris.  Have you got as far as completing the wiring and testing the motors etc ?  Looks like I will not be flying very soon. Its think-again time.

[Outrunner]

That doesn't sound good. How many Amps was your setup pulling? They look like very large props on them motors, could just be the photo though.

I hope you get it sorted as it looks a really nice model.

[Rapide]

2 hours ago, Outrunner said:

That doesn't sound good. How many Amps was your setup pulling? They look like very large props on them motors, could just be the photo though.

I hope you get it sorted as it looks a really nice model.

Thank you for responding. Do not know how many Amps it was pulling. I relied on the expertise of the set-up I was sold and  I still would believe that 4-Max know what they are talking about. They recommended specifically for the Dumas Rapide:

MOTORS            2 x Thumper T2822/27 B/L Motors SKU2973

PROPS                2 x APC E 8 x 4 Props. APCLP08040E

SPEED CONS     2 x 20amp ESC Units HW80060010

BATTERIES         2 x 3s 850mah Lipo or similar SKU2817

So we are looking for something else at present - wiring thickness perhaps? but I don't understand how that could affect the motors.  As for prop size (which came with the package supposedly designed for the actual Dumas model)  I was of course testing with props removed when the damage was done. I am assuming the ESP's can not be relied on.

All thoughts welcome...................

[Outrunner]

Should have been ok on 8x4 props but it would have been nice too have a watt meter connected so you knew what was going on.

I don't think it would have been anything to do with wire thickness as I assume you are using that supplied with the esc and motors.

That was really unfortunate to have two motors burn out. Perhaps it would be useful to talk to the supplier.

[Rapide]

I tried to edit the above but couldn't work out how to. The actual hardware order was:

2x Motor          PPOM-2314-2400    £14.99 each www.4-max.co.uk/ppom-2314-2400.html

2x ESC              4M-ESC12A              £13.95 each www.4-max.co.uk/4m-esc12a.html

2x Prop Driver  PP-PDRV30-50         £ 2.75 each www.4-max.co.uk/propdrivers.htm

1x Prop          APCE 6x4 Standard     £ 2.55 each www.4-max.co.uk/apc-props.htm

1x Prop          APCE 6x4 Pusher         £ 2.80 each www.4-max.co.uk/apc-props.htm

1x Battery      PPL-60C2S-1300        £11.00 each www.4-max.co.uk/lipos.htm

 

[Outrunner]

That lot is different to what you first quoted🤔

I would speak to 4 Max

[EarlyBird]

@George Worley - 4-Max is the expert.

[Rapide]

55 minutes ago, EarlyBird said:

@George Worley - 4-Max is the expert.

Thanks for your responses.  I assure you I am getting in touch with George as it was his recommended package for the Dumas Rapide that he sold me.  

For further info in case anyone can guess what went wrong I offer the following which is exactly how I wired it:-

 

[Rapide]

1 hour ago, Outrunner said:

That lot is different to what you first quoted🤔

I would speak to 4 Max

Yes - my mistake, the first was a suggestion from another company that I did not buy from. I then ordered the recommended package from George. 

[Rich Griff]

I still consider myself to be a  tyro with electric propulsion, so please forgive me if my question is daft....

 

If a separate battery is used to power the RC Rx, ESC control and servos, could a suitable quick blow fuse be used between propulsion battery and ESC as a protection device against high current load ?

 

High current load of the type that burns out motors and ESC's...an overload...

 

On motor start up and full power demand, "current" spikes may occur in the propulsion system system effectively blowing the fuse ?

 

I fit fuses to my electric powered boats ( slow speed ) but they have burgler alarm type batteries ( 10ah, 6 volt ) and dc motors ( 540 buggy type motors ).some have NiMH car racing pack batteries as propulsion power.

 

I use seperate Rx battery...no weight or

 volume problems....

 

Thanks...

 

 

 

 

Edited January 19 by Rich Griff

[EarlyBird]

14 minutes ago, Rich Griff said:

so please forgive me if my question is daft

You are forgiven.🤣

[EarlyBird]

As it's only the motors my thinking is that no prop would reduce the cooling and cause the motor temperature to rise above normal.

I only ever test a motor with a quick low throttle pulse to check rotation and of course that it works.

[Rich Griff]

Thanks for the heads up on that test method eb, thanks.

[Chris Walby]

Apologies as I have only read part the posts.

 

I don't know of any RC aircraft set ups that have fuses anywhere, either on ESC to motor or battery to ESC/RX. Two factors come to mind, firstly additional weight and secondly what are you trying to protect with a fuse as it will be either over or under rated so serves no useful benefit!

 

I have found very very few ESC's that have any form of over load or over temperature protection which its totally contrasted to industrial motor speed controls that normally have a mass of protection measures.

 

Example 12A ESC, so its rated at 12A then use a 12A fuse. 12A fuse will not even start to operate until 1.5 its rating hence >18A will be needed and with that level of current the ESC will be damaged. You could prop it down to 8A, but now it might not fly + you are hauling a load of extra weight (inc oversize motors) for no benefit. Now you get an overload of 12A and the fuse might blow after 20 minutes, well that was helpful! There is of course the possibility of a fuse operating due to start up surge (back off and re-apply throttle) which is not very helpful in mid flight.

 

 For the Rapide it appears to me that weight is absolutely critical to it flying well, shape of wings and drag being major factors.

 

PS Although I am not a marine Electrical Engineer, I have heard its standard practice NOT to have fuses on ships (of all sizes) on the rudder controls, the basis is that in the middle of a raging storm hunting around for a spare set of fuses will not avoid the rocks. The rudder either works or not!

 

Other might have a different view 🙂 

 

[Rapide]

George at 4-Max replied quickly as usual and his opinion is very logical so I accept his conclusion that it sounds like a dry/high resistance solder joint/s which work OK at low current levels but would become apparent when high current is drawn. If there is a bad solder joint on one or more of the 3 wires that go between the ESC and the motor, you no longer have a motor, but you have a heater, as there is effectively a direct short across one of the coils in the motor which will burn out if the power isn’t removed immediately. 

With my level of expertise, I am quite prepared to accept it was down to my soldering, especially as for each motor  there are 3 male and female connectors from the motor to the extension wires and 3 more from the extension wires to the ESC. For both motors, that is a total of 24 soldered connecters with no way of knowing if any or all are good.

 

Overheating due to no props (earlybird) is a good thought but I feel less likely as I only ran them low for about 10 seconds and the burnout then occurred about 3 seconds after full throttle was applied.

I hope this is all helpful to someone.  I shall finish the model (motor and wheel fairings - struts - aileron links) and return to motors later - perhaps. 

[Rich Griff]

Rcg, jeti, tx settable ?

 

Powerbox, whatever that is...

 

Probably mega expensive stuff......

 

Probably would not have prevented above motor burn outs.....hay ho, fun stuff with electric propulsion......

 

Fuses from ESC to motor.....a possibility ?

 

Those Motors are only £14 plus each......

 

 

 

Edited January 19 by Rich Griff

[Rapide]

As this is already the most expensive and time consuming model I have ever attempted, buying the motors/ESCs/Lipo/wiring/connectors/solder all over again is sadly a non-starter.  I have six other aircraft - 5 of which have flown carrying my soldering and hardware installations and all survived and only await decent weather to fly again. So I have decided to just finish the Rapide and hang it up to admire the first aircraft I ever flew in. That was nearly 65 years ago (not possible!) with my ex WWII RAF pilot Dad, flown by the first ever female commercial airline (BEA) captain from Bembridge on the Isle of Wight to possibly Southsea.
So thankyou all once again and I'll let you get back to building/flying.
Cheers, Ian

[Rapide]

Having had advice from all angles (which was very helpful) and read everything I can find on the subject, and taken apart the motors and tested my wiring, I have concluded as dry solder joints usually cause "oscillation" and that did not happen, that cause is unlikely. The main cause suggested by most, and ironically, that I now read on the 4-Max website a specific warning about, and that exactly fits with what happened, is these motors WILL burn-out if run at full throttle.  It would help if a prominent notice stating this fact was on the motor description AND on the package that it is sold in. 

[Rich Griff]

Mention that to George so he can get the motors labeled better.

 

I am sure he will relabel to save future hassle/customers.

 

Happy customers keep pay days happening.

 

I have made a note in my little yellow book so I won't forget in future.

 

Thanks for the heads up.