|J Moyler||11/10/2018 09:58:41|
|133 forum posts|
I normally just luck but I would add my support for you to get the condor flying again.
Regarding comments about the amount of power available. 100 watts per pound is fine. In my limited multii-engine experience I have found that multi engine planes tend to be more powerful than expected Link .
I am not sure how experienced you are with multi-engine planes but there was a post recently where someone used a ARTF Twin to gain experience before building a mosquito.Hope to see the Condor repaired and flying again.
I think that I should of chosen a better link but it gives an idea why twins appear to be more powerful.
Edited By J Moyler on 11/10/2018 10:01:11
11025 forum posts
I suspect that the arguments presented are misleading.
Take the argument to its logical conclusion, you do not have 2 or 4 propellers to improve efficiency you arrange as many as you can along the wing.
At the practical level, many multi engined full size aircraft were so because of the issues of suitable engines, as either single or twins.
Many aircraft designers went from 2 engines to 4 because of engine issues, rather than as the starting point. Although some multi engines were a consequence of regulatory requirements relative to reliability issues.
Without getting into the KE, area relationships etc. It is commonly accepted that a single propeller of the same area as a multiple of the same area is significantly more effecient. There are a number of reasons for why, it is not necessary to get into the sceince and maths. Althougth at a pracicle level there can be reasons as to why you may choose multiple power units.
I only have two models with twin set ups, what surprises me is the weight build up from the wires ESC etc.
The Delta is at 14 oz ft^-2 on with 360w.
The Me 110 is @ 360W not recorded the weight, nor wing area.
|Robert Parker||11/10/2018 18:31:47|
822 forum posts
I have some mixed experience with twins, Wellington and Catalina, and a Lancaster. The Wellington was total frustration under powered but just enough to get it of the ground and turn to up worse than the condor. The Catalina although a little difficult at first due to the ESC's timing being low once adjusted to medium she flew well take off being hit or miss actually flew quite well and the Lancaster flew like a trainer. I know where you are coming from though well we have to learn don't we sometimes the hard way.
Erfolg, Yes the wiring soon puts the weight on, the wings are most of the weight.
|Simon Chaddock||11/10/2018 20:52:23|
5216 forum posts
My own experience with 4 engines is it is easy to under estimate the effect of the prop wash that is spread over quite a large proportion of the wing. For some aerodynamic reason when under power the CofP of the 'washed' wing area is moved significantly forward so the plane acts like it is tail heavy with an aft CofG but with the power off it becomes controllable.
If the Condor has a reasonably thick wing section it will still remain longitudinally stable with a degree of down elevator applied so rather than use non scale down thrust it may be better for the throttle and elevator to be 'mixed' to achieve a consistent flight from full power to glide.
Pick the right plane that has really big engine nacelles then each can hold the motor, ESC and battery. Not only does such a layout structurally off load the wing but the only 'long distance' wiring is for the servos.
11025 forum posts
Your models are generally very light weight, getting by with low power (although possibly having an acceptable power to weight ratio), You even go to the length of shellacked wire as the insulator. Also you normally hand launch.
I find it is very easy to underestimate the power consumption absorbed by grass, where small wheels are involved, the grass is fractionally longer than usual and particularly with damp or wet grass.
I ere on the side of caution with my wiring,and it has surprised me how much weight there is in the wiring from a central battery, to nacelle mounted ESC. In resent times I have considered under specifying the wiring, living with the losses during take of, as once flying the power demands reduce significantly.
To be honest I do not know what the issue is with the Condor is. Although the A of A is a easy check. A forward CG reduces another risk.
Since swapping from gliders to power, and starting out as a watt miser, I now know from others and my own experiences with a range of models, there is no substitute for power when taking of or launching. Gaining height is your best friend, it provides time. The other major lesson is get a really competent flier to make the first flight, watch carefully, undertake a debrief after the flight, after checking stall etc. Then correct all the issues that are revealed.
|Cliff Bastow||12/10/2018 21:11:06|
747 forum posts
I feel for you, especially with my recent incident! with my Connie. Good luck with the rebuild, sure you will get there.
|Robert Parker||13/10/2018 08:18:26|
822 forum posts
Simon, the wing section is not too thick and the nacelles are also on the small side It was a bit of a squeeze getting the motor mounting plate to fix onto the bulkhead there was no room for a battery in each nacelle.
Thank you Cliff. I see your Connie is coming along with your rebuild.
As we are in for a wet and windy weekend here in deepest darkest S.Wales I might start looking at the wreckage once I've got the wing panel glued on my new project whilst the glue dries.
|Robert Parker||13/10/2018 19:03:55|
822 forum posts
Well with thanks to Graham Legg who checked my CoG calculations, it was found that my calculations were indeed wrong by 17mm rearwards which did not help at all, the CoG needs to move forwards by that amount. So one reason found for the incident.
Today I looked over the wreckage and checked out all of the electrics and servos, all fine and working correctly, so not mechanical failure. The wings only have a split in the top sheeting and no other damage was found even when trying to twist and push and pull on the panels.
I have started repairing the fuselage this afternoon as well as removing two of the servos and will re-position them when I get the flight pack in position and then fit the servos around it as it was a pain to fit the flight pack between the pull pull wires of the rudder.
Onwards and upwards
|McG 6969||14/10/2018 06:37:23|
2294 forum posts
Good to see that you're back to the Condor, Robert.
Very probably a daft question, but wouldn't it be more 'stable/steady' at take off with contra-rotating props? I suppose that in such a case you don't have to worry about the need for possible side?
Keep the mojo...
11025 forum posts
Being back by 17mm is probably a very significant amount. I know that many will be more concerned by the static margin, which is useful to know, Although as a philistine, I like the easier (at least to me) percentage average chord value. I find it is easier to get a feel of the ballpark pitch sensitivity (although both provide a feel as to how the model will behave).
Whilst you have been at your checks, have you verified the angular relationship between the tailplane and wing?
Given the model is electric the option of opposite or pusher propellors on one side is viable, quite often. Although then a debate ensues with respect as to which propellor should be rotating which way. For my Delta twin, it has conventional props, without any issues. The 110 has handed props, again with no obvious benefits, although no real left swing, when taking of. Perhaps those with proper multis can provide a better insight?
Another good option is to get yourself a good test pilot, they do allow you to concentrate on what you believe is happening, which can be compared to the pilots impressions. Takes a lot of load of you and makes for considered changes to the model easier,
|1933 forum posts|
That,s good to hear Robert all power to your elbow for the repair
|Robert Parker||23/10/2018 21:03:00|
822 forum posts
The re-building is now complete with just a bit of painting here and there still to do. I found that the paint "flashed" so I have done a trial taking it back to the next panel line.
I appeared that I was very thorough in picking up all of the pieces only having to make a couple of bit where the prop had struck the fuselage. On the whole I'm pleased with the result, once it is a 100 ft up no one will be any the wiser.
I have just checked the CoG and the flight pack has moved forwards around 3", however, when I retract the u/c the model becomes tail heavy due to the legs tucking back past the CoG position. So I have decided to balance the model with the legs retracted then when lowered the model becomes nose heavy rather than the other way around. The amount is 34mm to 49mm from the former in front of the wing.
I am open to anyone's opinions on the CoG position.
The dark grey panel shows a lot darker than it does in real life
Looks good in this light
Still not removed the mud from the nose. did not find the radio mast.
The pilots seem happy anyway now that they have been re-united since the co-pilot was ejected on impact.
I had to hand paint the "N" and "D" as they had been made into confetti by the prop.
What I have left to do is move the rudder and elevator servos and fit the battery tray in it's new position and re-check the CoG
Sorry about the picture quality, will take some more at the weekend, may even try to fly again.
That's all for now
|Tony Bennett||23/10/2018 21:24:17|
4911 forum posts
wonderful repair job young Robert.
looks as good as new now.
best wishes for the re-maiden.
|trevor wood 2||24/10/2018 00:10:12|
19 forum posts
Full size and model aircraft usually have acceptable handling characteristics over a range of CG positions that is likely to cover 5% of the chord. If your calculated position is correct this time and you have found the CG sweet spot, then everything should be OK. But to minimise the possibility of another 'upset' why not move the CG to what should be the forward limit for your second attempt (perhaps another 2.5% C forward), and then fine tune its position based on actual flight testing. The worst that could happen if you use up all the of the elevator up trim is that you would need to hold a bit of up elevator on the stick.
As someone said earlier in the thread, too far forward - flies badly. Too far aft - flies once.
|Dwain Dibley.||24/10/2018 00:32:22|
944 forum posts
Excellent work Robert.....Glad to see Her back in one piece.
Good Luck with the next flight, I am sure all will be well now.
Please login to post a reply.
Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!