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Regal Eagle refurb


Dad_flyer
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I have a Regal Eagle to refurb, courtesy of a kind Forum member.

1232148278_IMG_20210824_1912571282.thumb.jpg.62b7bf1d919bfdd8b841ac2a6dc9c626.jpg

It has clearly flown a lot on IC, being complete with grass embedded in the oil on the underside of the wings ?

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That will probably stay, as authentic patina. 

 

A nice big model with a two-piece 85" wing, so it fits the car much better than Double Diamond which has a one-piece wing with lots of dihedral that angles across the boot.

Edited by Dad_flyer
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The main task is to fill this gaping space with power.

IMG_20210824_191308329.thumb.jpg.fea01cb1e3847e04130d342e12100186.jpg

All my models are electric, mostly on 4s. This is quite a bit heavier. I think most people would put in 6s, but I shall double up 4s give 8s. It will then share 4s5000mAh with Child_flyer's Black Horse Renegade. The only issue with 8s is that it adds to the cost of the ESC, as mid-range ESCs will only take the voltage of 6s.

 

I am looking at 4-Max 6366 230kv with probably 20×12 or 20×11 prop.

 

With batteries the take-off weight is on the edge of 7.5kg. 

 

The question is, should I try to keep below 7.5kg, or should I live with the 400ft limit?

Edited by Dad_flyer
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If there is a heavy paint job on the wing then re-covering just the wing in film or lightweight paint might reduce the weight a fair bit and smarten it up at the same time.

That cowl looks as if it could take the lipos crosswise to help with CG.

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@kc the structure is covered with card or similar. It is a Paper Aviation model. It is finished complete with rivets, which looks great. The card over open structure gives a good impression of dented aluminium panels.

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I don't think I want to remove all of that, although it could take out quite a bit of weight. It obviously flew a lot, so must have flown well. So the weight is only about being over or under the magic article 16 number. I think it can be done, some batteries are lighter than others, and I can be careful with motor mount weight. But actually am I going to need to be over 400ft, and not at a site with authorisation?

 

You are right, the cowl is huge. I was planning a box in the centre for the motor mount, with the lipos one each side. To get the CG right I think the batteries do not go right forward and will stick out at the back of the cowl alongside the fuselage. I can make covers to channel cooling air and make them look like exhausts.

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A model of this size is quite practical to fly below 400’ but a large loop will be pushing it unless you’re confident enough to start and finish relatively low. Best to use telemetry to monitor your height - if your radio doesn’t support it perhaps a club mate could do a temporary installation of a sensor and receiver?

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21 hours ago, Dad_flyer said:

The main task is to fill this gaping space with power.

IMG_20210824_191308329.thumb.jpg.fea01cb1e3847e04130d342e12100186.jpg

All my models are electric, mostly on 4s. This is quite a bit heavier. I think most people would put in 6s, but I shall double up 4s give 8s. It will then share 4s5000mAh with Child_flyer's Black Horse Renegade. The only issue with 8s is that it adds to the cost of the ESC, as mid-range ESCs will only take the voltage of 6s.

 

I am looking at 4-Max 6366 230kv with probably 20×12 or 20×11 prop.

 

With batteries the take-off weight is on the edge of 7.5kg. 

 

The question is, should I try to keep below 7.5kg, or should I live with the 400ft limit?

I have the same motor in an 80” Laser 200 using 8 s lipos it weighs a bit more than your eagle and is well powered so you should be fine 

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Another part of the refurb is conversion from 35MHz. Out with the receiver, and unfortunately everything else because the plugs are different.

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Then crimp new connectors to the servo leads.

 

So I now have the servos out of the fuselage. Three Futaba S148 and a S3001. (I have only now realised that I did not do the aileron servo leads. Bother.)

 

Which is best for which control surface? Previously Rudder was an S148 and the elevator was driven by the S3001 teamed together with an S148.

IMG_20210815_180349484.thumb.jpg.90da7e790291e1c30e61fafe1945c005.jpg

Left to right: rudder, elevator, elevator, throttle.

 

The previous owner said it came to him like that, looks odd but works. I would have left it if I did not have to take the servos out anyway.

 

My thought is that mostly I see people put a bigger servo on the rudder than on the elevators. So if the S148 has been enough for the rudder on this model, than just the same should be fine on the elevator. Then I would not have to try to be sure that the two servos are not fighting eachother.

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  • 4 weeks later...
  • 5 months later...

It has been a very long while. A bit of thinking, a bit of saving up and a lot of winter.

 

I wanted to get a better radio and this was as good a reason as any. Radiomaster Tx16s is on order. 

 

Next step is to refit the servos. The assembled wisdom of the forum did not have an opinion on the double elevator servo back in September. Any advice now?

 

I am thinking s148 on rudder as before, and just the s148 on elevator?

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I'd be a bit dubious using 2 servos in tandem like that because I can see them fighting each other, at least to some extent.  I'd be inclined to select a more powerful single servo for the elevator - you can fly without a rudder and even with a single aileron but without an elevator the model is toast ?   I'd want one with metal gears, too. 

 

My first biggish model (it still is the biggest) is my Maher's Thunderbird with a Zenoah 26cc petrol engine and IIRC I went a bit overboard with servos on that but I can't remember which I chose.  It did give me peace of mind, though.  I haven't flown it for years but it got a lot of air time when I first had it.

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I remember the Regal Eagles being flown at shows in a pack of 4 or 5 back in, what… the late 80s/early 90s maybe? They flew well, but I remember my Dad commenting “…that cardboard construction will never hold up to fuel in the long run”. I guess he was wrong! ?

 

Re: servos, the choices mentioned above all look fine to me, but definitely ditch the two different servos driving the same surface setup! I don’t think you necessarily need metal gears though - there aren’t any major negatives to them, but on an electric they aren’t really necessary as the vibration levels will be so low anyway. Looking forward to seeing how this one turns out, should have plenty of performance on an 8S setup!

 

Edited by MattyB
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@Dad_flyernot sure if you've got the ESC yet but I can recommend the Hobbywing FLYFUN-110A-HV-SBEC-V5 as ideal for your setup. The 4-Max ESC I originally had in my Extra Wot (10s) suddenly stopped working so I replaced it with one of these and tbh it is excellent especially the braking functions that it has, plus you don't need a separate BEC.

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          Regal Eagle Racing was always be a popular slot at our Haverfordwest Model show in the 90's. The course went around a couple of small tree copse witch aircraft would sometimes go momentarily out of site behind. All to the exited tone's of DB sound.  Good fun.

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The power of the servo can be calculated but i use a simpler bit of guess work based upon the 3 factors that impact it. 

 

The 3 factors are control surface size, control surface deflection, and airspeed. 

 

a WWII fighter would have moderate surfaces, small to moderate deflections (apart from flaps), and moderate speed. 
A tiger moth has large surfaces, large deflection, but low speed. 

3d models have huge surfaces, huge deflection, but low speed. 

A jet as small surfaces, small deflection but very high speed. 

 

You can also factor in your own flying style. Do you love a stick bang, or are you smooth and gentle? Also how do you plan to fly the model? In the case of the eagle are you going to go Gee Bee racer, or more of a relaxed spacewalker or flybaby sort of thing?

 

Personally, if it were me on a model like that i would probably be looking at something slightly over the bare minimum spec as it sits between the WWII fighter and tiger moth in my list above. I am sure it could be flown safely with the 3001's etc, but i would probably shoot for something like the savox 351 run on 6v. It offers a little more torque than the old futaba, is digital so holds a bit better, and its not mega expensive either. They also use the futaba output spline so that is quite handy. 

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There are several on-line calculators which reveal just how small the requirements are e.g. here 

 

Don’t fall into the trap of assuming your model flies at 200 mph - they may look fast but most average sized models would struggle to better 70 - 80 mph in level flight…my mental calculations from your 8S setup from long ago in the thread would seem to agree with this figure, as would an Eagle from my own experience using a Laser 150 with a 16x8. 

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I clocked my La7 (80 inch warbird 300 4 stroke engine) at around 70mph some years ago on a flat out pass. It was a very crude measurement with stopwatches and a known distance travelled but yea, i absolutely agree that you do not need to go mad with servos which is why said La7 is fitted with 6kg servos on ailerons and elevator, futaba 148 on rudder and 9kg servos on the barn door flaps. I am sure these are overkill, but i have known people fit 20kg servos in 60 size models as they think they need it and its just wasted cash. I doubt the eagle here would be doing much over 60mph as you rightly say. 

 

If the servos are under spec it is usually not a problem as you will simply feel sluggish response as they blow back. However, a weak servo can be a problem should flutter begin to develop and then its game over. 

Edited by Jon - Laser Engines
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I certainly agree that flutter is a model killer but I think that a weak servo is unlikely to cause it. It might even act as a damper!

 

The cause is usually aerodynamic - flexible linkages, poor static balance, play in hinges, excessive gaps etc. 

 

Although plastic gears are more likely to fail if flutter is encountered, metal ones are more likely to develop play which might lead to flutter…

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9 hours ago, Ron Gray said:

…but can help prevent gear teeth shearing when the occasional 'mishap' occurs (banging a control surface, usually tail, getting the model in and out of a vehicle!).


I suppose so, but that in itself isn’t a reason to pay more for an MG servo - just be more careful going through doorways! A good halfway house are the Karbonite Hitecs, they wear better than an MG (developing very little slop) and are pretty resilient to bumps.

 

9 hours ago, Ron Gray said:

@Dad_flyernot sure if you've got the ESC yet but I can recommend the Hobbywing FLYFUN-110A-HV-SBEC-V5 as ideal for your setup. The 4-Max ESC I originally had in my Extra Wot (10s) suddenly stopped working so I replaced it with one of these and tbh it is excellent especially the braking functions that it has, plus you don't need a separate BEC.

 

Personally at these kind of model sizes I’d much prefer an opto ESC and a separate power supply - the weight penalty is often minimal/zero (just remove a bit of nose weight and add in the battery pack in its place), and there is no risk of an ESC failure taking out the RC link.

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