Simon Chaddock

My chosen solution to the motor/prop weight problem is to use two 1300kV BR221 motors turning CW &CCW 11x3.8 SF props. They will be scale diameter but obviously only 2 blade. The motor and prop should weigh about 28g rather than 70g. With smaller OPTO 10A ESCs with a 2A UBEC and smaller battery 850mAh 2s I might stand a chance of getting the V173 close to 8oz (250g) all up. At that weight even with the much reduced power it will still have close to 1:1 thrust to weight. I just have to wait for the bits to be delivered. 😉

Although an aerodynamic effect may not be significant on a current model it can be worth understanding the "what and how" as it might well be important a bit further down the line. Remember "adverse yaw" no matter how it is created can in some situations lead to a serious crash. A low slow final turn as an example.

The angle of the aileron horns will depend on the relative position of the aileron hinge line. In this case the angled horn is to is to get the horn pivot point perpendicular to the hinge line and not to create differential. The differential movement (more up than down) is created by the forward angle of the servo arm. A simple diagram of your Ruckus aileron linkage would help establish what is happening.

Starting to look at the V173 body I have run into a problem. With the 11x5 props at scale diameter the "pancake" is tiny with an area of just about 1 square foot. At this stage the best guestimate is it will weigh about 16oz giving a wing loading of 16oz/sqft. At such a figure a slow flyer it will not be! 😧 The problem is the 2822 motors are too powerful and heavy for such a small airframe and the props are no lightweights either. Each complete nacelle, motor and prop weighs 2.5 oz. Even 0n 2s the combined thrust will exceed its estimated weight. I want to keep scale diameter props so I am reluctant to simply make it bigger overall as with direct drive brushless motors the same problem is likely reappear. A smaller lighter motor but with the same kV and a lighter prop could be a possible solution. Even if I can get the all up down to say to 10oz it will still need that extreme ground angle to get a "slow" take off. We shall see.

Does your charger have a 90% charge option that you have activated in error? Otherwise it does look like you need a new charger.

After a bit of testing it became clear that with the original concept motor cooling would likely become an issue so a slightly revised nacelle. The spinner is 26mm diameter comparted to the motor's 28mm so there is a 1mm annulus to force air into the motor. An air outlet is provided behind the motor With this arrangement the motor can be run at full power on a 2200mAh 2s for a minute without the motor or the drum mount getting too hot. I haven't measured the thrust but resisting the pull just holding the nacelle needs a really firm grip. I very much doubt full power will be needed for more than a few seconds and even then only when going "vertical" At least I have the stl files to create the other nacelle. Time to start designing the V173 body.

toto You can see how easy it is for "life" to get in the way of RC flying and goes along to explaining why so many RC flyers are of that certain age 😉

I can only add don't be shy on the nitro. All Cox engines worked better with some and particularly the Tee Dee range need more before they ran like they should. I used to have a tin of Cox "competition" fuel. It was expensive and bought over the counter from the local model shop! From memory it had 30% nitro! 😃 Spill a drop on your hand an it felt cold from the nitro evaporation. H&S would now ban it from being sold commercially.

The bit that puzzled me about the XF-5U was the lack of counter rotating props if this picture is to be believed. Although this may have been trial "mock up" as much appears incomplete. When the fully articulated blades were installed, note the much bigger prop hub, they were counter rotating. And outward rotating as Charles Zimmerman originally proposed.

This is what the nacelle pf my V173 might look like with a scale 10x5 three blade installed. Printed in LW-PLA. It does look odd to have such a small diameter nacelle compared to the size of the prop. This would be the RH nacelle as on the V173 as the props rotated "outwards over the top". Motor cooling could be an issue on a lomg flight but I expect I might be on the third airframe before such a flight occurs.😄

Rare for an ESC to continue if it looses the input from the Rx unless a failsafe has actually been set to keep the throttle open. Is the radio a Futaba 2.4 by any chance? By default they have the throttle reversed. I have had to jump out of the way more than once when my plane was on approach flying directly towards. Its only when the plane gets really close does it dawn that it is actually going to hit me!

I built this a few years back to specifically find out what the effects of flaps might be. Counter rotating props to eliminate the effects of motor torque and two section flaps that go from 0 to 90 degrees fully variable controlled by a transmitter knob. The flaps do have to to be applied progressively to allow the pitch trim to be adjusted. At 90 degree flap the drag is such that almost full power is required to maintain level flight. The flight speed between 0 to 90 flap is remarkable. https://www.youtube.com/watch?v=6EyiWQ7YnlA&t=26s It made for a good learning experience.

Perhaps this is why the true Clark Y section developed in 1922 is still remarkably successful particularly in model aviation.

To keep a scale appearance I wanted to keep the motor bell within the diameter of the nacelle and be able to drive a scale prop. With a 10" prop the nacelle would be 28mm diameter. Using PLA about printing a test section of the nacelle and mounting a suitable Emax 2822 motor. This type of Emax uses a "drum" motor mount that is also 28mm dia . Nno prop yet but this is what the nacelle, motor and spinner looks like. The motor has a prop adapter fitted inside the spinner. The motor wires run down inside the nacelle. Exactly how the nacelle will be fixed to the V173 foam body is a problem for another day. Just for fun I ran it up "in hand" on a 2s. https://www.youtube.com/watch?v=vB0EphC7iK0 Next problem is to fit the 3 blade props when they arrive from China.!

A very crude "tell" is the number of capacitors. Single capacitor 30A or less. Twin capacitor 40A or more. All my 2-4s ESCs follow this guide but those intended for 6s or above may be different.

The V173 was simple compared to the XF5U and only 1/5 the weight. In its initial form the V173 actually used early F4U Corsair props but obviously at much lower RPM as each was driven by only 80hp rather than 2000! These were soon replaced lighter specially made props but of the same 13'4" diameter. The XF5U props were even bigger at 16' diameter! The intention is to size my V173 so 10x5 three blade are true scale diameter. It will thus need scale U/C and sit at the same ground angle!

Never one to shy away from trying something different the Vought 173. A small scale prototype of the proposed larger and much heavier XF5U. It was actually remarkably successful. first flown in 1942 by the time of its last flight in 1947 it had flown having flown no less than 176 times although the full size project for a Navy fighter was doomed by the advent of jets. It was powered by two Continental A80 flat 4 of just 80hp each. It was largely made of wood with fabric covering. As it flew so many times it seemed to me it should be possible to build & fly a foam electric version. Still thinking at this stage but one thing is for certain it likely would have "interesting" flight characteristics.

toto That front fence looks like its going to be more of a stockade than a fence. 😄 Two proper "security" padlocks on one of the sheds! Is there some gold bullion in there? 😉

The FK707s converts well but it pays to keep the weight down. This is my first conversion. Always paranoid about aerodynamics I added printed extensions to achieve a fine 1mm thick trailing edge. A small LE2204 motor and 3.7g servos (no rudder) it uses an 850mAh 3s in a slightly hollowed out cockpit. The motor has cooling vents built into the cowling which is printed in LW-PLA. The 10A ESC is mounted externally on the cockpit side. The receiver is inside under the wing. It weighs 320g and has quite a spritely performance. With a folding prop is glides well too. I fully understand that for slope work weight can be an advantage but on the Cheshire plain hills are few and far between.

Don Given that the OP's question was on a model flying web site quoting typical values for that application seems reasonable. Keeping above 4V/cell would make for pretty short flying times.😉

Skybird To answer what I think you mean. A LiPo should always be used fully balance charged to 4.20V/cell using a dedicated LiPo charger. A LiPo should not be left fully charged for much longer than a week. A LiPo should never be discharged below 3.3V/cell or it will be permanently damaged A LiPo should be discharged to at least 3.8V/cell for long term (weeks) storage. A LiPo that has become puffed should be considered for safe disposal. A LiPo must be fully discharged to 0V/cell for safety before disposal and then only at a recognised battery disposal point.

It is perhaps worth noting that the effect of IR on a planes performance does depend on the application. If the expected flight duration is less than 6 minutes, equivalent to an average 10c or more discharge rate, then an elevated IR will result in a noticeable drop in performance. It just wont have the same "punch" as when the battery was new. If the expected flight time is say 12 minutes (5c discharge) particularly in conjunction with throttle management then you are much less likely to notice any loss in performance although any related loss in battery capacity will be more evident. How you use a battery is the key. I have a couple of planes that can under ideal conditions fly under power for up to 45 minutes. As their batteries age there may be a loss in full power performance but unless I do a specific test each normal duration flight fells the same even after several years of use.

Agreed at it being incredibly cheap and quick way to create a modern scale jet but the really clever bit is by the person designing the print files needed to do it. 😉

Chris I hope to be there with a few of my light weights provided the weather is suitable for them. I look forward to using the new entrance!

Just an update. It does indeed fly pretty well but, there always seems to be a but, the pitch of the 11x3.8 prop is rather too fine. As expected loads of thrust at launch even at less than full throttle but try to speed up makes lots of noise but not much else. A further issue is the torque at full power at the rather slow speed through the air almost over powers the relatively modest ailerons. So first 30% bigger ailerons. Then an 11x7 e prop. With it the motor draws a measured 28A giving 333W on a fully charged 3s. Likely this prop is a bit too big for the 2830 motor but as the Big Dragon 3 only weighs 30oz that gives no less than 170W/lb. I doubt full power will be used for more than an occasional 10 second burst. The rest of the time a much lower throttle or even gliding is all that will be required. In addition as the motor is rather "stuck out in the open" it will be get adequate cooling Now it just need this "summer" weather (gales and rain 😧) to calm down a bit!