When Washington Irving published his short story titled Rip Van Winkle two centuries ago, little could he have imagined I'd be using the childhood classic as a reference for modelers who are returning to the sport after a long hiatus. In this caseSTUDY I'll try to bring you up to speed on the latest developments in RC modeling for if, like the Dutchman of the story, you've been out of circulation a while. Here goes;
Not long ago I got a servo order for 14 of our DS140DLHV servos, which as orders go, tickled my curiosity. This is because this particular servo is usually reserved for throttle use on 3D gasser models by guys facing a severe budget constraint (versus something like the DS305CLHV, which is specced by the better heeled amongst us for the same job).
So to see an order come across for fourteen of them raised eyebrows. Further to this; throttles only require about 10 oz-in of torque - but - I'm not going to bother making a servo outputting a mere 10 oz-in, so to get the speed, you have to accept being in overkill territory torque-wise . . . is what it is, but I digress.
So the order for fourteen of the DS140DLHV servos led me to contact the buyer and I was not surprised in the least to learn he's a recent returnee to the sport after a 30 year hiatus. Yup, a modern day Rip Van Winkle equivalent in our very own sport!
Folks, this is surprisingly common because guys get into modeling then life's responsibilities interfere (e.g. home buying, children, college expenses, work, etc.) and then at some point, they return to the fold . . . with both love and enthusiasm for building and flying intact, as if they had never left the sport!
Anyway, he (his name's Todd, not that that's especially germane) but Todd told me he'd bought the servos for three SIG kits; a Hog Bipe, a Somethin' Extra, and a Four-Star 60. Nominally, all three are 4-channel airplanes where even 140 oz-in is perhaps considered overkill, also that he'd selected these servos for their speed.
Honestly, his thinking is/was sound, but I felt I could better serve him by dishing some advice. This is because it's my experience servos you buy for one model often live on in another model versus just the one for which they've been initially purchased. In other words, we could easily have shipped him the order with a clear conscience and he'd have been fine, but there was a decent chance with guidance on recent developments he'd decide otherwise.
Reason is; there have been some changes in the sport since back in the day. Some are quite significant. And for the same or less money, I could offer him servos perhaps better suited to his models and their future use. Todd soon responded generously expressing thanks for my offer. What follows is what I told him - shared in hopes perhaps you too have been away from the sport a while in which case, maybe some of this will be of interest for you also . . . here goes;
Sorry for not responding more quickly but I realized this was going to turn into a missive because of your long absence from the sport. Ineeded to plan to do it when I could gather my thoughts in peace, which for me means whilst sipping a cup of coffee in the mornings before work.
Bottom line? I'm quite familiar with all three SIG models having built two myself and flown a third. They're fantastic models but in my opinion, the appropriate servo is the DS180DLHV (yes, all around, even throttle to keep things simple). This servo is $5 less costly than the DS140DLHV you purchased so we can readily update your order and refund you the difference and ship them today. But . . .
There are developments you have missed out on due to your 30 year hiatus. For example, while all three of these models were designed when one servo drove both ailerons, in recent years modelers have overwhelmingly adopted the practice of using one servo per control surface. Overkill? Maybe, but bear with me. Anyway, this means . . .
- Hog Bipe - 5 servos
- Four Star 60 - 5 servos
- Somethin' Extra - 5 servos
. . . 15 servos vs. the 14 of you ordered, which we can account for without more money out of what you've already paid (with something left over). The reason for this becomes obvious once you realize assigning one servo per control surface gives increased flexibility in what you can do with the model. Trust me on this even if you don't yet grok the implications.
However, then there's your BUSA P-51 (he had mentioned this on the phone but not in a follow up email but I remembered because scale models are my thing and I had popped over to the Balsa USA website to refresh my memory regarding the model, and yes, it's a beauty); and while you might very well use the same DS180 servo in this model also because at 75" it's not considered an especially large model these days, please allow me to share a bit of advice regarding its needs because I'm an experienced scale nut.
Two things; first, as a rule, Mustangs are flown quite differently
than the three smaller SIG sport models. In part it's because of the mood, or attitude whilst flying a warbird and also because of the nature of the maneuvers in which it's flown. For example, diving out of the sun for a high-speed ultra-low pass followed by a pull-up into victory roll is a hugely popular maneuver with WWII heavy iron. This imposes greater stresses on your avionics than a lightly loaded slower speed sport model. Second; as we discussed, if it's powered by a gasser it'll be significantly more massive - as much as 3X heavier and faster! Again, more stress on the components.
My advice thus, is to use DS270DLHV servos for this model, which cost the same as the DS140DLHV, or in the alternative, our DS360DLHV servos, instead, which cost $5 more than what you've paid (note; this last is my personal all around favorite servo). Why? Basically, because it's so useful for a wide range of models since while it's the exact same size as the DS180, e.g. standard size, it's much more powerful (especially for such a modest price increase).
This gorgeous P-51 requires 7 servos (two each for flaps and ailerons, or four for the flight controls of the wing). Plus three more if you opt to use independent elevator servos (along with rudder). I definitely recommend using two on the elevators - again, just trust me on this, please! Anyway, as it happens, scale modeling is my particular interest as a modeler and on the basis of my experience I feel very comfortable with this assessment regarding servos for this Mustang model (as well as for your sport-model fleet).
Another thing; there's been a sea change in battery technology since your last foray. For your three sport models I recommend this pack; LiIon-2S1500-15C (vs. old school NiCd or NiMH packs of 4 or 5-cells). These days, cells range in the 3.2 to 3.7V and pack voltages are derived from 2-cells in series (or sometimes 2S2P - two in series and then that pair wired in parallel - thus maintaining voltage but adding capacity). All modern receivers are equipped to handle the increased voltage of HV packs and servos will be labeled HV.
Note 1; I entered the servo business when this was beginning to come to the fore and simply side-stepped SV (standard voltage) servos altogether and focused solely on HV servos. Turned out to be a smart business move. Anyway, all of our product will operate on a wide input range (varying between 4.8 and 8.4V but obviously, perform best at highest voltage). My advice is jump in with both feet and enjoy the new technology because 2.4GHz radios free you from the tyranny of seeking frequency pins.
Note 2; I don't have a dog in the RF-fight so my advice is buy an 8 or 9-channel radio of whatever brand is popular in your area. Hard to believe but Kraft and JR are gone and Futaba is the underdog and may be fairly said to be on the ropes. These days Spektrum dominates at my local field, and there are many other contenders such as FrSky and Jeti. I continue to fly Futaba equipment but it doesn't really matter, they're all decent.
Anyway, back to your Mustang; for this model I recommend either of these batteries instead of the lower capacity pack mentioned for the sport models above; LiIon-2S2P3000-15C - or - LiFePO4-2S2500-20C
Of the two, the latter is slightly lower voltage/cell - but - it's also the safer chemistry (overall). In fact, I use the batteries with A123 cells (LiFePO4) in 'all' of my own personal models. This, despite the fact they're not quite as high a voltage, which means slightly less servo performance. This is especially the case with scale models where I use the pack for ballast and balance meaning it's less than convenient to remove the pack for charging.
So with regard to the slightly lower pack voltage, I get around the implication of this on servo performance by basically throwing a bit more servo than is strictly required for the model thus, ensuring more than sufficient power at the control surface (e.g. when adjusting for the slightly lower voltage differences). This is principally because the chemistry in A123 cells is less volatile, which means reduced fire risk when charging (and why I always remove other lithium chemistry packs from my models for charging and never charge them without supervision). So A123 packs are safer to live with, again, in my opinion. Also, while they're a little more costly, this is not usually a deal breaker, either. Anyway, there's an article amongst the askJohn collection on our website that goes into all this. Poke around.
In closing, we stand by for instructions regarding servos and/or batteries.
-- John 407-302-3361
PS, I'm not involved in the retract business either - but - my advice is to investigate electric powered retracts as a better way to go that either servo-powered mechanical or pneumatic like were popular back in the day. And eyeball the gorgeous sub-micro servos we offer, which you can readily bury within the wheel wells for operating gear doors (I'm especially fond of the DS75CLHV). Note; if scale is your thing 'this' is why 12-14, and even 20-channel radios are so popular. JB
. . . so I closed with some advice largely unrelated to servos, which anyone coming from the old school will likely find of use. Especially if they're into scale modeling like me. Frankly, these days, battery packs made up of 1.2V cells are largely relegated to the dust bin of history, yes, 72MHz radios still work (and some guys continue to use them) but quite honestly, 2.4GHz means more freedom and convenience. Added to which, independent servos on each control surface and loads of channels are the order of the day for good reasons.
And further to all this . . . none of this even 'touches' on propulsion developments where outrunner motors with an ESC replacing an engine and throttle servo, with a LiPo replacing the fuel and tank absolutely rule at many fields - mine included! Anyway, I hope you too find this summary useful. Please feel free to email your thoughts and I'll update the article as time goes by.