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. Anyway, not long ago I got a servo order for 14 of our DS90DLHV servos, which as orders go, tickled my curiosity.
So the order for fourteen of the DS90DLHV 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) 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 90 oz-in is plenty.
So while his thinking was sound, 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 have easily shipped his order with a clear conscience because the DS90 were 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 a bit more money, I could offer him servos perhaps better suited not only to those three models, but for future ones. So I shared with him what Matt (above) had said about servos for his Hog Bipe.
What follows is what I told him in one of my famously massive missives (I've got a terrible problem of over-answering). now I'm sharing in hopes perhaps others who have been away from the sport a while may find my thoughts, if not interesting, at least useful. Here goes;
Todd,
Sorry for not responding more quickly but I realized this was going to turn into a massive missive because of your long absence from the sport. Basically, I needed to plan for what to say, and this meant time when I could gather my thoughts in peace. Typically, whilst sipping a cup of coffee in the mornings before work.
Bottom line? I'm quite familiar with all three SIG models having built a Somthin' Extra and three Four-Star 60s myself. And I've flown the third, the Hog Bipe belonging to a fellow modeler. They're all three fantastic models but in my opinion, the appropriate servo instead of the DS90 is actually the DS130DLHV (yes, all around, even throttle to keep things simple). This servo is $5 more costly than the DS90DLHV you purchased and I hope you'll believe I'm not spending this much time with you for the money. Anyway, there are developments you have missed out on due to your 30 year hiatus which guide my thinking.
For example, back in the day models were designed when one servo drove both ailerons, but 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 you ordered. 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 and gives some built in redundancy. This is a good thing - 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). I remembered mention of this aircraft because scale models are my thing so I had popped over to the Balsa USA website to refresh my memory regarding the model, and yes, it's a beauty.
Anyway, while you might very well use the DS130 servos in this model also because at 75" it's not considered an especially large model (not these days), please allow me to share a bit of advice regarding its real 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 pilot's mood, or attitude whilst flying a warbird. And also because of the nature of the maneuvers in which it's flown.
Second, 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 especially at the 4 o'clock through 7 o'clock porton of the pullout.
Third, as we discussed, you're opting for a DLE-35 (a great engine, one of which I have installed in an 80" Bearcat and love). Anyway, it's a gasser, and the aircraft will turn out significantly more massive than if the model were powered by a four stroke 120. Your Mustang will be as much as 3X heavier (and faster) than the SIG sport models! Again, more stress on the components.
Fourth, advice is to use DS270DLHV servos for this model, or possibly our DS360DLHV servos plus DS180DLHV. Yes, all three are a bit more costly than the DS90DLHV you mentioned ordering in future for the Mustang but they're superb examples of today's modest cost standard size servos.
Basically, they're so useful for a wide range of models because they're the exact same size as the DS90DLHV but 3X, 4X, and 2X more powerful, respectively. E.g. they're also standard size, but being much more powerful may prove be useful (especially for such a modest price increase).
So your gorgeous P-51 requires 8-9 servos (two each for flaps and ailerons, or 4 for the flight controls of the wing). Plus 3 more if you opt to use independent elevator servos (plus rudder). And one or two for the engine. I recommend using two DS180DLHV on ailerons, two DS360DLHV on flaps, two DS270DLHV on elevator, another DS360DLHV on rudder, and a DS90DLHV on throttle (and choke if you so elect) because, as it happens, scale modeling is my particular interest as a modeler. 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; B2S2500 a LiIon-2-cell 2500mA pack (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. All modern receivers are equipped to handle the increased voltage of HV packs and servos thus rated are typically labeled HV.
Note 1; I entered the servo business just when this was beginning to come to the fore and thus, I simply side-stepped SV (standard voltage) servos altogether. We focused solely on HV servos and never bothered with 5-6V 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 to 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 (someone bought the name and is giving it a go, but it's definitely not the same). And Futaba, believe it or not, may fairly be considered the underdog (and at my field, may also 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. They're all decent.
Note 3; a word of warning, if you buy a radio system that suffers from brownouts under
load, then add a capacitor. These caps, in the hobby are called glitch busters because when a receiver resets
(brownout) the servos glitch when it reboots. The capacitor keeps it from
happening in the first place. Just Google the various radio brands plus the word
'brownout' and you'll quickly see if it's common in the
system you are interested in buying (or have already bought).
Note 4; naturally, this isn't
something the RF manufacturers like to talk about but
users will definitely bitch if it happened to them, count on it! Point being, if it's common with the brand you're interested in, you'll find folks complaining about crashing
model due to this phenomena. I offer this by way of a heads up, because you're planning on
installing high performance servos into a high performance model (the Mustang) and this isn't exactly cost-free.
Related to cost, I mean cost as in current consumption - distinct and separate from voltage. Basically, you
need an adequate current supply. Back in the day, servos operated on a couple hundred milliamps and these day,
it's 10X as much or 2-3A, and more! That's a lot of current draw. The specs
tab for our servos discloses maximum. Just multiply by the number of servos to get a feel for how high things can go and yes, I know it's unlikely more than two servos stall at any one time but heads up, eh? Better safe than sorry, eh?
What else should you be careful of? Extensions longer than 30". I advise you add
capacitance at the load end to anything longer. Very easy to do; just use a Y-harness and
capacitor (we have both on the site). Plug the servo and the cap
into the Y-harness, then plug the Y-harness into the extension. Or
if money is tight, then make your own (just be certain to use low ESR caps, soldering them to leads
and making Y-harnesses is an easy job).
Anyway, we list both of these along with extensions for if
you don't want to bother making them yourself. And remember, the trade name
for caps in the hobby is glitch buster so if you want to buy them at your local hobby shop, this is what you should ask for because asking for capacitors may produce a puzzled expression.
Returning to your Mustang; for this model, instead of the B2S2500, I recommend the B2S300, instead. Not for the added capacity but for the chemistry. Instead of Lithium-Ion it's LiFePO4 (lithium-iron-phosphate). Poke around on the site and you'll learn more. For example, there's an article titled; On Modeling's Different Chemistries you may find useful. There's an article on determining safe flight time based on battery capacity and actual rate of use. There's also an article detailing differences in a pack's native voltage and servo performance you may find useful.
Anyway, plenty of companies sell LFP packs so this isn't me just flogging my goods. What's different about ours is you get more connections to the receiver. Read this to learn why there are two JR type connectors present instead of just one.
Note 5; 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 or LFP) 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).
Why LFP packs despite them being lower voltage? 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. Also, they're a little more costly, but I hope this is not a deal breaker. Anyway, there's an article amongst the askJohn collection on our website that goes into all this. Like I said, poke around.
Finally, I'm going to recommend you begin a build thread on RCSB for your BUSA Mustang. If you're unfamiliar with the
site, it's where guys queer for scale models hang out. If I may
assume something about you, you'll fit right in.
Here are three links by customers of ours, which I'm following and in which I've
made comments (as may you). These are selections I suspect you will enjoy
browsing to get a feel for the place. And don't be intimidated by the
caliber
of some of the builds because there's a hierarchy for
everything, and some guys are just more serious than others.
Me, I'm
a decent builder but time constrains me so ARFs are about all I have
time for (RCSB has a section expressly for ARF builds). So despite
doing this 50+ years I'm always learning from others - most recently about peel ply. Point being, don't
be intimidated (I certainly don't let their incredible skills deter me
from contributing). Anyway,
that's my pitch for the RCSB forum, and no, I don't have any
financial
interest whatsoever in this. The owner, Mike Chilson, works for
SpaceX (not that far from us - we're in central Florida) and he's a
regular guy just like you and me.
1. This link is to an 18-page thread regarding an Antonov AN-2 biplane, an ARF by Maxford USA.
2. This link is to a 73 page (and counting) build thread of a 1/3-scale Royal Air Force S.E.2 aircraft and if you go to the last 10 pages or so you can decide if you
want to make time in your life to follow the build. Fair warning,
it's a master's level class in model building. For example, if you ever
wanted to know more about vacuum molding, this will toss you into the
deep end quickly. Also details regarding the use of a 3D printer - like to make stuff for detailing. Believe me, it's a
wow thread!
Note 6, when I first visit a thread amounting to dozens of
pages like this one, I usually skip
through after page 1, checking every 5-10 pages to catch up.
However, when presented this particular 'very long' build thread, even
though I wasn't especially interested in the S.E.2 in particular, it was
so incredible it grabbed me hard and I've read all the pages. Once again, you'll see me
participating and believe me, you're welcome to also!
3. This link to a Fokker G1, up to 44 pages and counting. it's another rarely
seen (never by my eyes) model at the field.
Honestly, there are many threads and even coming in midstream (assuming your Mustang is partly assembled already) would be wonderful
to follow. Point being, if you create an account with RCSB, then share the back story for your interest and also share
the link with me because odds are good I will follow your build, also!
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.
Moreover, none of this deals with the differences in servo motor construction. if you have time and are inclined to learn more, this article about RC servo motors is one where we cut some motors open on a lathe and show you what makes iron core motors different from Coreless motors and Brushless motors.
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.
