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Monday, May 23, 2016

Extra SHP__Less Power Better For Learning 3D

 
 
We are seeing so many new faces at RC Groups, and they are all wanting to know what the best plane for learning 3D is. Years ago the Extra SHP was unchallenged for it's confidence inspiring, if not downright silly amount of stability. This has changed a little as airframe technology has caught up with this ten year old design, but not so much that the SHP is not still a most excellent choice, if even not the best. It is still such an excellent airframe that I plan to always have at least one in the fleet.

Then again, I have always loved this plane, to the point that now I am so familiar with it that flying it is second nature. I know how to build and set one up (which isn't that difficult if you follow the manual), and exactly what to expect from it. This is not from any great amount of skill, rather extended experience flying the SHP. The plane is now like an old, well worn pair of slippers.

Not so by coincidence, this is also exactly what you need when learning 3D to begin with. You need a plane that is so stable it's hard to get into trouble, but agile enough that you can fly your way out of it. The SHP is as close to the perfect balance of capable, but forgiving as I have come across.

Most of You already Have 3s Packs
What is so beautiful about 3s power for new 3D pilots is most of you already have 3s 2200-3000 packs from your EFlite Apprentices and T29s, Mini Ultra Sticks and mini Pulses. You already have the packs and probably a good charger, so you can move right into a quality high performance 3D machine with a minimum of expense.

When you step up into a 4s EXP, things change pretty quickly, and these planes are really made for pilots with a little more experience. You can still easily learn 3D on an EXP, but they have also
tought me more than a textbook's worth about hardcore, ragged edge flying.

I have flown all of my EXPs on 3s and 4s packs, but since they are a little heavier and much, much  larger (regardless of nearly identical wingspan) they respond better to the 4s treatment. That, and they were designed to be totally bad ass, so it doesn't make much sense to fly one on 3s unless you want something really super gentle. The 3DHS Extra is a lighter plane, so it responds better to the lower power treatment. On 3s, all the EXPs are really good, but the SHP is a little better.

I have gone all over the place with the SHP on set up. I recently tried it n 4s, and it was a beast. The thing was scorching fast, but oddly flying on 3s seems to suit the plane's character more. Years ago the great Andrew Jesky shared his formula with me, and that was to shoot for 180 watts of power per pound. I need to weigh the current plane and take some power readings, but when this plane was called the SR we did the math with the Torque 2814 on Thunder Power 3s 2250 30C packs and a 13/6,5 APC prop at 200 watts per pound. This is a little more than Andrew's formula, but more power is more fun, and rather than prop down, I simply adapted to it.

Now running Thunder Power's superb 3s 2250 55C Lightning packs, I am sure I am getting a little bit more, but I've also added a little weight with dual ball link hardware, elevator SFGs and slightly heavier HS5070MH servos with a Castle BEC. My last SHP did not have these features, but I honestly can't tell the difference in flight outside of the servos being more torquey and responsive.  A little bit of weight doesn't hurt this plane much.
 



For learning 3D you not only need a solid airframe with benign handling characteristics, but also one that is light weight. As such, I was loathe to add any weight at all, but there was no way around it considering the additional equipment I added. I seriously doubt it was more than 1/2 ounce or so, but I will take the plane to the post office and weigh it to be sure.

A lighter plane is better for learning because it will stall at a lower speed, and accelerate faster into flying speed when you hammer the power. With this in mind, the smaller (3s 2240 compared to 4s 2700) and lighter packs make a noticeable difference, Even on 4s this is a pretty light weigh plane, but on 3s it's character becomes much more forgiving of mistake in near stall and post stall flight.


 
Dropping to 3s will cost you some power, and outright speed, but you don't need that when you are learning, or when you want a super easy flying plane. With less voltage coming in, the power delivery is a little less spikey. Imagine driving fast on a wet, curvy road. If you are in a Nissan Sentra controlling the 120 or so horsepower would be a lot easier than trying to keep from spinning the tires were you driving a 600hp Corvette. The power on the slower car doesn't explode and jump out from under you in the Nissan, but in the 'Vette you really have to be careful.
 
It's much the same with planes because in 3D a lot of times the plane is not travelling in the same direction as it is pointing. Essentially, you are sliding the plane through the air much like you would slide a car on a wet road, and lower power makes this easier to manage.
 
With big power it is harder to find a constant setting to maintain a hover or harrier. The power bursts can pull you out of post stall flight when you don't mean for it to, whereas it is easier to feed in smaller amounts with a less powerful set up.


 
Certainly you want enough power to punch out of a hover with good authority, and you don't really need to rocket out anyway. My initial thoughts when learning 3D was that I wanted monster power to pull me out of trouble, but when I dropped to 3s I found out that with less power I learned to stay ahead of the plane better so I actually got into less trouble to begin with. Couple that with lighter weight, I had more time to collect myself and fly out.
 
Equally crucial is that dropping to 3s allows you to go up in diameter from a 12/6 to either a 13/6.5  to a 14/7 propeller. This gives you a bigger cone of vectored thrust (air from the prop) flowing over the plane to provide lift and control response. I usually like the 13/6.5 because it gives you a really sweet balance between lots of vectored thrust and sport type top speed. The 14/7 gives you crazy vectored thrust and slow/stalled control, but the top end suffers a little too much for my liking. Still, the 14" prop the plane becomes more like a ceiling fan with turning vanes, so 3D is crazy easy.
 
Sure, big power is crazy fun, but that's what my 4s planes are for. When I want a super easy, no stress plane, I always take the SHP out on 3s packs. With less power I can keep the plane closer in, slow it down more, have better post stall control (thanks to the bigger prop). It is just easier to fly all the way around, but assuredly you give up some of the blistering insane performance that 4s delivers.
 
Any set up change you make is going to deliver a performance compromise, so to break this down in easier to understand terms, more power is more performance and less power gives you an easier to fly plane. For the new guys, the easier plane is going to be the best choice.
 
Just for grins, I also had a chance to fly a friend's 3DHS Edge 48" Edge 540 on 3s 55C and it was a hoot. I think the SHP is still probably a better plane for me, but the Edge was certainly really close. It was stable and easy and I liked it so much I plan to build one this summer. 
 

 
Just for reference, you can see the Extreme Flight Extra EXP is completely capable on 3s. I flew mine this way for a few months until I discovered it is better suited to 4s. The plane is so much larger in every respect that it creates more lift, but also more drag. 3s just is not enough to wring all the performance out of it, but it was still perfectly capable on 3s. It's just a world better on 4s.


Extreme Flight Extra EXP__Wind Games from Doc Austin on Vimeo.

So, you pick the kind of performance you are after to match the kind of flying you want to do. For extreme and high speed aerobatics on 48" class planes, 4s is tough to beat with it's monster power. For easy, slow 3D and lots of post stall control, 3s and the bigger prop and more vectored thrust works best.



3S As A pragmatic Choice
Yeah, pragmatism isn't the #1 goal when you are searching for performance, but in this case it makes complete sense. In addition to the lighter weight and bigger prop, 3S comes up big in the dollar column. We are running Thunder Power 3s 2250 55C Lightning packs in my SHP and they are terrific on every level.

Thunder Power 3s 2250 55C Lightning packs are very reasonably priced at $36.99 per pack. With this you get a two year warranty and a 30% off crash replacement policy. Occasionally you can catch Thunder Power having a 40% or 50% off sale, so if you consider you can get these for as little as $18, that's a really good value. These are another good reason that 3s makes a lot of sense.



Most of you who are flying 3s sport planes already have these packs from your EFlite Apprentices, T28, Mini Pulses and Mini Ultra Sticks, so you can just keep using them. You can keep using your same charger too, though the ones that come with the Apprentice and T28 are low power and slow. I also don't believe those chargers do balance charging, which you really want for more performance and long life.

There are a lot of good chargers on the market, but for these 3s packs I heartily recommend the Thunder Power TP610C AC/DC. Part of this unit's beauty is that you can use either 12 or 110 volts to power it. This means you can charge from your car battery or any 110 volt outlet.  If you don't have electricity at the field, or all the charge stations are in use, you simply hook it up to your car. Then when you go home, you can charge from a 110v outlet in your garage or shop.

Programming the 610 AC/DC is very simple and intuitive. I figured mine out without even consulting the manual, though it's always better to read the manual. The charger has 12 memories, so you set it up once and then pick the memory you want for the pack you are charging. even if you make a mistake, the charger reads the pack and knows how many cells and what capacity it's dealing with. If you put in the wrong number of cells, the charger kicks out and sounds an alarm.

When using 55C packs, the charger is well within the limits of what the battery can take, so you can't accidentally overcharge and potentially cause a charging fire through overcharging. Part of what I like about this charger and high charge rate batteries is that there is not enough power to put too many amps into the pack, even if you screw up.

 The charger is very, very versatile, and I jeep on in the flight box, and another under the seat in my car in case someone else needs to use it. Most of he time when I lend it out, those people end up buying their own.

With a 55C discharge rate, these packs have really good punch. that alone makes them worth it, but also remember they have a 12C charge rate. I use a Thunder Power TP610C AC/DC charger which pumps out 8 amps for 3s. The packs are capable of taking 32 amps, so 8 amps is not even beginning to push them hard.  At 8 amps I can charge one of these packs in about 12-16 minutes, which is jolly good.

 
With my Thunder Power TP820CD high power charger, I can get up to 20 amps per pack, and can charge two at a time. At 20 amp, I have charged a 3s 2250 in eight minutes, and you just about can't use them up fast enough.

By the time you put a pack on charge, get something to drink, and fly another pack, the first pack is almost always ready to go again, so you really only new two packs and you can fly all day with next to no waiting between flights.