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Multiplex Twister EDF

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Old 02-14-2018, 08:02 AM
  #101  
aeromax18
 
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Last week I tested the original fan/motor that came with the Twister. I placed the fuse with the fan installed and a 4 cell battery on a digital scale reading 980 grams of weight. I proceeded to apply full power and the scale read 1960 grams. That means that I got almost a 1000 grams of thrust. 1 to 1 power to wt. ratio. I ordered (from Turbine RC) and received my new 70mm CS XRP 13 blades fan 2600kV motor and ran the same test. Well, the results were quite disappointing. I only got about 600 grams of thrust from an engine/fan combination that the mfg. claims 1.36 kg thrust. Needless to say I'm very very disappointed. The sound was the only improvement. Not much comfort. I guess I'm putting the original fan motor back in.

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Old 02-14-2018, 05:06 PM
  #102  
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Aeromax, the biggest problem that the Twister has is air-inlet (air flow to the EDF). Those two small side fuselage inlets just don't let enough air in to feed a much more powerful motor and fan. I put a HET 6904 2w-20 in my last Twister and had disappointing results until I opened up the side inlets a bit more and then added an angular hole in the bottom of the fuselage ... which I got the idea from my HobbyPeople F-16's.

The bottom line is that with no modifications, the stock fan/motor are what the very smart engineers at Multiplex is what they designed it for, using all the air that can get into the fuse ahead of the EDF. If you want to experiment, Flare the side inlets a wee bit on the fuselage side, with a soldering pencil with a long tip, or use a Exacto Knife, and try the "cheater hole" in the bottom of the fuse half way between the side inlets and the motor. Start SMALL at first!! Cut that hole on a angle to encourage air wanting to pass easily from the outside to the inside. Just remember if you're landing on grass, cut the motor at touch down our you'll be spewing chopped grass out the back and maybe doing damage to the fan blades if they are plastic.
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Old 02-15-2018, 02:55 AM
  #103  
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cobrajocky,
This makes a lot of sense. . I think that since I'm getting as much as one to one power to weight ratio on the stock fan with 4's I'll try that first and see how it goes.
Thank you
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Old 02-15-2018, 04:41 PM
  #104  
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aeromax18 - if you're going to stick with the stock EDF plant, I would suggest you also only attempt to enlarge the existing side fuselage inlets no more than 20%. Again leave the outside of the openings as is, only skillfully enlarging the "tunnel" so less turbulence is is created. Think of it as a reverse funnel. VERY slow sculp with a long super sharp exacto blade or a very thin knife, little by little. Now Multiplex EPO foam (it was their own chemistry) has a really cool (reverse pun) feature, it can be sculpted with a warm to almost hot flat knife blade. You and also cut it with a hot sharp blade and it sort of coteries like a surgeons laser as you go. So use the warm flat blade to make the EPO foam smooth and formed for smooth air flow. Look at the inlets as stock, estimate a 20% increase ... it's not much removed material, so don't go nuts! You won't need an auxiliary inlet under the fuse or on the sides of the fuse under the high wings with a stock EDF powerplant. It's not until you are using a EDF that actually has a 50% to 100% increase in air flow that you need to worry about carving more air inlets. Remember, smoothness of the inlets to negate air turbulence is key. Good luck.
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Old 02-18-2018, 12:21 PM
  #105  
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cobrajocky, Can you shoot me a couple of photos showing what you did on the inlets and extra scoop on the bottom? A picture is worth a thousand words.
Thanks
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Old 02-18-2018, 06:02 PM
  #106  
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Originally Posted by aeromax18 View Post
cobrajocky, Can you shoot me a couple of photos showing what you did on the inlets and extra scoop on the bottom? A picture is worth a thousand words.
Thanks
I wish I could .... send you pictures, because I'd still have that Twister with the HET EDF in it, but sadly it decided (via pilot error) to play "Lawn dart" on some speed runs against another guys also modified Twister. I salvaged the HET EDF and ESC and it is now in a Hobby People EF-F16, actually in it's 2nd one as the first ate a tree when I misjudged distance and speed and "failed" to turn fast enough in a park ringed with trees we raced EDF's in. I only have one Multiplex Twister left, which has the stock fan but with a Hobby King Brushless that had a 200 higher speed with a 4S LiPO and better torque specs for spinning up faster. It hangs from the garage ceiling now, maybe flown only a couple times a year. I really got into F-16s and bought like 20 EF F-16 kits when Hobby People filed bankruptcy.

So what I was relating is what I recall from memory. If you are a newb to this kind of experimenting, I would suggest skipping the addition of any new openings, and just study the existing air inlets to see where you could increase the volume of air getting into the fuse. Work VERY SLOWLY and precisely, you can't put foam back. And don't cut away any foam that looks like it will weaken the fuse structure too. When using the "warm to hot" knife blade to "smooth" any cuts , start with a warmed blade first, if it doesn't "melt" the EPO enough to smooth, warm it a little more at a time.I like using "art painting blades" you'd buy at a at hobby shop. https://en.wikipedia.org/wiki/Painting_knife . They warm up faster, and are small for shaping with.

Wish I could help more.
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Old 02-19-2018, 08:23 AM
  #107  
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Thanks for your input here. I read thru this thread before starting assembling the Twister but found no hint of modifying the intakes or adding a cheater hole by any of the guys that upgraded it. . I agree with you 100% on the issue. Wonder why no one bothered to mention this critical step in upgrading the Twister. It would have been so much easier to modify the inlets before bonding the two fuselage halves together.
I'm probably going to explore the twister with a beefed up set up later on but for start I'm going to fly it with the stock set up with a 4's 3700mA .
Can you suggest appropriate control surfaces travel ?
Thanks

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Old 02-19-2018, 04:36 PM
  #108  
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I would guess that no one explored increasing intake airflow because the Twister always appealed to beginners (no disrespect), just as I bought my first Twister having very limited experience with EDF's. Nothing shameful here, that's what Multiplex had in mind. And everyone loves to custom paint (or cover if balsa) what they fly, and fewer like to dabble in "more juice" from their stocker model. The Twister was good for that the way the EDF is mounted. But beginners to mid-experienced EDF flyers have little to no understanding of how EDF's work in relations to air-flow "engineering". I flew UH-1 Huey gunships, OH-6 Cayuse and AH-1 Cobra's in the USAF during Vietnam (Cambodia, Laos and Thailand), all are jet turbine powered and pilots had to know the engineering as well as the crew chiefs/maint staff. So I like to "fiddle" with the engineering of stuff. It's why I like the F-16 EDF's, lots to modify. In air-flow a little improvement goes a long way."Play" slowly, quantify the improvements as you go.

The stock control surface recommendations from from Multiplex should be stayed with, especially while learning the craft in flight and especially if you do improve speed performance. This is an area you can increase as you feel completely competent flying it fast. Increase the travel if you want, but limit the actual throws with the transmitter setups. Consider some Aileron mixing with the Elevator in the transmitter so when you turn, the elevator compensates up a micro amount to any loss of altitude on turns. That's a problem with any model with no rudder control surface, "Aileron turns", which mean banking, always means losing some altitude.
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Old 09-26-2018, 01:04 PM
  #109  
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Default Finally Maidened the Twister

,Hi guys
I see nothing happened here foe a while. I veered off to other airplanes and then last week decided to get the Twister in the air. Decided to fly it first with the stock set up. I got about 1050 grams of thrust on fully charged new CHNL 4's bat. I set it up with forward c.g. My friend hand launched it with me on the sticks It took off nicely climbing to a safe hight then I reduced the power to about 50% and relaxed ( I have not flown in 4 months). I was positively surprised by the way it flew. Rock steady and responsive. I flew it for
4 minutes on low power and landed it easily. After a 10 minute break I took off again with a fresh bat. and did a couple of hi speed passes. I was just beautiful. I truly enjoyed this little jet. Relaxed the power and then after two more minutes It lost power and I had to glide it in. Glides in very nicely.
Upon inspection I discovered that the motor got cooked. That was a big disappointment as I was not pushing it hard at all. Got home and mounted an upgrade xrp 2840 - 2600kv motor 13 blades fan. I placed some weights on the tail to bring the CG to the factory recommended nipples location. I did not bother to increase the inlet area as was recommended here by some of you and just assumed it will fly at least like the original set up which I was fairly happy with.
Next day we launched it and what a disastrous experience that was. The plan was so under power and CG was so aft that it simply pointed up and near stalled . I managed to save it for a moment but the aft cg and extreme lack of power led to a crash. The nose broke off from the middle of the canopy and the rest of the plane survived. I hot glued the nose back in place ( will do a fiberglass repair job on it later) time to think now.

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Old 09-26-2018, 06:52 PM
  #110  
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Too much fan, not enough air flow .... simple. With that much fan and being air flow starved, it makes matter even worse by causing turbulence in front of the EDF, so even less thrust. I haven't flown mine is a Looooong time, but I seem to remember others have commented that the factory balance point is wrong and too aft.
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Old 09-27-2018, 01:02 PM
  #111  
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cobrajocky
You are right . that seemed to have been the problem. I remember your advise for cutting the inlets opening wider but then on the other hand I was quite happy with its flight with the 5 blades fan and 1050 grams of thrust. Honestly it flew pretty well. My thinking is to use a 5 to 7 blade fan / motor that was designed for a 4's and would give me that 1 to 1.1 kg thrust. Not fancy and inexpensive from Hobby King. I'll go that route before cutting the fuse for the 12 blade combo.
Thanks again for your input.
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Old 10-05-2018, 02:53 PM
  #112  
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I would suspect that Multiplex is pretty good at designing their models with power plants that live up to the limit of the air frame, though they did make some early models like the high-wing Magister (the large one) that came with a vastly under-powered Brushed motor system. I also suspect that they designed the Twister as a introductory - mid-level EDF plane meant to learn on and do "pleasure" flying .... which is does wonderfully. I'd suggest sticking close to the original EDF specs, though on the "Plus" side to eek out maybe 20% more performance and nothing more.

Some companies made EDF Jets that they intended to let well versed owners "push" to the extreme. I've always been and still am a nut on the old Hobby People EF-16 (F-16 Fighting Falcon) which you could buy as a ARF or a Kit and you supplied literally everything buy the air frame. I got hooked on them, crashed 4 so far, but pushed 132 MPH clocked with Police LIDAR. When Hobby People / Global Distributing went belly-up I bought 20 more "kits" at their "Garage sale" weeks before locking their headquarters office in Fountain Valley CA. That model is designed for "experimenting" and it seems to take any EDF / battery combo Iv'e tried. It always stays controllable, it's your capabilities that will fail first. Mine are getting stretched at 69 years of age and 132 MPH. Biggest problem is hitting unseen air turbulence during a straight power run and keep control (reacting fast enough) and slowing it down after hitting +120 to make a turn, as this F-16 copy like the real one likes to keep it's speed. I'm playing around adding speed brakes on the fuse actuated with one micro servo to save weight.
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Old 10-07-2018, 10:53 AM
  #113  
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Cobrajocky,
I looked it up (f16 - Pase 3) but it 's been discontinued. Where can I get one?
I spent few hours reading and learning the facts about EDF intake and Trust tubes. I feel like I know more now. I am going to try a couple of motors with different thrust tube diameter. Then I'll try cutting some off the intake and see what happens. right now I am getting 900 grams of static thrust and it flies pretty good. the launch is a chalange though. You need to get at least 1 to 1 ratio for a comfortable lauch. I did about 10 flights on it so far and look at it as a training step toward my Fly Fly L39 and Starmax F16. I am going to order the Fly fly Mirage 2000 on a 90 mm as a basic kit and fit a JF 90 in it. In between I'm flying my terrific King Cobra (Sig) w. OS 75. Purchased it used as a training platform before I step into giant scale. Love them all what can I say.
Do you still have some f16 left over ( a batch of 20 ahh? and for $27)
I can do with one of those.
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Old 10-15-2018, 09:51 AM
  #114  
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Improvements update:
I dropped a new power system in the Twister. A 12 blade Change Sun fan with a Cyclone Power CR480-2900-40DF. Suppose to provide 1.65kg of thrust. I also increased the Thrust tube exit to 60 mm from the original 55mm (Cutting a coffee cup to size). Static thrust check showed 1200grams of thrust which is almost 1 to 1 power to wt. ratio. . Took it to the field and launched it holding it in my left arm pushing the throttle to max rpm pulling on the stick for up elevator (right hand) before LAUNCH with my left arm. Boy, that was something. The Twister left my arm and started an Alfa flight then just lifted itself steady to a beautiful climb. What an improvement from everything I experienced so far. Top speed was awesome and I ended up doing 5 beautiful flights with the most exciting launch take off I ever had.
for now, I am going to leave the Twister as is and just enjoy it. Increasing the intake can wait. I want to have fun now.
Thanks

Last edited by aeromax18; 10-15-2018 at 09:54 AM.
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Old 10-15-2018, 09:21 PM
  #115  
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Hey aeromax18 , take some pictures and post, it may benefit others still flying Twisters.

Back to your question about the HobbyPeople Phase 3 EF-16, they went out of business a couple years ago now and like others I went to their warehouse "garage sale" to buy models for pennies on the dollar. I'm down to 6 unbuilt "Kit" versions after crashing a few and giving my son a couple, he'll likely get the rest I don't use as he's already put "dibs" on them. There are other EPO foam F-16 models that are nearly identical, some even have landing gear. Look for reviews for good ones and explore modding the one you chose.
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Old 12-13-2018, 09:20 PM
  #116  
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hello all, does anyone have a NIB Twister for sale...ill pay shipping....
thank you
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