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Jul 21, 2007, 03:47 PM
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Kev, I don't think you need anywhere near 1000 W to fly a 40 size trainer with authority. 500 W will do it.

Sorry to hear of the frustration and expense your uncle has gone through. That is really a pity, and I hope it does not turn him off electrics just because a few knuckleheads gave him bad technical advice.

Unfortunately, I also think a 600 rpm/volt motor and a 6S lipo pack are not a good match. With that much voltage, you will end up spinning a small 9" prop for 500 W input power. That is too small a prop for that much power - efficiency will be poor.

Unfortunately, I don't think a 600 rpm/V motor and a 3S pack are a really good choice either - you have to go all the way up to a 14" prop to get around 400 W into the motor. You may have ground clearance issues with a 14" prop on an Avistar. Maybe not, though, as I could just about get away with a 14" prop on my Sky Raider Mach I.

One interesting option is the big Himax 5030-390 motor your uncle already has on a 6S lipo pack. I know that motor is rather bigger and heavier than a 40 size trainer needs, but it will spin props in the 12" - 13" range at about the right power level on a 6S lipo pack. For instance a 12x8 APC E should get you roughly 450 W, 21 A, 60 mph pitch speed, 70 oz thrust (ballpark estimate).

-Flieslikeabeagle
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Jul 21, 2007, 03:53 PM
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Looks like you posted while I was composing post #151.

I think 6S1P will work, you just have to choose your prop so you keep current draw within reason. Remember, with a 6S pack you have some 22 volts under load - a mere 20 amps of current draw will get you around 450 watts, and 30 amps will get you around 650 watts. Most of todays lipos will handle 10 C (21 amps from a 2100 mAh pack) with ease, and many will be reasonably happy even at 30 amps. All you have to do is prop for a current draw somewhere between those numbers, and choose the prop pitch to get a reasonable pitch speed.

I think your uncles 390 rpm/V Himax, a 12x8 APC E or 13x8 APC E prop, and a 6S1P 2100 mAh lipo will work well for you. The 12x8 prop will put you in the 450W range, the 13x8 in the 550 W range, and around 25 amps current draw. Should be a very good match - that's what I'd use if it was my Avistar!

I'd save the 600 rpm/V motor for a 4S setup in some future model...

-Flieslikeabeagle
Jul 22, 2007, 12:13 AM
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Truglodite's Avatar
thanks for the advice. so a 14 prop might hit? i'm hoping his buddy's taildragger modification will help there. lol, i know, i wouldn't have done that either. his friend built it that way for him and told him it would handle better. i don't blame my uncle one bit for being a bit upset over that.

fortunately my uncle is a reasonable guy and is patiently trying to make his money go toward something he likes. he loves my aerostar 60, and my 3D and speed stuff, so he's not going to appreciate developing his skills on glider type planes. one thing led to another anyways, and now it's up to me to make 2 swell fliers out of this mess if parts.

considering the parts he has now, and the conditions in which he typically flies, i think i can come up with a few things. btw, he lives in concord, ca, and flies mostly in antioch and concord where winds never dip below 12mph, and more often than not you're forced to fly in 16mph+.

i think the himax will do great in a tiger 60 as a solid second plane starting with 6s, then progressing to 9s as his skills improve (thrill ride on 9s i'm sure. i told him how much fun i had learning basic aerobatics with a tiger 40 as my second plane and his heart has been set since. i have no doubts about a tiger 60 working with the himax, which i believe is good for the 40-60 sized range, but is a bit heavy for typical 40 trainers and works near the 1000W mark.

i got the uh motor because it's cheap, light, and gets 500-1000W on 4-6s. i wanted him to be able to use more common 3s2100's and not have to buy 4s stuff including a 4s charger (he has a bunch of 3s chargers already), that's why i was hoping 6s would be ok. ppl on uh who have tested this motor give these numbers:

APC-E 16 x 10
14.14 V
46.10 A
5325 rpm

APC-E 13 x 6.5
21.33 V
36.00 A
8952 rpm

APC-E 14 x 7
20.60 V
43.30 A
8362 rpm

APC-E 13 x 10
20.03 V
51.55 A
7763 rpm

on 4s, the prop would most likely not fit. if i go 6s, i'll have to go parallel (i doubt he's ready to spend big on 25c 6s stuff). the 14x7 still looks overpowered, but hopefully workable on a 6.5lbish 6s2p avistar 40 (remember, the intention is to be a bit heavy & overpowered for high winds). also, i really want to save the himax for his tiger 60, otherwise i'd break his heart.

will it be fliable for a beginner? i'll buddy box for him when i'm around, but in the end he'll have to learn to solo on it.

kev
Last edited by Truglodite; Jul 22, 2007 at 12:26 AM.
Jul 22, 2007, 02:36 PM
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Quote:
Originally Posted by Truglodite
So a 14 prop might hit? i'm hoping his buddy's taildragger modification will help there. lol, i know, i wouldn't have done that either. his friend built it that way for him and told him it would handle better.
Kev, I set up my Sky Raider Mach I for the largest possible ground clearance with the stock nose wheel and landing gear, and I have only about 1" of ground clearance with the 13x8 prop I'm using. Okay on an asphalt runway, inadequate for grass. I could probably cram in a 14" prop if I used bigger wheels for a bit more ground clearance and landed only on asphalt or other similar smooth and hard surfaces.

I've read a few other posts here on RCG where people converted trainers to taildraggers. I don't get the logic behind this: we all know taildraggers have a tendency to lurch to the right due to propeller P-factor during the take off run. Taildraggers don't handle better on the ground, they handle worse! And in the air there is no difference at all either way. So why would anybody do this?

I'm also not convinced that a taildragger mod helps with prop clearance at all. Sure, it gives you more prop clearance during 3-point landings - but what about during wheel landings, with the fuselage level? You get no more clearance than you would with a tricycle landing gear setup. And on a windy day, wheel landings are the preferred way to maintain control all the way down to the ground, since this allows slightly faster landing speed.

Well, on the bright side, your uncle will learn to cope with that P-factor during take offs, so he will be one step closer to flying more advanced taildragger models, I guess!
Quote:
Originally Posted by Truglodite
i got the uh motor because it's cheap, light, and gets 500-1000W on 4-6s. i wanted him to be able to use more common 3s2100's and not have to buy 4s stuff including a 4s charger (he has a bunch of 3s chargers already), that's why i was hoping 6s would be ok.
Gotcha!

Thanks for posting the real-world numbers; the specs on some of those UH motors are pretty loose. The label might say 600 rpm/V, but actually be something very different. There is no way a 600 rpm/V motor will spin a 16x10 prop on 4S lipo (14 V) and only draw 46 amps!

However if I lower the Kv to around 500 rpm/V, then those numbers start to make sense and match up with motor calculation software. So I will assume the actual Kv is more like 500 rpm/V for the rest of the discussion.
Quote:
APC-E 13 x 6.5
21.33 V
36.00 A
8952 rpm
Lessee, that amounts to nearly 770 W, and 56 mph pitch speed (and confirms a Kv around 500 rpm/V).

That's a lot of power, and not a lot of pitch speed for a 40 size model, IMHO. (The glow planes would be faster than the electric, and we can't have that, now, can we? ).

I am confident you can do what you want on 6S1P. No need for 6S2P. Since you have four 3S batteries, that will give your uncle a lot more stick time than using all four battery packs simultaneously and having monstrously excessive amounts of power. Stick time is very important to beginning fliers, it's the only way they will progress rapidly to being experienced fliers!

Using 6S1P 2100 mAh packs and an APC 11x5.5 "E" prop with this 500 rpm/V motor should get you roughly 25 A / 520 W / 65 mph pitch speed / 75 oz thrust / 6 minutes duration at full throttle (probably 9 - 12 minutes with throttle management). I think that is a nice setup for a trainer - plenty of power, and long enough flights to get lots of stick time. And you will be able to have a second flight while the first set of batteries is recharging.

-Flieslikeabeagle
Last edited by flieslikeabeagl; Jul 22, 2007 at 03:01 PM. Reason: Correct prop is 11x5.5, NOT 11x7. That was a typo. Sorry!
Jul 22, 2007, 02:41 PM
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Update: I searched United Hobbies for this motor, and found Miljenko's thread listing his measurements on the motor. Sure enough, he found that the Kv is around 500 rpm/V, not 600 rpm/V:
Quote:
Originally Posted by Miljenko
Io (16.4V): 2.5A
Io (24.6V): 3.2A
Rm = 0.077 ohms (77 miliohms)
Kv = 502 rpm/Volt
This confirms my estimate. Try the APC 11x5.5 Thin Electric on 6S1P 2100 mAh lipo, I think it will do everything you want. You won't get screaming unlimited vertical, but will get very strong performance for a trainer, without flogging your batteries to death from overcurrent.

-Flieslikeabeagle
Update: link to Miljenko's thread here:
http://www.unitedhobbies.com/communi...ts.asp?TID=117
Last edited by flieslikeabeagl; Jul 22, 2007 at 03:02 PM. Reason: Correct prop is 11x5.5, not 11x7. Sorry, brain slipped a cog!
Jul 22, 2007, 02:49 PM
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Quote:
Originally Posted by Truglodite
I told him how much fun i had learning basic aerobatics with a tiger 40 as my second plane and his heart has been set since.
Kev, can you tell me more about your experience with that Tiger 40? With those small control surfaces, were the roll rates high enough for good conventional aerobatics?

There are some inexpensive Tiger 40 clones around. Nitro Models lists one on their website but it is out of stock. Herm Perez found a similar model at texasrcplanes.com at a very reasonable price:
http://www.texasrcplanes.com/explorerl1.html

I've been flying aerobatic parkflyer models for a couple of years, and am long past the basic trainer stage; I built the Sky Raider Mach I because I had no previous experience with 40 size electrics, nor with cross-wind landings on a club field runway. Everything worked out exactly as I had calculated it, so now I am confident that what I learned on parkflyers I can successfully scale up to these larger models.

So now I'm thinking about choices for an aerobatic 40-size model (electric, of course!). I would appreciate your input on the Tiger 40.

-Flieslikeabeagle
Jul 22, 2007, 09:35 PM
know it all
there is something wrong, both the htx50-55A and 50-55B have the same constants in the milijenco data..
Jul 23, 2007, 12:09 PM
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Quote:
Originally Posted by hermperez
there is something wrong, both the htx50-55A and 50-55B have the same constants in the milijenco data..
Good catch! In fact United Hobbies has posted the same link URL under both motors.

More interesting yet: Miljenko's first post starts out with the words "Topic: HXT 50-55B-500 tested". (Colour emphasis mine).

I don't see a motor with this designation available on UH. Was this one of those silent manufacturing changes we keep hearing about? Did UH formerly carry a 500 rpm/V motor which they no longer stock? Your guess is good as mine!

All is not lost, though: if Kev is getting the 400 rpm/V version, it will work well with a 13x8 APC E on a 6S1P 2100 mAh pack (roughly 27 A/550 W/60 mph pitch speed/ 85 oz thrust). Or an APC 12x8 E prop will drop that to around 22 A/450 W / 70 oz thrust and give you longer flight times.

If Kev is getting the 600 rpm/V version prop size has to be sacrificed to run on 6S1P. An APC 9x6 "E" should work, or an APC 10x5 "E" will provide a bit more thrust at a bit less pitch speed.

Personally I don't like running 500 W through a small 9" prop as it costs you efficiency. But sometimes one doesn't have a choice!

Update: On the UH website, in the reviews for the HXT 50-55B-600 I found the following:
Quote:
Originally Posted by David

Note: This is not the same 50-55B as sold before June 2007.
This is a 600kv, the previous one was a 500 kv motor.


-Flieslikeabeagle
Jul 23, 2007, 01:09 PM
know it all
It is very confusing, I would really like to know before ordering one of them.. I think it is a good 60 size motor, also good for a 45 size plane if derated since the motor will run very cool. The 4130 class I consider a 90 size motor, but of course can be derated to 60 levels..
Sep 14, 2007, 03:19 PM
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Truglodite's Avatar
wow, thanks for all the helpful info Flieslikeabeagle! i owe you big time.

sorry i've flaked on this thread for so long, but work has been very busy, i've been building a bunch of smaller planes for myself, and most importantly my uncle was waiting on his parts to arrive (btw, he ordered a skytiger 60 arf with all the trimmings to house his himax 5030-390).

so 6s1p should be adequate for either the 600kV or 400kV versions. if it's 400kV i'll start with an apc9x6e, if it's the 600kV i'll start with an apc 12x8e [edit: lol, the other way around]. unfortunately i'm pretty sure he's got the 600kV version so he's going to be working the smaller props. we'll see what the wattmeter & tach say when it's all put together. i'll try to talk with him tonight & get more details on what he has in front of him for his 40T.

regarding my experiences with the skytiger 40:
i first flew it in the late 80's, and it was a superb second plane. it was a kit version that i bought already built (very nicely built & covered btw) with an os61sf installed, spinning an apc11x7. being my second plane, at first i was scared of the heavy motor & low wing, but i was impressed with how stable it was after the very first flight.

it was the kind of durable & predictable sport flyer you want to fly 3 times a day at least, and it is always up to the task regardless of runway or wind conditions. of all the planes i've flown, the tiger 40 was by far the easiest one to ground handle. i ended up installing a nose wheel brake, and the power up takeoffs & short landings really stole the show.

in flight it seemed just as floaty as my first plane (average .20 sized trainer) regardless of the extra weight from the .61 (16oz fuel drum too). stall was very forgiving & it slowed down to a jog for perfect 2 point landings even in 18+mph winds (on tricycle gear). even with such a gentle stall, snaprolls were still pretty "snappy" with a minimum amount of help from the ailerons.

you're right about the roll rate; it wasn't blinding fast with the huge wing & small ailerons, but imo rollrate was a perfect fit for the huge graceful lines that this plane does well with; nothing short of a good pattern plane can beat the perfect circular loops, cuban-8's, & inverted flight this plane is capable of. tracking is superb like a pattern ship, yet it flies much floatier than your typical pattern cruise missile. hi-rate rolls were easy, but some tail feedback was needed to hold altitude & heading through the exit.

low-rate rolls were a bit challenging unless airspeed was kept high; a side effect of KE coupling. like most sport planes from the era, it didn't lock in to KE like my modern 3d planes do. however i remember being very comfy doing 4-point rolls when i was first learning the maneuver way back when.

while i haven't owned many planes in this size & flight characteristic, but from what i've seen & flown i'd say the skytiger 40 flies most like a chipmunk 40. while it's not a balls out performer by today's standards, it was probably the most enjoyable plane i've ever flown. i wasn't the only one either; everyone that saw the plane fly fell in love with it (no exaggeration: grey haired old guard, kids, newbies... when i taxied her on to the runway just about everyone landed just so they could see her graceful dance). in fact i'd still enjoy flying her daily for the past 20yrs if i didn't terminate her on a low 4-point roll.

-kev
Last edited by Truglodite; Sep 14, 2007 at 04:03 PM.
Sep 21, 2007, 07:37 PM
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Wow, Kev, you have some good memories from your Tiger II!

Sadly, the cheap imitation (of the Tiger II) that I bought (called the Explorer L from TexasRCPlanes.com ) turned out to be a real piece of junk, horribly designed, poorly manufactured, and extremely overweight. I built it over several weeks, having to fix or modify almost every part of the ARF in the process, and eventually got it in the air. But I don't like the way it flies and one of these days I'm going to pull out my equipment and burn/crush/mutilate the airframe out of sheer spite for the torment it put me through during the build. For the full sorry tale, read the (depressing) build thread here: https://www.rcgroups.com/forums/showthread.php?t=727225

On that UH motor, the plot thickens: I found a thread on the United Hobbies forum discussing the "400 Kv" version of the motor; when measured, it turned out to have an actual Kv of 491 rpm/V!

In other words, it appears the current "400 Kv" version is exactly the same motor formerly sold as the "500 Kv" model. So with a 6S1P 2100 mAh battery and the so-called "400 Kv" motor, I'd start with a 11x7 APC "E" (calc prediction is about 25 A, 75 oz static thrust, 63 mph pitch speed, 500 W input power).

-Flieslikeabeagle
Oct 13, 2007, 03:12 PM
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Truglodite's Avatar
flieslikeabeagle, yeah i'll never forget that plane... i was very fond of it. sorry to hear about your experience with the knock off tiger 2. to be sure, the goldberg versions are top quality & great flyers. fyi, last month's issue model aviation had a 1/4 scale scratch built tiger 2 in the "readers ride's" column; a testimony to how good the tiger 2 really is.

thanks for all the input on the 5055 motor! looks like the specs on these motors can be vaporous. i'm pretty sure he ordered the 600kV version, but i'm going to have to run his motor up on the wattmeter/tach to see what he's got for sure. i just got up to speed on drive calc, and miljenko's data (posted on UH) gave me all the info i needed to simulate the 5055b. looks like the actual kV~500kV, so this motor will work as planned. looks like efficiency doesn't drop off much when current levels are pushed high, but i think a 12x6 is more than enough power and it'll allow us to stick with 1p lipos.

fyi, my uncle has had it with the avistar since his buddy hacked it up. he's going to mothball that plane with it's, lol, geared speed 400 motor (what was his buddy thinking? it was funny to look at anyways). at any rate, he wanted a different well proven long term trainer that would work with the 5055 setup, so i advised him to get a sig kadet lt40. he's coming to my town next weekend i can help him build it. i have a feeling he'll be very happy with the way it flies compared to his very underpowered avistar.

kev
Oct 31, 2007, 01:50 AM
Registered Aircraft Offender
Truglodite's Avatar
Quote:
Originally Posted by hermperez
there is something wrong, both the htx50-55A and 50-55B have the same constants in the milijenco data..
yes there are several confusing items on the UH site regarding these motors. i just figured out uh sells 400,500,& 600kV, but miljenko's data is for the 500kV version. lord knows why UH links that data to the 400 & 600kV pages? that certainly would add to the confusion.

i recently tested the motor & it is indeed 600kV. it pulled 39A on an 11x7 sport prop with 6s1p2200 (20-30C). you guys think that's too much for the pack?

i'm trying to decide if it's worth it to use a 2p 4400 setup.

kev
Nov 01, 2007, 07:55 AM
Registered User
Herm ,
Finally I got the Motor , Batteries , ESC all on the way .

I require help on how to connect the two 3 S 4200 Lipo packs together in series I guess .

Rgds
Sai

Quote:
Originally Posted by hermperez
Lol, tigershark teeth!

ok, just off the top of my head, a 1200W class motor is 15oz, 3oz for the mount, 3 oz for the esc (replaces throttle servo), two 3s lipo 4000mah packs are 26 oz.. so a total added weight of 2.9lbs. This will be a 90 class motor but you can run it as a 60 with no problems.. good to have an excess of power.

lipos, 2 needed:
http://www.unitedhobbies.com/UNITEDH...idProduct=4131
motor mount:
https://www.unitedhobbies.com/UNITED...idProduct=5283
motor:
https://www.unitedhobbies.com/UNITED...idProduct=4567
esc:
https://www.unitedhobbies.com/UNITED...idProduct=4691

Use a 13*8 prop for about 750watts, everything is oversized so it should be durable.. motor is good up to 1200 watts with a 16*8 prop.

Did you include the weight of the fuel in your plane?
Nov 01, 2007, 09:35 AM
know it all
This is great Sai, what kind of connectors for the batteries will you be using?

Quote:
Originally Posted by sbrv24
Herm ,
Finally I got the Motor , Batteries , ESC all on the way .

I require help on how to connect the two 3 S 4200 Lipo packs together in series I guess .

Rgds
Sai


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