Mountain_Flyer

you won't believe this .. but the Decathlon "will" fly inverted .. was attempting some outside loops ( i know .. insane ) and the battery power was getting a bit low and it didn't have quite enough power to pull it back up to the top of the loop so i just leveled her out ( inverted ) and flew half a circuit around the field maintaining level flight the entire time wasn't even very twitchy. this thing needs ailerons!! didn't think inverted flight was possible with an undercambered wing .. guess i was wrong!!.. but fortunately the decath wing has very little dehidral and very little cord either so it helps i guess

was using the 8x6 APC prop .. im really starting to like this prop .. great speed... very good power at lower throttle settings the plane will easily do a normal loop with a little more than half throttle now. I have to almost shut the motor completely down to land even at a quarter throttle with this prop the plane still doesn't want to come down

on a side note i noticed that the Decathlon doesn't like or need allot of control surface movement (elevator) you can actually hurt the handling of the plane by having too much. i have 5/16 of an inch of elevator deflection and its right on the verge of being too much i have to slowly apply elevator when going into a loop to about 2/3rds back on the stick then apply full stick just before the plane starts over the top of the loop .. if you yank the stick full back the plane will just pitch up then roll off to one side into a deathspiral... as for rudder i have a half inch of deflection on it and it seems fine with that .. now since im not using the normal parkzone electronics ( im using HiTec electronics) the control responces are "much" quicker that they were with the parkzone servos ( they were quite slugish ) this may also have some effect on how it responds in a loop...

( i can't believe i misspelled "deflection" how embarrassing [] thank god for the edit feature)

Greg Covey

I first saw inverted flight with an undercambered wing on the GWS IPS-powered Strega P-51 from Hobby Lobby.

The first time you see it is a real hoot! I hope my VMG Fireball motor arrives soon. The weather has been very nice here lately.

hillbillyflyer

i have a getle lady with a .10 engine and landing gear that will fly inverted it might not look good but it will do it

Greg Covey

If we review my original measurements (below), we can see that the new measurements with the Venom Fireball 370P motor show that it is only a slightly hotter wind. The construction looked similar to the stock Speed 300 motor although the Venom Fireball motor did have additional cooling vents in the case which cleared the stock gearbox. This should provide excellent cooling.

Stock Motor
The stock setup measured as follows using the 3.6oz, 600mAh, 7-cell pack:
[ul][*] 5.8amps, 43 watts, stock 8x4 prop[*] 5.8amps, 43 watts, GWS 9x4.7 SF prop[*] 7.0amps, 47 watts, GWS 10x4.7 SF prop
[/ul]

In essense, the stock setup, although properly designed, is a bit low in power for this plane at 36 watts/lb. The change to a GWS 10x4.7 prop provides an additional 10% more power but also taxes the motor more. This may be ok due to in-air unloading.

I also tried a few 2-cell Lithium packs with the GWS 10x4.7 prop:
[ul][*] 6.3amps, 40 watts using 3.0oz Kokam 1500mAh pack[*] 6.3amps, 40 watts using 1.6oz ThunderPower 860mAh pack
[/ul]

Of the two Lithium packs I tested, the lighter weight ThunderPower pack reduces the flying weight by 2oz or about 11% at 17.2oz.

Venom Fireball 370P
The Venom Fireball setup measured as follows using the 3.6oz, 600mAh, 7-cell pack:
[ul][*] 6.3amps, 47 watts, stock 8x4 prop[*] 6.5amps, 47 watts, GWS 9x4.7 SF prop[*] 7.7amps, 52 watts, GWS 9x7 SF prop
[/ul]

The motor swap did require the use of a pinion puller and some green Locktite to keep the original pinion gear on the new Fireball motor. This is not the easiest modification for people to attempt so I recommend caution. The result appears to be an increase of about 5 watts using a smaller GWS 9x7 prop which will help with ground clearance.

It will be interesting to test fly!

ElectricFlyer_17

Greg,

I may purchase this plane in the future and what simple upgrades should I do to improve the stock performance?

Greg Covey

Everything I have done with the Super Decathlon has been broadcast on this thread.

What i know about it, you now know.

Jet Jaguar

I have recently bought a super decath, and am very pleased with this plane. At First i was a little frustrated at flying, because it was my first plane i have ever flown. But you all have provided me with great information about this plane, and now i'm flying with great ease. All of your tips were point on, and i have a few of my own.

As far as power to weight ratios go, the decath is a little heavy in stock form. So here is what I did to get mine flying. First I took the wheel covers off, i also took the nut out of the engine compartment, also the rubber piece on the prop (although i would rather leave it on). Just those mods made a world of difference to the performance of the plane without changing the prop or engine. I have no problems doing loops, or other tricks, i have not tried flying inverted yet, it was too windy when i was going to try it.

I know other people have tried these mods, but I didn't want to spend more money on a new engine or prop. And with just those 3 mods it seems to fly just like ya'll have described with the new props or engines.

Great and fun plane to fly.

Oh one more thing, the prop shaft seemed a little loose when i first got it, and it ended up striping the gear because it was loose. So i added a plastic spacer, and it actually seemed to add a little hp.

Once again, Thanks for all the great advice on this plane.

thenamshow

i want this plane, i have flown my gas trainer and just finsished my slow stick do you think this is a good third plane for me?

the juicer

nice review

cool

Glacier Girl

My Feedback: (4)

Greg,
Been running the Fireball for a couple of months now in my Cub, RX is still running fine.
This simple mod has made a whole new plane out of the Cub, you should see quite a difference in the "D" with it. Old Cub WOT is now just above start point on TX. Flies a lot better in the wind with more power. I did a simple thrust check on a scale, aprox. 150 grams pulling power on stock setup, 270 grams with just motor change.
BJ

Greg Covey

BJ,

Thanks for the information. Your information seems to confirm the reports from Person_X.

Although I did not measure a significant power change after swapping the motor, I have not flown my Super Decathlon with the Fireball 370 yet. Perhaps it will be a surprising improvement.

5.0Rick

Anyone know where the CG is on the Decathlon? I am currently upgrading mine with an E-flite 370 brushless 9X7 prop, Jeti Speed Controller, Thunder Power 3 cell Lipo, JR radio and micro servos. Looks like it will end up gaining 4g in weight. If it works out, I will post some pictures and specifics on all the mods.

Thanks,

Rick

Glacier Girl

My Feedback: (4)

5.0,
I belive the rule of thumb is 1/3 the wing cord, 3" wing cord= 1' from leading edge.

Greg,
Update on Venom motor, built a Master Airscrew Speed 400 conversion, used same gears.
No fancy flight data, other than how hard they pull on static WOT test. Venom pulled harded,ran faster by a large margin. Could be a dud 400, or Venom is that much better.
BJ

Mountain_Flyer

actually the CoG on the decathlon is between 50 and 55mm from the LE. or for those metricly challanged people thats between 1 and 15/16ths and 2 and 3/16ths inches from the leading edge .. btw the cord on the decath wing is 152mm or 6 inches

Yak

As suggested by Person X, I removed the 5/16 nut from the cowling and added large 2" Du-Bro super lite wheels. The new wheels made a tremendous difference in landings on my lawn (actually my pasture) It also looks a lot cooler! I have the stock motor and battery and usually only get about 5-6 minutes of flight time per charge. I tried the GSW 947 prop and got the same duration of flight time but I thought it had better control at slower speed (landing). This may just be a combination of the loss of weight from removing the nut however. Until today, I could not get a loop out of her but I tried an E-flight 9X6 slow flyer prop and was able to get 4 consecutive loops before I decided to not press my luck anymore. With this prop, I also got the same 6 minutes of flight time.
Does anyone know how many amps and watts this prop is drawing? Also is there something wrong with my plane since I only get 5-6 minutes of flight and it seems like most others are getting about 10 minutes or more?
Thanks to all for the informative posts and I hope to continue to learn from ya'll...[sm=lol.gif]

scooterjay350

hey yak, i haven't pulled the nut off of mine yet, but will be this weekend thanks to a bent prop shaft on a failed rog adventure. the cub flies better, but the decathlon is much cooler looking. i get usually between six and seven minutes at mostly wot. i gave up on turning it into an aerobat in stock form, fly it in a scale manner much as the cub. i don't like the tip stall tendancy.

Mountain_Flyer

Scooterjay350,

i run a APC 8x6SF prop on mine most of the time. it provides much better speed and thrust than the stock 8x4 prop..
mine had a bad tendancy to tip stall also with the stock motor and prop .. the stock motor/prop combo just doesn't make enough speed or thrust to get the plane into its operating environment. once you get more thrust/speed you will find that its much less prone to tip stalls and will recover quickly if you do put it into a stall.

today i ran 7 batterys through my Decathlon its an absolute blast to fly now with the fireball motor and the APC 8x6 prop. i do use a APC 9x6SF prop in windy conditions ( it provided better thrust ..slightly more speed but less battery life) with the setup im using now i find the Decathlon to be a very capable "stunt" plane it will do everything you ask it to do ( within the limits of it only being a three channel plane) it would be even better if it had ailerons ( next project i guess )
The APC props will require you to use a different prop mount/adapter than the stock setup. ive flown the plane with the gws props ( 8x6, 9x4.7,9x7).. im just not impressed with them they don't deliver the same amount of speed or thrust as the APC's do for the same amount of power ( Amps/watts ) used. ive not tryed the E-Flite props though..

heres a pic of the prop mount i use:


also here is a picture that shows the ground clearance with the APC 9x6 with Du-Bro 2 inch wheels ( yes i run the 2" wheels on it also ..)



PX

Jet Jaguar

I just put the fireball motor in my decathalon this week. Great motor and good power, but i found that my plane wanted to track down and to the right. My rudder and elevator were set perfectly, so the only thing i can figure is the stock engine mount was to blame. So i adjusted the mount and that seems to have helped. Has anyone else had this problem with the motor change? Everything thing else is stock: prop, radio, speed control, and servos.

Cautrell05

Would the decathalon work with a DD speed 400 motor instead of the geared 370?
Nick

Yak

Ouch! This afternoon just after hand launching my Super Decathlon was just leveling out at about 15-20 ft. AGL and then it started to pitch up and down violently. As I tried to turn her back toward me and away from a tree line, she took a nice snap roll right into the ground. Oh, what a terrible site! The cowling is shattered, the prop sharply bent against the nose, prop bent, the black retainer over the landing gear snapped, and inner plastic bracing broken forward of the battery. The culprit? The control horn for the elevator snapped. Looks like this girl is grounded until I get some replacement parts including a new prop shaft and tail since the control horn was glued to the elevator and tore out a chunk of foam when I tried to remove it. Lesson learned: do a preflight every time before flight. I hadn't had any hard landings, but apparently there was some stress/force applied to the control horn enough to cause it to fail prior to this last flight.

scooterjay350

ah man...sorry to hear of the snap into the ground! i'll be sure to check the horns out before flying. i always check the clevises before flying (thanks to a failed elevator clevis on a c/l nobler) now i'll check horns, too. i haven't tried any upgrades to the decathlon yet. mine did not have a nut in the cowl, i'm going to move the cg back by repositioning the reciever. i've noticed that landings improve if you fly a "small field" approach.....a turning approach as opposed to a downwind, base and final approach.

Yak

Hey Person X, what size is that spinner prop nut on your AC? 1/4"? I lost my spinner in an unfortunate encounter with terra firma and that nut appears to be just the ticket!
Thanks!

Mountain_Flyer

its 3/16 and its part of a Mpi Collet Prop adapter. i use this for the APC Props since the hole in them is too large to be used on the 3mm shaft.
you may be able to look around and find one thats 1/4 inch....

the one thats on the plane in the above picture is now somewhere out in my field .. along with a APC 8x6 prop... it was the Jam screw type .. the collet type stay on better imo... btw the decath actually glides pretty darn good with out a prop.. found that out yesterday right after the prop went flying off

also had the ESC plug work loose from the RX the other day also ( was not a good day ).. i'd just completed a loop and i lost all control ( fortunately the controls locked with about 1/4 up elevator and the motor shut off so it just floated down to the ground ( i had no control what so ever ) and did a rough but exceptable three point landing .. man was i lucky or what!![X(]

heres a pic of the collet

Yak

Thanks for the information, Person X. I think I'll look for the collet type since I have not been as lucky as you with my mechanical problems Regardless, the Super Decathlon has proven to be pretty rugged based on my experiences since it has taken some pretty rough landings/crashes and still get out there and flies! I have yet to replace anything but there sure is a lot of tape holding her together[sm=eek.gif]. I going to give the 8x6 prop a try and see if it helps increase my flight times...

yellertoof

My Feedback: (2)

How did everyone that upgraded to lipos fit them in the decathlon? I was planning on modifying the battery cage for a 2 cell kokam 1500 by removing the 2 side tabs of the batt cage at the bottom and cutting a little bit of the fuselage on each side of the battery door to allow for the wider but thinner battery. I don't think this will weaken the structure too much and it's the best way I'm seeing for easy access.