Het F20 - Bungee Launch Ramp opinion

[edmond22]

Hi all,

As the F20's bottom is flat, there isn't any area practical enough to hold properly for a handlaunch. I have decided on Bungee launching and thought a ramp would best give it nice platform to launch from.

Constructed a simple ramp and thought it kind of short. Please give your comments if you have improvements to suggest. Need all the help I can get about bungee launching.

[Sunstorm]

Hi, I came across a link here.

http://www.tedlarson.com/airplanes/bungee/index.htm

and here.

http://www.yourzagi.com/launcher/

[Warbird]

Alternatively place it flat on the ground (short grass) and launch it from there.
I did this without problems with my F-16, F4, Lip20..... no issues.

We even launched the F-18 (flat bottom like the F-20) by placing them on the ground and attaching the bungee to a pedal. A bit of up elevator and once released the plane will, after a short slide of less then a meter, be airborne and flying. This also reduces stress on the wings.

[mave]

Hi, jsut curious, what is the length of bungee cord are we look at?
launching from the ground, isn't there a risk of hitting the picket holding the bungee cord?

Alternatively place it flat on the ground (short grass) and launch it from there.
I did this without problems with my F-16, F4, Lip20..... no issues.

We even launched the F-18 (flat bottom like the F-20) by placing them on the ground and attaching the bungee to a pedal. A bit of up elevator and once released the plane will, after a short slide of less then a meter, be airborne and flying. This also reduces stress on the wings.

[edmond22]

good question Mave kekeke, that is what exactly happened to me last weekend. Poor Sniper had a ding on the end of the wings now.

[edmond22]

btw, what is the Grass like?

[Warbird]

Hit the groundhook? the bungee is 7 meters + 2-3 meters of rope between the plane and Bungee. if streched you have around 25 meters to the hook. if you a not in the air by then something is wrong.......

hey, how about a mini edf meet?

Hi, jsut curious, what is the length of bungee cord are we look at?
launching from the ground, isn't there a risk of hitting the picket holding the bungee cord?

[mave]

What kind of speed should we expect for a successful launch? Ballpark figure?

Hit the groundhook? the bungee is 7 meters + 2-3 meters of rope between the plane and Bungee. if streched you have around 25 meters to the hook. if you a not in the air by then something is wrong.......

hey, how about a mini edf meet?

[edmond22]

Hey Warbird, thanks for you help.

I think it would be great if you can meet me at PFW this sat or sun. Will need you bungee launching expertise, if you can please bring along your bungee equipment.

My experience with Het kits has not being too fantastic unfortunately. Will need all the help I can get to get Het kits to fly, it is frankly quite alot of work compared to my other type of planes.

- Het F18 right wing broke in midair, post mortem suggest bad design, the breaking is at the spar and the fuselage area holding the wing tore off. It was not doing any high g then at all, simply a high speed pass. Only 4 flights. This f18 has got the worse covering job ever seen, massive wrinkles everywhere. You will need 3-4 hours to sort those out.

- F20, build as per instructions, no exhaust ducting provided, Instruction manual suggested antenna routing is strongly not recommended. Plane flew, 2nd turn, canopy pops out and all hell broke loose. The plane will not stay upright no matter how. Conclusion - the magnets method strongly not recommended, the F20 doens't fly quite right once the canopy pops out. I usually exercise some self mod for my 3D planes and such but I figured the magnet method will hold since there is no cooling holes to build air pressure and I am not going to do blender with it, hell I did not expect the thing come off when turning the plane round.

- Sniper, again no exhaust ducting provided, canopy building instructions looked great but the wood not supplied. In Sniper manual, the antenna routing actually states that the recommended routing method might cause severe glitches... I mean you need 3 het to see that sentence?!? Paint job is really bad, those lines between 2 colours are torn off when wet definitely. The wing on this set looks like a candidate that will fail like the F18, glassing the mid section recommended on RC Groups..

I was pretty dissappointed and googled abit on deciding for the next plane, I found a rcgroups review of the Het F16 and guessed what. Same kind of frustrations, ducting collasped and failed. Wing parts did not match correctly, the reviewer crashed the first set and was sent a second one. Second one flew and reviewer still noted some problems and most glaring one were the fact that he needed a great deal of right tailerons to fly level. Now that is disturbing and putting me off from buying that kit cos I experienced the same thing with F18 and F20, dun know about the sniper.

Disclaimer, not directed at Warbird or RC- Warbirds, their service has been great. Just quite frustrated with the quality of HET sets.

[Warbird]

Hi Edmond,

I agree with some of your points.

1. HET ARF planes need a bit of building, they do not pop together as easily as many other ARF. I guess this has to do with the need for a light airframe hence no extra parts to make it easier to put them together - EDF is not (yet) that powerful.

2. The first batch of F-16's had a problem with the intake duct. It was to weak for the more powerful motors. This was fixed and HET actually send new fuselages to all customers in need of one. I still have a 1st gen F-16 with a 2W-20 Motor. The duct collapsed after the first test run. A bit of epoxy and glass fixed this. The plane is now the fastest vac cleaner in Singapore
BTW, I had the same taileron issue with mine. A close look at the wing shows that I did not glue them on properly. One had a higher angle then the other.
A bit of realignment and it flies straight like an arrow.

3. The F-18 wing issue is very strange. I have flown a few of them and see a lot of people fly them at very high g and never came a wing of. Should something like this happen again (or if you still have the crashed plane) contact RC-Warbirds and they will get you a replacement if there is a product fault.

General: You should always let the antenna hang out of the back of the plane. Due to the small pace inside the fuselage and the high currents you run through the motor/battery cables there is no way you will have a glitch free flight if the antenna is routed inside the fuselage parallel to the power wires.

Magnets: Yes I had the same experience, they are in most cases not strong enough to resist the pressure difference (the cockpit is shaped like an airfoil and will get sucked up), especially if they are not mounted properly (make direct contact with each other). The jets are simply to fast. Do not use them, replace them with a proper wire/pushrod lock.

Exhaust ducting: best is to use some clear overhead projector film. The F-18 actually comes with a duct but the paper is not very smooth so I prefer to use a smooth film (can also be painted much better). Do you still need some? I will bring it when I meet you.

I can meet you on Sunday afternoon ~4pm. will you be at PFW (btw, where is that......). I will try to charge my F-16 and bring it along for some EDF fun

[edmond22]

Cool mate, thanks for the explanation.

I am thinking of another kit, and I am still leaning towards the F20 kekeke. I totalled the first one and will need some time to finance another one. I wrecked 2 already lol.

The F18 is really a structural problem, quite many witnessed it in PFW lol. I am quite a freak when it comes to wing alignment and trust me, I got em straight like my 3D planes and I still have the same issue. I believe it is more the case both wing panels are warp and I had to straighten them out with covering iron as best as I could.

Anyhow, I still have the sniper and I can meet you at PFW 4pm, would be great to get your help on the bungee thing.

[Warbird]

Cool. See you on Sunday at 4pm.

[$h@d0w]

Launch Ramp

Found this while surfing RC groups. It's a DIY Bungee Launch Ramp.

Ramp

[edmond22]

Hey Warbird,

I maidened the Sniper today succesfully. I decided to double up a friend's Hi start bungee and arrived at 8Kilo tension. Still using the same ramp, I was able to get it to fly nicely today.

1 thing I noted is that because of the small control surfaces, it is important to get the CG spot on, my could have been too nose heavy and plus it wasn't trimmed out made bungee launching much more trickier since I do not have pitch authority so as to speak.

Will try to get video and pics.

Thanks to Warbird and all too for your suggestions.

[Warbird]

Congrats !!! Looks like no need to launch together tomorrow then.
Have a lot of great flights with your SNIPER !!