bungie launcher for small hk parkjet? any suggestions?

[stuart]

hey gang,once again the hk parkjet had the nose broken off. seems i can't get good throwers for the off power hand launches.

i fear the power on toss as someone my get prop struck and i don't want that to happen. if i throw the hk pj it'll glide smoothly,if i ask for help...its a 50/50 chance it'll be recoverable,those are bad odds. i'd be glad to toss and let another pilot fly ,but it gets squirrelly to fly and small very quickly.

i love inventing contraptions to do whats needed,so i envision a small bungee cord ,like the kind we use on a car roof rack. a board on a slight angle and a rope pull release system......am i dreaming or is this possibly an inexpensive solution? i heard theres a contraption to lanch jets,but i don't need that kind of power to launch foam....

please let me know if you've seen or read about such a system home made.

i don't want a commercially built catapult that cost a fortune as the parkjet only cost $50 bucks or so. also i need to be able to set the launcher in the field and pull it back to the flight line once launched. thanks gang,stu

[earthsciteach]

I think some kind of contraption with a flywheel to prevent a tremendous jerk upon release would be advantageous. This would allow a smooth acceleration up to launch speed.

[gramps2161]

Here you go Stu this might get the grey matter thinking.
Looks real simple to make and easy setup.

RiteWing TL 50 Bungee Launch

[stuart]

hi gramps&et, i saw those online also john ,and like the teacher said regarding the jerk take off ,those bungee launchers would be great....except[there's always that...lol] i need to launch and get the launch apparatus off the field asap.mine is a very busy club..always a great group to hang out with ,always 2 or 3 birds flying. i love flying with others as it improves my skills,but we also get quiet days.

i was thinking along the lines of a board with a slot and peg action. the board would be 3ft long with a bungee cord pulled along the bottom and over & down the top. the top of the board would have a track routered in it that a small peg that is aproximatly 3/4inch stickin out of the slot.this peg would be pulled down the length quickly and at the end of the pull ,the peg drops down flush with the board...thus releasing the projectile[plane] smoothly,and quickly.

by cutting the slot a certain way in depth,the peg runs evenly till the very end ,where a bevel in the slot pulls the peg down.i have a picture of this in my mind,trick is getting it in wood.

by running the bungee around the bottom and top,i ensure theres tension on the peg even at the end of the throw range. the trigger/starter release mechanism could be designed in the base as a pedal action or a pull string, the base would have to also be approx 3' long with the slotted launcher hinged to it for varying the angle of launch.

modification to the parkjet is a laminated sheet of plastic with a small hole for the peg epoxied/glued on the fuse bottom near the tip of the nose. nothing huge,just enough to not give way under the force of the launch.the laminated plastic would also act as a skid plate for those rough landings.

none of this has been thought out any further than what i tried to explain,but i can go into the workshop with a 3' piece of 2x4 and wrap it with a cloth type bungee to see if i get power enough....i better wear safety glass...these type of bungee cords can slip when pulling and i knew a guy who lost an eye pulling a cord across a car load when it whipped around and got em.

who knows,maybe I'll become rich with a new invention......we all know this has already been built ,that is if it will even work

stu

[CHELLIE]

CHELLIE
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Originally Posted by stuart

i guess this is considered a crash....,once again the hk parkjet's nose broke off during a launch. i had to wait for a younger pilot to show up at the field. the guy who threw the parkjet had it down with such force it broke...no chance to power up slow and save it.

arrrrrggggg. it's looking pretty ugly now.....................but who cares as long as it flys again soon

Stu, Get a Highstart, and you can launch the plane yourself and its much safer too from prop bites. all you have to do is epoxy a small block of wood in the nose area, and screw in a L Screw and your all set

http://www.hobbypeople.net/index.php...tube-5005.html

[stuart]

thanks chellie,again...i think the high start method would require my using to much of the field while others are flying. my setup really is pretty quick for a ball field and i wouldn't feel comfortable screaming the skies.

a recent rule for hand launched electrics is to walk to center of runway ,toss it ,and retreat to a flight line gate...this do to someone looping over there own head and crashing in the pits sitting area...wasn't me.

hawk wrote in another thread "it's hard to believe someone can't throw that lil plane" and i think he's right. it's heavy for it's size but still glides nicely. it's fixed,so today I'll toss it and let Ben fly it til i take over the controls[or visa/versa..lol]. after i get airborne I'll ask someone to run my vid camera out in the field to hopefully record a Doppler measurement. that person can retrieve it quickly also.

get the perkjet up with no one else flying will be the tricky part. I'll have to sabotage all those slimmies......perhapes sugar in the tanks....[jk].

truly a grand day to go flying,but i can't spend the whole day like yesterday or my dear wife will feel neglected this holiday weekend.

[earthsciteach]

Stuart-sounds like you have thought out a nice concept! Hope to see the final product as I have the same issues with having others hand launch for me.

[stuart]

thanks teach...i just got home from the greatest day of flying. it so warm and sunny!the parkjet flew 2 times and is still in one piece. it took a beating as power off hand launch are the pits,so i threw it with 1/2 power and Justin flew it till i took over.it flys great and I'd recommend it to anyone with the exception of the launches...lol....

i won't be happy with others tossing it as they may not pull there hands clear of the prop.

even with power it rolls and swoops the ground like crazy...very fun stuff. we had a full field today and great fun was had by all. best of all ,i took videos of 3 ww1 bipe flying together. i also did flybys on the video camera with the parkjet to hopefully get a Doppler reading from some one here at wattflyer. i really don't think its very fast anymore as I've grown used to it's handleing.......seems if i make sharp ,tight turns it'll look like it's going 100mph,but i think maybe 70mph...just not enough kv in the motor. i think I'm going to p/u a multiplex funjet ,or the radjet kit from hk.

this desire to fly fast is irresistible.

[Supergeebee]

Good idea to use a lancher. It is better than 26 stiches on the left hand. Personal experience.

[tarheal63]

Stuart, this is the one I built and it works great. I got a really long bungee from Harbor freight for my launching. The parts are in post #7
http://www.rcgroups.com/forums/showthread.php?t=33639 It costs me about 20 bucks in parts.

[stuart]

tarheal, thats a great design ,but due to a bad electic toss that landed in the pit area...we have to hand launch a bit out on the field. i also don't belong to a club that use's bungeeies to launch.

i have learned to toss the parkjet with about 2/3rd's power on and off it goes. now i'v built hk parkjet#2 with 800watts /4cell....,can't wait to launch and fine tune her for those wot runs.overkill,i know.

i also have to maiden a funjet ultra at the same time...that should be an easyer toss do to its power and size.



superbeegee , yike's!...26! thats a nasty prop bite,been biten before,but not like that. hope all healed well. a picture of the new hkpj and funjet yet to be flown...can't wait for the warmer weather and the winds to die down.

[tarheal63]

I built my bungee launcher in response to prop bite, once bitten, twice launched.

http://www.wattflyer.com/forums/showthread.php?t=60772

[tampaflyer]

10-20 ft of tubing or bungee and some nylon line. you don't need a full ramp on a smaller one. you only need about 10-15lbs of pull( my HET MIG21 @4.5lbs needs 25lbs of pull . and thats when a luncher helps.)
the most critical is the placement of the hook. NOT ON THE NOSE(thats when you tow) NOT ON THE CG(thats a high start) need it about where the LE ext meets the fuse. the further forward , the more it pulls it toward the spike, further back it becomes a highstart for ALT. you just want to get to flying speed quickly. As you release you will be fast enough to glide for some distance. SO, release then power up.

also not haveing a launcher allows you to rotate into the wind easily.

[Hans_Svetty]

Originally Posted by tampaflyer

also not haveing a launcher allows you to rotate into the wind easily.

I don't understand this part?