Mark R Posted March 19, 2010 Share Posted March 19, 2010 Hi all, newbieto this forum ) I have myself an HET F15, not got much done to it as i am in a bit of a quandary....Too Bungee or not too bungee! Or Dolly or not too dolly! Have looked at both possible scenarios and the thought of 'straining' an elastic band (yeh i know its not elastic band really) to propel 5lbs+ of plastic into the air does somewhat scare me! Its the thought of the ground anchor deciding it would like to try flying itself and coming at me in a horizontal attack. Anyone used a dolly to launch one of these. The recommended engines give about 700 watts of power each (i believe), would this provide me enough power to launch from a dolly on a grass strip? If so what type of dolly, any plans available. Or if its going to be a bungee launch where can i get a decent set up from, preferably with a corkscrew ground anchor. cheers all Mark Quote Link to comment Share on other sites More sharing options...
Erfolg Posted March 19, 2010 Share Posted March 19, 2010 Mark There is no problem with the stake coming out of the ground if you use a "dog stake" (those helical screw in type) as used in days of yore by glider guiders. Erfolg Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 19, 2010 Share Posted March 19, 2010 Hi Mark and welcome aboard - I think this will need a bungee not a dolly, as you will be expelling so much energy trying to roll her along the grass to get up enough flying speed that your battery will be half empty by the time you achieve it. As Erfolg says, a properly anchored and substantial stake should not let go! Quote Link to comment Share on other sites More sharing options...
Mark R Posted March 19, 2010 Author Share Posted March 19, 2010 Hi guys.....okey dokey seems like bungee has the vote urghhhhh Timbo, was worried about expenditure on the battery power, using digital servos probably wouldnt of helped. Now i presume to get the best lift/speed would a ramp help? Presume ground dragging (over carpet or summit) isnt a good idea as its a taileron and could possibly have restrictions on the tailerons if its dragging on the ground. Checked the US websites and its a 50/50 split on ground dragging or ramp, guess a trip to B&Q is on the books Thanks again for help Quote Link to comment Share on other sites More sharing options...
Dusty Posted March 19, 2010 Share Posted March 19, 2010 Mark bungee the model... f-15 is a great flier! No you dont need a carpet etc! Do you have a release pedal? This is what I use and their release pedal.. I made a dolly like this and Bobs your uncle... safe, good self start, easy to setup! Quote Link to comment Share on other sites More sharing options...
Dusty Posted March 19, 2010 Share Posted March 19, 2010 Oh sorry you wont need 13m of bungee, 6-10 meter you will be fine with the dolly! 13m will be for a glider, 6-8m bungee cord is sweet with this model. You can get away with launching from waist height if done properly.. Quote Link to comment Share on other sites More sharing options...
Mark R Posted March 19, 2010 Author Share Posted March 19, 2010 Hey Dusty, cheers for that Quote Link to comment Share on other sites More sharing options...
stuey Posted March 20, 2010 Share Posted March 20, 2010 I vote for bungee too. Its not as scary as it looks, and better than a lame hand launch! I got my screw in stake from B&Q, feels perfectly secure with the 5-6kg pull I use. My setup is on a thread here somewhere, home made ramp and pedal. I got my bungee from Puffin, I think its the RBC one shown earlier. I use the screw stake at the bungee end, and the supplied straight one to restrain the pedal. The pull I imagine is spread between the two stakes. I hammer the straight stake in at an angle away from the pedal, which hopefully makes it more secure. Quote Link to comment Share on other sites More sharing options...
Tom Foreman Posted March 21, 2010 Share Posted March 21, 2010 Go for a bungee and a dolley, no need for a ramp, safer as well as it can't death roll on take off, the only problem I have experienced is the combination of long grass, heavy wing loading, zero head wind and a poor angle of attack which was easily remedied by moving the hook on the model. The hook goes onto the axle between the two tubes, the bungee attaches to the wire loop, with a length of nylon cord running underneath to a foot pedal to release the model. Take off is very smooth, just stand on the release pedal, hit full throttle and ease back on the elevator! Speak to Stephen Mettam at Modellhause, thats where I got my bungee, release pedal and dog stake from. Tom Edited By Tom Foreman on 21/03/2010 00:08:23 Quote Link to comment Share on other sites More sharing options...
Erfolg Posted March 21, 2010 Share Posted March 21, 2010 I would think twice about buying a bungee. Being a modeller I would make one. In the bays of bungee launched gliders, a bungee would typically be made of a 4:1 of line to rubber. Given that you only require a safe launch, the cheap bungee cord available from many camping shops is all you need, as a big launch is not the issue. Any reasonable strength mono filament line will do also. There is no need to waste money on surgical tube or square rubber, no deep sea high strength mono-filament, just cheap and cheerful. The other plus, bungee chord will last far longer than the more expensive stuff. Erfolg Quote Link to comment Share on other sites More sharing options...
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