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The Start of The SAB KR84 Design and Build.

Wildthing

Legendary member
#25
Starting in the center and going to work my way out . Most of the inner structure is done other then on a front section I still need to add a plate to where I can bolt on a bungee hook.
CF rods run through the sections. I initially was going to run one solid piece of cf rod and have the wing mount from the top but changed my mind just because it will be heavy and high wing load so lets mount the wing from the bottom.

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Piotrsko

Master member
#26
The closer to the cg you go aft, the more efficient the process is to produce altitude. Downside: the closer to the cg the hook is, the easier to break wings by minor attitude changes like that extra click of up trim or finger twitch of up. Using a winch, when you see the wings assume that bowed diehederal look, you slow down the winch or even stop for a second or so, toss in some down elevator trim. A bungee is all or nothing, you cant slow it, the BEST you can hope for is a full down elevator release of the hook as the plane speeds up. Many times it would get tangled up and require the landing with it attached which is a huge pain somewhere unpleasant.

See the comments made by @Hai-Lee to mayan about bungee launching test flights. I personally prefer to start about 2" forward of the TESTED cg and move back in 1/4" steps to no closer than 1/2 inch

This is also why most people carrying gliders use a nose hook for aero tow, and a cg hook for winch.
 
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Wildthing

Legendary member
#27
The closer to the cg you go aft, the more efficient the process is to produce altitude. Downside: the closer to the cg the hook is, the easier to break wings by minor attitude changes like that extra click of up trim or finger twitch of up. Using a winch, when you see the wings assume that bowed diehederal look, you slow down the winch or even stop for a second or so, toss in some down elevator trim. A bungee is all or nothing, you cant slow it, the BEST you can hope for is a full down elevator release of the hook as the plane speeds up. Many times it would get tangled up and require the landing with it attached which is a huge pain somewhere unpleasant.

See the comments made by @Hai-Lee to mayan about bungee launching test flights. I personally prefer to start about 2" forward of the TESTED cg and move back in 1/4" steps to no closer than 1/2 inch

This is also why most people carrying gliders use a nose hook for aero tow, and a cg hook for winch.
Thank You
 

mrjdstewart

Legendary member
#29
all my bungee launchers are forward of the CG. i usually try and set it about half way between CG and the nose of the aircraft. if your bungee launcher has enough incline launching should not be an issue. this sunday i took nothing but bungee launched planes to fly and had a blast. been a long time since i flew nothing but speed all day.

laters,

me :cool:
 

Wildthing

Legendary member
#36
Section 4 finally done after one mishap, 40% through the first print when the extruder passed over it knocked the print over.
Bottom side (blurry picture ) that is where the bungee hook plate is going to be mounted.

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