Englertracing
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- Joined
- Oct 17, 2014
- Messages
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[video=youtube_share;fhCw0X3W1Fg]https://youtu.be/fhCw0X3W1Fg[/video]
this is my first rocket since the one i built with my cousin 15 the motor didn't stay in the rocket... didn't really understand the violence of a g80 at the time.
details not shown in the video.
rocket weighed 220G ready to go.
the fins have 45* angles on the front a 60 on the rear for rocket rotation
the front of the fins have a notch that the rocket tube slides into
the fins are made from free for me G10 fiberglass from a shop i used to work at called plastifab
the motor mounts are machined from phenolic which i also got from plastifab, they actually claim they have the largest phenolic tube inventory in the u.s.
I marked the length of the fins on the body tube,
put the body tube in my late, My late has a pin behind the chuck and 60 holes on the drive that lets you index things in 6 degree increments.
i put a razor blade in the tool holder and every 120* i cut the body tube from mark to mark.
then i moved the blade 0.062" and repeated. bing bang boom perfect straight exactly 120* separation fin slots.
i got the fin design somewhere online they are 2d long 2d high and 1d at the tip
i know a small amount about aero from a book which is my bible, its called race car vehicle dynamics (its a college text book for vehicle design)
i figured the CP for the rocket and fins would be much further back
i got open rocket sim and boy was i surprised how far forwards the cp was. i realized it was really wrong to put my fins .250" from the end of the rocket and was verry concerned my cp and cg were too close togeather, but my fins were already made, and my fin slots were already cut but my streamer moved my cg far enough forwards not to matter and i ensured my stramer would stay in just below the nosecone
any new rocket i make will have the fins root end at the end of the rocket. and the tips likely behind to minimize fin size and get the cp as far back as i can
the way the fins are glued in they are STIFF s.o.b.s
but probably a bit heavy
i used autocad made a drawing of a circle (the body tube) with the fins radiating from it, the same width as my fins 0.062" and beyond the fins a flat so its sor of a hexagon shape.
i printed 3 of these, glued them to hardboard (back of a notepad) cut them out with a razor blade and ruler and used it as a gluing jig... ill post a pic of anyone is interested, actually i should probably convert my jiggy from a autocad dwg to a pdf then anyone could print it.
i machined a .250" slot in a 5ft 3/4x3/4" square aluminum tube for my launch rod
that slips into a 1x1 steel square tube which is welded to a 8x8 steel plate which was mean to have a 25lb iron exercise weight slipped over the 1x1 tube... but it didn't fit over the 1x1 so i buried the plate.
my launch lugs are a bit bulky but..... they are 0.88$ a pair at the hardware store
the lower one threads right into my lower centering ring/motor mount
the upper one threads into an aluminum tubby thingy that my streamer attaches to
id like to slim them down on the next rockets
the streamer is wound 1 foot clockwise 1 foot counterclockwise and attaches to the "shock cord" at the inside of the roll
as the streamer extends it comes out straight instead of wound up
also anyone have any idea why the heck my g80t exploded?
the fuel did not burn at all it was completely intact laying beside the rocket
also id like to build the same rocket with revised fin placement
and an I205 engine
do you think it will hold up?
should i use blue tube? its alot heaver
this is my first rocket since the one i built with my cousin 15 the motor didn't stay in the rocket... didn't really understand the violence of a g80 at the time.
details not shown in the video.
rocket weighed 220G ready to go.
the fins have 45* angles on the front a 60 on the rear for rocket rotation
the front of the fins have a notch that the rocket tube slides into
the fins are made from free for me G10 fiberglass from a shop i used to work at called plastifab
the motor mounts are machined from phenolic which i also got from plastifab, they actually claim they have the largest phenolic tube inventory in the u.s.
I marked the length of the fins on the body tube,
put the body tube in my late, My late has a pin behind the chuck and 60 holes on the drive that lets you index things in 6 degree increments.
i put a razor blade in the tool holder and every 120* i cut the body tube from mark to mark.
then i moved the blade 0.062" and repeated. bing bang boom perfect straight exactly 120* separation fin slots.
i got the fin design somewhere online they are 2d long 2d high and 1d at the tip
i know a small amount about aero from a book which is my bible, its called race car vehicle dynamics (its a college text book for vehicle design)
i figured the CP for the rocket and fins would be much further back
i got open rocket sim and boy was i surprised how far forwards the cp was. i realized it was really wrong to put my fins .250" from the end of the rocket and was verry concerned my cp and cg were too close togeather, but my fins were already made, and my fin slots were already cut but my streamer moved my cg far enough forwards not to matter and i ensured my stramer would stay in just below the nosecone
any new rocket i make will have the fins root end at the end of the rocket. and the tips likely behind to minimize fin size and get the cp as far back as i can
the way the fins are glued in they are STIFF s.o.b.s
but probably a bit heavy
i used autocad made a drawing of a circle (the body tube) with the fins radiating from it, the same width as my fins 0.062" and beyond the fins a flat so its sor of a hexagon shape.
i printed 3 of these, glued them to hardboard (back of a notepad) cut them out with a razor blade and ruler and used it as a gluing jig... ill post a pic of anyone is interested, actually i should probably convert my jiggy from a autocad dwg to a pdf then anyone could print it.
i machined a .250" slot in a 5ft 3/4x3/4" square aluminum tube for my launch rod
that slips into a 1x1 steel square tube which is welded to a 8x8 steel plate which was mean to have a 25lb iron exercise weight slipped over the 1x1 tube... but it didn't fit over the 1x1 so i buried the plate.
my launch lugs are a bit bulky but..... they are 0.88$ a pair at the hardware store
the lower one threads right into my lower centering ring/motor mount
the upper one threads into an aluminum tubby thingy that my streamer attaches to
id like to slim them down on the next rockets
the streamer is wound 1 foot clockwise 1 foot counterclockwise and attaches to the "shock cord" at the inside of the roll
as the streamer extends it comes out straight instead of wound up
also anyone have any idea why the heck my g80t exploded?
the fuel did not burn at all it was completely intact laying beside the rocket
also id like to build the same rocket with revised fin placement
and an I205 engine
do you think it will hold up?
should i use blue tube? its alot heaver
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They have all the licensing and permits required, tons of launch equipment, on-site vendors to sell your kits and motors, and lots of rocketeers having fun. I highly recommend attending their "legal" launches. 
