Got this finished yesterday and think it turned out fairly good. Here are the stats:
Upscale Factor: 4.81x
BT-5 to BT-80 (2.6") tube; BT-80 is 8.5" long thin wall (8.4375" for perfectionists)
Nose Cone is an E-Rockets BNC-80G4 thin wall (2.6" 4:1 Ogive) - perfect for this model
Motor mount/rings are an Apogee 29mm - 2.6" - I left the thrust ring out in case I go big someday
Retainer is an Estes 29mm special - light weight, low cost
Overall height sitting on fins: 27"
Fins: I up-scaled using the copier method (original fin on copier, then take the copy and enlarge to 481% : ) - easy
But here are the measurements
Root and tip: 5"
Leading and Trailing Edges: 8 3/4"
Sweep angle: 60 degrees
Thickness of stock (perpendicular leading to trailing edge) 2 1/2"
TTW tabs for BT-80 to 29mm motor mount tube - I made mine a little large, and sanded them down until flush
Decals: your vendor of choice. I have tried them all and all are GOOD.
I tried a new fin build on this kit - 1/8" balsa wood with 1/32" plywood skins glued on. Super strong, very light, but a little difficult to shape a leading and trailing edge. I discovered that dollhouse people have 1/8, 3/16. and 1/4" half rounds made of basswood - if you're into epoxy Plastruct makes some plastic ones for modeling. This worked great on leading edge but made the fin a little wider than perfect scale. It is tough to get the basswood on straight - it is a little warpy and some puttying is needed. Trailing edge reinforced with thin quick dry super glue.
I double-anchored some heavy Kevlar thread in the forward centering ring, making a loop that is inside the body tube (like a Boyce kit), and 4' of heavy duty shock cord - I may double it to 8 feet, it stretches 2x. Don't need a nose cone - body collision at apogee.
Stability - I built this on Rocksim and it was stable w/o any changes. Still, I added an ounce of BB's to the nose cone by drilling a hole, loading with glue, and installing a dowel. Also made a nice anchor point for the screw eye.
1.7 Cal stable empty, and 1.4 Cal stable with a G-80 or G125. I picked heavy motors on purpose.
Cp on this rocket is 1/2" up from the bottom end of the body tube, and Cg is right around where the leading edges of the fins attach to the body tube. Due to the design, the motor (lengthwise, including fins) is near the center of the rocket so Cg doesn't shift a whole lot. Dang, this hobby rocks now with the software, Web info, and new books!!!!
Maiden flight will be F26-6FJ second flight will be F50-6T - both to 1000-1200 feet, 6 second delay is near perfect.
On motors, with the super long fin chord, G80 is pushing it and G125 is possible flutter/airframe failure (near 500mph) at 1900 to 2000 feet altitude.
Shortcoming (literally) - very little room for the recovery stuff. The E-Rockets nose cone only has a 1 1/4" shoulder, but it will be a tight fit with dog barf, the cord, and a 24" Estes parachute. There is also the large F/G ejection charge bang, maybe a really long cord! Still, it looks really good and SHALL fly. Here are the pix:
Cheers / Robert
Upscale Factor: 4.81x
BT-5 to BT-80 (2.6") tube; BT-80 is 8.5" long thin wall (8.4375" for perfectionists)
Nose Cone is an E-Rockets BNC-80G4 thin wall (2.6" 4:1 Ogive) - perfect for this model
Motor mount/rings are an Apogee 29mm - 2.6" - I left the thrust ring out in case I go big someday
Retainer is an Estes 29mm special - light weight, low cost
Overall height sitting on fins: 27"
Fins: I up-scaled using the copier method (original fin on copier, then take the copy and enlarge to 481% : ) - easy
But here are the measurements
Root and tip: 5"
Leading and Trailing Edges: 8 3/4"
Sweep angle: 60 degrees
Thickness of stock (perpendicular leading to trailing edge) 2 1/2"
TTW tabs for BT-80 to 29mm motor mount tube - I made mine a little large, and sanded them down until flush
Decals: your vendor of choice. I have tried them all and all are GOOD.
I tried a new fin build on this kit - 1/8" balsa wood with 1/32" plywood skins glued on. Super strong, very light, but a little difficult to shape a leading and trailing edge. I discovered that dollhouse people have 1/8, 3/16. and 1/4" half rounds made of basswood - if you're into epoxy Plastruct makes some plastic ones for modeling. This worked great on leading edge but made the fin a little wider than perfect scale. It is tough to get the basswood on straight - it is a little warpy and some puttying is needed. Trailing edge reinforced with thin quick dry super glue.
I double-anchored some heavy Kevlar thread in the forward centering ring, making a loop that is inside the body tube (like a Boyce kit), and 4' of heavy duty shock cord - I may double it to 8 feet, it stretches 2x. Don't need a nose cone - body collision at apogee.
Stability - I built this on Rocksim and it was stable w/o any changes. Still, I added an ounce of BB's to the nose cone by drilling a hole, loading with glue, and installing a dowel. Also made a nice anchor point for the screw eye.
1.7 Cal stable empty, and 1.4 Cal stable with a G-80 or G125. I picked heavy motors on purpose.
Cp on this rocket is 1/2" up from the bottom end of the body tube, and Cg is right around where the leading edges of the fins attach to the body tube. Due to the design, the motor (lengthwise, including fins) is near the center of the rocket so Cg doesn't shift a whole lot. Dang, this hobby rocks now with the software, Web info, and new books!!!!
Maiden flight will be F26-6FJ second flight will be F50-6T - both to 1000-1200 feet, 6 second delay is near perfect.
On motors, with the super long fin chord, G80 is pushing it and G125 is possible flutter/airframe failure (near 500mph) at 1900 to 2000 feet altitude.
Shortcoming (literally) - very little room for the recovery stuff. The E-Rockets nose cone only has a 1 1/4" shoulder, but it will be a tight fit with dog barf, the cord, and a 24" Estes parachute. There is also the large F/G ejection charge bang, maybe a really long cord! Still, it looks really good and SHALL fly. Here are the pix:
Cheers / Robert