Based on some parts picked up over the past few months from members here on TRF, I am considering a Cherokee-D upscale (Cherokee-M or N). Of course, this has been done before, but like many, this rocket is an integral part of my childhood and thus the desire to recreate it in a "big way." Anyway, on to my question, although the Cherokee-D nosecone can be approximated by a 4:1 conical, it really isn't... Seems to be some type of Power series. Does anyone know for sure?
L3, TRA #11847 Tripoli Indiana #132
Tripoli Central Illinois #59 Central Illinois Aerospace (NAR) #527
Chicago Rocket Mafia, "Big Bucks" Dixon
___________________________________
Just a thought....Semroc produces faithful representations of classic cones, including the -55AC cone. With cone in hand, one could measure stations (0-5.4") vs. diameters and upscale to to desired diameter. This is your baby: http://www.semroc.com/Store/Scripts/...?idproduct=581
Actually it's easy to come pretty close with fiberglass/epoxy over foam.
Do this.
Get an original or SEMROC equal cone.
Measure the length and do a tiny bit of math to figure out the total length of your upscale nose cone.
Glue stack some foam to the length. I use the foaming Gorilla glue.
Mount the stack in a lathe or make something lathe like. It's foam! It doesn't have to be real industrial!
Something electric drill powered would even work. Or even hand powered by an assistant.
Make two! one for you and one for your assistant!
Make a correct shoulder first. This it the hardest part. The shoulder is your base so it's important.
Use sure form rasps and sandpaper (like 50 or 60 grit) to shape it.
Stand back, close one eye and line up the original nose cone. You can then see what more needs to be removed.
Do a little at a time until the cone matches the original in the "one eyed step back view".
Then fiberglass!
Oh...yea...a good dust collector really helps!
That foam dust is a PIA!
Last edited by sandman; 13th April 2012 at 06:08 PM.
"I'm a sandman. I've never killed anyone. I terminate runners when their time is up." Logan from "Logan's Run".
Thanks yes. Note on shoulder is important. Plan on using Blue Tube coupler section with foam extended from nosecone body and inset to be press fit / glued in place.
Originally Posted by sandman
Actually it's easy to come pretty close with fiberglass/epoxy over foam.
Do this.
Get an original or SEMROC equal cone.
Measure the length and do a tiny bit of math to figure out the total length of your upscale nose cone.
Glue stack some foam to the length. I use the foaming Gorilla glue.
Mount the stack in a lathe or make something lathe like. It's foam! It doesn't have to be real industrial!
Something electric drill powered would even work. Or even hand powered by an assistant.
Make two! one for you and one for your assistant!
Make a correct shoulder first. This it the hardest part. The shoulder is your base so it's important.
Use sure form rasps and sandpaper (like 50 or 60 grit) to shape it.
Stand back, close one eye and line up the original nose cone. You can then see what more needs to be removed.
Do a little at a time until the cone matches the original in the "one eyed step back view".
Then fiberglass!
Oh...yea...a good dust collector really helps!
That foam dust is a PIA!
L3, TRA #11847 Tripoli Indiana #132
Tripoli Central Illinois #59 Central Illinois Aerospace (NAR) #527
Chicago Rocket Mafia, "Big Bucks" Dixon
___________________________________
If you can wait a few weeks, I will send you the exact outline contour I traced from an original Cherokee-D. I used it to scale up my 54mm motor version:
Based on some parts picked up over the past few months from members here on TRF, I am considering a Cherokee-D upscale (Cherokee-M or N). Of course, this has been done before, but like many, this rocket is an integral part of my childhood and thus the desire to recreate it in a "big way." Anyway, on to my question, although the Cherokee-D nosecone can be approximated by a 4:1 conical, it really isn't... Seems to be some type of Power series. Does anyone know for sure?
It is a secant ogive with a rounded tip based on the Arcas.
Thank you Carl. The parameters R and L are easy in a secant ogive, but do you know what p (rho) is for that nosecone so I can scale it up?
The best fit I can get is L=7.9R and p(rho)=64.77R (from CorelDraw.) Don't forget the radius at the very tip is .055R.
The Atlantic Research drawings give the cross section length at various distances from the base. Entering these points into the equation shows the actual Arcas original nose cone was not an exact secant ogive, but was very close. This is all moot, however, since the Estes BNC-55AC was based on the original Arcas, but varied slightly over time, particularly at the tip. I would say you have leeway to do an upscale of the Cherokee-D without being too far off!
The best fit I can get is L=7.9R and p(rho)=64.77R (from CorelDraw.) Don't forget the radius at the very tip is .055R.
The Atlantic Research drawings give the cross section length at various distances from the base. Entering these points into the equation shows the actual Arcas original nose cone was not an exact secant ogive, but was very close. This is all moot, however, since the Estes BNC-55AC was based on the original Arcas, but varied slightly over time, particularly at the tip. I would say you have leeway to do an upscale of the Cherokee-D without being too far off!
Carl, thank you very much for the effort! I know I'll be very close (at least with my naked eye).
L3, TRA #11847 Tripoli Indiana #132
Tripoli Central Illinois #59 Central Illinois Aerospace (NAR) #527
Chicago Rocket Mafia, "Big Bucks" Dixon
___________________________________
This sounds familiar.... I made a nose-cone recently for my Cherokee M, thread posted in the HPR section on Rocketry Planet. I'd have to look to see how close I came to the suggested numbers. I didn't have these details when I designed it.
I haven't fiberglassed mine yet, but I'm inclined to think that I got it slightly too conical and not curved enough.
Mine was cut on my CNC router. Given the parameters, creating a cone kit that requires about 15 minutes of sanding after assembly is about 2 hours. Mostly in the computer work, the cutting of the foam is pretty quick as it's soft.
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Originally Posted by jpummil
