38 special build thread

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Joker050608

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So I figured today would be a perfect day to get my first fiberglass kit together. Since we're on shut down at work and there's about 8" of snow on the ground lets get things started. ImageUploadedByRocketry Forum1425601721.926486.jpg
All the parts out of the box, washed up, and ready to go.

I like to start with the little bits first. ImageUploadedByRocketry Forum1425601790.795348.jpg
Added an eyebolt to the nose cone bulkhead. Simple yet effective. After fitting it in the nose cone with minimal sanding I set them aside to work on the motor mount.
ImageUploadedByRocketry Forum1425601892.144081.jpg

Here I used a diamond file to notch out a little section to slide my shock cord through.

BeforeImageUploadedByRocketry Forum1425601941.470980.jpg
AfterImageUploadedByRocketry Forum1425601976.530344.jpg

ImageUploadedByRocketry Forum1425602123.768345.jpg
Tacked on the shock cord and started epoxying all the fitted pieces together.
 
looking good, make sure you sand every surface getting epoxied with 60ish grit paper, especially the fins.
 
I honestly fail to see the reason for sanding with such a rough grit. Epoxy is a chemical bond, not mechanical. Everything has been sanded with a 220P sand paper before being washed.
 
the epoxy alone is a chemical reaction, however you need a good mechanical bond between the two parts, the reason of roughing them up.
 
the epoxy alone is a chemical reaction, however you need a good mechanical bond between the two parts, the reason of roughing them up.

I agree. I just don't agree with using a roughness that would tear into the fibers of the composite part rendering them practically useless.

After installing the motor mount I tied my 750# kevlar shock cord to my deck and gave it a swift hard tug. The body tube just pulled out of my hands. Seems pretty strong to me.
 
I agree. I just don't agree with using a roughness that would tear into the fibers of the composite part rendering them practically useless.

After installing the motor mount I tied my 750# kevlar shock cord to my deck and gave it a swift hard tug. The body tube just pulled out of my hands. Seems pretty strong to me.

If sanding with 60 grit paper is destroying your FG parts, you need to reassess your sanding strategy. You are trying to make the smooth surface into one rough enough that the epoxy (which cures chemically, but still needs a mechanical bond to the surface) can hold on to it, not remove very much material.
 
Here's the little file that makes quick work of the fin slots. ImageUploadedByRocketry Forum1425654993.252692.jpg
ImageUploadedByRocketry Forum1425655004.696852.jpg

I have to say it probably cut my time down to almost nothing. Just a few passes in each slot was all it took.
 
Also got the bulkhead swimming in epoxy to create a nice seal and bond.
 
ImageUploadedByRocketry Forum1425656409.676555.jpg
Tacking on the fins with some 5minute instant mix. Then will go back and run some smooth fillets with some stronger epoxy.
 
If sanding with 60 grit paper is destroying your FG parts, you need to reassess your sanding strategy. You are trying to make the smooth surface into one rough enough that the epoxy (which cures chemically, but still needs a mechanical bond to the surface) can hold on to it, not remove very much material.

Lots of opinions on the proper way to abrade surfaces to be joined with epoxy but please read these couple articles supporting not abrading with course grits:

https://www.apogeerockets.com/education/downloads/Newsletter358.pdf
https://www.rocketryforum.com/showt...what-your-government-doesn-t-want-you-to-know

Greg
 
The 38 Special is a great rocket. I picked one up last fall. I was able to get in one flight on it before the winter set in here in the Northeast. Looking forward to lots more fun with it in the months ahead. Good luck with yours!

Jim Z
 
The 38 Special is a great rocket. I picked one up last fall. I was able to get in one flight on it before the winter set in here in the Northeast. Looking forward to lots more fun with it in the months ahead. Good luck with yours!

Jim Z

Thanks Jim. This rocket just looks ready to fly at any moment. Might get mine in the sky in April. What did you fly yours on?
 
I believe my maiden flight was on a CTI F59. I have dreams of at least flying it on maybe a G54 or some other long burn motor this spring. Since I didnt go the extra mile to build in any dual deploy capability, the only tradeoff on the high end will be how big the field is and how far I want to walk. I'll likely save the high performance fun for Red Glare. I did redesign the nose a bit so I could have a removable bulk plate to stow my tracker in the nose.

I expect to get the most use out of it on F's and G's for good performance on a reasonable budget. :)

Jim Z
 
I believe my maiden flight was on a CTI F59. I have dreams of at least flying it on maybe a G54 or some other long burn motor this spring. Since I didnt go the extra mile to build in any dual deploy capability, the only tradeoff on the high end will be how big the field is and how far I want to walk. I'll likely save the high performance fun for Red Glare. I did redesign the nose a bit so I could have a removable bulk plate to stow my tracker in the nose.

I expect to get the most use out of it on F's and G's for good performance on a reasonable budget. :)

Jim Z

Thanks for the info.
I was thinking about flying this at red glare also and might get a cable cutter for dual deploy. Then throw something like an H in it. Maybe vmax to push the limits on it. But I will take it easy on it for the first flight. An F should be plenty.
 
Hey, I just got the 38 Special to do my level 1 cert, all i have is the kit. I have a plastic nose so it would appear that I don't need the nose cone bulkhead. I am apart of my collegiate aerospace program so I have access to parachutes and shock cords, only thing I am wondering about is what to do for the motor retainer, does anyone have any ideas? If anyone has any additional advice that would also be greatly appreciated!
 
Hey, I just got the 38 Special to do my level 1 cert, all i have is the kit. I have a plastic nose so it would appear that I don't need the nose cone bulkhead. I am apart of my collegiate aerospace program so I have access to parachutes and shock cords, only thing I am wondering about is what to do for the motor retainer, does anyone have any ideas? If anyone has any additional advice that would also be greatly appreciated!

Commercial options are Aeropack or Slimline (Giant Leap) retainers. Just make sure you get the proper base piece for your mount size.

Given the small size difference between motor and body tubes, you won't have much room for threaded inserts for Kaplow clips or Madcow style retainers.


Side question: Are you prepared to recover this rocket? This thing is going to go pretty high on an H.
 
Commercial options are Aeropack or Slimline (Giant Leap) retainers. Just make sure you get the proper base piece for your mount size.

Given the small size difference between motor and body tubes, you won't have much room for threaded inserts for Kaplow clips or Madcow style retainers.


Side question: Are you prepared to recover this rocket? This thing is going to go pretty high on an H.

I talked to the program adviser and he said that he just used duct tape to hold the motor in place for his L1, also mentioned used a Gatorade bottle cap as a cheap version, thought?

I have also competed in the 2017 ESRA Spaceport America Cup, we build a rocket to carry a 9 lb payload to 10k AGL, so I am prepared for a hike to get my rocket back, I also plan on filling the nose cone as much as I can to lower the apogee (per adviser's recommendation).

EDIT: One of the centering rings has a small notch on the outside, how would it work to epoxy a hook through that to hold the motor in (similar to the retainer on the small Estes rockets, but more durable)
 
Picked one up last year with one flight on it. Made a 3/4" bulkhead plug for the nosecone to be retained by four countersunk screws in the NC shoulder.
Was able to fit a full length EggFinder with a 1/2 wave antenna on it. Can fit a Jolly Logic Chute release in the sustainer but it is a tight fit. One flight on it
so far and unfortunately I didn't have the chute protector placed properly so the chute "para-wadded" so the flight was unseen even though it landed
very close. I had a patch antenna on a 10' pole and had a signal when the rocket was down. Triapsed out, fiddled with the live map and picked it right up.
None the worse for wear and ready to go again.

I'd like to put it up on an I200 and let'r rip. Will try something milder until I can satisfy myself I can get the chute release to do it's thing properly with proper placement of the protector (my fault not the CR).
(Did Proline 4500 on the surface mount fins with substantial fillets. Took the hit of the hard landing just fine although it was in a no-till cornfield with
residual stalks and soft dirt to land in.)
Kurt
 
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