Estes Custom PSII from a Scion Kit - Build Thread

[bclark989]

Hi all,

This is my first build thread (and first thread on TRF period, actually), so go easy on me =p. A small rocket bio, since I'm new:

I'm Brian, and I joined Oregon Rocketry in January. I have been building low power models since I was probably 10 and finally found mid and high power rocketry at the age of 29 and joined OROC. I built my first high power kit over the winter, a LOC Precision Hi-Tech, which flew beautifully on a CTI I55 Mellow Yellow in May for my first L1 attempt. Despite watching it touch down gracefully, it was never recovered from the eastern Oregon sage brush. My next L1 attempt will be with an Estes Partizon in late August or September. The rocket is ready, just waiting for the day. I also have my L2 project on the workbench now, a LOC Precision Hyperloc 835.

On to the task at hand...

I recently purchased one of the Estes Scion kits. I feel like there are enough stock PSII builds out there, and at OROC's most recent meeting, a few of us discussed how great these kits are just for parts at the prices they have been at recently. I have been thinking for a while it would be fun to scratch build something, or at least modify a kit, so here it is.



I am going to leave it as a 3-fin (Scion) but turn them back around (Leviathan) and add a small second fin aft of each primary fin. The secondary fins will be cut from the fourth fin that came with the set (the Scion is just Leviathan parts, and as such comes with 4 fins even though the Scion only calls for 3). At this point, I am not planning on getting a fourth centering ring (to cap the secondary fin tabs). I don't think it will ever endure enough stress for it to matter. Only planning to put F's and G's in this bird.

Other add-ons / substitutions:

• Rail Buttons
• Eye bolt harness mount in front centering ring

Oh, and a name. "The Bagman's Gambit". So I am a huge Decemberists fan, and thought to myself recently that it would be fun to name my rockets after their songs. I have posthumously dubbed the Hi-Tech "The Infanta", which seemed fitting for a first rocket. This rocket be ever so slightly "customized", so I figure it's a bit of a gamble.

Thanks for reading! Questions / comments welcome!

 

[K'Tesh]

Hi Brian!

I think I know you... You were sitting with me and Brian (the other Brian) as we were talking about my Cherokee D, if I'm right.

Looking forward to seeing what you've got planed.

All The Best!
Jim

 

[bclark989]

你好 K'Tesh! Yep, that was me.

For PSII kits, do you usually stick with the stock shock cord, or sub in a proper harness? I feel like at this scale a shock cord is fine, but don't have a ton of experience with mid-power. Thoughts?

Brian

 

[K'Tesh]

你好 K'Tesh! Yep, that was me.

For PSII kits, do you usually stick with the stock shock cord, or sub in a proper harness? I feel like at this scale a shock cord is fine, but don't have a ton of experience with mid-power. Thoughts?

Brian

Hi Brian,

As these are closely related to the PSII kits, I'm Ok with the stock cord, but I've got precious few flights under my belt as a re-bar, and none of those are really MPR.

I'd ask the rest of the membership (here or at OROC) what they think.

Best!
Jim

 

[noffie79]

I'm looking forward to this build! I'm about to order a Scion myself, so I'm interested in seeing your technique.

 

[bclark989]

I was able to get started on this tonight.

Here is the kit itself...standard Estes offerings:


First step was to get my extra set of fins out of the spare. Not quite right at first...:


Good enough!


Next, added fin slots to the lower air frame. This "spare parts kit" comes with two Leviathan upper body tubes = no pre-cut fin slots . Fortunately, the kit comes with a handy template:


Here is roughly what the inside layout will be:


And finally, after more sanding than I thought it would take to make the fin slot large enough, a successful dry fit!:


Next steps will be to finish cutting out the other two fin slots, bevel the fins, and assembly the motor mount. I may end up cutting the fin slots all the way to the bottom so I can do internal fillets on the fins. I think the secondary fins are going to need the extra support since they won't have a leading centering ring.

Cheers,

BC

 

[noffie79]

Looks good so far. I like what you did with the spare fin, turning it into another set of fins!

 

[AlnessW]

Looks good so far, Brian!

As far as a shockcord goes - for your application, an elastic shock cord should be plenty. Just keep your eyes open for damage to the cord from ejection charges. For a rocket much larger, I'd recommended tubular nylon, available by the foot as "nylon webbing" from any REI store.

 

[bclark989]

Another little update:


I took a bit more off the secondary fin set to bring them in line with my design in Open Rocket. I haven't re-measured them yet, but they are pretty close now to the screenshot above. The whole army of fins is sanded, beveled, and ready for installation.


After cutting all three fin slots, I realized they were all pretty narrow and forcing the body tube to deflect to allow a fin to be inserted. This is no bueno, so I attacked them again with the knife. Gaps won't really matter once the fin fillets are built up.


Since I will use the slots to align the secondary fins fore and aft on the booster air frame, and the slot extensions weren't part of the original template, I checked them after cutting them out. Two of them were 0.810" from the bottom, but one was 0.830". Nothing a little sandpaper couldn't fix! (Also, I know this isn't the best measurement tool for this scenario. I could have been cutting into the tube a bit with the sharp ends of the calipers, but I don't own a square tipped height gauge, and this dimension probably isn't going to make or break the rocket's air worthiness...)


And with all of that, finally a full dry fit (guitar for scale...)


I think this guy probably summed up why dry fitting the whole thing together for the first time is so fun: SPACESHIP!

Cheers,

Brian

 

[bclark989]

Sorry everyone for the huge delay in an update on this. I lost my job in a round of layoffs two weeks ago and have had my priorities rearranged as a result. There is a launch this coming weekend, however, so time to finish stuff!

I was going to try and do the fins without cutting the assembly out for fillets, but decided I like this way more, and its faster when you already know how to do it.


I'll spare you a bunch of pictures of caking on wood glue reinforcing. Here is the eye-bolt installed in the top centering ring for the shock cord. A nomex sleeve will definitely go on the cord since I will be using the motor ejection.


Once I was satisfied with the layers and layers of glue in the corners, the fin can assembly was re-installed and glued in place. The air frame was sticking out a bit for some reason so I rubber banded it to help it maintain the correct shape while the glue cured.


Instead of having the rocket separate at the nose cone (which is how they are design), I made a bulkhead from a flat piece of ABS, beveled it, and epoxied it to the coupler. This was glued into the upper air frame and an eye-bolt will provide a mount for the other end of the shock cord and the parachute.




All in one piece! All that's left is fin fillets, static ports, and launch lugs (forgot I wanted to do buttons and didn't have time to order them before this weekend's launch).


Prior to fin fillets, I had to patch the airframe from cutting the fin can out. This was done with wood filler and more wood glue. I wanted to do foam inside, but again, between time and just the lack of real need, I skipped it.



That's all the photos I have. The wood glue patches on the fin cutouts are dry as well as some wood glue fillets (which aren't very fillet-ish, but for mid power, they provide enough reinforcement. I am not trying for altitude records with this rocket). I also installed the launch lugs last night, so all she needs is paint. I will get that done tonight or tomorrow hopefully and post some photos of the finished product, hopefully followed up quickly by a flight video after this weekend.

Thanks for looking!

 

[noffie79]

Looks great! Job well done. Can't wait to see it painted!

 

[bclark989]

All done and painted! I am a little sad that I turned the end of this project into a bit of a rush job, but it still turned out pretty well I think. Abandoned the Scion paint scheme since I abandoned the design. Once upon a time my wife got into making hula hoops, so I have about 40 rolls of various colors and types of vinyl tape in my house. This is just Krylon "Cherry" and fluorescent orange tape.



Flight video next week hopefully!

 

[noffie79]

It looks great. Post those vids when you get them!

 

[pyrobob]

I'm normally not a fan of split fin designs but I have to say this looks really cool. Nice job! I'll keep it in mind for future builds for sure.

 

[bclark989]

I'm normally not a fan of split fin designs but I have to say this looks really cool. Nice job! I'll keep it in mind for future builds for sure.

Thanks! I also actually am not a huge fan of split fins, but I thought building one might be a fun challenge and might help me appreciate them a bit more. It was a fun build experiment, and while obviously biased, I am also a fan of how it turned out looking =)

 

[bclark989]

Here is the video. By a strange series of events, it ended up being my cert flight!

[video=youtube;M0WQkU-UIrk]M0WQkU-UIrk[/video]

Thanks all for following along! Level 2 is planned for next month...

Cheers,

BC

 

[pyrobob]

Sweet. I'm drooling over your launch site .

 

[K'Tesh]

Congrats! We both certified at the same launch event... Now if I can only get my images to upload to flickr.