Build: Sephydra

I think I may have started something interesting. Here's an image of the motor mount, exactly full-sized with no distortion.

Looks like 4 29mm and 3 38mm, but they came out a little oval for me.

Does sound interesting. Needs sepfins too.

Actually, I guess it prints to full-size but displays on the screen to a larger size. The oval shape is intentional though....more to come.

So is it 3 29mm and 4 24mm?

Here is the aft-most portion of airframe: a 3-inch heavy mailing tube with bevel cuts at both ends. The cluster is 3x24 + 4x18 for about 130Ns, which puts it between a G and an H.

Nice. Ater seeing the CR picture I wondered if the MMTs or the CRs would be canted, and it appears from the BT that it's the CRs.

It took me a whole day of work, but I've finally got the aft CR perfect.

The other CR was a lot easier. I've cut the tubes and started the installation process. There's still a couple surprises planned for the MMT assembly.

The design is not fully formed yet, although I have the general notion in my head and some scratch work in Rocksim. The overall design is inspired by two designs in Craig McGraw's BARCLONE site. (Does he visit TRF?) There's also a nod to Layne's Bucky, which I've admired from the day it was released.

More in the days ahead....

G

You've been on a tear here lately Geof! Go Boy Go! I enjoy keeping up with your scratch threads. In spite of the noted inspirations, your work always has a certain creativity that is not seen very often. If any of your stuff never made it to kit, it would be a real shame.

I agree with Craig, your designs are always very unique.
I really enjoy you build threads.
You do very nice work.

Thanks for the comments, guys. I'm still working on the motor mount. Between glue drying times, I've made two more (off)centering rings.

Tomorrow I get back home and can work on this again. I've been fretting about the fins. Options are:

The same ply as the CRs (3/32 I think, or maybe it's 1/8)
1/4 Balsa
Heavier ply (I have some 1/4 handy)

Fins are likely to be large and ttw. The seven motors put it between a G and an H. My concerns are mainly flutter and landing impact. But I don't want excess weight. Advice?

geof said:

Fins are likely to be large and ttw. The seven motors put it between a G and an H. My concerns are mainly flutter and landing impact. But I don't want excess weight. Advice?

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What kind of weight are you estimating?

No real estimate yet because the design isn't fully determined. If I had to guess, maybe 18-24oz.

geof said:

No real estimate yet because the design isn't fully determined. If I had to guess, maybe 18-24oz.

Click to expand...

That is fairly light...I think TTW bass would be fine.

Still asking about fins. The sims suggest a worst case scenario of
max acceleration = 18 gees and max velocity of 425 fps = 290mph.

Fin choices are:
1. 1/8 hobby plywood
2. 1/4 hobby plywood
3. 1/4 balsa
4. 1/4 balsa fg tip to tip, but I'm not enthusiastic about this option

The fin span is 4.625 in and let's suppose that at least some of
the fins are surface mounted.

Anyone have advice?

Geof

EDIT: I just looked at an Estes Alpha III on C6-7. It seems to have twice the acceleration and roughly equal max vel. I'm going with the thin ply unless anyone convinces me otherwise before I glue.

The motor mount is finally finished. Believe it or not, it took me a week of work! With that many tubes and things, it provided plenty of opportunities for goofs. I installed one mmt backwards and had to reverse it. Another one had a crooked engine hook on the first try. Another one had the hook shifted too far back and had to be adjusted.

There is so little CR material that I decided to glue in some balsa spacers to attach the tubes to each other. Now it feels very solid. The final unit weighs 1.5 oz and is ready to install in the body tube.

G

Sweet!!

That's awesome!

GOOD HEAVENS! Charge up the battery for that launch!

Added a bit more body yesterday. Today, it's fins, fins, fins.

This is becoming more and more interesting with each update! Is this going to have a glider fly with it?

Hah! You know how much I like big gliders, but....NO WAY!

Haha, I didn't expect a glider, thought it would be awesome if there was one.

This looks like an awesome rocket! Can't wait to see the finished product.

Sunday's work. Got one fin on the aft body section. Two more are in the "flattener" (*). The whole rocket will be longer than what you see here. After the fins are on, I get to begin the most interesting part of the build.

G

(*) My standard fin technique: Paint each side with thick diluted (foamy/muddy) wood putty. Use space heater to dry first side quickly. Dry only enough to handle, so some moisture is still in the wood. Place in the flattener for 24-48 hours. My flattener is a stereo speaker on table, with a stack of National Geographics and 2 bricks on top. To keep the desk and speaker clean, I place fins between wax paper layers. Remove from flatter and sand smooth. Glue on rocket and add fillets. Paint diluted putty over fillets. If unsatisfied with fin smoothness, repaint fins, too. Sand smooth. Spray with primer paint. Repeat iterations of putty (over blemishes) and paint until totally satisfied.

You sure do some awesome work Geof!:surprised: This is turning out to be an amazingly cool design.

dpoceta said:

You sure do some awesome work Geof!:surprised: This is turning out to be an amazingly cool design.

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I completely agree. I wish I could come up with designs as unique and interesting as yours.

Thanks for the comments, everyone.

I've had only a tiny bit of time the last few days, but I've made a bit of progress, with all main wings now glued on and two filleted. Here's a couple pics.

I'm excited because now I get to begin work on the cool part. I'll keep you up to date with pics after I make some more progress.

geof said:

Thanks for the comments, everyone.

I've had only a tiny bit of time the last few days, but I've made a bit of progress, with all main wings now glued on and two filleted. Here's a couple pics.

I'm excited because now I get to begin work on the cool part. I'll keep you up to date with pics after I make some more progress.

Click to expand...

Begin working on the cool part!?!
That looks pretty darn cool so far.
Can't wait to see what the cool part will be.