Cobalt upscale build

[qquake2k]

Like a lot of you, I like stubby rockets. And also like a lot of you, I like upscales. I've been thinking for a long time of building a Fat Boy upscale. But there are a ton of them already out there, and I decided to do something different. I've never seen an upscale of the Quest Cobalt. Mine will be an approximately 3.5x upscale, based on LOC 5.54" tubing. It will have a 54mm motor mount, and I'll also make a 38mm adapter for it.

I decided to build it slightly longer than scale, for the stability. The original Cobalt is 7.5" long, which would make the upscale about 26.25". Mine will be about 27.5" long, a little over an inch longer. But that extra 1.25" means I'll only need 8oz of nose weight, instead of 20oz or more. That's a significant weight savings. I've also reshaped the fins slightly, to increase the stability further.



View attachment cobalt_5.5_38mm5.ork

View attachment cobalt_5.5_54mm5.ork

 

[qquake2k]

I normally use hole saws to cut out centering rings. But I don't have one big enough for 5.54" tubing, so I used my homemade circle cutter on my bandsaw. I cut two 5.5" squares of 1/4" birch plywood, and drilled 5/32" holes in the centers. I used a #8 screw to attach the blanks to the jig, and cut the circles. Then drilled them out to 1/4" to attach them to the lathe.

 

[qquake2k]

As usual, I did the final sizing to the OD of the centering rings on my woodlathe, using a coarse file. I cut the center holes with a 2-1/4" hole saw, which works out to be the perfect size for 54mm motor tube. I also drilled holes for the tee-nuts in the aft ring.

 

[qquake2k]

I epoxied blocks to the centering rings for the tee-nuts and rail buttons. After the epoxy set, I sanded the rail button blocks flush with the stationary disc sander, and drilled out the holes for the tee-nuts.

 

[qquake2k]

I pressed the 8-32 tee-nuts into the blocks, and covered them with epoxy so they can't push out.

 

[bradycros]

These techniques should be named after you! You've got all the bugs hammered out of the sub assemblys.

 

[qquake2k]

These techniques should be named after you! You've got all the bugs hammered out of the sub assemblys.

I don't know about naming them after me, but I've certainly found what works for me.

 

[TopRamen]

Subscribed! This looks like something I can learn a lot from.op:

 

[rocketgeek101]

These techniques should be named after you! You've got all the bugs hammered out of the sub assemblys.

I don't know about naming them after me, but I've certainly found what works for me.

CLNS (Captain Low-N-Slow) Approved!:wink:

I'm watching (as usual)

 

[qquake2k]

I had printed the fin template on card stock, and cut it out. Normally when I cut out fins, I first cut out rectangular "blanks" for simplicity. But in this case, I wanted to get all the fins cut from one 12"x24" sheet of plywood. So I marked all four fins on the plywood, to be able to cut between them.

 

[qquake2k]

As I usually do, I drilled 1/4" holes in the fin tabs and pinned them together with 1/4" dowels. That way I can cut and match sand them all at once.

 

[qquake2k]

Got the fins cut out and sanded. By the way, I used 3/8" plywood for the fins for a couple of reasons. One, the thickness is more to scale. Two, they'll be stronger, since they'll stick out so far from the body tube. And three, I just like thick fins! I haven't decided yet if I'm going to round the leading edges or not.

 

[qquake2k]

Got the u-bolt installed in the forward centering ring.

 

[thobin]

These techniques should be named after you! You've got all the bugs hammered out of the sub assemblys.

I don't know about naming them after me, but I've certainly found what works for me.

I think he is just showing us the same build pictures every time and passing them off as a different rocket. Other than the fins look different hummm?


TA

 

[qquake2k]

Got the forward centering ring epoxied to the 54mm motor tube. I use the 1/2" nylon spacers to set the position of the centering ring on the motor tube, and keep it level.

 

[qquake2k]

Subscribed! This looks like something I can learn a lot from.op:

It'll be a simple build, using my same old tried and true techniques. But I appreciate the interest!

CLNS (Captain Low-N-Slow) Approved!:wink:

I'm watching (as usual)

The CLNS Seal of Approval! LOL

I think he is just showing us the same build pictures every time and passing them off as a different rocket. Other than the fins look different hummm?

TA

You know, sometimes I wonder why I keep showing the same build techniques over and over. But then I think, what if someone who hasn't followed any of my builds before happens across one of them? I've learned so much from this forum, this is just my way of paying it forward. Besides, I enjoy posting the build threads.

 

[thobin]

You know, sometimes I wonder why I keep showing the same build techniques over and over. But then I think, what if someone who hasn't followed any of my builds before happens across one of them? I've learned so much from this forum, this is just my way of paying it forward. Besides, I enjoy posting the build threads.

And we enjoy watching them, keep em comin!


TA

 

[chris m]

Yes great build threads . Your a go to guy on these scratch builds

 

[qquake2k]

Does this look like a 5.5" elliptical nose cone to you? Me either. Since I had success with the two nose cones I turned for Cherrybomb and Gooniot recently, I decided to try turning one for Cobalt XL. I may have bitten off more than I can chew this time...

I couldn't find a 6x6 block of basswood anywhere. So I got four 3x3 blocks to glue together. I'm using wood glue, a small foam roller to spread out the glue, and every long enough clamp I own. I know that most people use too much glue when gluing up wood pieces, myself included, so I used it a bit more sparingly than in the past. I hope I didn't go too minimalistic.

 

[qquake2k]

That there's a lot of clamps. I hope they're enough.

 

[qquake2k]

I'm a little concerned about some cracks in two of the basswood pieces. I'll be gluing them so that the cracks are on the inside, so hopefully that will help. I'm also a little concerned with some gaps, but we'll see what happens. As long as it holds together long enough to turn it to shape, I can always fill exposed cracks and gaps. I'll be gluing these together tomorrow into one 6x6x12 block. I'm planning on starting the turning on Sunday morning. Wish me luck!

 

[JPVegh]

This is too cool Capt, rocketry and wood working in one place. You're kinda getting into making those nose cones huh? Sometimes I'll turn a few nose cones for no reason at all, it's sorta theraputic. I've never turned one from a lay up before so this will be very interesting for me. Just when we think we've seen all of your tricks, you come up with a new one.

Thanks for sharing and keeping it interesting

 

[o1d_dude]

Now this is an upscale project I can really get into.

I'm a fan of stubby rockets and am glad to see you've embraced the 54mm motor mount. You've got the hardware so you may as well build to accommodate it.

Great idea to turn your own nose cones, as you certainly have the woodworking equipment for it.

For those reading along, I can vouch for Jim's skill in turning out exceptional centering rings. Never able to produce ones of my own that could hold a candle to his so...I just hand him a sheet or two of plywood and next time I see him, there are my rings!

 

[qquake2k]

This is too cool Capt, rocketry and wood working in one place. You're kinda getting into making those nose cones huh? Sometimes I'll turn a few nose cones for no reason at all, it's sorta theraputic. I've never turned one from a lay up before so this will be very interesting for me. Just when we think we've seen all of your tricks, you come up with a new one.

Thanks for sharing and keeping it interesting

Turning the two previous cones was fun, but only because they turned out so nice. If this experiment fails, it won't be fun anymore. :tongue:

 

[qquake2k]

Now this is an upscale project I can really get into.

I'm a fan of stubby rockets and am glad to see you've embraced the 54mm motor mount. You've got the hardware so you may as well build to accommodate it.

Great idea to turn your own nose cones, as you certainly have the woodworking equipment for it.

For those reading along, I can vouch for Jim's skill in turning out exceptional centering rings. Never able to produce ones of my own that could hold a candle to his so...I just hand him a sheet or two of plywood and next time I see him, there are my rings!

I really don't have any great talent, just great tools. You could make centering rings like I do if you had the tools and desire. My father was an accomplished turner, but I could never hope to achieve what he did. He used to turn the most beautiful bowls. Probably one of the best projects I remember him doing was turning offering plates for our church. I remember he glued up hardwood pieces with some kind of glue that he set on fire before he pressed them together. That was very exciting to my young boy eyes!

This is one of the offering plates he turned. Still looks pretty darned good after well over 40 years! I believe this one is oak, that he got from some old pallets he picked up on the freeway one time. He also built a pulpit, alter bench, music stand, and communion table from the same oak. He was an amazing man, and I miss him dearly. He also turned some offering plates out of cherry wood that were even prettier. Looking at this one, it appears to have some spalting in the wood. Gorgeous.

 

[qquake2k]

The faces of the blocks for the second glue up weren't very square, but I expected that. Using a combination of my stationary belt and random orbit sanders, I got them pretty flat.

 

[qquake2k]

Now that's a gap I can live with! Especially considering how tight it is without clamps.

 

[qquake2k]

While I was busy creating clouds of wood dust, I decided to round the leading edges of the fins. They turned out pretty nice.

 

[qquake2k]

I put glue on both faces, and spread it out with the foam roller. Then clamped the blocks together.

 

[qquake2k]

If this doesn't work, it won't be for a lack of clamps! There are three different kinds of clamps there. I'm a little concerned with the gaps in the ends, but it is what it is. We'll see what happens tomorrow when I start turning it.