New scratch build, Fat Alpha and Fat Omega

There has been some discussion on the forum recently, of epoxy vs. wood glue. Not regarding their strengths, but their weight and (for me at least) their setting time. I've decided to build two identical rockets, using epoxy throughout for one, and wood glue throughout for the other. I will carefully weigh all the components for each rocket separately before I begin, and then weigh the finished rockets (before paint) to see if there is in fact a difference.

I was planning on ordering two identical kits, like the Alpha or Astra, or Baby Bertha. But I've decided it will be more fun to scratch build two identical rockets, because I enjoy scratch building so much. I'm calling them Fat Alpha and Fat Omega, and they will be short fat (you guessed it!) Alphas. They will be BT-60 based, 15" tall, and have a single 24mm motor mount.

When I initially weigh the components, I won't include things like parachutes or shock cords, just the actual rocket components. Regardless of the outcome, it should be a fun build. And I can have my own drag race with them when they're finished!



View attachment fat_alpha2.ork

I ordered the components, which I hope will be here by the weekend. But I cut out the fins yesterday, which will be 1/8" birch plywood. As I have been doing on my scratch builds lately, I drilled and pinned all the fin blanks together with 1/4" dowels, so I could cut out all of the fins at the same time.

With all the fins still pinned together, I match sanded them with my 6" stationary belt sander. I sanded around the tabs with my 1" belt sander. Sanding them like this when they're pinned, makes it easy to keep them uniform. I clamped them to a flat surface to keep them from warping until I do the final sanding of the individual fins. Today, I'll cut out the centering rings, which will also be 1/8" plywood.

qquake2k said:

I was planning on ordering two identical kits, like the Alpha or Astra, or Baby Bertha. But I've decided it will be more fun to scratch build two identical rockets, because I enjoy scratch building so much. !

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Imagine my surprise when I read that.:y::y::rofl: Will be interesting to see the outcome and the 2 rockets ,which I am 100% sure will look AWESOME!!!!

Scotty Dog said:

Imagine my surprise when I read that.:y::y::rofl: Will be interesting to see the outcome and the 2 rockets ,which I am 100% sure will look AWESOME!!!!

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I'm sure the rockets will look awesome, too. Until I start to paint them...

qquake2k said:

Until I start to paint them...

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Still go that thorn in your side AH?

Scotty Dog said:

Imagine my surprise when I read that.:y::y::rofl: Will be interesting to see the outcome and the 2 rockets ,which I am 100% sure will look AWESOME!!!!

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I agree...

Wish I had all those cool tools to cut my own fins...oh well one day I hope.

Scotty Dog said:

Still go that thorn in your side AH?

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Painting has never been one of my strong points...I might hold off on building rockets. Maybe buy some new tools. Spray gun and compressor for starters

I'd guess final weigh in should be abt 72hrs dry time w no paint or spiral filler. Should be interesting results. My money is on wood glue depending on how bold you are with epoxy fillets.

RocketManDan said:

I agree...

Wish I had all those cool tools to cut my own fins...oh well one day I hope.

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I grew up with woodworking. My father and grandfather were woodworkers and cabinet makers. My skills are nowhere near what theirs were, but I am blessed with some nice tools.

RocketManDan said:

Painting has never been one of my strong points...I might hold off on building rockets. Maybe buy some new tools. Spray gun and compressor for starters

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I have a compressor, and have thought about getting a spray gun. But the paint is very expensive and the techniques can be very complex. Not to mention cleaning the spray gun. I've decided to stick with rattle cans for now.

El Cheapo said:

I'd guess final weigh in should be abt 72hrs dry time w no paint or spiral filler. Should be interesting results. My money is on wood glue depending on how bold you are with epoxy fillets.

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I'm pretty sure the wood glue rocket will be lighter. How much lighter is the question. Will it be enough to affect performance? We'll see.

Scotty Dog said:

Still go that thorn in your side AH?

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More like a railroad spike in my side. Stupid paint.

Using hole saws as usual, I got the centering rings cut out. I mounted them on the lathe to cut and sand them to their final diameter. I used a 1-3/4" hole saw for the outside diameter, and a 15/16" for the inside diameter. I'll use a sanding drum in my Dremel to sand the inside diameters to their final size.

I haven't decided yet whether I'll put baffles in the motor tubes. But I went ahead and cut out the disks just in case. I sealed the pilot holes with epoxy, and will cut about a third off each disk after the epoxy sets. I thought about sealing the pilots holes in two of the disks with wood glue for use in that rocket, but I wasn't sure if it can handle the heat from the ejection charges. Regardless, it won't affect the weight test, since the baffles will be weighed initially with the rest of the components.

qquake2k said:

I'm pretty sure the wood glue rocket will be lighter. How much lighter is the question. Will it be enough to affect performance? We'll see.

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It's all going to depend on how much weight the epoxy adds to the tail end. If it's enough to warrant more nose weight to bring both rockets to the exact CP/CG relationship as well as the same caliper of stability, then it will effect performance.

qquake2k said:

I have a compressor, and have thought about getting a spray gun. But the paint is very expensive and the techniques can be very complex. Not to mention cleaning the spray gun. I've decided to stick with rattle cans for now.

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Yeah that's true. It seems like there is always a trade off

I got the recovery anchors bent and cut from brass rod, the centering rings drilled, the ejection baffle disks trimmed, and the fins sanded. Now I'm just waiting for the rest of the components, which I'm hoping will be here today. I went and bought some Gorilla wood glue. The wood glue I had looked old and discolored, and I didn't want to take any chances.

I got the components in the mail today. I marked the body tubes and cut the fin slots. I also cut the 9" BT-50 into two 4-1/2" 24mm motor tubes.

Now for the weigh in. Alpha's components weigh 57 grams, and Omega's weigh 58.

Got the motor blocks glued in, the forward centering rings glued on, and the recovery anchors installed and glued.

Got the motor mounts glued in. As usual, I haven't glued in the aft centering rings yet, so I can do internal fillets.

Got the fins epoxied on Fat Omega. Next I'll glue the fins on Fat Alpha.

Since you are the newest member of weights and measures, will you be mixing any silica (can't remember name of the light bubblie stuff) in the epoxy for your fillets?

qquake2k said:

There has been some discussion on the forum recently, of epoxy vs. wood glue. Not regarding their strengths, but their weight and (for me at least) their setting time. I've decided to build two identical rockets, using epoxy throughout for one, and wood glue throughout for the other. I will carefully weigh all the components for each rocket separately before I begin, and then weigh the finished rockets (before paint) to see if there is in fact a difference.

I was planning on ordering two identical kits, like the Alpha or Astra, or Baby Bertha. But I've decided it will be more fun to scratch build two identical rockets, because I enjoy scratch building so much. I'm calling them Fat Alpha and Fat Omega, and they will be short fat (you guessed it!) Alphas. They will be BT-60 based, 15" tall, and have a single 24mm motor mount.

When I initially weigh the components, I won't include things like parachutes or shock cords, just the actual rocket components. Regardless of the outcome, it should be a fun build. And I can have my own drag race with them when they're finished!

Click to expand...

I just finished my last build,used Titbond III.Only used JB Weld to cover the half moon plates for my baffle and top plate to hold my screw eye.Came in at 6oz.BT60(18" tube)7" nosecone.1/8" birch plywood for the fins and 3 centering rings.I think the Titebond III saved me some weight.Really like your design.

Now for Fat Alpha's fins with wood glue. These took considerably longer waiting for the glue to set, as opposed to the fast setting epoxy. But if you're not impatient like me, wood glue would work fine. It certainly is easier to apply because you don't have to mix it. It's also a lot less expensive than epoxy.

I came up with a new method of holding the body tube to my fin alignment guide. Bungee cord and a cord lock. It worked much better than the elastic, and is easier to adjust with the cord lock. I also made a stand to hold both rockets while the fillets set.

They sure are cute!

El Cheapo said:

Since you are the newest member of weights and measures, will you be mixing any silica (can't remember name of the light bubblie stuff) in the epoxy for your fillets?

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Micro balloons? No, I've never used them, and I doubt if the average LPR builder would either. I usually use Titebond Molding glue for fillets, since it doesn't run. But for the purposes of this experiment, I'm using epoxy and wood glue for the fillets.

cjp said:

I just finished my last build,used Titbond III.Only used JB Weld to cover the half moon plates for my baffle and top plate to hold my screw eye.Came in at 6oz.BT60(18" tube)7" nosecone.1/8" birch plywood for the fins and 3 centering rings.I think the Titebond III saved me some weight.Really like your design.

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I would be very surprised if the wood glue version isn't significantly lighter than the epoxy version. Thanks for the compliment. I basically just "squashed" an Alpha.