Gary Larsen's Farside Rocket - A BT-80H Scratch Build

[lakeroadster]

Fin Can Assembly - Day 01

I got all the fin can parts glued together with an initial fillet of Gorilla Wood Glue. I ended up sanding the o.d. of the C-80 coupler in the area where the lower BT-80 goes in order to get a sliding fit. I then use Elmer's Glue All to secure it in place.​

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I'll add glue fillets now.​

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[lakeroadster]

Fin Can Glue Fillets

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[lakeroadster]

Fin to Cone Cheaters

I cut and installed some basswood cheaters on the fins.​

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Now... if I could just find a cone development program for an offset eccentric cone.... not a concentric cone.... not an eccentric cone.... an offset eccentric cone.​

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[Blast it Tom!]

I used Solidworks to do mine. I think the layout is on either my build thread or my plea for help with 3D printing. I could convert it for other CAD formats, and you could push it to your dimensions...

 

[lakeroadster]

I used Solidworks to do mine. I think the layout is on either my build thread or my plea for help with 3D printing. I could convert it for other CAD formats, and you could push it to your dimensions...

Thanks Tom. I'll give it a shot here 1st.​

Cone Development

I'll do this "old school". I used the rocket to make the cone template. I cut and taped paper to the rocket, removed the template and transferred it to 11 x 17 paper.​

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Now... to find some suitable cardstock or poster board to make the cone out of.​

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[Blast it Tom!]

Nice! Sheesh, I was at the wrong end! I thought you were doing the nose cone!

 

[lakeroadster]

Internal Nose Cone Support / Recovery Anchor

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[Daddyisabar]

It's like watching the old PBS show Live From Off Center. It can get a little weird, but in a good way.

In my best Bob Uecker voice: "Just a bit off center!"

 

[lakeroadster]

Nose Cone Hub

I turned the nose cone hub from a scrap piece of a Southern Yellow Pine 4 x 4. Then cut the 22-1/2 degree angle with my chop saw, and drilled the 1" dia. hole.​

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I mocked up the upper tubes and the cone hub to check the fit.​

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[Capt. Eric]

And I thought I built a heavy rocket!
I hope that wooden sculpture gets off the ground! But I get what you're shooting for, and it looks good. Good luck with it.

 

[ljwilley]

This rocket is coming along great! I hope it works!

 

[lakeroadster]

And I thought I built a heavy rocket!
I hope that wooden sculpture gets off the ground! But I get what you're shooting for, and it looks good. Good luck with it.

LOL... Open Rocket... Use It.​

 

[Blast it Tom!]

And I thought I built a heavy rocket!
I hope that wooden sculpture gets off the ground! But I get what you're shooting for, and it looks good. Good luck with it.

You see the by-line under his avatar, right?! Now I gotta find the fellow's who says "Push anything hard enough and it will fly!"

It's a beauty so far...

 

[teepot]

It's going to fly great. I have confidence.

 

[jqavins]

It's going to fly great. I have confidence.

I have more than a reasonable home. Basic expectation. A good feeling. But confidence? I'm afraid not. It'll be a good show no matter what. It's a(nother) great build.

 

[lakeroadster]

Now I gotta find the fellow's who says "Push anything hard enough and it will fly!"

Sure. But it's the straight "up" trajectory and successful undamaged recovery that's the tricky part. ​

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[OverTheTop]

I'm curious to see if it flies straight in the sims .

 

[Daddyisabar]

I'm curious to see if it flies straight in the sims .

Easy. Just input all the atmospheric factors acting on the slightly off center nose cone through out the boost and glide. Toss in some asymmetric drag and a few base drag hacks and waala...perfect simulated safety assurance!

Like the old Master told me. Thrust and nose weight are not to be used as a crutch to overcome poor rocket design! DO THE MATH!

No need for a Butlerian Jihad, just trust the Machines!

 

[lakeroadster]

Upper Body Segments

Kind of hard to see, but yesterday I used Gorilla Wood Glue to coat the inside of the intermediate upper body tube to Lower body tube joint.​

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I then cut some masking tape down to 3/16" wide and wrapped it around the 1" dowel. This allows the hub to sit on the tape. I applied some Gorilla Wood Glue into the bore of the hub, and then inverted it onto the dowel. The tape keeps the glue from running down the dowel, yet while the glue was still "fresh" I could rotated it to get optimal fit of the upper body tube.​

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The upper body tube is removable at this point so I can get a good glue joint of the hub to the dowel.​

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[lakeroadster]

Upper Body Tube

I placed a glue fillet on the hub and let that dry a bit. Then, slathered some Gorilla Wood Glue on the O.D. of the hub and then slid the upper tube in place... secured with a thumbtack.​

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Then I injected some more wood glue into the access opening I punched into the tube and spent the next couple hours slowly rotating the rocket to coat the inside of the joint. There's really almost no loading on this joint due to the internal dowel.​

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There's a major snow storm that just arrived... just about 5:00 pm. We'll see how much we get. They are saying epic proportions.​

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[Capt. Eric]

Today's Far Side calendar looks familiar.

 

[lakeroadster]

Today's Far Side calendar looks familiar.

Well look at that. Perfect timing. Thanks. ​

 

[lakeroadster]

Launch Lug

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[Blast it Tom!]

Launch Lug

View attachment 635879 View attachment 635880​

Ah! Internal! I like it! I was considering the same for my ACME Spitfire, but it wouldn't work on that design unless it went all the way through the nosecone.

 

[Rob Campbell]

Launch Lug

View attachment 635879 View attachment 635880​

Gary Larson is proud of you.

 

[BABAR]

I'm curious to see if it flies straight in the sims .

Do sims tell that? I figured they were good for stability, acceleration, altitude, but didn’t know they would predict corkscrewing.

 

[OverTheTop]

I guess it depends on the fidelity of the sim. Not sure how good RS or OR are regarding 6dof.

 

[Blast it Tom!]

I guess it depends on the fidelity of the sim. Not sure how good RS or OR are regarding 6dof.

I don't think either consider a geometry such as this and the possible trajectory effects.

 

[jqavins]

I guess it depends on the fidelity of the sim. Not sure how good RS or OR are regarding 6dof.

I don't know about OR. RS does 3DOF: altitude, up/down range distance, and pitch/yaw, which are the same thing for a simple rocket. Apogee had, or had, a product called RS Pro that does 6DOF, but they want $1000 for it. I wonder if they've ever sold one copy.

 

[lakeroadster]

I don't know about OR. RS does 3DOF: altitude, up/down range distance, and pitch/yaw, which are the same thing for a simple rocket. Apogee had, or had, a product called RS Pro that does 6DOF, but they want $1000 for it. I wonder if they've ever sold one copy.

Do sims tell that? I figured they were good for stability, acceleration, altitude, but didn’t know they would predict corkscrewing.

I guess it depends on the fidelity of the sim. Not sure how good RS or OR are regarding 6dof.

There's no way in Open Rocket to make the nose cone "askew". I offset the nose cone hub to reflect the offset CG.​

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At some point you just simulate what you can... do a swing test... and then just launch it.​

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