First Time Scaling A Rocket

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Sam Chamelin

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Hey all! Brand new to the forum, but not new to rocketry. However, this quarantine has me rediscovering my enthusiasm for the hobby with my kids:)

I want to build a scaled up version of the old Estes Eclipse. Unless I'm mistaken, the old Eclipse was just a current Estes Yankee with a different color/decal scheme. So two questions:

1. Is that true?
2. Does anyone have plans for a scaled up Yankee that I could use?

Looking forward to hanging out with y'all:)
 

Bruiser

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You can go here https://www.oldrocketplans.com/estes/est0846/est0846.pdf to see what was used in the original rocket and scale that up for your new rocket. What size were you thinking of scaling it to?

Have you downloaded OpenRocket yet? It is a good tool to use to make sure your scaled rocket will fly well and it'll tell you what kind of performance to expect. It can also be used to help pick which engines to fly on.

-Bob
 

Sam Chamelin

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You can go here https://www.oldrocketplans.com/estes/est0846/est0846.pdf to see what was used in the original rocket and scale that up for your new rocket. What size were you thinking of scaling it to?

Have you downloaded OpenRocket yet? It is a good tool to use to make sure your scaled rocket will fly well and it'll tell you what kind of performance to expect. It can also be used to help pick which engines to fly on.

-Bob
Thank you so much for the reply!

Yes, I've downloaded the plans, but I wasn't aware of OpenRocket, so that's a great tool, thank you! I'm looking to upgrade it from a mini to an A/B/C model. The original model is a BT-20B body tube, and I want to size up to a BT-50. But I'm not sure how to scale the other parts - nose cone and fins mostly. So I'm looking for some help on how to do that.
 

neil_w

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OpenRocket will do all the scaling for you. Enter in the original design in its original size, then go to Edit -> Scale.... After it's done, you'll need to adjust everything but it gets you started.

Entering a design like the Eclipse is quite easy, and a good exercise in learning how to use OpenRocket. If you need help, just ask.
 

Bruiser

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neil_w knows his way around OpenRocket very well so if one of us can't help he surely can.

I've scratch built several rockets and I find it is more cost-efficient to buy a kit that has everything you need. It usually ends up costing less than buying everything individually and you have some spare parts left over :) This is especially true if you can buy the kit local (like at Hobby Lobby) but I realize that is impossible at this point in time with Hobby Lobby and hobby shops in general being closed.

You can still order though so I did a little research. The only kit I found using a BT-50 body tube that seems long enough is the Estes Multi-Roc. The only thing is the fin material. I am not sure you would be able to use the material that comes with the kit for your fins.

If you want to upsize just a little more, the Estes Nike-X is a prime candidate for a donor. It uses a BT-55 body tube that is long enough and you would need some fin stock. You can not use the fins that come in the kit as they are to small to turn into Eclipse fins.

If you want to order the parts separately there are many places to do so. eRockets has a huge selection; AC Supply has excellent prices (and blasa stock). There is also Jon Rocket and so many others I could go on and on.

When you order your rocket parts consider ordering some engines, wadding and such at the same time to save on shipping

Oh, and I didn't answer question one in your original post. I don't think the Eclipse and the Yankee are the same. The fins look like they might be but the nose cone is different.

-Bob
 

Bruiser

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Did you download OpenRocket yet? You'll need it to open the attached file of a BT55 sized Eclipse. I used the nose cone from the Nike X. The fins were the hardest because of the orientation. I had to draw them out then get the measurements in the directs the program wants them.

There are three tabs at the top. One for the rocket design, one for the motor info and one for flight simulations. I loaded up a few of the probable motors you would use and you can see the flight data.

Anyway, you can play with the design and see how little changes here and there affect the cg and center of pressure. Let me know if you have any questions and I'll try to help.

-Bob
 

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Sam Chamelin

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OpenRocket will do all the scaling for you. Enter in the original design in its original size, then go to Edit -> Scale.... After it's done, you'll need to adjust everything but it gets you started.

Entering a design like the Eclipse is quite easy, and a good exercise in learning how to use OpenRocket. If you need help, just ask.
I'll probably need help, thank you. How would you like to do that?
 

Sam Chamelin

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This is easily the nicest, most helpful forum I've ever been on...thanks so much y'all! And keep it coming:)
 

Nytrunner

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This is easily the nicest, most helpful forum I've ever been on...thanks so much y'all! And keep it coming:)
Ahahahahahahhahaaaaaa
This one has not been around here very long

In all seriousness, yes this forum is very helpful. You can learn stuff and techniques from others even if you've been doing high-power for years, and folks are generally friendly.
We have our Characters, and occasionally a discussion hits a nerve, but there are definitely worse corners of the internet than this one.
 

neil_w

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I'll probably need help, thank you. How would you like to do that?
Not sure what you're asking here, please clarify.

If you like, start with the file that Bruiser posted above. Adjust the fin size ('cuz they are too big), and then try scaling the rocket as I described above. To scale from BT55 to BT50, set the scaling factor as "From 1.33 to .976". After you're done, change the fin thickness to something reasonable (probably 3/32" or .093"), make sure the body tube wall thickness is set correctly, and swap in a commercially available nose cone that is close to the right size and shape. You've finished the first steps.

Then add motor mount and launch lugs as needed.

Alternate approach: enter the rocket from scratch, in the original BT-50 size. Use the plans from JimZ as a reference: https://plans.rocketshoppe.com/estes/est0846/est0846.htm. Then scale up to BT50 size, and make all the adjustments described above.

Note that Mark Hayes has vinyl available for this rocket: https://stickershock23.com/product/estes-eclipse/. If you're gonna stick with the stock white-on-black color scheme, you're not going be able to do it (at least not easily) with self-printed decals, so vinyl would be a good way to go, and it's pretty cheap for a BT50-sized rocket.
 

Sam Chamelin

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Awesome, thank you! So how do you "scale up" in the program? I've got the file, and I've messed around in the program a bit, but I'm afraid to do anything without knowing what I'm doing:). Where is the "scaling factor?"

I appreciate the help a lot! And by the way, I already bought the vinyl from Mark - very excited:)
 

neil_w

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Don't be "afraid" to do anything, as long as you have saved your file (and make a separate copy, if you're really nervous) you're OK. You can only learn by trying stuff.

Here's the "Scale design" dialog (accessed from Edit -> Scale...)
upload_2020-4-5_9-19-38.png


You can either use the percentage to scale (easy when you want to do an even multiple, like 200% or whatever), or use the "Scale from ... to..." to map one body tube size to another. It'll fill in automatically the body tube diameter of the design you're working on.

So, to scale up from BT20 (shown) to BT50, you would put the diameter of a BT50 (.976") into the "to" field, then click "Scale".

After this is done your design will be a perfect scale-up. But since most standard parts don't scale that way, you'll need to go and clean up lots of things, like replace the nose cone with a commercially available one, fix the wall thicknesses of all the tubes, fix the motor mount diameter body tube (if you've put on in your model), fin thickness, centering ring thickness, etc. The important thing you get from the scaling operation is that all exterior dimensions including fins are perfectly scaled up; the rest is up to you.
 

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Sam Chamelin

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Don't be "afraid" to do anything, as long as you have saved your file (and make a separate copy, if you're really nervous) you're OK. You can only learn by trying stuff.

Here's the "Scale design" dialog (accessed from Edit -> Scale...)
View attachment 411399

You can either use the percentage to scale (easy when you want to do an even multiple, like 200% or whatever), or use the "Scale from ... to..." to map one body tube size to another. It'll fill in automatically the body tube diameter of the design you're working on.

So, to scale up from BT20 (shown) to BT50, you would put the diameter of a BT50 (.976") into the "to" field, then click "Scale".

After this is done your design will be a perfect scale-up. But since most standard parts don't scale that way, you'll need to go and clean up lots of things, like replace the nose cone with a commercially available one, fix the wall thicknesses of all the tubes, fix the motor mount diameter body tube (if you've put on in your model), fin thickness, centering ring thickness, etc. The important thing you get from the scaling operation is that all exterior dimensions including fins are perfectly scaled up; the rest is up to you.
I JUST came on here to ask about this, thank you so much. This is absolutely fabulous. Thanks again.
 
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