So you want to do your first scratch build.

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Well-Known Member
TRF Supporter
As someone that has just gone through it and is still going through it, I have some words of advice.
First off, by scratch build, I just mean you aren't using a kit.
If you are doing it to save money, you are doing it for the wrong reason. The owner of Apogee components is going to be able to retire on what I've spent there.
In my opinion, there are only two really legitimate reasons to start scratch building.
1-you get satisfaction out of designing what you launch.
2-you plan on going on to enter competitions or go for records, even if only personal records.

Before you buy a single piece of building material, build at leas one kit.
Read up on design and construction.
Get Open Rocket, learn how to use it and design several complete rockets.
Check out your suppliers and see what parts are available for the different sizes. You will have the greatest choice for 18mmm motors and 24mm body tubes. Your options for some sizes are very limited.
Consider your goals. If you want to break the sound barrier or reach a mile in altitude, an 18mm motor isn't going to do it. If you just want to have fun on the cheap, 18mm, or even 13mm, is the way to go.
Consider where you will be launching. If you will be launching on the local baseball diamond, probably a huge rocket with a huge motor isn't a good idea.
Pick one or two motor and body tube sizes and stick to them. Every time you change motor or body size, it's going to cost you. But if having a bunch of different size rockets is what floats your boat, that's great, but expect to spend a lot of money.
This can be a pretty inexpensive hobby, but the costs can add up fast, if you aren't smart about it.
There are a lot of good companies out there. When buying Estes products, I usually buy it from them. Almost everything else I get from Apogee components. I've gotten good service and I can get everything else I need from them. They are also a great source of information. A lot of people use Balsa Machining, but every time I go to their site I get a warning that it isn't secure.

rklapp

NAR# 109557
TRF Supporter
I bought rocket plans from Uncle Mikes and they’re horrible. If you'd like, I can send them to you.

Old School Doug

Stan!! I told you....NEVER push the red button!
As someone that has just gone through it and is still going through it, I have some words of advice.
First off, by scratch build, I just mean you aren't using a kit.
If you are doing it to save money, you are doing it for the wrong reason. The owner of Apogee components is going to be able to retire on what I've spent there.
In my opinion, there are only two really legitimate reasons to start scratch building.
1-you get satisfaction out of designing what you launch.
2-you plan on going on to enter competitions or go for records, even if only personal records.

Before you buy a single piece of building material, build at leas one kit.
Read up on design and construction.
Get Open Rocket, learn how to use it and design several complete rockets.
Check out your suppliers and see what parts are available for the different sizes. You will have the greatest choice for 18mmm motors and 24mm body tubes. Your options for some sizes are very limited.
Consider your goals. If you want to break the sound barrier or reach a mile in altitude, an 18mm motor isn't going to do it. If you just want to have fun on the cheap, 18mm, or even 13mm, is the way to go.
Consider where you will be launching. If you will be launching on the local baseball diamond, probably a huge rocket with a huge motor isn't a good idea.
Pick one or two motor and body tube sizes and stick to them. Every time you change motor or body size, it's going to cost you. But if having a bunch of different size rockets is what floats your boat, that's great, but expect to spend a lot of money.
This can be a pretty inexpensive hobby, but the costs can add up fast, if you aren't smart about it.
There are a lot of good companies out there. When buying Estes products, I usually buy it from them. Almost everything else I get from Apogee components. I've gotten good service and I can get everything else I need from them. They are also a great source of information. A lot of people use Balsa Machining, but every time I go to their site I get a warning that it isn't secure.
All good points but two in particular stand out.

Scratch building is definitely not for the faint of budget. Although if you plan accordingly and buy in sufficient quantity, the cost per build can get pretty close to kit costs depending on who you order from (specifically as it relates to LPR and MPR builds as those are my areas of experience so far).

OpenRocket is a must have. It's a great free tool and gives you sufficient data to minimize the possibility of an unstable design.

As a side note, I've had the same security warning on the Balsa Machining (BMS) site. While researching it I found that there's a "security certificate" that's out of date and that's what generates the warning. I believe it's an issue with their web hosting company and not with BMS itself. I've ordered from them numerous times this year and have never had a problem. Not taking anything away from Tim Van M and Apogee components. While their pricing is a bit higher than others, there is a huge level of value added due to the newsletters, educational articles, and videos he provides. I too have contributed to the "Apogee retirement fund" on a regular basis!

Well-Known Member
TRF Supporter
I bought rocket plans from Uncle Mikes and they’re horrible. If you'd like, I can send them to you.
No thank you, I can make my own horrible plans, and have done so.

Well-Known Member
TRF Supporter
All good points but two in particular stand out.

Scratch building is definitely not for the faint of budget. Although if you plan accordingly and buy in sufficient quantity, the cost per build can get pretty close to kit costs depending on who you order from (specifically as it relates to LPR and MPR builds as those are my areas of experience so far).

OpenRocket is a must have. It's a great free tool and gives you sufficient data to minimize the possibility of an unstable design.

As a side note, I've had the same security warning on the Balsa Machining (BMS) site. While researching it I found that there's a "security certificate" that's out of date and that's what generates the warning. I believe it's an issue with their web hosting company and not with BMS itself. I've ordered from them numerous times this year and have never had a problem. Not taking anything away from Tim Van M and Apogee components. While their pricing is a bit higher than others, there is a huge level of value added due to the newsletters, educational articles, and videos he provides. I too have contributed to the "Apogee retirement fund" on a regular basis!
That had occurred to me. Good to know as they are cheap.

Well-Known Member
TRF Supporter
Here's my most recent debacle: when I ordered parts for my first rocket I decided to use the screw cap type engine retainers.
The ones for 18mm motors work perfectly with 24mm body tubes.
When I decided to move up to 24mm motors and 33mm body tubes I ordered the appropriate retainers. Yesterday, I finally got around to making motor mounts for the 33mm bodies and discovered that the 24mm engine retainers have a larger outside diameter than than the 33mm body. I was able to sand one down till there was a smoother transition, but it was a lot of work and they will never work for the 29mm rockets I ordered parts for. It never occurred to me to check the outside diameter of the retainer. I just assumed they'd fit. So I ended up placing another order to try and fix the situation. It never seems to end.

Nytrunner

Pop lugs, not drugs
24mm retainers go well with BT-60 tubes (~40mm I think)

29mm retainers go well with 2" tubes

mbeels

Yes balsa
TRF Supporter
Yesterday, I finally got around to making motor mounts for the 33mm bodies and discovered that the 24mm engine retainers have a larger outside diameter than than the 33mm body. I was able to sand one down till there was a smoother transition, but it was a lot of work and they will never work for the 29mm rockets I ordered parts for. It never occurred to me to check the outside diameter of the retainer.
Can you extend the motor tube further aft, so the retainer sits behind the body tube?

dr wogz

Fly caster
I prefer the old metal clip retainers. lighter, and self contained: nothing to loose (or break)

And I assume cheaper..

neil_w

Hunkered down and slowly going crazy
TRF Supporter
24mm retainers go well with BT-60 tubes (~40mm I think)
Closer to 42mm. But in general, no one refers to low-power body tubes by mm measurements.

33mm -> BT55
42mm -> BT60
24mm -> BT50

etc.

(this is not directed at you @Nytrunner)

neil_w

Hunkered down and slowly going crazy
TRF Supporter
I prefer the old metal clip retainers. lighter, and self contained: nothing to loose (or break)
Well, the screw-retainers are nice to work with, and very secure. But I agree, probably overkill for 18mm, borderline for 24mm.

Charles_McG

Ciderwright
Well, the screw-retainers are nice to work with, and very secure. But I agree, probably overkill for 18mm, borderline for 24mm.
Which is why I like to print them for 13mm

That and I have religious issues with motor blocks - even at 13mm motors. Because the 13mm Centuri M motors are over-long for clips. So it's a tape thrust ring and screw on retainer. And a couple grams of nose weight to offset.

boatgeek

Well-Known Member
...
If you are doing it to save money, you are doing it for the wrong reason. The owner of Apogee components is going to be able to retire on what I've spent there.
...
This can be a pretty inexpensive hobby, but the costs can add up fast, if you aren't smart about it.
All good points but two in particular stand out.

Scratch building is definitely not for the faint of budget. Although if you plan accordingly and buy in sufficient quantity, the cost per build can get pretty close to kit costs depending on who you order from (specifically as it relates to LPR and MPR builds as those are my areas of experience so far).
...

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gna

average joe-overbuild member
It doesn't have to be expensive. I recommend BMS. If you use Open Rocket, their body tubes are in the database. I wanted to "clone" some designs, so I guess that counts, but my first scratchbuilds and designs were built around nosecones. My LHS was getting rid of stock so I got many balsa nosecones for cheap.

Engine hooks are from wiper blade steel I picked out of the trash, per hcmbanjo. Centering rings I cut from mattboard. Someone gave me a pile of cut offs from a framing shop, so I've got lots. An Olfa circle cutter really helps.

Other supplies were given to me--I've been at club launches where someone will show up and give away a bunch of old rockets and parts because they left the hobby/only fly high power/their kid left it behind.

It's fun seeing something you designed and built fly.

Alan R

Well-Known Member
I scratch build sometimes because I have a cool idea, and want to go through the creative and engineering process to make it real.. Mai Hai Tai, Spudnik, and now 3Cubed.
Building lots of pre-packaged kits means I learned most of what I need to know about construction and feel confident to put one together starting with nothing more than some kraft paper.
Its more of an artistic endeavor than anything. Just to see if it can be done. Plus I'm semi-retired and have lots of time to play with things.
Those I linked are all (almost) complete scratch builds. That means I made my own body tubes, CR's, etc. Fine for low power stuff. Pretty sure i wouldn't skimp on CR's and engine tubes for 29mm+ though. Although 3Cubed is going to need a home-rolled 24mm engine tube. Just because I don't happen to have one laying around.
And hey @neil_w ... I have no idea what size a BT50 is either. What I do know is I need a an 18mm engine tube, or a 24mm engine tube, or I want a 2.6" body tube, etc.

rklapp

NAR# 109557
TRF Supporter
i'll second that: why bad? which ones? curious more than anything.. (I draw plans / drawings for a living, so I am 'professionally' curious also!)
Too much exposition and not enough drawings. Plus there’s no reason why they couldn’t be downloaded and save me the shipping cost. They look like it was printed on a lithograph.

dr wogz

Fly caster
RKLAPP, not sure what you mean by "exposition"?

I believe Mike has had the drawings for years, and never got around to digitizing them.

What's wrong with a lithograph print? I would assume they would be more accurate than a photocopy.. (unless you mean something else?) Drawings rarely go thru a lithograph process, that's more for art work prints..

can you post a pic of the plans / drawings?

neil_w

Hunkered down and slowly going crazy
TRF Supporter
And hey @neil_w ... I have no idea what size a BT50 is either. What I do know is I need a an 18mm engine tube, or a 24mm engine tube, or I want a 2.6" body tube, etc.
You are free to go by whatever dimensioning system works for you. However, if you work in the LPR realm, then knowing and using standard BT designations is useful, both for communicating with others (more people will immediately know what you mean by "BT55" than "33mm") and also when purchasing parts. It is simply a convention.

Here's a snippet from the Balsa Machining centering rings product page:

I know that BT20 is an 18mm motor mount, and that I want to fit one into a BT55. So I go and order a CR2055. You can certainly go through all the decimal measurements if you like, but to me that's a lot harder. Likewise, nose cone designs are typically named by BT designations (PNC50Y or BNC60AH).

There are only 7 common BT designations to learn, which will cover 95% of LPR building. Then there are a bunch of oddballs, which I usually have to go look up.

Again: this is simply a naming convention in LPR that most people use.

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Alan R

Well-Known Member
I know that BT20 is an 18mm motor mount
I know a BT20 is 18mm, and a BT50 is 24mm. I've known those since my teenage rocket days. That's about the end of it though.
As for the metric measurements, that comes from Open Rocket (body tube database is listed in metric sizes) as well as designing rocket parts for 3D printing which all has to be done in metric measurements. That's because of the design software and tight tolerances required.
Just the way it is for me now. I can roughly calculate metric to inches in my head, but not metric to standard BT sizes.
As for CR's ... if it's not in a kit, I'm cutting my own from OR patterns. Standard sizing doesn't matter.

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