Jr. L1 Cert Build Thread/ Intro.

Hi all,
I have finally started receiving parts for my build, so I figured I'd post this thread/ intro.

This will only be my second build thread so bear with me. I'll also be working around my high school schedule so it might be a bit slow for some people's taste. sorry in advance.

The rocket (name open to suggestions, paint scheme still in the works) will be LOC 4" tubing, with a 4" payload section to extend it, and for any payload type things I might eventually put in, It will be 57 in. tall. I could give you all the specs, but Here's an OR file:View attachment junior level one rocket.ork.

Here is the MMT (which is also LOC; 29mm Motor mount tube) that arrived today. It will be cut shorter obviously, but will still have a bit of a "stuffer tube" since I won't have any extra black powder, so whatever comes with the motor is what I'll be using:

I'll be using these nice Estes retainers I got on sale for $6 for a two pack:

I'll be using a quick link and swivel from my local hardware store:

The fins will be made from 1/8 plywood, and will be TTW using LOC's pre-cut airframe tubing: (not sure why this one is upside down )

The CRs will be made from some 3/16 (or maybe 1/4 in. plywood) my dad had laying around in his wood shop using a drill press and a circle cutty thing (I think that's the technical term...) We've done some test cuts and it should work okay.
please pardon the thumbnail at the bottom
can't figure out how to remove it.

Here's one of the CR blanks with shock cord and U bolt attached: I was planning on making this setup the upper CR, but IDK if this is SOP or if the cord is usually mounted lower
suggestions on this?

The Shock cord is 20 ft. of 1/2 in. tubular nylon that Ted Chernok so generously gave me for this project:
The rocket will also have a 12X12" nomex chute protector, a 36 or 60" nomex shock cord protector, a standard 4:1 ogive NC, and will probably cert on an H128 or H165more build stuff will come probably over the weekend or when more stuff arrives

Nate

Looks like your doing fine . The Estes retainers are good , great at 6 for 4 of them . I use a dremel with the circle cutter . I would use 1/4 ply
But that's me .

So far so good. It looks like you have things well in hand. My only suggestion would be, put a 38mm MMT in it. There are many good reasons for putting a 29mm MMT in a L1 rocket, but it does limit you to the lower half of the L1 range of motors. A 38mm MMT will allow you to fly the full range of L1 motors.

Nate,,,,
It looks like you've got the bases covered........
Let me know if there's anything I can do to help........

Teddy

Handeman said:

So far so good. It looks like you have things well in hand. My only suggestion would be, put a 38mm MMT in it. There are many good reasons for putting a 29mm MMT in a L1 rocket, but it does limit you to the lower half of the L1 range of motors. A 38mm MMT will allow you to fly the full range of L1 motors.

Click to expand...

For a rocket that size, putting in a 38mm MMt limits you to the upper range of L1 motors, due to the increased weight. Usually.

Yes you are well on your way.. looks like a well thought out build .

I like 38mm for this type of rocket, but 29mm has advantages too - especially on costs.. estes retainer is much cheaper than aeropack, no hazmat on most Aerotech 29mm motor reloads .

I would recommend a nomex shock cord protector for the harness part nearest to the motor mount. They are on rocketchutes.com hut I can't to a direct link to the item. Another alternative is to have a short kevlar harness coming off the mmt and hooking your nylon one to it forward so your chute protector can protect it also. If you do the kevlar you can actually loop it around the mmt and tie off.. then notch your centering ring so it can pass when the mmt assembly is mounted.

I am curious about how much you think this project will weigh when completed and what motor you are thinking of.

Kenny

Looks like you are off to a great start, Nate! I eagerly look forward to your progress, and of course eventually getting to see it fly!

Jim Z

chris m said:

Looks like your doing fine . The Estes retainers are good , great at 6 for 4 of them . I use a dremel with the circle cutter . I would use 1/4 ply
But that's me .

Click to expand...

1/4 ply for the Centering rings?

I'll look into it, so far all the wood for this project has been free, and I think my dad might have some on hand. I'll have to check.
Thanks for the recommendation.

Handeman said:

So far so good. It looks like you have things well in hand. My only suggestion would be, put a 38mm MMT in it. There are many good reasons for putting a 29mm MMT in a L1 rocket, but it does limit you to the lower half of the L1 range of motors. A 38mm MMT will allow you to fly the full range of L1 motors.

Click to expand...

I did seriously consider going 38, but for price's sake, and simplicity's sake I decided to stick with 29mm.
I did notice that there are only so many HPR 29mm motors, but it is what it is.

It's fine if you cert with 29mm , but try to be able to fly the range of motors for 29mm I.e F -I . It's easy to adapt down ,38-29mm

CarVac said:

For a rocket that size, putting in a 38mm MMt limits you to the upper range of L1 motors, due to the increased weight. Usually.

Click to expand...

This is absolutely correct........
With the best of intentions,,,,,
You'll want to build stronger to tolerate the higher impulse,,,,,
Thicker, centering rings, larger motor mount, more epoxy,,,,,
when your done,,,,, the finished product isn't so light anymore
and the smaller H's will no longer lift it.......
I'd have been the first one to tell you "leave your options open,,,
go with a 38mm mount and adapt it down to 29 mm mount"........
I learned this by doing it,,,,,,,,
When you go up a size in motor mount,, you'll go up a bit in weight
and your driving the cost per flight up......

Someone else said to you in another thread and they were right,,,,,,,
by the time the novelty of the HP 29's wears off and you want to fly the 38"s
you'll surely want to build another rocket by then........

Teddy

KenRico said:

Yes you are well on your way.. looks like a well thought out build .

I like 38mm for this type of rocket, but 29mm has advantages too - especially on costs.. estes retainer is much cheaper than aeropack, no hazmat on most Aerotech 29mm motor reloads .

I would recommend a nomex shock cord protector for the harness part nearest to the motor mount. They are on rocketchutes.com hut I can't to a direct link to the item. Another alternative is to have a short kevlar harness coming off the mmt and hooking your nylon one to it forward so your chute protector can protect it also. If you do the kevlar you can actually loop it around the mmt and tie off.. then notch your centering ring so it can pass when the mmt assembly is mounted.

I am curious about how much you think this project will weigh when completed and what motor you are thinking of.

Kenny

Click to expand...

I like the shock cord protector idea; that seems to be the simplest and cheapest method.
If I went with my current U bolt setup, would I make that the upper centering ring? that makes the most sense to me, but I don't know what most people do.

I'm looking at about 36 oz and thinking of an H128 or H165 for the cert flight.

onebadhawk said:

This is absolutely correct........
With the best of intentions,,,,,
You'll want to build stronger to tolerate the higher impulse,,,,,
Thicker, centering rings, larger motor mount, more epoxy,,,,,
when your done,,,,, the finished product isn't so light anymore
and the smaller H's will no longer lift it.......
I'd have been the first one to tell you "leave your options open,,,
go with a 38mm mount and adapt it down to 29 mm mount"........
I learned this by doing it,,,,,,,,
When you go up a size in motor mount,, you'll go up a bit in weight
and your driving the cost per flight up......

Someone else said to you in another thread and they were right,,,,,,,
by the time the novelty of the HP 29's wears off and you want to fly the 38"s
you'll surely want to build another rocket by then........

Teddy

Click to expand...

That makes a lot of sense now. I hadn't fully considered how much extra weight I would end up putting in for 38mm, so it looks like 29mm is still the better option.
I do hope to eventually build my HPR fleet, but it might take a while... at least before I can afford the 38s

JimZNJ said:

Looks like you are off to a great start, Nate! I eagerly look forward to your progress, and of course eventually getting to see it fly!

Jim Z

Click to expand...

Thanks, depending on how the build goes, and how the weather holds out (I've had bad experiences flying in the winter) I might be able to start flying her in October, or I might decide to wait for spring if I don't have it ready then.

Got a bit more work done today. I now have the general shape of the fins cut out. I, or rather my dad, was using a table saw for this, and it seemed to work rather well:

if all goes well, I should be able to use a band saw for the final few cuts, but we'll have to see, I think my dad's 30+ year old saw might be out of commission for a while.

You doing fine. 1/8 ply is fine. You could cert with basswood and it would work. And keep it simple. 29mm are fun and there are a wide variety. Especially CTI. But even that is for later. If you stick with it, you can always get a 38mm casing. People over build. Especially if your launch site is not rock hard. Mine is :y:

Have fun!

gdjsky01 said:

You doing fine. 1/8 ply is fine. You could cert with basswood and it would work. And keep it simple. 29mm are fun and there are a wide variety. Especially CTI. But even that is for later. If you stick with it, you can always get a 38mm casing. People over build. Especially if your launch site is not rock hard. Mine is :y:

Have fun!

Click to expand...

Thanks, It would be cool to eventually step it up to the bigger HPR stuff, but, as you say, that is for later.
Our launch site is (lucky us) a sod field, so I guess it coming in a little fast isn't as much of an issue.
speaking of recovery, what are people's thoughts on rocketchutes.com for High power?
the other option is top flight recovery, but there are some other things I would probably get from rocketchutes, so if I only have to pay shipping once that's better for the budget.

Sorry if you've already mentioned this but have you thought about how you are going to mount the rail buttons? If you are going to provide some wood hard points for the buttons to mount to then you want to make those before installing the motor mount.

JPVegh said:

Sorry if you've already mentioned this but have you thought about how you are going to mount the rail buttons? If you are going to provide some wood hard points for the buttons to mount to then you want to make those before installing the motor mount.

Click to expand...

Nope I haven't mentioned this yet, but I'll be using dog house rocketry rail buttons. I don't know the technical term but they're the ones you put the rubber thingy in and then tighten it so it expands
I Will post a link in a little bit
here's the link:https://doghouse.blastzone.org/DogHouseRocketry/Rail_Buttons.html

:rofl: I thought you were going to wait awhile before you go for JrL1 :rofl:
I knew you'd go for it by years end :wave::w:

JJSR said:

:rofl: I thought you were going to wait awhile before you go for JrL1 :rofl:

Click to expand...

Hmmm... So did I...:lol:
Oh well
With summer fast ending, and I don't like flying in winter, I decided now was the time, and with redarrowhibbies deal on the 28/180 case I think it was a a sign

Nate,
I have plenty of chutes to choose from,,,,,,
you just need a final weight to pick one,,,,,,
and I'm pretty sure I have rail buttons as well........

Don't buy those items,,,,,,,
if you're not coming to the launch on Saturday,,,,,,,,
how can I get this stuff to you ?????????

Teddy

onebadhawk said:

Nate,
I have plenty of chutes to choose from,,,,,,
you just need a final weight to pick one,,,,,,
and I'm pretty sure I have rail buttons as well........

Don't buy those items,,,,,,,
if you're not coming to the launch on Saturday,,,,,,,,
how can I get this stuff to you ?????????

Teddy

Click to expand...

Gosh, Thanks Ted!
I really can't keep taking stuff from you like this...
Do you normally attend the meetings? That could be an opportunity to discuss in person etc.
if not, I might be able to make it out to the launch mostly as a spectator, but it seems pretty unlikely at this point.

Hmmm.... I would have to think about that...

onebadhawk said:

This is absolutely correct........
With the best of intentions,,,,,
You'll want to build stronger to tolerate the higher impulse,,,,,
Thicker, centering rings, larger motor mount, more epoxy,,,,,
when your done,,,,, the finished product isn't so light anymore
and the smaller H's will no longer lift it.......
I'd have been the first one to tell you "leave your options open,,,
go with a 38mm mount and adapt it down to 29 mm mount"........
I learned this by doing it,,,,,,,,
When you go up a size in motor mount,, you'll go up a bit in weight
and your driving the cost per flight up......

Someone else said to you in another thread and they were right,,,,,,,
by the time the novelty of the HP 29's wears off and you want to fly the 38"s
you'll surely want to build another rocket by then........

Teddy

Click to expand...

I agree that using a 29mm for a cert and flying some will get you building a 38mm soon.

I disagree with your assertion that moving from 29mm to 38mm will make it too heavy for small H motor to lift it. The difference between a 38mm and 29mm MMT and any extra epoxy is minimal. In fact the 38mm might be lighter since there's less fin material in the TTW with the larger diameter MMT. The epoxy should be the same since the number and length of the fillets are the same on both size MMT. If you can put a 29mm in the rocket and fly it on a AT H128W (baby H) which has an initial thrust of 35 lbs so you should be able to fly at least a 5 lb rocket, you would have to add 2 lbs or more with the 38mm MMT to make it too heavy. I think that assertion is based on faulty assumptions on how much extra weight would be added when moving up in MMT size.

Handeman said:

I agree that using a 29mm for a cert and flying some will get you building a 38mm soon.

I disagree with your assertion that moving from 29mm to 38mm will make it too heavy for small H motor to lift it. The difference between a 38mm and 29mm MMT and any extra epoxy is minimal. In fact the 38mm might be lighter since there's less fin material in the TTW with the larger diameter MMT. The epoxy should be the same since the number and length of the fillets are the same on both size MMT. If you can put a 29mm in the rocket and fly it on a AT H128W (baby H) which has an initial thrust of 35 lbs so you should be able to fly at least a 5 lb rocket, you would have to add 2 lbs or more with the 38mm MMT to make it too heavy. I think that assertion is based on faulty assumptions on how much extra weight would be added when moving up in MMT size.

Click to expand...

For those people who are.... less-endowed in fins, using a bigger motor may require nose weight.

CarVac said:

For those people who are.... less-endowed in fins, using a bigger motor may require nose weight.

Click to expand...

Very true, but not if you're going to use an adapter and fly the small 29mm. The adapter weight may be a factor, but the way I look at it, if you're scratch building a rocket that has a stability marge that close that a 29mm small H vs a 38mm I motor makes that much difference, your design is very specific and exact and your experience, design, and building skills should make this whole discussion mute.

It's the less experienced ie. L1 cert attempt folks, that can benefit from the discussion about MMT size, weight factors, and trade offs. I just have a problem with someone saying that if you change from a 29mm to 38mm MMT in a specific design, it is going to eliminate the possibility of flying it on low end H motors that you could use with a 29mm MMT. I do not believe that to be accurate. An example would be putting a 38mm MMT in a GForce. That certainly doesn't stop you from flying it on G motors, why would it eliminate small H motors?

Reguarding the motor mount:

*napoleon dynamite voice* Do what your heart tells you. That's what I always do.

Have fun with the build. I hope to see you join the JR cert club pretty soon. We're the best.

Alex

Aksrockets said:

Reguarding the motor mount:

*napoleon dynamite voice* Do what your heart tells you. That's what I always do.

Have fun with the build. I hope to see you join the JR cert club pretty soon. We're the best.

Alex

Click to expand...

Thanks for the good wishes Alex!

nute said:

I like the shock cord protector idea; that seems to be the simplest and cheapest method.
If I went with my current U bolt setup, would I make that the upper centering ring? that makes the most sense to me, but I don't know what most people do.

I'm looking at about 36 oz and thinking of an H128 or H165 for the cert flight.

Click to expand...

Very cool .. if you are buying hardware you may wish to go up to 240 case, you can fly with a spacer with the loads you are eyeing . If price is a consideration the dms H135w is a new alternative.


Kenny