N3TJM Level 3 Build (Certify With Us)

[n3tjm]

First of all I want to thank everyone involved with the "Certify with US!" program. Kevin and Jeroen are awesome guys who didn't have to do this .

During my Christmas Vacation, I stopped by Jack Caynon's house to pick up a Performance Rocketry 7.5" Patriot kit. It turned out not to be 100% the original kit. He had used some parts for other projects. He used the 4" motor tube in another project so he gave me a new tube which I may trim down to a shorter size. Another thing I may have to do is replace the Tube Coupler. I don't think this coupler is the original length. It's approximately 7" long. I'm not sure that is wise to a coupler that short. The sections will be bolted and sheer pined together. Comments?

He gave me a few extra parts which I may or may not incorporate. Extra Centering rings and bulkheads, and parts of an old e-bay.

To save costs I will be using as much stuff I have on hand. Altimeters will be borrowed from the Ladyrobin and Super Magnum. A while back I purchased a 15 foot military chute. That is what I plan to use for recovery.

Robert DeHate is my L3CC.

I plan to fly this with a CTI N1800 (98mm 4Grain White). I'm aiming for Red Glare XIV although there is a scheduling conflict with my Girlfriend. I would like to attend all three days. But she may not be able to take the Friday off, and Sunday most likely wont work for her. Right after Red Glare, we are headed up to NH to visit my parents. And she may decide she does not want to go. And if she decides not to go at all, I may decide to leave for NH on Saturday. So if not at Red Glare, I may launch it at a later MDRA launch.

 

[jus_rockets]

Congrats on getting chosen, and Good luck on you L3!

 

[chadrog]

Congratulations, sounds like a solid plan. I love big patriots. By rule of thumb, that coupler should be twice that length.

 

[MasonH]

This is gonna be cool!

 

[n3tjm]

Does anyone know if a PML 7.5" Coupler tube will work with Performance Rocketry 7.5" fiberglass tubes?

 

[patelldp]

Measure your coupler, then go on to PML's website and look at their dimensions.

 

[Mightyrocketman]

Theses are the dimensions of a Performance Rocketry G10 coupler ID 7.330 OD 7.516 7.5 Inch Coupler 16 Inch
and the PML is Phenolic Coupler Tube ID 7.35" wall thickness 0.080".
Performance Hobbies has a Performance Rocketry 7.5" coupler on their website but it is $100. That is a little cheaper than the G12 performance rocketry coupler on the Wildman site.

 

[Pantherjon]

Does anyone know if a PML 7.5" Coupler tube will work with Performance Rocketry 7.5" fiberglass tubes?

Possibly..Although, PML lists the coupler as being only 12" in length..Personally I would e-mail Rocketry Warehouse and see if they have any 7.5" fiberglass couplers.They list the 7.5" airframe on the site but no coupler that I could find..I would be a little leery of using a phenolic coupler in a fiberglass rocket- would rather use a fiberglass coupler in a fiberglass rocket..But that is just my :2:

 

[Scott Evil]

Think dissimilar materials and all the QT vs. Phenolic Piston threads we've seen. Couplers could behave the same way. Not something I would want to chance considering the dimensions.

The filament wound PR couplers I have took a little elbow grease and scotchbrite to get them to tightly fit in and out of it's big brother 7.5" tubing.

If you're in a bind, let me know and I'll get a PR coupler to ya. (PM me)

-S

 

[bandman444]

You could try posting a wanted thread see if someone could sell you one cheaper. I wouldn't use a 7in long coupler.

 

[patelldp]

I agree. Buy a new coupler. I don't see an issue with a PML coupler, as long as you apply some glass on the inside of it. My experience shows that the FG tubing isn't susceptible to the same expansion/contraction of Blue Tube or Quantum tube. Get the Phenolic coupler to fit once and you should be fine.

Use that coupler you received with the kit as a depth stop for the coupler that you buy. Basically figure out the depth that you want the coupler at in the upper tube (most likely 50/50), apply some epoxy inside of the upper tube just above that depth, and push in the short coupler with your new coupler. That will eliminate the need for a switch band (a BEAR to cut on these larger tubes). I've done this with my Intimidator 3 and it worked like a charm.

YMMV.

 

[Coop]

I plan to fly this with a CTI N1800 (98mm 4Grain White). I'm aiming for Red Glare XIV ....

OUTSTANDING! Am very much looking forward to this and hope to get to see it fly!

Congratulations on being selected for this opportunity--will be following this build for sure!



Later!

--Coop

 

[n3tjm]

Measure your coupler, then go on to PML's website and look at their dimensions.

I don't have anything to accurately measure a tube that size. A ruler or a tape measure won't be as accurate as a caliper. Also I was at work so I didn't have time to try to find the dimensions although I did think about that after I posted

 

[n3tjm]

I agree. Buy a new coupler. I don't see an issue with a PML coupler, as long as you apply some glass on the inside of it. My experience shows that the FG tubing isn't susceptible to the same expansion/contraction of Blue Tube or Quantum tube. Get the Phenolic coupler to fit once and you should be fine.

Use that coupler you received with the kit as a depth stop for the coupler that you buy. Basically figure out the depth that you want the coupler at in the upper tube (most likely 50/50), apply some epoxy inside of the upper tube just above that depth, and push in the short coupler with your new coupler. That will eliminate the need for a switch band (a BEAR to cut on these larger tubes). I've done this with my Intimidator 3 and it worked like a charm.

YMMV.

$100 for a new coupler is a bit steep for me right now. So I am looking at all the options. I was thinking of glassing the pml tube coupler, but I have concerns that 12" may be to short, especially since I like my couplers to have an external "Switch" band.

I am intrigued how you say a depth stop will eliminate the need for a switch band? Do you have a thread about your Intimidator 3 build where I can see what you did?

 

[patelldp]

Do you have a thread about your Intimidator 3 build where I can see what you did?

I do not, but I can take pictures later. On my Competitor 5, I do not have a switch band or a depth stop. The bay is held in with 3x 10-24 bolts and I have never had a problem in its 6 flights.

 

[n3tjm]

Looky Looky what Scott Evil offered to send me

 

[patelldp]

Appears you're all set. Looking forward to this build, and hopefully seeing it fly at RG.

 

[Pantherjon]

That is awesome of Scott! Though it does kind of tarnish his 'Evil' moniker!..LOL

 

[n3tjm]

Well, now that the GF seems to be getting better I was able to spend a little time with Rocksim and do some initial planning.

This here will be the basic layout of the rocket.

I will be starting the fin can section first. After that is built, I will move onto the electronics bay and the nose cone.


Questions:
What should I use for sheer pins and how many? All my previous rockets used 4-40 nylon screws. Would this be adequate or should I use a heavier gauge?

How do I attach the bulkhead inside the nosecone. The bulkhead is only a half inch thick. Not much room to bolt it down?

Do I want to use a drogue chute? My previous Dual Deploy rockets are usually drogue-less. If I do want a drogue chute, what type of chute and what size?

 

[n3tjm]

Here is the screen shot of the initial sim with a CTI N1800. More sims will be down when I actually know the final weights, length, and balance points.

 

[n3tjm]

And Here is an idea what the paint scheme will look like

 

[patelldp]

Wow, naming the rocket after the girlfriend. That's serious.

 

[kandsrockets]

Questions:
What should I use for sheer pins and how many? All my previous rockets used 4-40 nylon screws. Would this be adequate or should I use a heavier gauge?

How do I attach the bulkhead inside the nosecone. The bulkhead is only a half inch thick. Not much room to bolt it down?

Do I want to use a drogue chute? My previous Dual Deploy rockets are usually drogue-less. If I do want a drogue chute, what type of chute and what size?

For the bulkhead in the nosecone. Epoxy it in leaving a 1/4 to 3/8" of a lip below the bulkhead to do a nice fillet around the edge. Then you can counter sink #4 x 3/4" wood screws through the side of the nose cone into the bulkhead. I would use 8 to 10 of them. The bulkhead will not go anywhere once done.

On a rocket this size I would use a drogue and size the drogue to keep the rocket around 70 fps.

 

[troj]

Questions:
What should I use for sheer pins and how many? All my previous rockets used 4-40 nylon screws. Would this be adequate or should I use a heavier gauge?

4-40 is plenty

How do I attach the bulkhead inside the nosecone. The bulkhead is only a half inch thick. Not much room to bolt it down?

Your diagram says "payload" in the nosecone -- I assume so you can add a tracker, etc? What I do is put washers & nuts on the end of a piece of all-thread that's long enough to run from the tip back up to the shoulder. I then epoxy it into the tip of the nose. Next a bulkhead gets epoxied 3 to 4 inches deep inside the shoulder, as well as nuts & washers tying it to the allthread. I then put one or two 38mm motor mount tubes on that bulkhead, cut short enough that I can fit the final bulkhead inside the coupler.

If you look at this thread, you can see how I did it. In that thread, I have a metal tip nosecone; I do it the same way, whether metal tip or standard gelcoat nosecones.

Do I want to use a drogue chute? My previous Dual Deploy rockets are usually drogue-less. If I do want a drogue chute, what type of chute and what size?

I'm not a fan of drogueless; if it were me, I'd use an 18" - 24" drogue.

-Kevin

 

[kandsrockets]

If you are looking to have a tracker bay in the nose you could do like I did with my L3. Pictures below.

 

[n3tjm]

Your diagram says "payload" in the nosecone -- I assume so you can add a tracker, etc? What I do is put washers & nuts on the end of a piece of all-thread that's long enough to run from the tip back up to the shoulder. I then epoxy it into the tip of the nose. Next a bulkhead gets epoxied 3 to 4 inches deep inside the shoulder, as well as nuts & washers tying it to the allthread. I then put one or two 38mm motor mount tubes on that bulkhead, cut short enough that I can fit the final bulkhead inside the coupler.

I'm not a fan of drogueless; if it were me, I'd use an 18" - 24" drogue.
-Kevin

Exactly. I was also thinking about seeing if one of the science classes would want to come up with some kind of experiment to take a ride in the rocket .

Later on after thinking about it some more, I thought about using one of the extra centering rings to mount a 4" tube inside the nosecone. I like the threaded rod idea going thru the forward bulkhead. Only problem is I don't have a piece of 4" tube long enough. Fortunately 4" tubing is relatively cheap. Cardboard of phenolic? I would think since its just a payload bay inside a nose cone, cardboard would work just fine?

Would a PML type chute be good for drogue?

 

[n3tjm]

If you are looking to have a tracker bay in the nose you could do like I did with my L3. Pictures below.

That's what I was thinking of Scott . Thanks

 

[kandsrockets]

How long of a piece of 4" tubing do you need. I have some 16" long pieces sitting here if that will work. Also if you need rings cut to fit in the nose I can cut them for ya.

 

[troj]

Cardboard of phenolic? I would think since its just a payload bay inside a nose cone, cardboard would work just fine?

I use LOC 38mm MMT tubing to create bays in my nosecones. Inexpensive, easy to cut, easy to bond, and it works just fine.

Would a PML type chute be good for drogue?

Should be fine.

-Kevin

 

[Aksrockets]

If you wanted to turn this girlfriend into more then just a girlfriend, this would be a really awesome wedding proposal. Maybe it's inappropriate that I'm saying this and I'm sorry if it is. I don't know anything about this relationship.
You have to admit, it would be pretty cool!

Good luck with the build! op: I LOVE patriots!

Alex