L3 Certification Build: 8" Upscale Frenzy

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Okay getting back to the very serious business of rocket building . . . I mounted the Aeropack retainer on centering ring #4 and then installed it.

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All centering rings are now DONE! Next step: installing the baffle in the payload tube.

The nice thing about that 75mmt is that there's plenty of room to retrofit for outboards... :cool:
 
First attempt at a paint design. This is a variation of a paint job that I did on a 29mm minimum diameter a few years ago which I liked. This would be silver and metallic red.

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Sorry to derail, but what is the difference between a unistrut button and a 1515 button?
 
Beautiful design Nathan..
Could you bring a red stripe up the white payload section...

Teddy
 
Sorry to derail, but what is the difference between a unistrut button and a 1515 button?

Dan,, unistrut is a manufacturer of a channel product used in construction a lot..
Kindorf also makes the same channel,, you may know it by that name,, that's the manufacture I used to sell..
Google up 3 Kindorf #'s,, B905,, B917,, and B911-3/8" and you'll see what the stuff is and get an idea how it's used...
It has an 1 1/2" width... It's pretty big stuff for our purposes...

Teddy
 
Beautiful design Nathan..
Could you bring a red stripe up the white payload section...

Actually I was thinking about putting one or two stripes on the payload section, but I wasn't sure how to do that in OpenRocket. I'll play around with it. In any case I haven't decided on this paint design or even these colors.
 
Unistrut is about twice the diameter of a 1515.

I think 1515 rail could handle the ~70 lb weight of this rocket. But I would prefer to launch it from the taller and sturdier Unistrut rail towers. Only downside is that those big Unistrut button look like a couple of doorknobs stuck to the side of my otherwise sleek looking rocket. And I assume they create a lot of drag.
 
I think 1515 rail could handle the ~70 lb weight of this rocket. But I would prefer to launch it from the taller and sturdier Unistrut rail towers. Only downside is that those big Unistrut button look like a couple of doorknobs stuck to the side of my otherwise sleek looking rocket. And I assume they create a lot of drag.

I have two SCP teardrop airfoiled Unistrut buttons. They are lower profile and definitely more aerodynamic. I'll bring them to the July launch so you can check them out.
 
I think 1515 rail could handle the ~70 lb weight of this rocket. But I would prefer to launch it from the taller and sturdier Unistrut rail towers. Only downside is that those big Unistrut button look like a couple of doorknobs stuck to the side of my otherwise sleek looking rocket. And I assume they create a lot of drag.

It definitely can. I launched my 68lb Formula 200 off of the large quad pads MDRA has. Another option to consider is a 1515 to unistrut adapter. I am putting one together so I can launch my larger airframes with 1515 off the unistrut towers. It should just slide into the unistrut on the tower and bolt down.
 
I think 1515 rail could handle the ~70 lb weight of this rocket. But I would prefer to launch it from the taller and sturdier Unistrut rail towers. Only downside is that those big Unistrut button look like a couple of doorknobs stuck to the side of my otherwise sleek looking rocket. And I assume they create a lot of drag.

1515 Would be perfect for this. That's what is on my L3 rocket which was 60lbs ready to fly. At MWP one year, we launched Wildman Ultimates off of 1010 rails with N5800s. Not a rocket had guide issues. For my buttons, I put weld nuts inside the airframe, but the post of the nut went through the wall and inside the button, so all I had sticking inside the rocket was the weld nut flange and a larger fender washer for surface area. I had to drill out the inside of the button to clear the post of the weld nut.

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1515 Would be perfect for this. That's what is on my L3 rocket which was 60lbs ready to fly. At MWP one year, we launched Wildman Ultimates off of 1010 rails with N5800s. Not a rocket had guide issues. For my buttons, I put weld nuts inside the airframe, but the post of the nut went through the wall and inside the button, so all I had sticking inside the rocket was the weld nut flange and a larger fender washer for surface area. I had to drill out the inside of the button to clear the post of the weld nut.

That's how I do it. Heck, I thought that's the way everyone does it? :)

Now I understand why folks have been concerned about laundry catching on the inside.
 
The baffle is done. A test fit of the recovery gear showed that the 120" main chute packed in a chute protector needs about 13" of space and the nose cone shoulder is 8", so I installed the baffle 21" down the tube. I've never tried this before so I'm hoping that the baffle can withstand getting repeatedly blasted with about 10g of black powder from short range.

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Next step: external fin fillets.
 
... For my buttons, I put weld nuts inside the airframe, but the post of the nut went through the wall and inside the button, so all I had sticking inside the rocket was the weld nut flange and a larger fender washer for surface area. I had to drill out the inside of the button to clear the post of the weld nut.

Learn something every day. I had never thought about drilling out the base of the button to clear the weld nut. Thanks for the tip. You just might have changed the way I do buttons.... :)
 
I would also have the same concern, but cannot provide you any insight...time will tell. However what is the purpose of the baffle?

That's his "shelf" to keep the chute from sliding down the tube and against the top of the coupler and changing his CG. I got a huge amount of room in my 8" PR Mad Maxx too, and this is a excellent idea to keep the chute up near the cone.

Correct me if I'm wrong Nathan...
 
Learn something every day. I had never thought about drilling out the base of the button to clear the weld nut. Thanks for the tip. You just might have changed the way I do buttons.... :)

I drill them snug, so they fit tight on the nut. The counter bore in the button only needs to be deep enough to clear the nut. It depends on the thickness of the backing washer(if you use one) and the rocket wall thickness. If you can't find weld nuts at your local hardware store and don't want to order them from McMaster Carr, you can use the wood T nuts and just smoosh down the prongs. They're still gonna get covered with a smear of epoxy anyway.
 
That's his "shelf" to keep the chute from sliding down the tube and against the top of the coupler and changing his CG. I got a huge amount of room in my 8" PR Mad Maxx too, and this is a excellent idea to keep the chute up near the cone.

Correct me if I'm wrong Nathan...

Yes the baffle is a shelf to keep the main chute from sliding down the tube, but this rocket is pretty heavy and very stable so the chute sliding down the tube would not significantly change the CG. My concern is that the chute fits loosely in the 8" tube and that flopping around in the payload tube could cause the chute protector to unwrap. The baffle creates a compartment to keep the burrito-wrapped chute pressed against the nose cone bulkhead until deployment.
 
Instead of an open baffle I also considered mounting the ejection charges on a bulkhead up in the payload tube. That would have had the advantage of reducing the volume of the huge payload section and reducing the amount of powder that I would need for main ejection. The bulkhead would actually be a centering ring and the ejection canisters would be on a removable panel that bolts to the centering ring. Not a problem since I've done something similar a couple of times with nose cone av bays. But when I started designing it, it got more complex. That centering ring would also have to be the attachment point for the recovery harness. I wasn't sure if it would be strong enough if I just epoxied a single G10 centering ring to the inside of the payload tube like I did with the baffle. So if I was going to do that I would have had UpscaleCNC make me another 1" thick plywood CR and screw it to the airframe. Instead I just went with an open baffle to support the chute and left the charge canisters on the av bay lid.
 
Are you concerned about your recovery harness getting abrasions from going through that baffle?
 
Are you concerned about your recovery harness getting abrasions from going through that baffle?

I think there will probably be less abrasion from the baffle than there is from the top edge of the airframe tube. That's because the harness will have to pass almost straight through the baffle. So when there is tension on the harness there won't be much force pressing the harness against the baffle. And I have also sanded the edges of the center hole to a rounded profile. I will be checking my recovery harness for wear and if it's a problem I will reinforce a few inches of the harness with some self-fusing silicone tape in the section where it contacts the baffle. I use the same stuff to reinforce loops on Kevlar harnesses to make them abrasion resistant. Works great.

The harness will attach to the U-bolt on the av bay lid and I have determined that I will be able to pull it through the baffle and pack almost all of the harness above the baffle with the main chute. The chute is bulky enough that it will prevent the harness from sliding back down through the baffle during ascent.
 
I think there will probably be less abrasion from the baffle than there is from the top edge of the airframe tube. That's because the harness will have to pass almost straight through the baffle. So when there is tension on the harness there won't be much force pressing the harness against the baffle. And I have also sanded the edges of the center hole to a rounded profile. I will be checking my recovery harness for wear and if it's a problem I will reinforce a few inches of the harness with some self-fusing silicone tape in the section where it contacts the baffle. I use the same stuff to reinforce loops on Kevlar harnesses to make them abrasion resistant. Works great.

The harness will attach to the U-bolt on the av bay lid and I have determined that I will be able to pull it through the baffle and pack almost all of the harness above the baffle with the main chute. The chute is bulky enough that it will prevent the harness from sliding back down through the baffle during ascent.

+1...
If the harness is passing straight through a hole
I don't see an abrasion problem at all...

Teddy
 
I like this one too Nathan..
Isn't anyone else big on making one fin a different color to make it easier to see rotation on the way up ??
I always do that..
I don't remember where I picked that up...

Teddy
 
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