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And after all that work, I need to re-cut my centering rings. Centers of the outer holes were supposed to be a 4.25" radius, and I cut them on a 4.5" radius. Le sigh.

Good thing I checked before I started gluing!
 
What got me suspicious about my centering rings was when I started doing some mental math and wondering how the heck my fuel tanks were supposed to fit in the upper airframe with its smaller diameter. It couldn't.

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So today's task was recutting centering rings. I think I've gotten better at it. The first time it took me about 4 hours to get it all done. Today I managed in about an hour and a half. It's amazing the difference a quarter inch of radius makes.

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But hey, it's not all wasted effort. I'm thinking drinks tray, or glue caddy... :lol:

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If you're thinking of doing something like this in the future, don't call me. Seriously! :p
 
What got me suspicious about my centering rings was when I started doing some mental math and wondering how the heck my fuel tanks were supposed to fit in the upper airframe with its smaller diameter. It couldn't.View attachment 301461So today's task was recutting centering rings. I think I've gotten better at it. The first time it took me about 4 hours to get it all done. Today I managed in about an hour and a half. It's amazing the difference a quarter inch of radius makes.View attachment 301460View attachment 301459But hey, it's not all wasted effort. I'm thinking drinks tray, or glue caddy... :lol:View attachment 301458If you're thinking of doing something like this in the future, don't call me. Seriously! :p
I thought that was "And don't call me "Shirley""
 
When I started to put the centering ring inside the body tube, it became immediately obvious that a solid disk was much stronger than on with holes cut in it. The wood between the tank holes wasn't particularly thick. This will probably be fine once the tank tubes are in place, but most of the fin assembly will require that they not be there. So I reinforced my centering rings with 2 layers of carbon fiber on each side. The result is much stronger for less weight than doubling the thickness which was my other option. I may still double up the base plate as that will take more stress, but I have a while before I have to worry about that. It still has CF on only one side as I need to order more (including enough for the fins)

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It still needs a lot of sanding to fit, for the circumference and for each of the inner rings.

At this point I've spent more time on 3 centering rings than I have on most of my rockets, with more to follow! :wink:

This will be the last update for a couple of weeks. Work travel interlude. Pesky job I need to buy rocket parts!
 
I'm home and working on rockets again. Yay! I did a lot today, even though the results won't be visible for a while.

I started with my concrete former mandrel. As it is, it's a little too large and a little too eccentric for the upper part of the rocket. So I started first by seeing if I could peel off the paper layers one at a time. No go. Out comes the sander. As you can see, I can sand it down to where I can get my template to fit on. All it takes is lots of sanding and patience. I'm going to split this over a few days for a few reasons. One is that both my hand and my brain go numb. Another is I don't want to mess it up after all that work because I get impatient. I'll be using fiberglass on this part and it will be less forgiving than carbon fiber. I've done the end as a proof of concept, and I've also done a complete pass over the entire mandrel. Also, my 15 year old palm sander is starting to complain of old age. It may retire before the project is complete.

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With that I took a break and started with the centering ring for the engine skirt. I enlarged the center hole the small amount required for the blue tube 75mm motor tube to fit. I then trimmed the outsides so it would fit in the CF tube. I'd just started on enlarging the holes for the 8 tank tubes when I was saved by the rain. Time to head indoors and order pizza. I may need a few extra grinders for my dremel before this is done. I think my tube may be slightly conical though so I'm not entirely sure how well this will all work. If worse comes to worse, I have more CF and can try again, but I'll do my darndest to prevent that.

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I have to do the eight tank holes on this and then repeat for 2 other centering rings. I think my weekend will be filled with grinding and sanding. Le sigh. I hate sanding!
 
LOL...we all hate sanding!! looks like real progress to me!! this 1b is going to be beautiful!

I'm home and working on rockets again. Yay! I did a lot today, even though the results won't be visible for a while.

I started with my concrete former mandrel. As it is, it's a little too large and a little too eccentric for the upper part of the rocket. So I started first by seeing if I could peel off the paper layers one at a time. No go. Out comes the sander. As you can see, I can sand it down to where I can get my template to fit on. All it takes is lots of sanding and patience. I'm going to split this over a few days for a few reasons. One is that both my hand and my brain go numb. Another is I don't want to mess it up after all that work because I get impatient. I'll be using fiberglass on this part and it will be less forgiving than carbon fiber. I've done the end as a proof of concept, and I've also done a complete pass over the entire mandrel. Also, my 15 year old palm sander is starting to complain of old age. It may retire before the project is complete.

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With that I took a break and started with the centering ring for the engine skirt. I enlarged the center hole the small amount required for the blue tube 75mm motor tube to fit. I then trimmed the outsides so it would fit in the CF tube. I'd just started on enlarging the holes for the 8 tank tubes when I was saved by the rain. Time to head indoors and order pizza. I may need a few extra grinders for my dremel before this is done. I think my tube may be slightly conical though so I'm not entirely sure how well this will all work. If worse comes to worse, I have more CF and can try again, but I'll do my darndest to prevent that.

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I have to do the eight tank holes on this and then repeat for 2 other centering rings. I think my weekend will be filled with grinding and sanding. Le sigh. I hate sanding!
 
While I was away I received some CF. The stock I'd had on hand had run out, and I still needed to apply to the back side of the remaining 2 centering rings. Before I did, I cut access panels in the base plate that will allow me access to the airstart wiring. The advantage of having been away from the build for so long is that I'm thinking that far ahead. And after all this work I'd hate to have to rip the whole fin can apart to debug a cold solder joint.

I measured right but cut at the wrong spot. Not critical here as it's the base plate, but I'll need to be more careful as I progress with the build. The access holes look off center as a result but they're not - the panel is. Also my cuts weren't straight, which I'll need to factor in as I cut an access panel in the upper body tube. I backed this with some more plywood which will allow me to attach t-nuts later so I can screw the panels into place. Doing that now allowed me to bond with the CF and the baseplate.

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Obviously there's some clean up work that will be required, including grinding the holes to the correct size for the motor mount tubes. Four of the mailer tube fuel tanks will be used for the 38 mm outboards.

Finally, as I said in my last post, I've been grinding away at the first centering ring. As I mentioned in earlier posts, the hole cutter cut just too big or just too small. So I cut too small and used a grinding stone with my dremel to enlarge the holes. For the first centering ring, this took me about 3 hours including the outer circumference allowing it to fit in my CF body tube. Only 2 more to go! (Plus some for the forward body tube that I haven't made yet!) If I get all three complete by the weekend, I'll be happy. Then I can finally start dry fitting and gluing stuff!

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Hole shaping is complete on all three centering rings, so time for a dry fit.

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The plan is a CR at the front, one butted up against the fins, and a base plate. The problem is, with the 3 of these together the tolerances are tight. This will be made even tighter when I add one up at the top of the stage. As it is, getting the tubes in place isn't quite working. I think the solution is to make the holes in the middle CR a little larger, but there really isn't much material between the tanks. So my choices are to make the holes elliptical, which gives me some play in the inboard-outboard direction but not the radial direction, skip the middle CR, use a middle ring that butts against the fins but which isn't the full diameter, or make the baseplate holes a little larger and fill any gaps with epoxy. I'm not sure which I'll do yet, but I don't think I really have to decide until the fins are in place.

As it is, I'm going to have to trim a couple of mm off the side of each of the tubes to get the fins in there. On the real rocket, the tanks never extended into the lower fuselage so this wasn't a problem. My tubes are certainly thick enough they won't notice the missing material, and I can seal them with a little West Systems epoxy. In addition to the width of the plywood, I'll be doing a CF root-to-tip internally so that will be an extra bit of width to handle as well.

The next step is to glue the fore CR in place, and with the rear CR fitted but not glued, glue the CF tube in place, and trim to size. That's right... I said glue. It's time for a commitment!
 
Since the rings were done by hand, you might try a couple of rotations of a few of the rings to see if one way fits better than another.
 
Since the rings were done by hand, you might try a couple of rotations of a few of the rings to see if one way fits better than another.

Yeah, thought of that. I'l probably do a combination of that and hole grinding when the time comes, but I'm not going to worry about it for now.
 
At any rate, this is going to look pretty sweet. Nice work, sir.
 
Glued the forward centering ring in place last night using rocketpoxy and added a fillet on the top side. The rear side has no fillet to allow for the fins. It will get reinforcement later.

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I also washed the fuselage piece with alcohol, soap, and water to remove any mold release. Test fit looks good. I'll glue it later when it's all dry. I have the baseplate fitted in place but not glued. At this point I've only done a rough cut on the piece. I'll trim the forward part once glued so that it's flush with the CR. For the rear piece, I'll trim close to the baseplate but not flush saving that until after it's glued into place.

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I can attest to the strength of Blue Tube. Stupid strong for the price. No fiberglass dust. My 7.5" bird is Blue Tube. It incurred some flight damage that I think may have fractured a fiberglass tube. Put a gash in the Blue Tube, but it was still really strong. I put a coupler in it and filled the gash. No more problem.
 
It dried up enough that I could go outside and do some cutting and grinding again. I trimmed the lower airframe to size. At this point I also cut slots for the fins. This pretty much had to be done now while I was still able to use the CR to guide me. The fins will also have to be in place before the tanks, as the space between the tanks isn't large enough for the through the wall fins. They'll have to be trimmed on the outside. More on that later.

To make sure the fin cuts were straight, I used Mr. Macklin's fin guide. Even though it's not large enough for my tube, with a square and an aluminum angle I was able to make it work.

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After cutting the slots (I'm getting a lot better with the cutting wheel!), I taped the fins into place just so I could feel I was making progress, and to see how it looks. Not bad.

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I'm starting to think about the tank fairing now. At it's core, it's a simple transition with holes cut for the tanks. This site (https://meatballrocketry.com/saturn-construction-tips/) has a good description for how to make the holes, but I'm thinking it's just an ellipse. I'll try an ellipse pattern later to see how it works. I'll start with the transition first, and then cut and trim the tank slots after it's in place.

I started in rocksim to design the transition and printed the template.

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This is on plain paper, so excuse the lack of stiffness. I tested the fit and it looks ok. To make this in CF I have a few options. One is to put some ribbing in place and cover that. That's not a good plan here because the tanks get in the way, so any ribbing would be so minimal as to be useless. Another would be to put a temporary structure in place (such as foam core), layup the CF, and remove the frame. I haven't fully discounted this. Another method would be to build a stand alone frame, lay the CF on that, trim to fit, and glue into place. I'm tending towards that option as my experience with CF is one of frayed edges. Making it over sized and trimming gives me a better margin for error. Any thoughts from the forum?

As a final note, and a warning to anyone tempted to work with carbon fiber, wear your PPE, and don't do this in your living room! I showered just before I started this part!

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Cleanliness is over rated! :D
 
Another method would be to build a stand alone frame, lay the CF on that, trim to fit, and glue into place. I'm tending towards that option as my experience with CF is one of frayed edges. Making it over sized and trimming gives me a better margin for error. Any thoughts from the forum?
I'd go with the stand alone frame - and make the part slightly oversized at the edges, and trim to fit. Better than having it end up undersized....and have to stretch it after the fact.
This transition is probably the most difficult component of the build, as it is a complex shape with several openings and there are a lot of opportunities for a misfit in several locations.
I can see where you would have to make alignment marks for the eight tank tubes and ensure there will be no gaps when you refit the transition shroud. There could be minor variations at each tube location, and it would probably help when installing the completed shroud if they aligned at the exact same tube hole locations when it was fabricated.

Fins came out really nice - Looks like you got the fins between the tube locations - and thru the wall, to seat on the core/central body tube...did they reach?
 
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Fins came out really nice - Looks like you got the fins between the tube locations - and thru the wall, to seat on the core/central body tube...did they reach?

These aren't the final fins - just the plywood cores. There's still a HUGE boatload of work before they're done. No, they didn't reach. When I specified the laser cutting, I expected a slightly smaller, less accurate diameter. I'll put pieces of plywood on either side of the fin as a slot for them to fit in. They'll all be reinforced with an internal CF root to tip as well, so it shouldn't be that big of a deal. More on that later.
 
I've created a mandrel of sorts for the tank fairing out of some of the messed up centering rings I'd created earlier and some foam core. I'll cover this with some thick mylar before laying the CF. If all goes well, I'll do that tonight or tomorrow.

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It even has its own base! I may have spent more time on this than I have on some of my simpler rockets
 
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