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

That's some thick foam core, I use thinner foam core or balsa strakes but more of them to give shape ....but it ought to work ok.
Maybe you can round off the flat edges on the foam core if the mylar needs more curvature when laid on.

What is the diameter at the top of the transition...?
 
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That's some thick foam core, I use thinner foam core or balsa strakes but more of them to give shape ....but it ought to work ok.
Maybe you can round off the flat edges on the foam core if the mylar needs more curvature when laid on.

What is the diameter at the top of the transition...?

The jig is oversized so that I can make it longer and trim to size. Sanding was always my intent, and the mylar I'm using is very thick so it should keep the shape quite well.

The diameter at the top of the fairing is 8.5 inches, but on the jig I've made it 7. Again, this will allow me to make it oversized. That should help with the shape as well.
 
The jig is oversized so that I can make it longer and trim to size. Sanding was always my intent, and the mylar I'm using is very thick so it should keep the shape quite well..
The diameter at the top of the fairing is 8.5 inches, but on the jig I've made it 7. Again, this will allow me to make it oversized. That should help with the shape as well.

Ok. Think I got it. This the transition from the fin can ring to the tanks tube section ...
You have added some excess length in the forward section.....which can be trimmed off.
That's probably why it looked a little narrow at the top, compared to the diameter of all the eight tank tubes.
What kind of mylar is that you are using?
 
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Ok. Think I got it. Is this the transition from the fin can ring to the tanks tube section ...?
You have added some excess length in the forward section.....which can be trimmed off.
That's probably why it looked a little narrow at the top, compared to the diameter of all the eight tank tubes.

Yes, this is the fairing from the fin can to the tanks. I'll have excess fore and aft that I can trim. Given my lack of precision that's always a good idea! :)
 
Yes, this is the fairing from the fin can to the tanks. I'll have excess fore and aft that I can trim. Given my lack of precision that's always a good idea! :)

I'm all with that!.
My brother is in the stone contracting business - they say "you can't stretch marble", so if you err, - err on the side of extra length.
They also say...."measure twice, and cut once".
 
I'm all with that!.
My brother is in the stone contracting business - they say "you can't stretch marble", so if you err, - err on the side of extra length.
They also say...."measure twice, and cut once".

.....then cut again! 😃
 
I cut the mylar oversized as promised. It's thicker than what I used on the concrete former and it keeps its shape quite well. I also placed it on the fin can to verify its size.

IMG_1512.jpgIMG_1513.jpg

The mylar also works well as a template for cutting the CF.

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Sadly, after the issues I had with it on the fin can, I had to iron my peel ply to keep the creases from ruining my finish. It worked fairly well but it still annoys the hack out of me that I need to do it. So, CF laid, peel ply on, my UFO was ready for lift off. A quick check on my fin can and all looks good.

IMG_1515.jpgIMG_1517.jpg

Next up is trimming to fit and gluing in place. I have a few ideas on how to make that easier, but that's for a later post.
 
:wink:
Sadly, after the issues I had with it on the fin can, I had to iron my peel ply to keep the creases from ruining my finish. It worked fairly well but it still annoys the hack out of me that I need to do it. So, CF laid, peel ply on, my UFO was ready for lift off.

Those darn peel ply fold creases - after my initial CF lay up, I sourced peel ply on a roll, no fold creases to deal with. A tad more expensive, but easier to work with.
This transition piece looks good, and there is always the opportunity to use filler if the outer layer needs some touch up.
What are you going top use to cut and trim the CF....that will be fun :)wink:)
 
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:wink:

Those darn peel ply fold creases - after my initial CF lay up, I sourced peel ply on a roll, no fold creases to deal with. A tad more expensive, but easier to work with.
This transition piece looks good, and there is always the opportunity to use filler if the outer layer needs some touch up.
What are you going top use to cut and trim the CF....that will be fun :)wink:)

I ordered off a roll. They quite helpfully folded and creased it before mailing it. I was not impressed.

The cutting and trimming is quite easy with a dremel. I've been using their fiberglass reinforced cutting wheel and their grinding stone.
 
I ordered off a roll. They quite helpfully folded and creased it before mailing it. I was not impressed.
The cutting and trimming is quite easy with a dremel. I've been using their fiberglass reinforced cutting wheel and their grinding stone.

You ordered from a roll and they folded it for shipping?
Geeez. Hope you didn't pay a premium.

I ordered a pre cut length from a roll and it came shipped on a roll.
Rolled goods shipping charge of $7.00 applied, but I was ok with that.

Sounds like they didn't ship what they advertised or they misrepresented what they sold.
Think I'll stick with my vendor.
https://www.avtcomposites.com/cgi-bin/commerce.cgi?preadd=action&key=PEELPLY
 
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You ordered from a roll and they folded it for shipping?
Geeez. Hope you didn't pay a premium.

I ordered a pre cut length from a roll and it came shipped on a roll.
Rolled goods shipping charge of $7.00 applied, but I was ok with that.

Sounds like they didn't ship what they advertised or they misrepresented what they sold.
Think I'll stick with my vendor.
https://www.avtcomposites.com/cgi-bin/commerce.cgi?preadd=action&key=PEELPLY

I would happily have paid the premium. I'm pretty sure it was the shipping department cheaping out. Your vendor is now added to my list of vendors.
 
Placing the tank fairing on the fin can is going to be a challenge. The edges on the part aren't straight, so there's no reference for getting things lined up and cut straight. The solution? Make a hat!

Start by drawing concentric circles for the main motor mount and the top of the fairing. Then use this to cut a piece of foam core. Add a uniform rim of poster board around the edge. Slip it over the motor mount and use a square to make sure things are straight. Voila! Cutting starts tomorrow when I can do it outside.

IMG_1518.jpgIMG_1521.jpgIMG_1520.jpg

The scallops for the tanks are much easier than my earlier link suggested. Make an ellipse with the minor axis the same size as the tank diameter. For the major axis, b = a * tan(60) where a is the tank radius. The result fits better than shown here. This is just office paper taped into place so I can take a picture. I now have a pattern I can use to cut the scallops in each of the 8 places.

IMG_1519.jpgIMG_1522.jpg
 
I leave Saturday for another 2 week work trip, so I decided to finish sanding the mandrel and make the upper air frame. The weather is already getting cooler and this really needed to be sanded outside. So here it is:

IMG_1523.jpg

I may get some more done on the tank fairing, but I won't have much to show until I return. See you in a couple of weeks!
 
I leave Saturday for another 2 week work trip, so I decided to finish sanding the mandrel and make the upper air frame. The weather is already getting cooler and this really needed to be sanded outside. So here it is:
View attachment 303302
I may get some more done on the tank fairing, but I won't have much to show until I return. See you in a couple of weeks!

In the picture of the mandrel..... is a layer of something on that mandrel tube in the photo?
Maybe I missed something earlier in the thread, and you were adding width to the main airframe mandrel to make it true scele/rounder with a layer of FG .

Have a good trip.
 
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In the picture of the mandrel..... is a layer of something on that mandrel tube in the photo?
Maybe I missed something earlier in the thread, and you were adding width to the main airframe mandrel to make it true scele/rounder with a layer of FG .

Have a good trip.

The mandrel is the concrete former sanded down to make it smaller (about 1/4" all around) and rounder, a layer of thin mylar, the FG layup, and then the peel ply. The peel ply extends past the end of the FG and that's probably what you're seeing.
 
The mandrel is the concrete former sanded down to make it smaller (about 1/4" all around) and rounder, a layer of thin mylar, the FG layup, and then the peel ply. The peel ply extends past the end of the FG and that's probably what you're seeing.

oh...I get it now.
That did look like peel ply in the picture.
When you said you were "sanding the mandrel" before you left for business - you were actually sanding the FG air fame that is laid up ON the mandrel.
Picture had me confused.
 
oh...I get it now.
That did look like peel ply in the picture.
When you said you were "sanding the mandrel" before you left for business - you were actually sanding the FG air fame that is laid up ON the mandrel.
Picture had me confused.

No, I was sanding the concrete former, not the FG. It was too thick and not quite round.
 
Ok. Sanding the mandrel (concrete former)...THEN you did the FG layup with peel ply on the mandrel?
I wasn't seeing the sequence here.

Yes. Sanded the mandrel. Placed a layer of mylar over that and sprayed with mold release. Laid up the FG and added a layer of peel ply. The peel ply came off this morning, but my garage was cool so the tube is still on the mandrel curing.
 
Back from my trip, but it's late so no building tonight.

I did get a chance to look at the fiberglass tube that's been curing since I left. I though I'd have to struggle to get it off, but a couple of small taps on the floor and it just started sliding off! I couldn't have planned it better!

IMG_1541.jpg

It looks quite good, but a lot thinner than what I'm used to working with (4 wraps apparently isn't much). It isn't really structural so it shouldn't be a problem, and its really only dings and scrapes I have to worry about. Ironing the peel ply definitely helped with the finish.

Also thinking ahead a few steps, I received a bunch of styrene strips I'll be using for the stringers. I've been thinking a lot about detailing, and there's a few things I want to experiment with before I start using them on the rocket.

IMG_1542.jpg

Tomorrow I start working on the fairing scallops, and cutting some more centering rings since the weather looks like it will be good for some outdoor work. Then I have to tackle my clogged 3D printer and crashed hard drive to get some 3D printing done. I need to make some jigs for my fins!

With MaxQ building again, the race is on! :p
 
Chipping away, I did manage to get a little bit done in between jet lag naps.

I got the fiberglass tube for the upper airframe (SIVB stage) trimmed to length. I trimmed the top of the engine fairing.

I've started on the fairing scallops. Getting everything aligned is critical. My first attempt was to use my Macklin fin guide and a square to get my lines straight, but a quick visual inspection showed things were way off. Plan B was to use a spare mailer tube, trim off the outer portion where the fairing would be, and use that to mark the scallop location. That worked much better. I marked with my ellipse card stock, but as I checked the fit, I saw I had to grind out more than I thought. But it worked. One scallop cut and the tube fits excellently! This is going to take a few days to finish though.

I had some pictures, but as I was getting ready to take another, my phone started acting up and now the screen is non-functional. Le sigh. So, I have no phone, it's raining, I have a computer with a dead hard drive, and my 3D printer is clogged. Time for a cigar and some football.

I'll use my digital camera and post some pictures later this week as I make progress.
 
she is looking good! The evergreen plastic strips are fantastic! million and one uses for them! Hope the technical difficulties get cleared for you...nothing wrong with a little football! I just came back from a football road trip with my son..watched Penn State play at Purdue and then watched his beloved Colts play on Sunday in Indy. Walking Purdue campus is really cool knowing that Neil Armstrong and Gene Cernan among others walked the same sidewalks.
 
Progress! I'm still having technology issues but I get a new cell phone tomorrow, and I have a new hard drive for my desktop. Its rebuild and the 3D printer issues will wait until I return from my next work trip. But I have the tank fairing done!

My first attempt to mark the scallop locations was a dismal failure. I tried to use my Macklin fin jig and a square to get things lined up, but it didn't pass even a basic visual inspection.

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So on to plan B. I cut the end of a spare mailer tube to show where the tank met the fairing and used my ellipse pattern from there.

IMG_1706_web.jpgIMG_1707_web.jpg

After that it was a question of cutting. If you're ever going to try this and don't have a dremel or similar tool, stop what you're doing and go buy one. It's pretty easy with one and almost impossible without. I use two attachments: a heavy duty cutting wheel and a grinding wheel. You'll go through many of these before you're done. Always when doing a subtractive process like this, cut a little, check, cut a little more, especially if you're like me and can't cut a straight line!

IMG_1709_web.jpgIMG_1708_web.jpg

You'll also find when cutting carbon fiber you look like a coal miner, so be prepared for your SO to insist you change clothes before coming into the house. A couple of hours later though and you'll have your fairing!

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At this point I couldn't resist another dry fit.

First up, a comparison between the engine section and the S-IVB airframe section. Both were made using the same concrete former! You can see the size difference where I built up for the engine section and sanded down for the S-IVB.

IMG_1713_web.jpg

Putting the tanks in place was a bit of a struggle. As I get into a final fit after the fins are in place I may need to fine tune some trimming.

IMG_1715_web.jpg

The centering ring used here is actually for the fin can, so it's a bit large for the forward section. I still need to make that one. Finally, I just had to put the S-IVB airframe on. It's starting to look recognizable!

IMG_1721_web.jpg

I still have a long ways to go, and only 2 weeks left before new years where I'm not traveling somewhere. Getting this in a flyable state for URRF is going to be a challenge.
 
That is some fine work, sir. Nothing like a hard deadline to motivate.
 
At this point I couldn't resist another dry fit.
Putting the tanks in place was a bit of a struggle. As I get into a final fit after the fins are in place I may need to fine tune some trimming.
View attachment 304491
The centering ring used here is actually for the fin can, so it's a bit large for the forward section. I still need to make that one. Finally, I just had to put the S-IVB airframe on. It's starting to look recognizable!
View attachment 304490

Dave - coming along nicely.

Those eight fins set into the fin can shroud are a big challenge, looks like so far - you got it licked.
Any thoughts on how to do the permanent fin attachment yet? Like to know more on how you are doing that.

I'm worried on my project - keeping them resistant to hard ground hits on recovery, especially if it hits diagonally or gets dragged.
 
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