An "R"-powered rocket build

[davdue]

Starting this week I’m going to wipe down the G-12 tubing inside and out with lacquer thinner. Every bit of the “release” and other contaminants need to be completely removed before sanding with 220 grit aluminum-oxide sandpaper. This is to prep the G-12 to best accept the U.S. Composites thin epoxy on the interior and primer/paint on the outside. For the stringers I’ll be using the Pro-Set epoxy but will discuss this once I get to that point on the build.

Another thing that needs to be done is removing a very thin layer on the OD of the centering rings. I ordered them just slightly too large. Haven’t measured exactly how much needs to be removed but it’s minor.

I’ve got a belt sander to do this work so it should go quickly.

After cleaning and sanding the G-12 I’ll start building the “coupler assemblies” which are the internal strength of the rocket. I’ll post pics once I get started so you can see what I’m talking about.

As always I’m on this forum to share the build and to listen to your ideas/suggestions. Sometimes you guys come up with a way of doing something that is faster and/or more accurate.

Thanks.

Chuck C.

I have one of these from Harbor Freight. I use the disc sander it makes short work of sanding CR’s down to size.

https://m.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html

 

[Ez2cDave]

Chuck,

I have been going over thermal heating issues . . .

Last night, something occurred to me . . . What is the average Air Temperature @ 40,000 - 45,000 ft. AGL ?

The reason I ask is that we have been addressing aerodynamic heating and thermal heat transfer from the motor itself. BUT, we have not looked at how the various adhesives and resins will react during cooling. Specifically, during rapid cooling from 500 deg F +/-, in an environment where the air temperature might be as reflected in the chart below :

PDF file attached . . .

Dave F.

https://aviation.stackexchange.com/questions/36882/what-are-isa-10-isa-15-and-isa-30

 

[Rail Dawg]

I have one of these from Harbor Freight. I use the disc sander it makes short work of sanding CR’s down to size.

https://m.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html

Dave that sander you posted is exactly the same design I picked up a few weeks ago. Should do the trick nicely.

Thanks!

Chuck C.

 

[Rail Dawg]

Chuck,

I have been going over thermal heating issues . . .

Last night, something occurred to me . . . What is the average Air Temperature @ 40,000 - 45,000 ft. AGL ?

The reason I ask is that we have been addressing aerodynamic heating and thermal heat transfer from the motor itself. BUT, we have not looked at how the various adhesives and resins will react during cooling. Specifically, during rapid cooling from 500 deg F +/-, in an environment where the air temperature might be as reflected in the chart below :

PDF file attached . . .

Dave F.

https://aviation.stackexchange.com/questions/36882/what-are-isa-10-isa-15-and-isa-30


View attachment 376502


View attachment 376503

Thanks Dave. Something we need to consider.

Chuck C.

 

[Rail Dawg]

Ok it’s bath time for the G-12 airframes and couplers.

Using Dawn soap and water to remove the fiberglass dust.

Chuck C.

 

[Nytrunner]

Geez that's large tube compared to that trough

Probably took a lot of double scrubbing to make sure all the mold-release and oils are off

 

[rcktnut]

Starting this week I’m going to wipe down the G-12 tubing inside and out with lacquer thinner. Every bit of the “release” and other contaminants need to be completely removed before sanding with 220 grit aluminum-oxide sandpaper. This is to prep the G-12 to best accept the U.S. Composites thin epoxy on the interior and primer/paint on the outside. For the stringers I’ll be using the Pro-Set epoxy but will discuss this once I get to that point on the build.

Thanks.

Chuck C.

220 grit paper sounds good for paint prep but doesn't sound good for bonding parts together. I use 60 or 80 for bonding fiberglass parts together.

 

[Andrew_ASC]

I’ve heard some rocketeers on the forum say the higher mesh number of 220 allows better surface adhesion of the epoxy. I’ve seen some L1 kits specify 60-80 grit. I’ve flown both methods and can’t tell personally. Maybe I’m just not pushing it ha-R-d enough.

 

[Ez2cDave]

View attachment 376762

Ok it’s bath time for the G-12 airframes and couplers.

Using Dawn soap and water to remove the fiberglass dust.

Chuck C.

Chuck,

You're gonna need a bigger "horse trough" . . . LOL !

Dave F.

 

[Rail Dawg]

Geez that's large tube compared to that trough

Probably took a lot of double scrubbing to make sure all the mold-release and oils are off

Yeah the Dawn soap was just to get rid of the pesky FG dust.

Next step is to hit the airframes and couplers with lacquer thinner until nothing shows up on the rag. That should do a good job in getting rid of the release and other contaminants.

For those asking about the sandpaper grit I'm following the guidelines of the sticky thread at the top of this forum. If you haven't read through it give it a quick overview and you will see why I'm making some of the decisions I'm making.

Always open to ideas however.

Chuck C.

 

[Theory]

For those asking about the sandpaper grit I'm following the guidelines of the sticky thread at the top of this forum.

SMART!!!!

 

[Steve Shannon]

220 grit paper sounds good for paint prep but doesn't sound good for bonding parts together. I use 60 or 80 for bonding fiberglass parts together.

I use 80 as well. I’ve never tried 220 grit for surface prep. My usage could be more habit than science.

 

[Ez2cDave]

Always open to ideas however.

Chuck C.

Chuck,

You need to have GOOD MUSIC playing in the shop . . . For me, it's a mixture of 70's Classic Rock, 80's Pop, and "milder" 80's Metal !

Dave F.

 

[Rail Dawg]

I use 80 as well. I’ve never tried 220 grit for surface prep. My usage could be more habit than science.

I used 80 grit aluminum-oxide for every G-12 rocket prior to this one.

However after reading the "Properly Bonding Composites" thread I learned 80 grit is tearing into the fiberglass fibers thus decreasing the strength of our fiberglass.

The PBC thread states a grit of 120-240 is the correct range. We want an evenly abraded surface without damaging fibers.

Unless someone can pose an argument stating otherwise I'm going to follow the guidance on the PBC thread.

Always learning.

Chuck C.

 

[Ez2cDave]

I used 80 grit aluminum-oxide for every G-12 rocket prior to this one.

However after reading the "Properly Bonding Composites" thread I learned 80 grit is tearing into the fiberglass fibers thus decreasing the strength of our fiberglass.

The PBC thread states a grit of 120-240 is the correct range. We want an evenly abraded surface without damaging fibers.

Unless someone can pose an argument stating otherwise I'm going to follow the guidance on the PBC thread.

Always learning.

Chuck C.

Chuck & All,

Link to the "Properly Bonding Composites" thread . . .

https://www.rocketryforum.com/threa...your-government-doesnt-want-you-to-know.58389

Link to the "Sanding Fiberglass Tube" Thread . . .

https://www.rocketryforum.com/threads/sanding-fiberglass-tube.56789

Dave F.

 

[MClark]

I blast with glass beads.
Dish washing liquid can leave a residue unless rinsed with enormous amounts of water. We wash FG casting tubes with TSP as it leaves no residue.

 

[Ez2cDave]

We wash FG casting tubes with TSP as it leaves no residue.

"TSP" = Tri-Sodium Phosphate ?

Dave F.

 

[MClark]

Yes

Or use methanol

 

[Rail Dawg]

I blast with glass beads.
Dish washing liquid can leave a residue unless rinsed with enormous amounts of water. We wash FG casting tubes with TSP as it leaves no residue.

Good point. Going to hit the tubes with lacquer thinner tomorrow. Then when it comes time to build the coupler assemblies will use 220 grit to get rid of any last “release” before applying the epoxy.

What epoxy do you guys like using on the FG? We are going with US Composite’s thin epoxy for laying the carbon fiber over the birch stringers. Pro-Set epoxy for the stringers themselves as it doesn’t run.

Chuck C.

 

[Paulb06]

I used 80 grit aluminum-oxide for every G-12 rocket prior to this one.

However after reading the "Properly Bonding Composites" thread I learned 80 grit is tearing into the fiberglass fibers thus decreasing the strength of our fiberglass.

The PBC thread states a grit of 120-240 is the correct range. We want an evenly abraded surface without damaging fibers.

Unless someone can pose an argument stating otherwise I'm going to follow the guidance on the PBC thread.

Always learning.

Chuck C.

I've always sanded with 120....then if I'm gluing centering rings I lightly crosshatch the areas of contact with 80 grit

 

[Rail Dawg]

I've always sanded with 120....then if I'm gluing centering rings I lightly crosshatch the areas of contact with 80 grit

I used to do the same thing. I’m following now the guidance from the “Properly Bonding Composites (PBC)” sticky thread in this forum.

On there it recommends 120-240 grit so I’m going with 220.

Following that thread’s guidance should produce a very clean surface rough enough to help with the bonding. Not so rough though to cut FG fibers.

Chuck C.

 

[Rail Dawg]

 

[Rail Dawg]

Wiping all the tubes down with lacquer thinner to remove any release and other contaminants.

Also worked on the centering rings to get them to perfectly fit in the tubes. With a belt sander it's quick work.

 

[Theory]

YEEEEEAAAAAAA BUDDY!!!!!!!!

 

[levi seaton]

Wiping all the tubes down with lacquer thinner to remove any release and other contaminants.

Also worked on the centering rings to get them to perfectly fit in the tubes. With a belt sander it's quick work.

View attachment 376962 View attachment 376963

It’s exciting to see progress!! How do you plan on attaching the rail guides to this beast?

 

[Rail Dawg]

It’s exciting to see progress!! How do you plan on attaching the rail guides to this beast?

The rail guides (unistruts) are going to be stout. They will be secured through the G12 wall and into over an inch of birch plywood that has been carbon-fibered.

They aren't going anywhere lol.

Chuck C.

 

[Rail Dawg]

Ok guys put on your rocket thinking caps.

I’ve got to sand the inside of 5’ G12 tubes to make it better for the epoxy.

Going to use an orbital sander but of course can only reach a couple of feet in. Been considering ideas like sandpaper on a stick or duct-taping an extension to the sander.

Thought maybe you guys could come up with an even better idea lol. Got to be a way I can get a little bit of elbow grease onto the sandpaper.

Thanks.

Chuck C.

 

[Nytrunner]

This may sound old fashioned, but a sanding sponge on the end of a stiff dowel doesn't sound like a bad idea.

You can even make measuring marks on the stick so you know you're sanding around the right spot.
Say you start sanding and move the stick in and out between marks 3 and 4 on the stick, and do that all the way around, then you move to between marks 4 and 5, so you get even coverage and don't miss spots

 

[Ez2cDave]

WOO-HOO !

I see PARTS . . . BIG parts !

Dave F.

 

[davdue]

This may sound old fashioned, but a sanding sponge on the end of a stiff dowel doesn't sound like a bad idea.

You can even make measuring marks on the stick so you know you're sanding around the right spot.
Say you start sanding and move the stick in and out between marks 3 and 4 on the stick, and do that all the way around, then you move to between marks 4 and 5, so you get even coverage and don't miss spots

I was thinking sort of the same thing. Except use a flap sanding disk on a rod with a drill. Still mark it so you know where you are sanding. Don’t need to sand the whole thing, just the spots where you are glueing.