Banishing Tube Spirals

[neil_w]

For the record, I fill in spirals with sandable primer, not Elmer's CWF. This is because I'm usually building a BT-20 rocket and CWF doesn't easily fill in the very narrow spirals. I also sand the primer with 400, 600 and 1,500 grit sandpaper. 220? What am I trying to do, turn a 2x4 into a toothpick?

What is the benefit of sanding primer with 1500 grit? I can't see what that would accomplish.

 

[Donnager]

What is the benefit of sanding primer with 1500 grit? I can't see what that would accomplish.

It'd polish the inconsistencies pretty well, but it won't flatten the high spots. My paint application is such that I can't make that step.

I'd smooth it (220 is not for finishing) with 220, make another primer or glazing putty/CWF fill, then re-scratch the high points with 220. then 330. Once you get here, then you have decisions to make--more primer for slicking the finish, or step the sanding to finer materials, or paint with a light coat and start the polishing.

This is why body work isn't my favorite.

 

[hcmbanjo]

Here's a good example of a two-step seam filling process:
https://modelrocketbuilding.blogspot.com/2021/09/estes-super-mars-snooper-7309-build_16.html
Step 1. Sometimes I draw a line down the spirals with a mechanical pencil before filling. It makes the spiral easier to see.
Using an older blade to direct the filler into the seams, no bubbles or gaps.
Two steps, no visible spirals.

Step 2. I've used every filler/primer out there - the best is the Duplicolor Filler Primer #FP101.

 

[SolarYellow]

I stop at 400. Gets me a smoother base than the Acryli-Quik will dry to, even in a wet coat.

 

[mh9162013]

What is the benefit of sanding primer with 1500 grit? I can't see what that would accomplish.

I use 1,500 because even 600 grit sandpaper will leave behind a finish that can sometimes be seen through my color coat of Rustoelum 2X spray paint.

I don't use 200-300 grit because they sand through the primer and down to the cardboard main body tube way too quickly. They also leave such large gouges in the primer or cardboard that it takes another coat of primer and sanding to get rid of them so they don't show up under my color coat.

Note that the above is what I use when creating a shelf queen rocket. If it's a regular rocket, I may or may not even fill in the spirals, let alone care if slight sanding gouges show up in my color coat paint finish.

I've only used CWF a few times on BT-20 tubes to fill in spirals, but both times I didn't thin it. I think if it was thinner, it might get into the very narrow channels of BT-20 tubing a bit easier. I may try using thinned CWF the next time I fill in BT-20 spirals and see how that goes. Dunno if it'll save time, effort or money, but it's another option to use. Might be a little healthier as I can avoid VOCs a little more.

 

[KenECoyote]

I just thought of something...

Has anyone ever tried string or floss (unwaxed) glued into the spirals?

I might try that this week.

BTW- Don't bother trying these since they ended badly with fuzzy raised spirals. You're welcome!

 

[mh9162013]

THAT is dedication to the craft. Or insane. One of those two.

Oh, it's only effort I put in for shelf queen rockets. These are rockets that I want look near perfect, even from a few centimeters away (a goal that's still a work-in-progress...need to figure out how to put on the perfect clear coat with a spray can). And most of the rockets I build aren't shelf queens.

 

[ep29030]

Oh, it's only effort I put in for shelf queen rockets. These are rockets that I want look near perfect, even from a few centimeters away (a goal that's still a work-in-progress...need to figure out how to put on the perfect clear coat with a spray can). And most of the rockets I build aren't shelf queens.

My best finishes come from applying clear coat after paint and decals, followed by sanding with 1000+ grit wet sandpaper, then re-applying clear coat.

 

[SolarYellow]

That gets heavy surprisingly quickly. I've started not only building with a gram scale, but painting with one, too.

Would be an interesting science project to compare the performance of a lightest-possible finish vs. a smoothest-possible finish and the respective weights. Of course, the result will differ greatly depending on the rocket design. A minimum diameter MPR or greater often comes out below optimum mass, so adding weight to reduce drag is a win-win. On the other hand, a non-MD BP-powered rocket is almost always somewhat above optimum mass.

Maybe a bulk pack of Alphas would be the ideal starting point for such a test:

Two with 18mm mounts, built as light as possible.​

Two built MD for 95mm motors​

In both cases, one built as light as reasonably possible with "acceptable" finish and letting the mass creep up to get a polished-smooth finish. For the 95mm motor MD versions, I'd run the polished version both however it comes out and ballasted as necessary to reach optimum mass.

 

[ep29030]

That gets heavy surprisingly quickly. I've started not only building with a gram scale, but painting with one, too.

Would be an interesting science project to compare the performance of a lightest-possible finish vs. a smoothest-possible finish and the respective weights. Of course, the result will differ greatly depending on the rocket design. A minimum diameter MPR or greater often comes out below optimum mass, so adding weight to reduce drag is a win-win. On the other hand, a non-MD BP-powered rocket is almost always somewhat above optimum mass.

Maybe a bulk pack of Alphas would be the ideal starting point for such a test:

Two with 18mm mounts, built as light as possible.​

Two built MD for 95mm motors​

In both cases, one built as light as reasonably possible with "acceptable" finish and letting the mass creep up to get a polished-smooth finish. For the 95mm motor MD versions, I'd run the polished version both however it comes out and ballasted as necessary to reach optimum mass.

My limited experience with light applications of paint came from an R/C guy at the hobby store. He advised me to use an airbrush to apply water acrylics, and use alcohol as the paint thinner. I was able to apply a very thin layer of paint with his technique. But then again, most of the time I'm not going after altitude or duration records, so I'm OK with the heavy paint that looks nice and holds up well in abuse. You are correct that paint can add a significant weight (several ounces) to your rocket.

 

[Tractionengines]

I would pay a small premium to have spirals pre filled to be honest.
I’ve already wasted enough time! And I’ve only been doing this for a year or two!

All I can say is BT size fiberglass rockets...pay the material premium...but NO SPIRALS.

 

[Imaknow]

I stop at 400. Gets me a smoother base than the Acryli-Quik will dry to, even in a wet coat.

Just started using Acryli-Quik and noticed that it is not as smooth as I would like.

What steps should I take after the wet coat? Looking for advice to make it smooth and shiny enough for decals.
Thanks for any insights.

 

[CoolRockets]

I just finished applying “Tube Spiral-B-Gone” (Elmer’s Wood Filler).

I may have overdone it a bit.

One day to work on rockets before busy work week. Work is overrated.

View attachment 573970

Why would you want them gone? They make the rocket look like a true kit, that’s just my pinion anyway, I’m a big fan of tube spirals

 

[Imaknow]

Why would you want them gone? They make the rocket look like a true kit, that’s just my pinion anyway, I’m a big fan of tube spirals

Interesting take.
I waver back and forth, personally.
If it is not scale it is rare for me to fill.
Performance, baby!

 

[Alan15578]

Why would you want them gone? They make the rocket look like a true kit, that’s just my pinion anyway, I’m a big fan of tube spirals

Well, you do need the Persian flaw, otherwise people will just think it a lousy plastic RTF kit.

 

[CoolRockets]

Well, you do need the Persian flaw, otherwise people will just think it a lousy plastic RTF kit.

I don’t mind the RTF kits

 

[brockrwood]

I don’t mind the RTF kits

I like kitbashing the RTF kits. A Quest “Brighthawk” makes a great sustainer. Then you epoxy a couple of Estes “Gnome” BT-5 kits onto it as “booster pods”. Kitbash cluster. With A10’s in the pods, the “GnomeHawk” gets off the pad fast!

 

[CoolRockets]

I like kitbashing the RTF kits. A Quest “Brighthawk” makes a great sustainer. Then you epoxy a couple of Estes “Gnome” BT-5 kits onto it as “booster pods”. Kitbash cluster. With A10’s in the pods, the “GnomeHawk” gets off the pad fast!

This rocket has the CoolRockets cool stamp of approval.

 

[dpower]

Here's a good example of a two-step seam filling process:
https://modelrocketbuilding.blogspot.com/2021/09/estes-super-mars-snooper-7309-build_16.html
Step 1. Sometimes I draw a line down the spirals with a mechanical pencil before filling. It makes the spiral easier to see.
Using an older blade to direct the filler into the seams, no bubbles or gaps.
Two steps, no visible spirals.

Step 2. I've used every filler/primer out there - the best is the Duplicolor Filler Primer #FP101.

FP101 is really good stuff. The only other gray primer I'll use is 3M/Bondo 720 filler primer - every bit as good as Dupli-Color - it seems to have somewhat fewer solids, but dries even faster, if that's possible. Full of VOCs!

 

[mh9162013]

FP101 is really good stuff. The only other gray primer I'll use is 3M/Bondo 720 filler primer - every bit as good as Dupli-Color - it seems to have somewhat fewer solids, but dries even faster, if that's possible. Full of VOCs!

The stronger is smells, the better it works...usually.

 

[Angel_of_the_Skies]

I can’t remember who I saw mentioning this technique I’m using on my current build. Someone suggested to tape off the spirals with masking tape so that only CWF (Carpenters Wood Filler) gets on the spirals, and not much on the tube



Using 3M sharp line blue tape (which I use for painting rockets but decided to use for filling too), I was able to accomplish this



Once smeared, I used a razor blade to scrape the CWF and further push as much into the spiral

 

[neil_w]

Be careful, I have had blue tape pull the surface layer off of unfinished tubing when removing it.

 

[Angel_of_the_Skies]

Once smeared with a razor, it looks like this




Here are the results





After sanding with 400 grit (I prefer 400 grit on CWF as it is less abrasive on the tube, I use 220 on primers / fillers) it looks like this

 

[Angel_of_the_Skies]

Be careful, I have had blue tape pull the surface layer off of unfinished tubing when removing it.

Oh yeah, I forgot to mention, I place the tape on my work surface a couple of times to make the adhesive less sticky.

I accidentally forgot to on a strip and I can confirm it did peel a tiny bit of material and made the surface fuzzy, but nothing 400 grit won’t solve.

+1 on this tip

 

[SolarYellow]

Can also use the purple “delicate surfaces” tape to reduce/eliminate lifting tube material.

 

[Hobie1dog]

the blue tape just about ruined my one rocket, and I took it right over and tossed it to the trashcan.

 

[Angel_of_the_Skies]

Can also use the purple “delicate surfaces” tape to reduce/eliminate lifting tube material.

3M ? This is good stuff, I use blue 3M tape ‘sharp lines’ for masking when spray painting rockets

 

[mh9162013]

If your'e worried about tape damaging the surfaced it's placed on, try washi tape.

 

[brockrwood]

This rocket has the CoolRockets cool stamp of approval.

I will take a picture of it when I get back into town and then post it here. It also has a Quest Big Rage payload bay on top, to give it a bit of a extra length for stability, IIRC. A true “Frankenrocket”.

 

[SolarYellow]

3M ? This is good stuff, I use blue 3M tape ‘sharp lines’ for masking when spray painting rockets

https://www.homedepot.com/p/3M-Scot...ter-s-Tape-with-Edge-Lock-2080-24EC/100166232