Building at a higher level

[KILTED COWBOY]

When I was a kid I just used to slap them together cause I wanted to fly them fast.
When I was helping by young sons build I tried to let them do most of the work so
the quality was not good.
Now I am back into it for myself. Older and more patient.
I never bothered to fill in body tube spirials, now I will.
I know how and what to use. My question is do you do the filling before you attach
the fins etc. Or do you do the filling on the naked tube before anything else
Thanks

 

[neil_w]

Easiest time is to fill the naked tubes before you attach anything. You'll be removing the vast majority of the filler. If it's something porous like CWF, it won't affect the fin glue bonds much, and if you want you can do some extra sanding on the fin root locations (many folks do that anyway to scuff or remove the glassine layer.)

Recently, at least for smaller tubes, I've started shmearing the thinned CWF over the entire tube with my finger. I find it easier than trying to track along the grooves, both with application and sanding. For what it's worth.

 

[KILTED COWBOY]

Thanks

 

[Charles_McG]

Neil, how do you avoid tube 'hairiness' at paint time? It seems like whenever I fill before priming, I somehow end up over sanding, leaving the tube prone to lifting fibers during painting.

 

[neil_w]

Neil, how do you avoid tube 'hairiness' at paint time? It seems like whenever I fill before priming, I somehow end up over sanding, leaving the tube prone to lifting fibers during painting.

Hmm, I don't do anything specific to avoid fuzzies, which means either
a) I'm just lucky, or
b) I have fuzzies and don't realize it

Let's go with (a)!

Anyway, I cannot therefore describe my fuzzy-avoidance procedure; the best I can do is tell you what I do, and you can see if anything looks interesting.

1) Apply CWF. In the past, I just applied to the spirals, now I generally do the whole BT.
2) Sand it off. I usually use 220 grit *gently* to remove the heavy top layer, then as quickly as possible move to 400, then finish with 800. Generally, I'll end up running 800 over the entire tube.
3) (usually) Filler/primer on the tube. Same sanding regimen as for the CWF. I usually leave more on the tube than (e.g.) @hcmbanjo, who really takes off the whole filler/primer layer except what's filling the valleys.

And... that's about it. After step 2 my tubes feel pretty smooth; after step 3 they're *extremely* smooth.

Anything look significantly different from what you do?

 

[Charles_McG]

Anything look significantly different from what you do?

Yeah, I'm a hack when it comes to tubes. Prime and paint. Well, often just Rusto 2X "paint-n-prime" with a base white/grey, and then color. I only sand the primer to scuff it for later layers, not (usually) to fill/smooth.
I do lightly sand the glassine all up and down the tube pre-primer, and I'm considering alcohol final wiping. I've come to the conclusion that (nearly) all my color coat crazing problems stem from poor initial adhesion, rather than drying issues or paint mismatches (except for Rusto regular metallics - over 2X, THAT's a mismatch.) I can't tell you what grit, because I prefer emery cloth over sandpaper, and it simply doesn't have the same grading system.

I CWF fill and sand on balsa and plywood fins. 2-3 times. But I'm reluctant to get tubes wet.

Since I make my own 3.44" tube, I -really- don't CWF that, even though it needs the most spiral filing. That paper fuzzies at the drop of a hat.

 

[neil_w]

(except for Rusto regular metallics - over 2X, THAT's a mismatch.)

I have done this on many rockets and it works perfectly. One of my favorite combinations in fact. *Love* the Rusto metallics.

 

[Charles_McG]

I have done this on many rockets and it works perfectly. One of my favorite combinations in fact. *Love* the Rusto metallics.

The Rusto 2X Aluminum - works great. Love it.
The Rusto Universal metallics - work great. I love the Dark Steel, but the gold and rubbed bronze have worked well for me, too.
The Rusto-StopsRust-BrightCoat gold and silver? not so much.I find them to be -really- hot , solvent-wise.

 

[neil_w]

The Rusto 2X Aluminum - works great. Love it.
The Rusto Universal metallics - work great. I love the Dark Steel, but the gold and rubbed bronze have worked well for me, too.
The Rusto-StopsRust-BrightCoat gold and silver? not so much.I find them to be -really- hot , solvent-wise.

So far I've used the Stops Rust Black, Blue, and Silver metallics over 2x with no problems whatsoever. How long do you wait between colors?

 

[Charles_McG]

So far I've used the Stops Rust Black, Blue, and Silver metallics over 2x with no problems whatsoever. How long do you wait between colors?

Several days. I have gotten them to work by backing the distance off and using lots of misted coats. But the Universal series goes on like the 2X. MUCH easier to handle.

 

[neil_w]

But the Universal series goes on like the 2X. MUCH easier to handle.

I'll have to try one of those sometime. Still don't know the difference between the Universal series and the 2x.

Apologies to the OP, this has gotten a bit off-topic.

 

[Charles_McG]

Apologies to the OP, this has gotten a bit off-topic.

Oh yes, the original poster

Kilted, along with surface prep, I think the other major step in upping your building game is to take the time to make jigs to get fins/outboard tube assemblies straight, square, and plumb.

 

[Bruiser]

I fill the spirals with watered down cwf then sand with 220. I do get fuzzies but I prime it with the Rustoleum filler primer than sand it with 220. That gets rid of my fuzzies. I spray on a second coat of primer and I wet sand that with 400 to prep for the color coat.

I use a spray bottle from eye glass cleaner. It puts out a nice, manageable mist. I spray a small area, sand it and wipe it off. Spray another area, sand it and wipe it off and so forth until the whole tube is done. I doesn't take long at all. Wet sanding goes so much easier than regular sanding and the paper doesn't clog hardly at all. You can also "feel" when to stop sanding.

If I do get a sand thru I set it aside and let it dry. Once dry I sand the area and maybe apply some cwf if needed to fill/smooth the area. After the cwf dries, I sand the area smooth and re-prime.

-Bob

 

[neil_w]

Wet sanding primer on paper tubes can be risky because it is porous and can allow moisture through to the paper BT, which you don't want. This has been a contentious issue on this forum in the past.

Certainly, if it works for you then great. I do my filler/primer sanding dry, and it works just fine although I do need to clean the sandpaper frequently with a wire brush (the 400 in particular will clog fairly quickly).

 

[Bruiser]

Yep, that is true. The first time I wet sanded a tube I stood in front of the sink with the water running, wet my sand paper and went to town. I had a lot of spots to fix

Then I got a little smarter and learned one squirt of water from the eye glass cleaner bottle wets a small area and is much easier controlled. It's spray, sand, sand, sand and wipe off and it takes about as much time to do as it took me to type that but I only use two fingers . The first couple of strokes feel like you are sanding sandpaper then suddenly the sand paper almost glides over the surface and you're done.

Of course if you are putting on the lightest of primer coats to save weight well then this may not be for you. You really don't want sand-thru's. They are a pain because they really slow progress down.

I don't think I've ever heard of cleaning sandpaper with a wire brush before but I am going to give that a try next time I have some clogged paper.

-Bob

 

[KILTED COWBOY]

Thanks y'all. Also I think that jig idea for fin placement will be a must for me.
Really want to up my game and make my build display worthy.
I think I have the skills with my wooden and plastic ship modelling

 

[neil_w]

For real "game-upping" ideas go read through @hcmbanjo's blog, if you haven't already done so. https://modelrocketbuilding.blogspot.com/

 

[KILTED COWBOY]

For real "game-upping" ideas go read through @hcmbanjo's blog, if you haven't already done so. https://modelrocketbuilding.blogspot.com/

Just added the link to my favorites, will study it when I get home.
Thanks, really appreciate all the help and support.

 

[Charles_McG]

By the way - which tartan?

 

[KILTED COWBOY]

Tulloch is our surname. Part of the Ross clan

 

[Charles_McG]

McGonegals apparently weren’t highlanders, so we don’t appear to have a tartan- other than for Warner Brothers.

I wear Gordon Ancient.

 

[KILTED COWBOY]

Low lander, well won't hold that agin ya.
Interesting spread you have there on the table.
My tastes usually take me to the single malts, but I could probably have my arm twisted to try some of your wares.

 

[dr wogz]

My name's from a little twon on the english / scottish border: Peeble.

We're a family of moat diggers. And the two halberds on our crest is attestation to that, that we were usually the first into battle.

Our tartan is soo old, it's monochrome! it's black & white. It's apparently one of the first tartans, a 'working man's tartan.

"Shepherdson" of the family 'Shepherd'. And teh seamstress hates me, hates the tartan, as yo can go crazy tryign to sew with it!

 

[BABAR]

Reviewing the on-topic posts above, again emphasize CWF is fine to put on tube before attaching fins, because white and wood glues will soak right through it and provide good adhesion.

PRIMER is another matter. Priming the area of fin attachment may result in poor glue adhesion. Priming and PAINTING before attaching fins is even worse.

Not that you CAN'T use primer before attaching fins, but you will need to mask the fin attachment points off before spraying on the primer. It IS do-able, however.

YMMV.

 

[neil_w]

PRIMER is another matter. Priming the area of fin attachment may result in poor glue adhesion. Priming and PAINTING before attaching fins is even worse.

Not that you CAN'T use primer before attaching fins, but you will need to mask the fin attachment points off before spraying on the primer. It IS do-able, however.

I think you're overstating the case a bit here. Priming before assembly is not only "doable", it is done all the time, at least for filler/primer (which is all I'm considering). You are of course correct that you don't want to glue onto the primer, but there are (at least) three ways to deal with it, none very difficult:
1) Mask the fin attachment areas. This is what I usually do; for fins up to 1/8" thick I'll use a 1/4"-3/8" piece of tape, centered on the fin line.
2) Sand the primer completely off from the fin root areas. This is what @hcmbanjo does.
3) After priming, score and remove the glassine layer from the fin root areas, taking off the primer with it.

The advantage of filler/priming the pieces before assembly is simply that it is *way* easier to sand.

 

[jqavins]

How good are you looking for? There's a long distance between the work of an impatient kid and that of a master builder going all out. Me, I go for "Yeah, that feels smooth, looks good" but I don't go for "Oooh, perfect!"

I fill spiral grooves with 3M foam spackel plus primer. I push it into the groove for a couple three inches then scrape off with a hotel card key or the like, and move on to the next couple three inches. Go a little way at once, because it dries so fast that scraping it off one end of the tube is difficult by the time you reach the other end if you try to do it all at once. Let it dry more thoroughly, which takes about two or three hours, then sand; starting with 320 grit lets you go fast or you can just go straight to 400 because the stuff is soft. It's now ready to prime and paint, rubbing down with 400 grit between coats. I do need more practice with rattle cans and frequently end up with drips and runs which need more sanding; one can get better at that. My paint of choice is Rusto 2X.

I use the same spackle with primer, scrape with card, 320 to 400 grit technique for balsa fins.

For fin alignment, I'm in love with my Estes grey fin jig. For anything that won't do I make jigs because my work absolutely sucks without them.

I also use the spackle with primer for decorative fillets. Use wood glue or something for strong fillets first, then use that for larger fillets if you want them for looks or aerodynamics. (Aerodynamically, larger is almost never needed in low power size models.) I've been having porosity issues on these fillets which I don't have on tubes and fins. I'm not sure why it would be an issue in one application and not another, but it is; probably something to do with the thickness. So sealing the fillets is a good idea. An extra coat of primer should be all it takes; shoot the fillets, sand lightly, then shoot the whole rocket. I haven't done this yet, yet I'm pretty confident it should work. I bet dope or any other good sealer would also work

I wouldn't put my rockets in a beauty contest up against many of the builders here, unless the contest is judged from 30 feet. By the 30 foot standard mine come out just fine.

 

[BABAR]

I use the same spackle with primer, scrape with card, 320 to 400 grit technique for balsa fins.
.

do you have any warping problems with spackle, compared with CWF?

 

[jqavins]

do you have any warping problems with spackle

No, not yetanyway.

compared with CWF?

I haven't tried CWF. A lot of people talk of using CWF thinned with water, and I'd think one might get plenty of warping that way, wouldn't one?

 

[neil_w]

No, not yetanyway.I haven't tried CWF. A lot of people talk of using CWF thinned with water, and I'd think one might get plenty of warping that way, wouldn't one?

If you're applying to both sides of the fin the warps cancel out. I do both sides at once and stand the fin up on some tape; @hcmbanjo does (according to blog) one side at a time.

I did have massive warping problems the first time I tried it, doing one side at a time. I attributed this to bad wood; I had other problems with those fins as well. Since then, no problems. But of course I paper whenever possible.

 

[Binder Design]

I prime first, then automotive spot putty the spirals and any defects in the fillets.