Painting lighter

[lr64]

I used to know a couple of guys who did beautiful finishes on model airplanes. Very light fiberglass (1/2 or 3/4 ounce glass) applied with epoxy, then sanded and finished. One of them would do finishes that looked really great, but on very close inspection, you could see wood grain through them. He told me that such a finish didn't weigh any more than Monokote, which works out to a couple of ounces per square yard or so. The other guy would apply lacquer, wait a month, and buff it. Or maybe they both did that.

If one is working with water resistant materials, wet sanding is more pleasant than dry sanding.

For lowest drag, maybe move the seam where the rocket separates for chute deployment a bit below the predicted transition to turbulent flow. I'm guessing that would be a little below where the body becomes a straight cylinder. Or one could build with a very long, hollow nose cone. It wouldn't do any good, though, if the finish wasn't free of shallow waves, which can trip flow. Or, this is what I understand from the reading I've done. If you can't move the seam, and it isn't air tight, maybe vent the inside of the fuselage at that point to a low pressure area.

It may help to make the fins with an airfoil that's intended to promote laminar flow, at least if you're willing and able to shape them accurately enough and put a smooth enough finish on them. NACA 65-006? That might be good in the low transonic range, too, I'm guessing.


Almost all of the above is based on subsonic aero. I don't claim to know much about transonic and supersonic.



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Maybe, with high altitude and small rockets, the trick would be dual deploy. First, tiny air brakes, then a streamer at 300 feet. Or maybe no air brakes, if the streamer is strong enough. A clever person might figure out a streamer that deployed gradually or was strong enough to withstand high speeds.

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Free flight glider guys sometimes have a thin strip of heavier veneer, 1/64 ply, etc at the leading edges of their wings. Sanded to shape, of course. I've also heard of slotting the leading edge and inlaying a strip of carbon fiber laminate, edgewise. I'm sure other strong materials would also work.

 

[astronwolf]

Unless you are building a competition rocket, "Painting Lighter" isn't really a factor. The weight of the paint is insignificant when compared to all the other components. The added weight of CWF, Primer and Paint might scrub off a few feet of apogee... but who cares?

Thoughts?

Disagree. Years ago, the Jedi Masters team (myself and M. Nowak) squared off against the Flying I-Beam Kids (Schafer, Foster, and Brohm) in the Classic Model event. This was at one of Pittsburgh Space Command's regional meets. Yes, this was competition but hear me out.

Both teams entered the Estes Trident as our classic model. I built the Jedi Master's team entry, and John Brohm built the Flying I-Beam Kids' entry. As far as craftsmanship skills go, Brohm's most sloppily put together rockets probably look like museum pieces next to my rockets. I am no craftsman. And comparing our Tridents, mine looked somewhat shoddy compared to John's. But their model weighed about 3-tons because of the dozen coats of paint that was used. I just filled in the grooves and the grain, and hit it with a coat of primer and a coat of white lacquer paint - very minimal. My Trident would fly well on a B6-4. We used a C6-5 to deliver a beautiful, graceful flight that complemented the grace and beauty of the Trident. I thought it looked good. Meanwhile the Pittsburgh team's Trident barely got off the pad on a C6 motor. The difference in performance was enough that just for a moment there we thought we might actually snag First Place. Wow! I forget what they did, but they got their lead pipe of a Trident to fly good enough to carry the day. They deserved it - their Trident did look really nice.

So over-finishing does add a sh*t-ton of weight. And performance suffers. Not just by a few feet. Who cares? You do. You will care when your heavy, heavy model doesn't fly too well. And we like it when our models fly well, not just in competition, right? If you are building a safe queen, then have at it. Otherwise, easy does it.

 

[neil_w]

I would surely not want to compete against a John Brohm model.

 

[SolarYellow]

So over-finishing does add a sh*t-ton of weight. And performance suffers. Not just by a few feet. Who cares? You do. You will care when your heavy, heavy model doesn't fly too well. And we like it when our models fly well, not just in competition, right? If you are building a safe queen, then have at it. Otherwise, easy does it.

One of my first builds, I did just a chunk of BT-60 body tube with a 1/8 launch lug. I think it was actually the tube from a Baby Bertha kit. I failed to weigh it before starting finishing, but OR's default weight for that length of BT-60 said about 9 grams. The finished painted part was about 19 grams. So I more than doubled the weight of the body tube with paint. And I wasn't trying to do anything very special, just make sure there were no spirals showing through.

That was the genesis of this thread.

 

[lakeroadster]

Disagree. Years ago, the Jedi Masters team (myself and M. Nowak) squared off against the Flying I-Beam Kids (Schafer, Foster, and Brohm) in the Classic Model event. This was at one of Pittsburgh Space Command's regional meets. Yes, this was competition but hear me out.

Both teams entered the Estes Trident as our classic model. I built the Jedi Master's team entry, and John Brohm built the Flying I-Beam Kids' entry. As far as craftsmanship skills go, Brohm's most sloppily put together rockets probably look like museum pieces next to my rockets. I am no craftsman. And comparing our Tridents, mine looked somewhat shoddy compared to John's. But their model weighed about 3-tons because of the dozen coats of paint that was used. I just filled in the grooves and the grain, and hit it with a coat of primer and a coat of white lacquer paint - very minimal. My Trident would fly well on a B6-4. We used a C6-5 to deliver a beautiful, graceful flight that complemented the grace and beauty of the Trident. I thought it looked good. Meanwhile the Pittsburgh team's Trident barely got off the pad on a C6 motor. The difference in performance was enough that just for a moment there we thought we might actually snag First Place. Wow! I forget what they did, but they got their lead pipe of a Trident to fly good enough to carry the day. They deserved it - their Trident did look really nice.

So over-finishing does add a sh*t-ton of weight. And performance suffers. Not just by a few feet. Who cares? You do. You will care when your heavy, heavy model doesn't fly too well. And we like it when our models fly well, not just in competition, right? If you are building a safe queen, then have at it. Otherwise, easy does it.

Gotta be more to the story. All things the same, the lighter rocket wins. Unless your rockets surface finish was really rough.​

​

Did they actually weigh the rockets, or are you merely speculating?​

 

[astronwolf]

I would surely not want to compete against a John Brohm model.

Why not? It's fun and you might learn a thing or two.

 

[astronwolf]

Gotta be more to the story. All things the same, the lighter rocket wins. Unless your rockets surface finish was really rough.​

​

Did they actually weigh the rockets, or are you merely speculating?​

The lighter rocket did not win. There were only 100 points for flight characteristics. You can look up the rules yourself. And they don't weigh the rockets. But seeing them, handling them, talking about them, watching them fly - get it? You don't need a remote sensor like a balance - just your own senses and a brain. The point was that the lighter rocket flew better.

 

[lakeroadster]

The lighter rocket did not win. There were only 100 points for flight characteristics. You can look up the rules yourself. And they don't weigh the rockets. But seeing them, handling them, talking about them, watching them fly - get it? You don't need a remote sensor like a balance - just your own senses and a brain. The point was that the lighter rocket flew better.

No weighing was done, you just "knew" it was lighter. Thanks​

 

[John Brohm]

Gee Wolf! That's a stretch back. The event you refer to was our Steel City Smoke Trail Regional in May (or was it June?) of 2013.

I can't say how much heavier our model was compared to yours, but it likely was. Finishing does add weight, no question, so to your point, one needs to be sure what the mission is and finish the model accordingly. Our Trident wasn't going to break any altitude records, but then that wasn't its purpose either.

Steel City Smoke Trail XXIV is coming up this June 22/23 (two days of competition, sport flying and HPR), so we'd be happy to see you out at Weber (and anyone else, for that matter). Check out the website at www.PSC473.org.

 

[astronwolf]

No weighing was done, you just "knew" it was lighter. Thanks​

You couldn't tell which one was heavier if I handed you two rockets? Wow.

 

[astronwolf]

Steel City Smoke Trail XXIV is coming up this June 22/23 (two days of competition, sport flying and HPR), so we'd be happy to see you out at Weber (and anyone else, for that matter). Check out the website at www.PSC473.org.

Planning on it. See you then.

 

[Hobie1dog]

I wondered why people didn't try using RIT Dye on body tubes to put color on it.

 

[bjphoenix]

One of my first builds, I did just a chunk of BT-60 body tube with a 1/8 launch lug. I think it was actually the tube from a Baby Bertha kit. I failed to weigh it before starting finishing, but OR's default weight for that length of BT-60 said about 9 grams. The finished painted part was about 19 grams. So I more than doubled the weight of the body tube with paint. And I wasn't trying to do anything very special, just make sure there were no spirals showing through.

BT60 is a tough size with 18mm BP motors. I have a baby bertha, an old Nike Smoke and an Estes Patriot Missile that fly well enough on B and C motors, the larger BT60 rockets I have, including an ESAM, barely fly with B6 and can be problematic with C6 because they get off of the pad slow and can turn horizontal. Bigger BT60 rockets should probably be built to use C11 as a minimum. This is unfortunate because I like that tube size and HobbyLobby doesn't sell C11.

 

[bad_idea]

Bigger BT60 rockets should probably be built to use C11 as a minimum. This is unfortunate because I like that tube size and HobbyLobby doesn't sell C11.

BT60 is perfect for 3x18mm clusters though, and Hobby Lobby does sell a variety of 18mm motors.

 

[bjphoenix]

BT60 is perfect for 3x18mm clusters though, and Hobby Lobby does sell a variety of 18mm motors.

I still have an Astron Ranger that I built almost 60 years ago, I think it is retired and won't fly again. Actually a lot of my BT60 rockets I built with 24mm mounts but that points out another thing about BT60- it can be too big for C6 and too small for D12.

 

[SolarYellow]

I like C11 more and more.

 

[lakeroadster]

You couldn't tell which one was heavier if I handed you two rockets? Wow.

Probably not.... when it's 2.3 ounce rocket, and you're talking some percentage of that weight.​

 

[Cape Byron]

Go old school and use dope instead of paint.

Tried it, man, but the buds really aren’t aerodynamic.

 

[BABAR]

Tried it, man, but the buds really aren’t aerodynamic.

Just don’t turn this into a glue thread!

 

[lr64]

Tried it, man, but the buds really aren’t aerodynamic.

Just extract the "oil", add some Japan drier ( https://www.sherwin-williams.com/homeowners/products/crown-japan-drier ) and you're good to go.

 

[Sandy H.]

I remember my wife showing me a video on youtube about people doing abstract art with an alcohol based dye (I think). It was some sort of swirl method and there were lots of videos. I wonder if that substance is compatible with a filler primer or clear coat? Seems like it would weight as close to nothing as possible. If it needed to be shiny afterward, I'd see if a lacquer clearcoat was compatible and then use rubbing compound to get the final shine.

I have not tried any of the above (except lacquer and rubbing compound), so this is just a thought, not a verified solution.

 

[lr64]

I remember my wife showing me a video on youtube about people doing abstract art with an alcohol based dye (I think). It was some sort of swirl method and there were lots of videos. I wonder if that substance is compatible with a filler primer or clear coat? Seems like it would weight as close to nothing as possible. If it needed to be shiny afterward, I'd see if a lacquer clearcoat was compatible and then use rubbing compound to get the final shine.

I have not tried any of the above (except lacquer and rubbing compound), so this is just a thought, not a verified solution.

Was it aniline dye?

 

[Sandy H.]

Was it aniline dye?

I think it was called alcohol ink.

 

[BABAR]

For color with for all practical purposes no weight penalty, using white body tubes and white plastic nose cones I’ve had satisfactory results with black markers, usually using a Magnum Sharpie (which is kind of an oxymoron.). Often has a black purple sheen kind of like the feathers of a Grackle.

That’s been on tubes with no spiral filling. Would probably work on white or gray primer.

Red comes out okay, harder to get an even shade. Works on bare tubes, probably would work on white primer.

My bar for finishing is pretty low, most of my stuff is weird (or preferably what @kuririn calls “avant-garde”.). So my rockets are more about, “how do they fly and recover“ and less “how do they look.”

 

[lr64]

You can get fairly light results if you decide the paint doesn't have to look opaque from close up and you use an airbrush or something, plus paint with really fine pigment. It helps if the different materials are close to the same color.

 

[Azamiryou]

A point of reference: I just completed an Estes Vapor, spec sheet says mass is 99g. I added a laundry shelf, chute protector, electronics bay (coupler, bulkhead, sled, Eggtimer Apogee and battery), and papered the fins. Before painting it came in at 180g.

Painting was
1) Harbor Freight's sandable primer - several coats sanded off almost completely until the rocket was smooth
2) A final light coat of primer (to even out the color), lightly sanded.
3) Two coats of Krylon Fusion matte white, lightly sanded after each coat
4) Two coats of Krylon Fusion gloss purple, to get even color over entire rocket
5) Apply decals
6) Two light coats of Krylon gloss clear to seal down the decals. These were applied just heavy enough to get a good gloss

After painting, the rocket came in at 195 g.

So it's less than 10% paint by weight - that's lower than I expected for a heavy, high gloss paint job.

 

[lr64]

A rocket with a short burning, high thrust motor may coast higher if it's relatively heavy. With a long burning, low thrust motor, it will likely go higher if it's light.
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For maximum altitude per total impulse, the long burning motor in a light, aerodynamically clean rocket is best. Assuming there's enough initial burst to get it off the rail safely and that we aren't going really high in the atmosphere. If you start at 30,000 feet, things might be different. The difference in altitude between a long and a short burning motor can be quite remarkable, at least according to Openrocket. The maximum speed will be achieved with the latter, and it might even stay below the launch ceiling.

 

[DaHabes]

In the Midwest where your painting months are limited (November through April is too cold and July and August can be too humid, requiring long drying periods), perfection is the enemy of good enough. I fly half of my finished rockets naked...

 

[lr64]

In the Midwest where your painting months are limited (November through April is too cold and July and August can be too humid, requiring long drying periods), perfection is the enemy of good enough. I fly half of my finished rockets naked...

Some paints can be used with stuff called retarder, which will reduce blush, caused by humidity. Some polyurethane paints will cure faster with more humidity, though I don't know what it does to the appearance. I suspect this is what went on with some polyurethane spray paint a friend had. It was taking a long time to cure, so he put it in the driest place he could find, in the winter. I think he said it took a month, and even then he wasn't happy with it.