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filler/sanding and painting techniques and products

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KrisR

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Looking for some tips on good filler product for balsa fins and nose cone. Just starting out building some basic kits. I just used the typical "carpenters filler" but its so thick it seems impossible to get great results.

Also looking for tips on good types of paint. I used a basic spray primer followed by several coats of gloss enamel but the whole thing has a slight gritty texture to it. Is there anything better that gives really smooth results?

Thanks.
 

luke strawwalker

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Here's a couple tricks I've learned...

I use regular Elmer's Wood Filler. Put a dollop in a baby-food jar and put a few drops of water in with it, and work it together using an old paint brush (I have an old 1 inch brush I use specifically for applying filler) Add a drop of water or a pinch of filler until you get it the consistency of mustard or ketchup. You can easily brush this onto the parts in fairly thin layers and have it dry quickly and coat well, and be fairly smooth before sanding and it fills the pores in the wood well. I always harden the balsa parts by applying THIN CA glue (Hobby Lobby pink bottle stuff works well for this and is cheap) by using the CA bottle tip like a magic marker to 'color' the stuff onto the wood. Do this outside as it liberates some irritating fumes and stay upwind! Once dry you'll have to give the parts a light sanding with 220 grit sandpaper to take the 'hardened fuzz' and grit off the parts and get them smooth for filling, but doing this really toughens up the balsa to resist dings better and makes it stronger, and it seems to minimize any water absorption by the balsa which could lead to warping, especially if your wood filler is overthinned. You CAN omit this step if you want, but be sure you don't get your filler TOO runny with water or it COULD potentially warp the fins after applying it if the balsa absorbs too much water from the filler.

Once your fins are filled and dried (couple hours at least or overnight is best) sand with 220 grit paper to take most of the filler off. Filler should only fill the wood grain; most of it should be sanded off. Once you've got the parts sanded smooth, give them a few good coats of primer. I've been using the Walmart house brand "Colorplace" gray and red primers and have good luck. Red has a bit more solids it seems, but gray sands easier (so it seems) and paint covers it easier (fewer coats). Let that dry at least half a day (overnight is best, longer in cooler/damper weather of course) and sand gently with 220 grit using a circular motion, and keep round parts like nosecones moving by turning them gently in your hand as you sand to avoid sanding spots. Once you take the primer down, tack the dust off with a damp paper towel and hold it up to the light, feel it, and look for rough spots. Anything rough enough to feel or see easily should be reprimed and sanded again lightly. I usually put down at least two heavy primer coats before I sand, and try to take the primer down til it JUST starts to break through the primer to minimize added weight but still get good coverage. Once you've got it pretty smooth with 220 grit, I then switch over to a 600 grit wet/dry paper and using a small bowl of water, I wet the paper, shake off the water, and wet sand the part to take all the sanding scratches out of the primer. It doesn't take long and the wet sanding process goes pretty quickly. You have to periodically wipe the part off with a paper towel to remove the 'sanding mud' liberated from the primer that's been sanded off. Use a circular motion with light pressure and rotate the round parts as you sand. Wipe the part off after making a couple passes and hold it up to the light... when you get a nice smooth reflection off it (light will show defects that you can't feel) the part is ready for paint. Wipe it off thoroughly with a damp paper towel and a dry paper towel and let it air dry awhile, then you can paint.

For most painting I've been using the Colorplace Walmart brand for basic colors like black and white. It's cheap and seems to cover as well and do as good a job as other paints for the basic colors like this. For more varied colors I'd go Rustoleum, as it seems fairly universal that most folks don't have anything good to say about the new formula Krylon (basically all you can get in Krylon anymore).

It sounds like if you're getting a 'gritty' texture you're probably experiencing "orange peel" or dry spray. Try moving the can a little closer to the part you're painting, and make your spray pass a little faster (move the can a bit faster past the rocket as you paint. Put a nice coat on (not so thick that it runs, but this comes with experience) so the coat is wet, and it should lay down nicely. Remember the paint coat is ONLY going to be as good as your surface prep was... if it was rough before you started painting, it's going to be rough when your done! Paint doesn't miraculously 'hide' a rough surface it's applied to-- in fact it's usually the opposite... any surface blemishes are usually MORE visible after painting than before. SO, if you want an excellent paint job, you HAVE to do a good job on the prep work.

Hope this helps! OL JR :)

PS... I usually do the majority of filling and sanding on the nosecones... for fins I generally paper them now-- makes them REALLY smooth and nice for priming and painting without filling and sanding, and the paper adds a LOT of strength for minimal weight. Once you've sanded your fin to the airfoil you want (rounded leading edge, tapered trailing edge, or on more 'scale like' rockets usually either rounded or wedge leading edges and square trailing edges) simply cut some printer paper about triple the size of the fin in a large rectangle, apply a fairly thin uniform layer of white glue to one side of the fin, lay it on top of the paper with the leading edge of the fin near the center of the paper, press it down firmly and squeeze out as much of the glue as you can, apply a thin layer of glue to the topside of the fin, and fold the paper over the leading edge and press it down against the fin. Gently work the paper toward the trailing edge of the fin, squeezing out the excess glue as you go (be careful and DON'T use too much glue as it's counterproductive) and smooth the paper out across the whole top and bottom faces of the fin. I then burnish (outline) the fin with the rounded end of a ruler, marker, etc. to seal the edges of the paper and fold them over the edges of the fin. Set them aside to dry, usually under something heavy like books if the fin is large to prevent warping. Let dry overnight. The fins can then be carefully trimmed around the edges to eliminate the excess paper. Finish them off by drawing the fin toward you with it tilted slightly across a piece of 220 grit sandpaper to take the fuzz off the edges and voila they're ready to glue on the rocket and should be quite smooth and strong! Good luck! JR :)
 
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GlennW

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I just do the old fashioned way, a couple of coats of sanding sealer on nose cone or fins, sanding after each coat. Then prime and paint, etc. You will see if you've done a good enough job when you prime. If you can see the fin is not smooth you can sand off most of the primer and do another coat.

I do like your papering idea though, especially for larger fins.

Glenn
 

hardinlw

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I use Behlen's sanding sealer from a woodworking shop. It is lacquer-based and fills/sands well. Use 220 paper for the initial sanding and finish with 320. Once the grain looks pretty well filled, I let it dry at least overnight and then apply a filler/primer. The "spot filling sandable primer" from automotive stores like Pep Boys works well. This stuff clogs sandpaper, so you'll have to change paper often. I usually use 320 here. The advantage of the primer is that it is colored (grey/white/red) and will show up defects that you would miss with the clear sanding sealer. The red lacquer putty can be used to fill any remaining grain or defects. You may want to thin it out with lacquer thinner. For the color coat, I've used automotive paints, Krylon, RustOleum, etc. Almost anything can be put on over the lacquer base if you let it dry a couple of days first.
 

KrisR

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Wow, great. Thanks guys! Good info. Any reason to fill/sand fins and nosecones after its been built? I just built this kit that instructed me to first assemble everything, fins and nosecone, fillets, etc....then do the fill and sand. Sounds a bit backwards if you ask me. I managed ok and it looks pretty good for my first kit but in hindsight, I think it would have been better to sand/finish the parts first before gluing them onto the body.
 

RimfireJim

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I do most of the filling and sanding before assembly. This includes fins, nose cone, and body tube spirals. Like you're thinking, much easier. Just don't have paint on surfaces that need to be glued.
 

hcmbanjo

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Regarding Fill N' Finish (now sold as Elmer's Carpenter's Wood Filler)
Some prefer the "Stainable" type, they say it sands easier. I can't see much difference between the two different formulations.
I put a big spoonfull of filler into a small Tupperware style container starting with a mixture of 1/2 filler to 1/2 water. Simply snap on the lid and shake. When mixed, check the consistency, for me it works best if the thickness of heavy cream. Depending on the age of the opened container of filler, it may take some stirring. Add more filler until it is brushable.
When you paint the filler on 1/16" balsa, it can warp the fins a little. Ususally when you pain the filler on the other side, the warp will go away.
I sand with 400 grit on a block. I try to leave a thin coat of filler on the flat surfaces.
After spraying, if there is a little bit of grain showing, lightly sand with 400 grit and spray again.
If you wet sand, be sure you only use water on surfaces that are sealed! You can leave your sandpaper in the water dish, it won't deteriorate. Shake off the sater and sand. Wet sanding keeps the sanded surface lubricated and keeps the paper from loading up.

A note on brands, I've had real good results using the Rustoleum "Painter's Touch" brand from Home Depot. This is the newer "Painter's Touch" (colors)Rustoleum, not the old standard brand of Rustoleum. It covers very quickly and can run is sprayed too thick.
Don't use the Painter's Touch Clear Coat! I was just finishing up a model and it crazed the surface! I couldn't believe it crinkled right over the orange undercoat. This used to happen when you painted Butrate Dope over enamel.
But the same brand over the same brand?
Sometimes it makes a lot of sense to fill grain before gluing the fins on. You can't sand off filler near white glue fillets. And, if you are painting the nose cone a different color than the body, don't glue your screw eye (and attach parachute) until after painting. It'll save some time on masking.
Stop by my website if you have a chance. It was written to answer questions regarding rocket building and painting.
 

MarkII

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Here's a couple tricks I've learned...
...

...as it seems fairly universal that most folks don't have anything good to say about the new formula Krylon (basically all you can get in Krylon anymore)...
Most folks, but not all... ;) :D (I might be the only person on TRF who gets consistently good results with the new Krylon. I have not been able to determine why that is so. :confused2: )

Otherwise, great write-up! The only things that I do differently are that I don't always harden the nose cone with thin CA, because it is often unnecessary on very small nose cones and it can sometimes leave rough areas on the surface that are hard to sand down afterward, especially if the cone has a complex shape. You should try not to do too much dry sanding of a balsa nose cone anyway, because it is easy to end up with a misshaped piece from too much sanding. (Been there too many times.)

The other difference is that instead of using wood filler, I use a combination brush-on sealer/filler to seal and fill the wood grain. I usually use Delta Ceramcoat All Purpose Sealer. You can usually find it in the tole painting supplies section of craft stores like Michael's, A. C. Moore or Joanne's Fabrics, or in the crafts section of Walmart. I usually give the cone 3-4 coats, wet-sanding after the second coat and after each subsequent coat, using the technique that luke strawwalker described. If you can find it in a hobby shop, Pine Pro Sanding Sealer is even better; it is thicker, harder and doesn't need to be applied in as many coats. Neither product gives off any bad fumes, and both clean up with just soapy water. One thing to remember with them, though, is that you never want to dry sand either coating, at least not very much. You should only wet-sand objects that have been coated with them.

There are a few other techniques for making balsa nose cones more durable, including brushing on thinned white glue, coating them with a thin layer of either epoxy-based or polyester-based laminating resin, or dipping them one or more times into Minwax Wood Hardener (works well, but expect to wait a long time for the product to fully cure all the way through). But coating the surface of the cone with anything will add at least some toughness to it, including coating it with primer and paint. And one of the best ways to keep the nose cones from getting dented is to place your rockets on stable stands during the 99.9% of their lifetime spent sitting on a shelf at home. Nearly all of the damage that they get comes from the rocket getting knocked over while it is standing on its fins, and the nose cone striking something hard on the way down. And if you have 30 or more of them all crowded together on top of a desk (see attachment), you get the "bowling pin" effect: one tipping rocket takes down six others. :rolleyes: I know - that picture is of my desk. :eek:

Don't get too obsessive about protecting your balsa nose cones from any form of dent, though - it can't be done without turning them into rocks. Having ultra-hard nose cones in model rockets would be a safety issue, anyway; one of the key safety elements of a model rocket (not a high power rocket) is that it is built out of frangible materials, so that in a collision the rocket breaks, not the thing that it collides with. It is natural for a balsa nose cone to pick up shallow dings and dents over the course of its lifetime (just like people); if those occur during flights, then they are well-earned. Balsa can be repaired; major dents can easily be filled and the cone can be made to look brand new again. (That's not so easy to do for the "finish" on people, although many have tried.) And if the nose cone is too badly damaged, or you get tired of repairing it, you can always just replace it with a new one. For scale models or real nice display models, it can even make sense to have two nose cones - one that is used at the range to take the wear and tear during actual flights, and another pristine one that gets swapped in when the rocket is put on display.

Luke's advice about the fins is spot on. I can't think of anything to add to it.

I apologize for being so long-winded. I like to help out beginners with painting/finishing tips, because I am still a beginner in this area, too. When I learn something new, I'll try to pass it on. Together we'll get this all figured out.

MarkII

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luke strawwalker

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Wow, great. Thanks guys! Good info. Any reason to fill/sand fins and nosecones after its been built? I just built this kit that instructed me to first assemble everything, fins and nosecone, fillets, etc....then do the fill and sand. Sounds a bit backwards if you ask me. I managed ok and it looks pretty good for my first kit but in hindsight, I think it would have been better to sand/finish the parts first before gluing them onto the body.

You can do it however you want to do it... I find it's usually FAR easier to sand/fill/prime nosecones/fins or paper the fins before they are put on the rocket. Read through the instructions and if you can't find a valid reason NOT to do it before gluing the fins on, then go ahead and do it.

Remember that kit instructions usually reflect the building habits of the person writing them, and there is usually some flexibility in how you actually go about building the kit, so long as you get to the same end configuration, especially with regard to the CG/CP relationship. The rest is up to you...

later! OL JR :)
 

Sandy H.

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One comment that improved my finishes a huge amount is to use a true tack cloth to wipe the rocket down prior to applying a primer or paint. I used to do the damp paper towel and air dry, but after some really disappointing woodworking projects (poly finish, not paint) I tried the tack cloth. It grabs everything and I have never had a finish problem related to dust ever since.

I use latex gloves when I use the tack cloth as they are sticky. If you are interested in trying them, they are a couple of dollars at the Home Depot etc and I still have some that are a few years old in ziplock bags. They are made for larger wood finishing projects, so a rocket or 10 is not a real challenge.

Just another thought.

Sandy.
 

accooper

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NjCo

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Most folks, but not all... ;) :D (I might be the only person on TRF who gets consistently good results with the new Krylon. I have not been able to determine why that is so. :confused2: )

MarkII
You're not the only one. I've had quite good results with the new Krylon. Can't complain at all. It leaves me scratching my head wondering why so many others have had problems. Maybe it's the low humidity here in Colorado. Then again it might be all the offerings I leave to the paint gods! :) Who knows.
 

Micromeister

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You can do it however you want to do it... I find it's usually FAR easier to sand/fill/prime nosecones/fins or paper the fins before they are put on the rocket. Read through the instructions and if you can't find a valid reason NOT to do it before gluing the fins on, then go ahead and do it.

Remember that kit instructions usually reflect the building habits of the person writing them, and there is usually some flexibility in how you actually go about building the kit, so long as you get to the same end configuration, especially with regard to the CG/CP relationship. The rest is up to you...

later! OL JR :)
KrisR: Being Old school; I leaned to finish models after building is complete. it's all about how we learn, Back in the day both Estes and Centuri taught finsihing after construction.
Either way has very little to do with the finished look of the end product. I find it much easier to blend in fillets and smooth out attachment points before applying fillers or in my case forgoing all that straight to primer.

Some years back I wrote a batch of articles for our club newsletter on finishing going from bare materials into detailing. They have been archived in the clubs library files under Tech-Tips at www.narhams.org All are downloadable and have been periodically updated to add changes and some of the materials. Haven't updated since the Krylon's formula change, but Most of the info still hold ture and can greatly help most anyone better their finishing skills. TechTips-002-005 cover most questions. there is also a later tip on making your own decals etc.
Hope this helps.
 

NjCo

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I like papering fins with full page labels. It makes the entire process so much easier. I basically do no sanding at all before putting the fins on the label page. The adhesive on the label binds well to the wood and you get a nice smooth layer of paper. You don't have to worry about bubbles or the glue warping your fins. Then you just cut around the fin with a razor knife. Really simple and fast. After that I apply very thin CA around the edge of the paper about 1/8" or so to ensure the paper is well sealed at the edges and to be sure the paper doesn't peal up during sanding. After the CA dries but before sanding I always apply a good coat of primer to the surface. This is important as it protects the bare paper from getting roughed up by the sanding. Then just round the edges of the fins off. The whole process can be finished in hours as opposed to the days it usually took me when I was using multiple coats of Fill 'n Finish or some other form of sealer. This is especially true on rockets with complex fin patterns like the Orbital Transport that is staring at me from my build pile. Finishing that baby looks a whole lot less daunting than before I came across this technique of papering. My last two builds were actually enjoyable - I HATE sanding!
 
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