Stuka Stunt Main Forum · 13 of 13 known posts recovered
Craig Beskow
Craig Beskow
Craig has the right idea. That's the way I do it. I first read of the trick in Noel Drindak's column in Stunt News.
It makes for a very neat installation, and the feedthrough goes in after the finishing is all done, so you don't have to sand and paint around it.
I do use thin CA to hold it in place, but also make a small fillet on the inside with epoxy, as the CA will eventually give up.
Here's how it looks.
Cheers,
Warren W
You could use a little drop of JB weld on the inside once you have installed the tube.
It would also add a little strength to the joint from the inside.
That is a cool idea.
Warren,
Nice work on the engine bay! how about a pic of the rest of the plane?
Stephen,
The Buc 740 would be a very good next plane. That was my first plane I competed with and it went along way.
I love the 740 size. I have one built right now with a pipe tunnel. If I ever paint it it will rule!!
Doug Moon
Thanks Doug. I posted pics of the plane last year, so you may have seen it. It's a 40 sized Time Machine, Tom Dixon kit, Quick Build foam wing, Ultracote and Rust-oleum for the finish. The engine is a Randy Smith prepared OS40FP.
It's my #1 machine, and the best flying plane I've ever flown. It turns corners so sharp that I think to myself "...I can't believe that's me flying... !" <g>
Cheers,
Warren W
Yes.
Polycrylic is an acrylic. Dope is an acrylic.
As far as I know there is not paint that is commonly used for modeling that will not go OVER PC.
The City Smasher
Doug, I'am in the process of building an orential and when I'am done I'am going to put the Ro-Jett .40 on it and get use to the engine my winter project will be the Buc 740..
From the new article:
This article will attempt to outline a finishing method that could be substituted for the old “dope and tissue” method. This method was outlined to me by the Fort Worth finishing guru Bill Wilson, at the 2000 Dallas Stunt Symposium. I have taken Bill’s method and added a few extremely minor twists, but for the most part it is Bill’s methodology and method, and I am just a humble, humble, student of the Master.
One thing to keep in mind is that any new finishing method will follow a learning curve on the part of the user. I can assure you that an expectation of perfection on the first attempt will lead only to disappointment. I know that the doping techniques used by a large part of the control line stunt world have been in development for some time now (about 70 or so years). I would hope that the modeling community would embrace a method of finishing airplanes that can have a killer finish applied in a matter of days instead of weeks or months. However, it is still every modeler’s responsibility to understand that any new method will require patience.
This is the method in a nutshell (look I’m in a nutshell!)
1. Starting with a balsa airframe, the solid sheeted surfaces are finished with Minwax Polycrylic (PC) and 00 silkspan. PC is available at Home Depot and Lowes and comes in gloss, semi and flat versions. I have always used the gloss version, and I do not know if there are any advantages to the other versions. Minwax PC has several advantages due to the fact that it is a water based acrylic. Being water based, it simply has very little solvents and almost no stink. Being an acrylic makes it a UNIVERSAL undercoat for just about any type of acrylic paint (all of the paints used in modeling are acrylic). It dries in 24 hours, and once dried it takes on a character that is very similar to hardened thin CA. Balsa impregnated with PC becomes ROCK HARD (much like thin CA impregnated wood). It is really not necessary to use any paper with the PC (Bill Wilson sees no advantage to it), but I have found that, for my uses, it is truly wonderful over sheeted surfaces when used with thin silkspan. Using 00 silkspan in conjunction with the PC helps to level the surface at application. To attach the silkspan, first wet the surface with the Polycrylic (there is no need to pre-coat the surface like a dope application), and WHILE THE PC IS STILL WET apply the slightly water dampened silkspan. Once all the edges have been pulled and the wrinkles are all pulled out, trim the edges of the silkspan. Once trimmed, wet the entire surface of the silkspan with a coat of PC. Make sure to do the entire surface evenly and get all of the edges. At this point it is possible that there may some “relaxation” in the part, especially for long flat parts like flaps, but no need to worry. Typically, the relaxed parts will return right back to their former shape upon drying. For added security, a good method is to lay the “tack free” drying parts on a sheet of Teflon on a flat surface and weight down slightly. This will basically guarantee that the parts will dry DEAD FLAT and will not warp in the future. Subsequent coats will have little, if any effect. Let this first coat dry for a minimum of 24 hours and begin DRY sanding the surface with 180 grit ADHESIVE BACKED 3M OPEN COAT.
Note on sandpaper: Not all sandpapers perform the same, period. For our uses, except for the case of wet sanding the clear coat, all other sandpapers are severely lacking. The 3M open coat paper can be found at ANY local body shop supply store. I have purchased two different kinds, one is made for air files, it is 3” wide YELLOW and comes on a roll, the other kind is 6” sticky back YELLOW DA discs, both are the same paper. Either one will work. DO NOT SUBSTITUTE!!! The ONLY acceptable substitute is the generic for 3M (Nikka). It is EXACTLY the same and costs about $10 less. A roll of 3m will cost about $30 and will last for many, many airplanes and will be the best all-purpose sandpaper you have ever used. If in doubt, buy the 3M, it is still cheap in the long run.
At this point watch for a few different conditions. One, that the entire weave of the silkspan is filled. If it is, you should basically be able to sand all the silkspan wrinkles, edges, and surfaces exactly the same. You see, PC makes the silkspan solid. Each individual layer is not longer unique, like when you use dope. The silkspan simply serves as a very thin sponge to accept the liquid plastic. Once the weave is filled the silkspan is fully impregnated with plastic. I use double layers of silkspan over edges that are not quite perfect, fill them with PC and sand it all down flat, so the paper and PC works like a filler. The PC will sand with some work, remember it is HARD STUFF, but hard is good for balsa airplanes, especially for a base coat. Second, you will notice that the paper will cut all of the surfaces about the same because the PC has served to make all of the surfaces of a uniform hardness. Glue edges will be the same hardness as punk balsa. This is a good opportunity to do the final shaping on joints and flatten everything out and get rid of the ridges that can appear on edges of dissimilar hardness (I really love this part of the process and I like to spend a little extra time here). Lastly, if you do see an edge appear in the silkspan as you are sanding YOU DID NOT FILL THE PAPER (it will appear white if it is not filled). Re-coat that area and all other dry areas and sand the next day.
2. For strength, add a second layer of PC and paper to the nose. Re-coat with a third coat after sanding the second coat. The nose will be nice and shiny and ROCK HARD! I have found that the PC prepared nose is harder and more dent resistant than even a nose finished in fiberglass and epoxy, and there is no weave to appear later. It is also a good idea to re-coat at the fillet areas (we have no fillets at this point). Make sure that area gets good and shiny also. This allows you to sand the final fillets without gouging the wood, as the shiny areas will be extra hard. Please don’t go crazy with the PC at this point. One coat of PC is equal to about 4 coats of unthinned dope. Too much all over will add up, so why do it? A fully sheeted plane should appear to have a slight “plastic” look. The nose should absolutely look like it is fully “plasticized”.
3. For very small dings during the pre-primer stages I use plain old spackling (not the light spackling). In small quantities I have never had any shrinkage problems, especially when saturated with the PC. For fillets I use Epoxolite or 5 minute epoxy depending on the size of the fillet. Blend sand the Epoxolite on the PC, you will notice the PC hardness will give you more freedom to be aggressive without cutting into the wood, but still watch carefully. DO NOT overcoat the finished fillets with a coat of PC. I have found that PC over Epoxolite is a dicey proposition, so don’t do it! Wait to overcoat the fillets with the primer.
4. For open bays use medium Sig silkspan or Polyspan and filled with three coats of nitrate dope with zinc stearate. This is the slowest step in the entire process. On my designs I have no open bays, which eliminates the needs for dope altogether. I have tried PC on open bays, and I have yet to make it work. Bill does, and he is very happy with it. I use nitrate, because that is what I am comfortable using on silkspan in open bays.
5. The next step is to shoot the entire plane in auto primer. Typically, I use cheap “lacquer primer surfacer” from English Auto Supply (a local Dallas body shop supply chain). Every auto supply has the same lacquer based primer surfacer. Despite the fact that this primer is lacquer based, I absolutely recommend using only urethane reducer in the primer. I only use Omni urethane reducer. Omni is a very reasonably priced line of reducers that is produced by PPG. I frankly, can’t tell any difference between the Omni reducer and the PPG reducer that cost 2 to 3 times as much (they even smell the same). Omni reducer comes in four heat ranges, which include fast, medium, slow, and super slow. For primer I would recommend starting with medium and thin the first coat 2 to 1 to 1 ½ to 1 (for over 90 degrees try the slow). The second coat can be thinned closer to 3 to 1, depending on how much is left to fill. The first coat is sanded (DRY! ALWAYS DRY!!! NEVER EVER WET SAND!!!!) with 180 open coat paper. The second coat is sanded with 180 and finished with 320 open coat.
There is really no comparison between the lacquer primer combined with lacquer thinner and the same primer combined with urethane reducer. The less aggressive urethane reducer allows the primer to “stack”. A stacked surface appears almost shiny and will appear very flat with a very thin coat, also it will shrink less and absorb less color and clear coats. A stacked coat will also sand like it is very thick even when it is not, and it will also allow the clear to shine more. Faster drying, more aggressive lacquer thinners have a tendency to create a primer surface that is more like a “forest of trees”, if you will. The trees are all standing up and it takes an incredible amount of material to fill up to the top of the trees. The primer used with urethane reducer is more like a forest with all the trees laying their sides or “stacked”-like bricks in a wall.
On my latest plane I switched to the catalyzed PPG urethane primer K-36. All of the primer coats on this airplane were urethane and I only used lacquer primer for fast spot fills. The K-36 is really kind of a hassle to use, as it is only sandable after a full 12 to 16 hour drying time. It also did not tend to “fill” very well as it tended to wick away from imperfections as opposed to wicking into the voids like the lacquer surfacer. Even though, after all was said and done there were aspects to the K-36 that I really liked. The “holdout” (the ability of the primer to resist shrinking and swelling at the application of the clear) was really impressive and it sanded very nicely. It is also very solvent resistant, which can be handy. For the next airplane I plan to use the lacquer primer for the base and the K-36 for the final primer coat.
SANDING THE PRIMER
The goal is a uniform coat of primer. The idea is to get it so thin there is no real weight penalty. If you sand gray auto primer until you can almost read small newspaper print through it, it is PRETTY DANG THIN. I don't care if you shot on your primer an 1/8" thick, if you sand it down until it is uniformly semi-transparent there can't be a lot of weight there.
Applying primer is really pretty simple. Make sure you put enough on to fill every imperfection you can see or you will just end up sanding and re-shooting again. Put on enough coats with the material thick enough to fill. This is a different philosophy than the “dust on a coat and sand, dust on a coat and sand” philosophy that the dope guys use. As far as the level of fill, your mileage may vary depending on the type of primer used. The PPG K-36 requires 2-3 full coats to fill every bit of the wood grain in a well-prepped model. Lacquer primer surfacer can typically do that in one coat with some spot work here and there. Catalyzed primer does has a shrinkage advantage, which is nice because you hope that all that sanding will be not be in vain once the first coat of clear is applied.
The first part of the sanding process is to “block” the large flat surfaces. I bust the surface with 180 grit and sand until the very first transparent spots start to appear and then I move on. Sand in larger strokes across the known imperfections as much as possible. At this stage you will start to see the major imperfections (such as wood grain) disappear as you sand. Once the entire surface is done to this level you should see semi-transparent spots periodically but the surface should still be opaque.
Now it is time to remove the 180 scratches, as much excess primer as possible, and bring the primer coat down to a uniform thickness. Switch to 320 and sand all of the more opaque spots until the surface is as uniformly NEARLY transparent as possible. Only sand the opaque areas. Stay away from the transparent areas! You should be sanding in very small strokes or circles at this point and being very specific about where you are removing material. Sanding in long strokes will only serve top break through the more transparent areas. Then, switch to 400 and take the surface down one more level of transparency (this only takes seconds). At this point there is a layer of primer so thin that 5 more strokes of 400 grit would bust through the surface. You seriously can't get it any thinner. Busting through the surface is a very bad thing, and accomplishes nothing. These areas will inevitably swell with the clear and just show the imperfections. So it does no good to "sand it all off"! This is a huge misconception about the use of primers (including sanding sealer or dope and talc). Sanding the primer until only little slivers of gray are left in the wood grain is not a “coat”. If you sand this far you have effectively removed the entire coat, so why bother? There must be an unbroken LAYER of primer remaining. I think most would be better served to err on the side of a slightly more opaque stopping point than more transparent. More opaque means there is less chance for dissimilar surfaces, which leads to swelling. The difference in weight in two shades more opaque is most likely not even a factor in the final analysis.
6. For color use 1 to 1 non-catalyzed polyester basecoat. Common types are Dupont Chromabase or PPG Omni for a good, not too expensive solution. I use Omni, PPG and Valspar (mostly Valspar). A lot of people are truly confused about the function of the basecoat part of the basecoat/clearcoat process. A lot of talk is made of auto clears but there seems to be very little discussion about the basecoat. Simply put, the stuff is really wonderful to work with. It has so many advantages over the lacquer-based colors. One advantage is that it has no gloss binders. Gloss binders create a sheeting effect across the surface that it is applied. This sheeting effect creates the gloss. These gloss binders add needless amounts of weight and are the main culprit for the paint trying to “wick” underneath the masking tape when applying trim. Basecoat “sticks straight down”, it does not have any gloss binders so it makes no attempt to stick to itself “sideways”. The sole function of the basecoat is to apply color, so no gloss is needed. Also, basecoat dries in about 5 to 10 minutes (always use fast reducer) and can be taped on top in that time.
7. I use 3M blue vinyl masking tape for sharp edges. I use regular masking tape for all others. I recommend 3M/Scotch masking tape only. I also use a 3M paper/mask dispenser that I bought at the Sherwin Williams home painting store. Please, do yourself a favor and drop all the newspaper and tinfoil masking and go the system used by every serious car painter in the world. I recommend that every human being on the planet purchase a tape/paper dispenser. There simply is no substitute. The paper rolls (I use the 9” rolls myself) can be found at home Depot or Lowes’ and are definitely worth the $1.50 price. I told everybody about the 4 ½ hour paint job Doug Moon and I did on my 2002 Nats plane the Shear Panic. I believe the paper/mask dispenser was one of the factors that made that kind of speed possible.
8. The clear I am currently using is the Matrix MS-42 2 to 1 premium urethane clear, with the MH006 hardener or the MH008 hardener in hot weather. All of the major paint companies offer a “premium” 2 to 1 clear. You could substitute PPG or Dupont, and in particular PPG’s bargain line of paints called Omni has a very nice 2 to 1 clear that is very suitable to our application. I have also used 4 to 1 clears, including Chromaclear and Valspar and they behave exactly the same as each other. I like the 2 to 1 clears better. When I first started using the clears myself I had no love of Matrix, and Bill Wilson happened to give me the clear, as it was a sample from a sales rep. I would have normally been using Valspar brand, because that is what Bill uses, but I took home the Matrix clear and that is what I have been using ever since. In fact, I have grown to really love the Matrix clear, as it performs wonderfully and is priced very reasonably, at nearly half the coat of Chromaclear.
I thin (or reduce) the clear coat from 33% (2-1-1) to 100% (2-1-3) depending on what I am planning to shoot. I typically shoot at close to 100% reduction or slightly less. I use Omni medium, slow, or super-slow urethane reducer depending on the temperature. I use the Omni reducer because I have found that it is IDENTICAL to the PPG urethane reducer that I was using before, and the Omni costs about one-fourth as much (it is also what my local shop carries). A gallon of Omni reducer costs less than $20 and can be used in the primer also. Feel free to use whatever brand urethane reducer you want, as I am sure they are extremely similar.
The real function of the reducer in the clear is to give the modeler a chance at a light clear job. We are painting model airplanes after all not cars, so a thick heavy coat of clear, (while desirable) is not practical. Auto clears are “high solids”. High solids content simply refers to the fact that there is actually more material in the can and less solvents (epoxy, for example would be considered 100% solids-as it loses no weight as it cures). This has been the trend in auto paints for years, resulting from enormous pressure from the EPA. Dope clear for example, is typically a 10% solids and 90% evaporating solvents, so it would take 6 times as much dope clear to equal a 60% solids auto clear (it also takes much more time to gas off). The urethane reducer used in the clear serves to stretch the material into a thinner coat, resulting in a reasonable weight. The reducer can also serve help the clear flow and flash a little slower if the hardener is a little fast, as most spot repair hardeners often are. The slower the clear dries the more it will lay out typically, but it will also serve to allow more “trash” to stick to the wet surface, especially if you are painting in your garage. Everything is really a compromise in the end.
I have been doing pretty well with using “one slower” when thinning the clear if a slow hardener is not available. So, for example, if the temperature calls for medium reducer (70 deg.-80 deg.) I use the slow (80 deg. -90 deg.). Don’t get cute and think that using a super slow reducer when it is 60 degrees will result in a finish that looks like a mirror. Most likely you only succeed in trapping the solvents in the first coat and “popping” the surface with the second, which will result in a bunch of tiny little air bubbles to appear in the surface.
3 oz of clear, 3 oz of reducer for a total of 6 oz in the gun will do a Nobler sized plane if the overspray is kept to a minimum. The result will typically be a 1.5 oz clear coat (see note). The first coat is shot semi-gloss, the second is shot a little wetter. Allow 10-15 minutes in between to let the reducer gas off out of the previous coat. Don’t try to fix all the orange peel until you give the material 10 minutes to flow, you might be surprised how much it will. The 2 to 1 clear is just so much easier to shoot and seems to not want to run if "stacked" like the 4 to 1 clears. Not to mention the shine is at least triple.
Note: If a clear is a 2 to 1 mixture it is typically 60% solids (thank the EPA). I use a gravity fed "HVLP compliant" Harbor Freight gun, which averages about 75% of transfer. That being the case, 75% of 60% of the weight of the clear (actual clear, not reducer) will end up on the airplane. Using rough numbers, 50% of the clear in the gun will end up on the plane. I found that this does definitely work in practice. When shooting my profile P-Force I used the 6 oz mixture and 50% of 3 oz ended up on the airplane, so the clear weighed about 1.5 oz. The mistake I have made in the past was not thinning the clear enough to allow the material to flow out nicely (or cover the area). This is not a car, after all, and 50% of what is needed on a car is still quite a lot of clear. When I first started using the auto clears (read that”did not have a clue”) I typically used a lot of material to try to get the material to "lay out". I shot 12 oz of clear on my Oriental unthinned. I wish I could go back and do that again. My guess is that clear job weighed about 5 oz. People who are used to shooting dope, which is closer to 10% solids will typically shoot WAY TOO much of a high solids clear. Using logic, one coat of 2 to 1 clear is equal to 6 coats of dope at FULL STRENGTH. Which, by my numbers, equates very nicely to about what the dope guys end up shooting on a plane (10 to 15 coats-Windy uses a quart on a plane). The difference being that two coats of thinned urethane clear will lay flat and will only need rubbing if you are a true aficionado. Most guys would be sufficiently impressed with "OEM" car shine.
EQUIPMENT:
I recently added a "clear only" gun and a Harbor Freight detail gravity feed gun for painting trim colors. The trim gun works very well for the task of shooting masked areas as it naturally shoots very "dry", which is perfect for basecoat. The gun I use for primer, basecoat, and clear is the Harbor Freight HVLP "compliant" gravity feed.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=43430
This is the gun that started the gravity feed revolution for stunt community (I am sure there were also the previously enlightened). Bill Wilson was using one at his shop, and after The Moons and I used it, we had to have one. I bought one, the Moons bought theirs, and I got one for Al Rabe, which he gave to Frank McMillan, and so on, and so on...
This gun is capable of shooting paint at very low pressures (around 10 to 5 psi depending on the viscosity of the material). Since it does not rely on the air pressure to feed the paint to the nozzle, overspray is truly minimized. The transfer rate of the gun is approximately 75%.
I recently acquired a detail version of the same gun. It was on sale for $34.95 with the regulator and I just could not turn it down.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46719
This little guy is great for dry coats of small trim, or simply freehanding a camouflage job on your semi-scale. It is capable if a fan varying from 1/8" to about 3", and could be used as a main gun, but it would be SLOW GOING. I would recommend buying the big gun first.
I would recommend a filter unit for your air supply. They can be had real cheap at Harbor Freight, though.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42035
I would recommend putting the filter unit as close to the gun as possible. I actually mount mine right after the compressor unit and make sure to keep my hose short enough that there is not a lot of condensation in the feed line. If you choose to not use a full size regulator/filter unit I would suggest a disposable filter/water trap that can be attached to the base of the gun. These can be found at your local auto body store.
As far as an air compressor, I have a Cambell-Hausfeld 3 hp single stage with a 20-gallon tank that I bought Wal-Mart more than a several years ago. This compressor is really more than enough for any painting operation I have ever done, and is adequate for most body shop and mechanic's air tools. It is really not necessary to go quite this big for painting alone. Harbor Freight has a good 2 hp pretty cheap.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=40400
By the way, I in no way guarantee that YOU can do this system the first time. There is learning curve that must be undertaken, just like any other new system. This is not dope by any means. There is definite learning curve to auto paints, and I have a lot of help in Bill Wilson. I could have never figured out any of this stuff on my own.
Safety:
I just so happened to buy a new organic vapor mask, so I took the opportunity to call the 3M Technical Service Line to get the 411 on the effectiveness of organic vapor “carbon masks” on diisocynates (the bad stuff present in the auto clears). Much to my surprise, they are completely affective against these chemicals, even more so than most solvents. The use of “fresh air systems” is not even advocated by OSHA under normal conditions. The only reason fresh air systems were EVER advocated for diisocynates was because there were no “warning signs” for these chemicals (like a smell). You can read the whole article here.
http://www.3m.com/occsafety/pdfs/respirator1.pdf
This is the nuts and bolts of the article.
Misconception No. 1: Air-purifying respirators should not be used because diisocyanates have poor warning properties.
Although OSHA specifically permits change schedules in lieu of sensory warning properties, some health and safety professionals argue this is not a safe practice. They believe diisocyanates could enter a facepiece through a spent cartridge or defect (e.g., a torn exhalation valve), and the user would be unaware, risking prolonged exposure.
Misconception No. 2: Air-purifying respirators cannot remove diisocyanates.
In fact, it has been known for many years that diisocyanates are adsorbed by activated carbon and retained extremely well. Cartridge breakthrough equations predict very long service lives for diisocyanates under plausible use conditions.
Misconception No. 3: Air-purifying respirators are not approved for gases and vapors with poor warning properties.
NIOSH supports OSHA’s requirement for change schedules and recommends against relying on warning properties. In addition, NIOSH recently directed respirator manufacturers to change the cautionary language on cartridge and canister
approval labels and user instructions to be consistent with 1910.134. Specifically, the statement “do not wear for protection against organic vapors with poor warning properties or those which generate high heats of reaction with sorbent” must be changed to “follow established cartridge and canister change schedules or observe ESLI to ensure that cartridges and canisters are replaced before breakthrough occurs.”
The City Smasher
Its just the kind of information I need after my disasterous efforts at finishing the Bearcat.
It was perfect at the basecoat stage, but a bad choice of additives in the clear coat rendered it a basket case. (5 1/2 hours of non-stop sanding with 400grit w/d paper removed just 5 grams of trouble-making epoxy clear and only served to expose millions of microscopic bubble cavities to ruin subsequent coats...)
Lots of retarder thinner and nice clear laquer fixed that as well as I'm bothered with fixing it, so next time I'll follow your method.
The retarder also fixed many of my eternal gloss problems... At Last!!
The mask info is valuable too. I've wanted to try isocyanate containing products for a while on cars, bikes, guitars and planes (the objects of my employment). Now I know where to start!
Well Done 
Thanks!
Godzilla, can you elaborate on your attempts to use PC and silkspan on open bays? and others who are successful, how did you do it?