stunthanger.com
Building Tips and technical articles. => Paint and finishing => Topic started by: Alan Resinger on February 11, 2013, 02:06:58 PM
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Seeing Sparky's post about burn out got me thinking. I'm in the process of finishing up my new ride for 2013. My second Hunt Crossfire with E-flite 32 for power. Doing a light weight finish is imperative for a competition PA plane and doing it without adding extra weight is not an easy task. My finish added 8 oz. to the total weight which is what I usually shoot for on a model this size. It all starts with the woodwork. Paint doesn't hide building mistakes. I've long ago given up on an absolutely perfect finish. I'll leave that to guys like Sparky, Derek, PTG, Larry Fernandez, Ted, Paul and some others. Over the years I've seen some truly great finishes but perfection is getting harder and harder as I get older. One of my biggest problems the last few years has been my shoulders just don't handle the stress of the hand rubbing involved. I've been looking for some sort of buffer to aid and have finally found something that really works.
The answer is a 3" random orbit buffer that is made for detail polishing of automobiles. The unit shown in the picture below is about $100 and available from Griot' Garage. The orange polishing pads cost $13 for a three pack. There is a small learning curve as figuring out the correct speed to run the unit will depend on the type polish you use.
The model shown was finished with Randolph dope. The clear used is A-1690 which is their untinted non-tautening dope. I let the final clear coats (6-8 coats) sit and cure for about 2 weeks. The model was then sanded with 3M paper in grits 800-1200 depending on the quality of the painted area. This is wet sanding using Sikkens M600 as a lubricant. Open bays are given another sanding using 1500 and then 2000 grit paper.
The polisher is great for large areas and works pretty well in confined areas also. Letting the weight of the unit provide the pressure is ideal. There doesn't seem to be problems with buring the finish due to the random orbit motion of the unit. First polishing is done with McGurie's #2 fine cut polish. This is followed with Novis #2 plastic polish. Mcguire's Show Car Glaze is finally used and after waiting 6-8 weeks, McGuire's yellow wax will be applied.
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I hope mine looks that good and is as light. My airplane is at 27 OZ and no color. All the prep work is almost done. I think I will sand some more off with 320 to try and drop a OZ but dont bet on that. So that beind said 27 OZ ready to paint and 27 OZ of hardware 1 oz of tip weight leaves 5 OZ for color and clear.
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Sparky,
Did you go with the equal length panels or did you shorten the outboard wing? Last years plane had equal panels and mine needed about 1.5oz. Chris Cox's needed about 2.25. We went to 3/4" assymetry this year. I've already had mine in the CG balance rig and will need about 3/4 oz. What batteries and ESC are you going to use?
Alan
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E-flight Power, 25 Hyperion 4s 4000, and a castle 45. 12x 6 EP and a tru-turn spinner. Mine is equal pannel. I'm looking for 60 OZ. Don't know if I will find it but one can look.
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Great post Alan, thanks for the detailed info! y1
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How much does your weigh before hardware?
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I wanna build like you guys when I grow up.
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Here is a weight breakdown.
Battery - TP 5S 2700 300g
Timer - Hubin FM9
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Here is a weight breakdown.
Battery - TP 5S 2700 300g
Timer - Hubin FM9
How much does your airplane weigh before you add the equiptment? I have all the stuff to weigh except your plane
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The total airframe weight was just over 30 oz. Your batteries are about 3oz. heavier that what I use.
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The total airframe weight was just over 30 oz. Your batteries are about 3oz. heavier that what I use.
Finished?
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I looked at that buffer for a while but opted to go another route.
I am still very interested in that buffer and now that someone in our world is using it with good results it might just be what I was looking for.
What I would like to know is what RPMs do you get out of that buffer? What kind of surfaces are its recommended uses? Does it specify that is it for polishing already finished automotive finishes or do they talk about buffing out a clear finish? I wasnt sure if the random orbital would do the trick. Most of the buffers that I have seen that take the clear from sanded to shine are just a plain spinning pad. I could be mistaken.
I know you did this on Dope but I am wondering how it will work on sanded automotive clear. The compound I use has no grit in it. It only acts as a heat transfer and keeps the clear safe while you heat it up with the buffer. It's one step after sanding to shine. All the sanding is what makes the clear jump once the right temp is reached.
I did mine last year with a 3" hookit in my adjustable electric drill. BUT that little buffer looks like it would be alot easier to handle around the plane than a large Hitachi drill.
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Sparky,
Sorry I read that wrong. All my power equipment (motor, battery, ESC, timer, prop/spinner and mounting gear) weighs 24.25 oz. Total weight ready to fly is 63 oz. so the total aircraft weight is 38.75oz.
Doug,
The polisher has variable speed and is made for auto polishing. Go to the Griot's Garage website as they have some videos that show the polisher inaction. This thing doesn't build up much heat even at the fastest setting. These things are for auto buffs that like to wash polish their cars all the time. I don't think auto finishers would use even their bigger 6" version.
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Sparky,
Sorry I read that wrong. All my power equipment (motor, battery, ESC, timer, prop/spinner and mounting gear) weighs 24.25 oz. Total weight ready to fly is 63 oz. so the total aircraft weight is 38.75oz.
Thanks for the clarification. It had me worried as I think my plane painted will be around 32 oz finished with the 27 oz hardware package should be at 60 to 61 OZ ready to fly. Meaning its the equivalent of a 53 OZ IC stunter. I am liking this already!
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Here is a little better deal. On this page there is a kit that comes with six pads and two polishing towels for $109.99 with free shipping. My birthday is coming up, it came UPS today.
http://www.autogeek.net/griots-orbital-polisher.html
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Helpful hint- Because the yellow disc on the buffer is hard plastic and the same size as the foam pads, I found it helpful to reduce its diameter by .25". This allows the pads to hang out away from the disc and eliminate the risk of scaring near by surfaces such as the fuse side when trying to get the last bit of the wing surface near the fillet.
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Very Nice work Alan! I would say it is on par with all the names you mentioned above! ;)
I think I will be buying one of those buffers too. i have always used a drill with a big foam pad that I got from Gene Martine years ago. It works well but it is a handful and kind of dangerous. The orange buffer looks much more user friendly.
Derek
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Alan's airplane is lovely. It got 19 appearance points at the Western Canada Stunt Champs; Chris Cox's got a mere 18.75.