Author Topic: Finish weights (Read 2852 times)

ash · « **on:** January 16, 2008, 03:19:41 PM »

What sort of weight do you expect to gain out of your preferred finish on say, a full size 60" stunt model?

~How much does a full gloss dope finish add?

~How much does a full gloss auto finish add?

~How much does a film finish add?

Give some ballpark/range figures based on your experience...

Thanks!

Randy Powell · « **Reply #1 on:** January 16, 2008, 05:01:39 PM »

Ash,

I usually budget about 12oz for a finish on a plane the size you mention. I can often come in under that, sometime a lot under, but I try to leave the space. If the plane is a bit porky before finish, the finish process may get short shrift. Doesn't matter what I'm using for finishing materials. There's only some much weight to spare for being pretty.

Randy Ryan · « **Reply #2 on:** January 16, 2008, 05:57:00 PM »

I agree with Randy, though I always shoot for a lower number, 10-12 Oz in pretty good.

Bill Little · « **Reply #3 on:** January 16, 2008, 06:06:25 PM »

I'm with the Randys here. Most of the time a finish on a 650-700 sq. in. plane will be in the 10-12 oz. neighborhood. But I am disappointed if I go over 10 oz., myself.

Randy Powell · « **Reply #4 on:** January 16, 2008, 07:20:16 PM »

I always try to give myself the space if I can. Good example is the PA plane I'm getting ready to finish. My target weight was about 55oz. It could survive at anything under 60, but probably best in the 53-56 ounce range. It's about 640 square inches and right now, ready to fly with engine tank etc. but just in the frame ready for finish, it weighs 42oz. So that actually gives me a finish budget of about 13oz to hit my target weight. Less is, of course, better and if I can manage to be judicious with the filler and don't get carried away with the clear coats, I can probably bring it in around 8oz. giving me a finished weight of near 50oz. That would be cool, but I'm to expecting it. At 13oz, I can get a little crazier with the trim scheme and have some grams left over for a nice clear coat.

I was actually a bit surprised by the ready to finish weight. I could stand a 50oz, 640 square inch plane powered by a RO-Jett 65 one a pipe. Could be cool.

ash · « **Reply #5 on:** January 17, 2008, 03:42:24 AM »

Thanks for the input, guys. That was about the range I was hoping for. When I posted the question I figured I had about a 15oz finish budget...

But this afternoon I realised my numbers didn't account for the lead lined carbon veil I put on it. So after primer it was already 15oz OVER target weight. I nearly cried, but kept it down to cursing and mumbling. I knew it seemed too good to be true...

Hit it hard with the sander, burned off 5oz of primer and veil and did some serious number crunching tonight. Depending on balance, I'm probably going to have to put in a much lighter motor and fabricate some much lighter hardware than I had lined up for it, just to get it in the ballpark. Otherwise the last 6 months of building will have been a waste.

Randy Powell · « **Reply #6 on:** January 17, 2008, 06:13:18 PM »

>>Otherwise the last 6 months of building will have been a waste.<<

Hmmm, that's not good. Transparent Monokote?

Crist Rigotti · « **Reply #7 on:** January 17, 2008, 09:26:47 PM »

Usually if an airplane is overweight, it'll be tail heavy. Going with a lighter engine may not be the best way to go.

ash · « **Reply #8 on:** January 18, 2008, 05:00:43 AM »

In this case I'm expecting the opposite. The airframe itself isn't too bad for weight, most of its excess chunk is apparently in the wing itself... epoxy/veil/glass and oversized U/C mounts. The engine is seriously heavy to start with, though. In hindsight, I should have been aiming for an extra-light airframe to account for engine weight. I will have the painting mostly done this weekend and can check the balance situation before I go any farther. I've calmed down about it a bit now. Its going to be a heavy monster with a honking big engine up front one way or the other. And it will look great in the sunlight.

Mark Scarborough · « **Reply #9 on:** January 18, 2008, 09:05:37 AM »

FOr me, I build it as light as I can, finish it as light as I can, when I get ready to fly, then I weigh it,, whatever it weighs,, thats my exact target weight,, and I always obtain it,, lol

RandySmith · « **Reply #10 on:** January 18, 2008, 09:47:29 AM »

Quote from: ash on January 16, 2008, 03:19:41 PM

What sort of weight do you expect to gain out of your preferred finish on say, a full size 60" stunt model?

~How much does a full gloss dope finish add? 10 ounces

~How much does a full gloss auto finish add? 13 to 16 ounces

~How much does a film finish add? lighter but not close to the same finish

Give some ballpark/range figures based on your experience...

Thanks!

HI

A dope finish on my 60 size ships normally weigh from 9 to 11 ounces. I have seen the same anywhere from 8 to 26 ounces so they will vary wildly..... Most alway a car paint finish will be heavier because the paint is heavier, If you use an automotive lacquer , shoot thin coats , as most will cover much better than dope. Do not treat it the same as shooting a dope finish. It is possible to use automotive lacquer and obtain a light finish you just have to be careful.
A film finish is lighter but the two do not compare with each other, Film does not add much strenght to you airframe as paint does ,and does not compare in the quality of finish with a properly done and properly rubbed paint finish

Regards
Randy

Randy Powell · « **Reply #11 on:** January 18, 2008, 12:28:15 PM »

Randy make a very good point. I mix my own colors using auto paint toners and clear dope as a binder. It works well, but there is a lot of pigment in auto paint store mixed paints. A lot. and it's heavy, so you have to go easy.

Much like shooting catalyzed polyurethane. Commonly on a 60 sized plane, a coat of urethane weighs about 2 ounces if you don't lay it on too thick. A coat of clear dope is about a 1/4 oz for a medium coat. The advantage of the urethane is you need exactly one coat and you're done. You need to build up the dope over successive coats so it can actually be heavier in the end. And the urethane is fuel proof. The best dope finish is fuel resistent. Barely.

ash · « **Reply #12 on:** January 24, 2008, 01:46:01 PM »

Well, the spraying is finally done. I ended up with 5 Oz of colour and clear and 2-3 Oz of primer on it. Another coat of clear would be nice, but the extra time and weight probably won't be reflected in a significant improvement, so I won't bother. The finish is Mirotone acid catalysed lacquer, a furniture product that I use on my guitars. Candy apple red will look awesome in the sunlight...

Thanks for the hints! I'll post better pics when its all in one peice.

Randy Powell · « **Reply #13 on:** January 24, 2008, 02:27:45 PM »

Very cool. I like the color combination a lot.

ash · « **Reply #14 on:** January 25, 2008, 04:25:48 AM »

Here's a better sunshine pic. Start putting it together tomorrow, should get a flight on Monday with any luck.

Brett Buck · « **Reply #15 on:** January 25, 2008, 06:41:01 PM »

Quote from: ash on January 16, 2008, 03:19:41 PM

What sort of weight do you expect to gain out of your preferred finish on say, a full size 60" stunt model?

~How much does a full gloss auto finish add?

~How much does a film finish add?

Give some ballpark/range figures based on your experience...

I snipped out the dope part, since I don't know the answer. For my Epoxy/Auto Clear finishes (just including primer and paint) have been 5.75 and ~6.5-7 oz from silkspan/nitrate base. The 6.5 was the most recent, and it was 17 points at the 2006 NATs.

For the Monokote, I always painted the fuselage with epoxy (or earlier, Formula U and Chevron) and it was usually around 3.5 oz. The last one I did that way got 15 points at the 1994 NATs.

I have never done a full dope finish to the necessary quality level (nor would I) but I think the above are considerably less than the average dope job for top-notch quality. And the epoxy/car paint was much more durable.

Brett

Dick Fowler · « **Reply #16 on:** January 25, 2008, 07:10:47 PM »

Ash, I just visited your website. It's obvious that you have more than a passing knowledge of finishing. Very nice work... both airplanes and guitars.

Well done.

http://www.ashcustomworks.com/index.php

Chris Edinger · « **Reply #17 on:** January 25, 2008, 07:30:56 PM »

Question for the two Randy's.... in your automotive urethane clears.. which brand do you use.. if you dont mind sharing.. I know most automotive clears are thick and are not supposed to be thinned... I have used a less expensive clear that is much thinner, sprays great, and has a great gloss..just wanted to see what you were using..thanks..

Chris

Mark Scarborough · « **Reply #18 on:** January 25, 2008, 10:29:46 PM »

Im not Randy or Randy, but I do work as a painter on cars, now days restorations mostly. I use PPG 2021 clear. One of the really common misconceptions about reducing urethane clear is that you cant. I overreduce my clear substantially. After talking to the PPG paint rep about this, he explained that the current recomended reduction rates are simply devised to be able to mee the VOC standards for emmisions. It hurts nothing to reduce the clear a bit more. In my case, when clearing a car or some such, I typically will mix 4:1:1.5. the 1.5 being reducer, that is 50% more than normally used and it makes a HUGE difference in spraying. ON my models I spray I have gone another 25% higher reducer, so its 4:1:1.75. I also spray this with a SATA Minijet, or other small detail gun, my other favorite is a Devilbiss touch up gun. both atomize exceptionally well and spray a very consistant shaped pattern so the overreduction is not a problem to control.
MY two cents worth,,

Randy Powell · « **Reply #19 on:** January 26, 2008, 12:15:21 AM »

Yea, I've been using a 2:1 clear (Matrix) and usually do as Mark suggests. Depends on the temp, usually. Either 2:1:1 or 2:1:1.50 sometimes a bit more if it's cool when I spray. Just have to remember that it's not like spraying dope. It will run much more easily so keep that gun moving.

Chris Edinger · « **Reply #20 on:** January 26, 2008, 11:34:10 AM »

Mark and Randy....

I to do restorations... and have used the extra reducer but maybe its my paint booth but i sometimes get solvent popping with the added reducer... I have been going to PPG Training schools for many years now so am famiiliar with all the clears and 2021 is great stuff... but sometimes when I do a ... shall we say.. used car lot job .. they want the cheapest stuff available.. and I have used the 5 star clear with great success and is much more economical.. am thinking it would be good for models as it is much lighter its unthinned state.. just a thought...a dollar here and there.. lot of guys dont have a gallon of the good stuff sitting around like we do..

Chris

Randy Powell · « **Reply #21 on:** January 26, 2008, 12:28:30 PM »

Chris,

I'm used Omni with good success. Can be pretty good if you get good conditions to paint in. It's been my experience that the more expensive clear are also a bit more tolerant of conditions. The Matrix I've been using lately seems to do better when I have to shoot it in sub-60 degree temps. The Omni gets touchy at those temps, but does fine when it's in the 70-85 catagory.

I've also used DuPont stuff and had good success. But again, it tends to be a bit pricey.

ash · « **Reply #22 on:** January 26, 2008, 01:36:44 PM »

How much is a mixed pint of your auto clear worth? I was watching a metalflake how-to video and the guy said his mixed up pint was worth about $80 and used it on a small panel repair. I shudder to think what a car's worth would be. My AC lacquer is cheaper than dope per litre and goes farther too. About US$60 a gallon, or $4 per model including wastage.

Randy Powell · « **Reply #23 on:** January 26, 2008, 09:53:04 PM »

ash,

At my local auto paint place, the Omni is about $25 a quart and the hardener is around the same. A quart will paint 4 or 5 planes. Maybe more if you're careful (which I'm not). The Matrix is a bit more expensive at about $35-40 a quart and about $15-20 a pint of hardener. It's a bit better stuff and will go a little further to maybe 6 planes, so it even out. You start getting into DuPont and pPg paints and the price goes up.