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The 24 year itch

Old 12-27-2014, 10:42 AM
  #201  
combatpigg
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Hey Crosscheck...nice to hear from you..!
Yes, the trial and tribulations of being stupid...this time with wood selection. I would say that I know better than to use this stuff in a 3/8 HP plane, but the video just doesn't lie.
Epic Fail X 2 at the 1/2 A level is kind of hard to be at fault for, but I've proven that if you keep trying, anything is possible. In a way, this "BIG" 1/2 A plane puts more stress on the firewall with quick changes in direction but all I was doing was gentle stuff.
You are correct about this grainless wood, it will just drink thin CA until it weighs as much as Spanish tile and it will still be fragile.
Back in the day there were solid balsa fuselage plane models called "Log Planes" and I believe they just used solid logs of this super light, punky wood to quickly shape a plane, then core out a tunnel inside the carving, leaving generous thickness on the walls of the fuselage. I've held one of the planes and it was amazing how light it was.
Old 12-27-2014, 12:09 PM
  #202  
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The Comeback Trail.
The firewall was epoxied back in place, but there were some voids. A small batch of epoxy mixed with saw dust was spread into the voids with a credit card, then covered with clear packing tape. After curing, the tape was peeled off and a little bit of Bondo was used to fill any low spots that the epoxy wood dough didn't.
After sanding the repair back even with the surrounding wood surfaces I misted some 3/4 oz cloth with 3M77 and applied it to the circumference of the firewall to help strengthen the balsa fuselage sides. With a latex gloved finger I spread medium CA over the cloth then let it air dry. It takes very little CA to saturate the cloth, but the photo reveals a small spot that I missed.
Next, I'll dowel the firewall with round toothpicks into the balsa tri-stock behind the firewall. That seems like an easy and lightweight thing to do.
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Old 12-27-2014, 02:53 PM
  #203  
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I once bought about $400 of balsa at dealer price to stock up my new workshop after we moved here. I requested primarily medium grade or medium light. 50% of the stuff I got was 6 lb or less.. but low density and crappy instead of contest grade, about the only thing it is good for is building the Kon Tiki II. I had a 1/2a model essentially start cracking apart everywhere. Not worth fixing.. Burns great tho'.
Old 12-27-2014, 03:10 PM
  #204  
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That is what this stuff does..it will crack cross grain almost as easily with the grain.
I think it has hope if you try covering it with .75 oz cloth and Minwax. Then shoot it with fuel proof paint or cover it.
The hope is to find a way to make this stuff worth it's weight.
BTW, the single stage 2 part automotive paint I used on the .049 plane's cowl has proven to be fuel proof [10% nitro] so far.
The color I have is metallic silver which might be the heaviest color of all, but it looks good without a heavy build up or any primer.
Old 12-27-2014, 03:29 PM
  #205  
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CP... What is the brand of the 2 part paint your using?
Old 12-27-2014, 04:27 PM
  #206  
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Summit racing sells it by the gallon and possibly by the quart too.
It's reported to be "Kirker" brand paint, which is considered mediocre from what I can tell from the auto body forums.
Old 12-27-2014, 08:45 PM
  #207  
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I just tested some two part paint that I painted a model with. It was leftover from a patch on the Vette. It seems good with pure nitro for 30 seconds and a good rubbing. I think most of the 2 part paints are OK. Some guys are using a higher quality household enamel with the automotive hardener too. I haven't tried that yet. Was thinking of Tremclad or whatever I have in the house. You can test automotive paints by using nitro on your neighbors car, or your own in a hidden spot.
Old 12-27-2014, 09:30 PM
  #208  
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What year is the Vette and what does it have for motivation...?
I've never had a ride in a vette.
Some of the less desirable year models are surprisingly affordable, yet the most desirable year models are surprisingly unaffordable.
I think the '63 split window Stingray is the one that is a rare whale. I remember seeing a new one as a 8 year old kid and thinking that it looked like the coolest thing I ever saw.

All I know about paint is the nastiest , most super toxic ones are usually the toughest.
For about a month after shooting my car, there was what I would call a toxic atmosphere in the small room where the car sat as it cured.
I spent hours during that stage color sanding and rubbing the paint and those sessions gave me sinus head aches.
Old 12-28-2014, 05:17 AM
  #209  
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Great ! I just put a couple of brake rotors and pads on my Toy. Sequoia just this last month and got the parts from Summit. I'll have to look at the catalog on paint options. I remember my first order through Summit, waaaaay back in 72' I believe, I had ordered a shatterproof Lakewood bell housing, Schaeifer aluminum flywheel, and a Hurst 4 speed "Competition" shifter assembly. Ah memories.

Many moon ago, I shot, the bad stuff - Imron - still have some left over. Bulletproof as it was though. I've shot PPG Deltron enamel and hardener through the years on my models, good results. Interesting concept on the "house" enamel and automotive hardener though, way cheaper and avail. in small quantities.

Aspeed: I thinking rubbing your car with Nitro, is much like rubbing a good steak with seasoning, you get more out of it, a lot more "flavor"
Old 12-28-2014, 07:28 AM
  #210  
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I have my doubts about the ability of isocyanate curatives to cause any cross linking in household enamels.. gotta look into that one to be convinced. Don't add them to your 1/2a fuel because castor oil is a trifunctional (three hot spots per molecule) and will cross link and gel up.. It was used as a modifier in rocket propellant binder systems which are also isocyanate cured in many cases.
Old 12-28-2014, 07:50 AM
  #211  
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Summit has a separate catalog just for auto body and paint. The main catalog does not list everything they have in this category.
Shopping on line is an option, but mostly if you already know exactly what you need. Beware of some of the sales help, ask for someone with real world experience who has done this themselves. I try to be nice, but firm about who I want to talk to.

MJD, I thought it was pretty amusing to hear that someone even tried mixing that concoction up...! I've got some Rustoleum and some urethane catalyst...hmmm.

I'd be afraid to run it through a gun. With a factory engineered paint system, if you don't follow the instructions to the Nth degree, you'll run into problems like solvent popping or peeling. With a "Home Brewed" system of random ingredients, either the "inventor" really knows his stuff or is just very lucky.

Last edited by combatpigg; 12-28-2014 at 07:59 AM.
Old 12-28-2014, 09:05 AM
  #212  
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For the curative (it's not a universal hardener) to have any effect, it has to find compatible sites on the other molecules with which to react to form the chains and branches of a polymeric network. The common functional group on the resin side is the hydroxyl group, -OH. These react with the isocyanate -NCO sites on the curative to form urethane groups linking the moleculesinto a polymeric network. A&B, hook and chain. Not being an egghead, just the fundamentals. If you have reactive sites, something can happen. If not.. nada. Castor oil is a triol - three reactive OH groups per molecule. Typical elastomers have a bit over 2 on average, resulting in lots of chains but not so much branching = mobility and flexibility. More branching = more rigid. Bla bla.

Point being it is that simple.. A reacts with B to form C, which is really ABABABABAB linked by the common urethane group (and in 3D). So if the enamel happens to have some reactive sites on the molecule, it could crosslink a bit and increase chemical resistance and toughness. Key word = "if". I've seen reference to this trick in auto paint discussions as well. I'm interested to find out if there is any legitimacy. I've seen enough completely bogus "hot tips" to be skeptical until proven.

Nitrocellulose lacquers will crosslink btw - there are reactive -OH sites on the NC backbone.

Yes in general you will find that your automotive two part PU finishes are tough and quite chemical resistant.

Last edited by MJD; 12-28-2014 at 10:37 AM.
Old 12-28-2014, 10:30 AM
  #213  
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BTW I wasn't trying to sound clever.. I can assure you these are no more than the fundamentals. My point was to encourage you to treat this with some suspicion until you have some evidence there is any fact to it. I know just enough about polymers to be dangerous, but the little I do know makes me automatically skeptical until I see some data that legitimizes the claim.

I would feel safe with any automotive two part polyurethane system until proven otherwise (fuel proof wise I mean).

The danger is - other than the usual health and safety cautions with solvents and spraying - don't ingest, breath, or coat your skin with isocyanates, unless you really enjoy serious allergic reactions such as anaphylaxis. I got the T-shirt a long time ago - my arm and face swelled up until I looked like a pimply raccoon. Shot of epinephrine in the leg, shake for a couple of minutes, then sweet relief.. .
Old 12-28-2014, 10:53 AM
  #214  
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I used Helmsman Spar Urethane on a boat and the nitro munched the inside floor of the engine bay to sticky goo. I allowed the reaction to neutralize and harden some then epoxy coated to fix the mess.
Old 12-28-2014, 11:53 AM
  #215  
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MJD I think you were sounding clever anyway. Beyond me. I had trouble in grade 12 chemistry with valances etc. Great in physics though. Some guys are painting their "larger" models with house paint, and the using automotive clear coat for fuelproofing. Sounds heavy to me. Even the automotive paints are going to a water base. I always use a charcoal mask when I paint unless I am doing a small job outside. The Vette is a high mileage 350 Throttle Port Injection 1985. The 84's were supposed to be bad news, the newer ones had aluminum heads that would grind on the head gaskets, and way more electronics to go bad. Anything older has a bad frame around here. I thought a 1967 would be ideal really, but couldn't find one for less than $10,000. I sold my 32 3 window coupe at an auction, and wanted a Vette, or Mustang or something to replace it, and this thing came up right after mine sold, for way less $ so I got it. It is ok, but I didn't know that it had 360,000 km on it!!!
Old 12-28-2014, 12:02 PM
  #216  
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MJD, did you just say that nitrocellulose dope can be improved with urethane hardener..? I'd like to do some tests if that is feasible.

PS, I've had WBPU turn to gooo with light exposure to fuel spray [after reading at RCU that it works just fine]. Is the Spar Urethane oil based..?
There is a poster at RCU named Sensei who raves about using oil based poly urethane to apply lightweight cloth to balsa. I'd like to know more about that, but I'd like to think that every layer of the finishing system is reasonably fuel proof and not just the top coat.
Old 12-28-2014, 12:05 PM
  #217  
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Just to separate my thoughts a bit here, I got some polyurethane paint at a swap meet in Florida, Ferrari yellow, to paint my planes with. The sales guy whom I wanted to somewhat believe, said the generic hardeners would work on the urethane, as well as the regular acrylic enamels that they are made for. I hope he is right. On some other thread, maybe here somewhere, or RCG, the "industrial or commercial?" Tremclad, or some other large commercial brand was supposed to have worked well with the automotive hardener. Another thing I would like to believe. I tested a two part epoxy water based floor paint on a flutterboard to make into an airboat. It is kind of heavy, but seems to be very fuelproof. Grey or a tan colour kind of sucks.
Old 12-28-2014, 12:20 PM
  #218  
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Aspeed, are aluminum heads on iron blocks hard on gaskets in general..?

I see nice heads for about the same price that they were when aluminum after market heads first showed up years ago.
I know that the original Top Fuelers had lots of problems with the aluminum heads growing and causing nasty fires.
It took them awhile to figure out a cure..high temp silicone.
That's pretty impressive that your vette racked up so many miles. That says a lot about the fuel injection system doing it's job not just to deliver good power and economy, but also to safe guard the engine's health with built in fail safe modes. They are complex and full of expensive sensors, but after forcing myself to learn how the one in my Jeep works and how to identify what all the gizmos are called and what they do, I'll do whatever it takes to keep it running. I'd still like to have a simple carb, manifold and point style distributor just in case we get attacked by Martians.
Old 12-28-2014, 12:37 PM
  #219  
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Planes in the Hospital.
The yellow cowl was cracked and missing a chunk. I feathered all the cracks with a dremel cutoff wheel to a shallow angle, then used a few layers of clear tape on the inside to help support the wet patch. I think the patches were 1.5 or 2 oz cloth.
The purple plane got a full nose job with a blue foam plug contact cemented to the firewall and shaped with 120 grit. The rough foam blank is first band sawed to the general outline before attaching to the firewall. I use swatches of clear tape over the foam, then go crazy with the West Systems epoxy and several layers of 2 oz cloth to arrive at a wall thickness of 1/16" or so..[at least]. I use duct tape to protect the covering before block sanding. This epoxy sands easily after 24 hours. I'll estimate that by the time it's trimmed to fit the engine and painted there will be 4 hours invested. It will take a lot of successful flights to get paid back in full.
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Old 12-28-2014, 01:08 PM
  #220  
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Don't confuse spray cans of polyurethane or cans of brush on polyurethane this or that, with the two part automotive systems. There is quite difference in the properties of the finished films, chemical resistance being a big one.
Old 12-28-2014, 04:36 PM
  #221  
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If you want ironclad paint, a great alternative to Imron is Allgrip. Has better flex too. Great adhesion even to fiberglass. They have a brushable thinner too.
Old 12-28-2014, 05:26 PM
  #222  
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Awlgrip has to be better than the junk I did my outdoor wood with.
I used Man O War marine varnish and it blistered and peeled off all the porch railings in just a couple of years. It was so bad I had to dismantle everything, strip it all off piece by piece. What a nightmare.
Old 12-28-2014, 05:29 PM
  #223  
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Aluminum heads are nice and light, but are hard on gaskets. That is pretty much why composition gaskets came about with the teflon coating. I normally use an airbrush or touchup gun for the planes, unless it is a patch or very small job. It is almost easier to clean a basic single action airbrush than a paintbrush. The 365,000 km is about 226,000 miles. I have heard of them going 300,000 miles before a rebuild if the timing chain doesn't go. The old carbs rinsed off all the oil from the cylinders and made them wear faster than the fuel injection. It puffs blue smoke on startup sometimes, and if you boot it for a long time. The gauges blink on and off when they feel like it, pops out of second and third gear when downshifting... Still fun though. I want to sell it, but for maybe $4,000, it is better to play with it. Insurance is only $180 a year, and I go through a tank or two a year. Awlgrip $102 a quart yikes.

Last edited by aspeed; 12-28-2014 at 05:35 PM.
Old 12-29-2014, 07:50 AM
  #224  
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I just read at a vette forum that the '85 could do 14.3 @ 97 mph right from the dealership. With very minor tweaks it would get into the 13's.......so that's pretty good for a luxury car.
Gearing is the single best thing that you can do to any hotrod. With the over drive 5 speed trannies, running a 4:11 or 4:56 rear is no big deal now. Plus these new trannies come with 3:1 first gear, so your launch can be done at 12:1 or better. The 85 vette has plenty of room for wide sticky meats, so there really isn't much need to do much with the engine except tune it for 6000 - 6500 rpm shifts.
I've priced the 5 speed OD swap for my Ford and it would be about $4000 with the TKO 500 trans and all the other components to convert from an automatic trans.. The standard "World Class 5 speed is only rated for 300 Ft Lbs and I haven't seen any 400 Ft Lb options
Old 12-29-2014, 08:55 AM
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Originally Posted by combatpigg
MJD, did you just say that nitrocellulose dope can be improved with urethane hardener..? I'd like to do some tests if that is feasible.
Yes CP - but I've never got around to trying it out yet. The cellulose molecule has three-OH (hydroxyl) groups on it, those are the guys that react with isocyanates. When it is nitrated, the -OH groups are converted into -O-NO2.. but not all of them, esp in coating grades. In highly nitrated cellulose, i.e. as used in explosives & pyrotechnics, more of them are converted, whereas in lacquer/film grades the nitration is lower (level of nitration is expressed in % N) and as a result there are more functional OH groups available. (oh yeah, and they are less dangerous too..)

So yes, addition of an isocyanate should result in some degree of crosslinking. Crosslinking will harden, toughen the film, and increase chemical resistance to some degree. I can't qualify the amounts off the top, I'd have to know the curative side formulation (% of isocyanate and which one) and do some chicken scratching to come up with a starting point.

To do it by experimentation I'd use uncut nitrate dope, and make a sample matrix with 10, 20, 30, 40% by volume of your chosen curative, paint them out and also retain a small sample in a shallow dish, as in 1/8" deep, to flash off and form a small disc that you can fool with to see the properties., i.e. bend, flex, hit, chew. Use the materials neat when you mix them, then if you have to add solvent after do it then, to make it easier to maintain control of the amounts. By doing this, you should get a feel for the % that might be of benefit. Adding excess curative will result in weakening of the film too.. the unreacted

And with all isocyanate cured systems, moisture is your enemy. Water, yes is H20, but can be thought of as H-OH (aha! A reactive -OH group), and isocyanates tend to react preferentially with it to form CO2 and urea, rather than react with the (typically) less reactive prepolymer. That's the essence of the bad news with water and two part PU's - the water steals the curative and makes spoodge in the process.

You could find a guy that sells propellant binder ingredients to amateur rocketeers, and buy a bit of curative.. if you're ambitious that is.

PM coming.

Last edited by MJD; 12-29-2014 at 08:34 PM.

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