Author Topic: How Too.....mostly  (Read 1449 times)

Online Flem

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How Too.....mostly
« on: October 30, 2020, 09:42:01 AM »
Thought I would do a how too. Awhile back bow bender (Royce) was lamenting the lack of how to resources.That and there always seem to be finishing questions hoping up here on the bench, so here ya go. But it  seems us mortals cannot start a thread in the how to forum or even post replies? Heck, I even PMed Terry Green to ask him about it, but he blocked my message. Second time I’ve been dissed lately! Oh well the next best place is the Bowyers Bench, we are the ones making stuff, right?

So this is a thread on how to get set up for spraying finish, not the actual spraying technique. Might have a few tips on spraying, but honestly if you want to learn the movements involved in spraying, watch videos of robotic arms spraying Ferrari’s till your eyes bleed. Its about consistency and nothing is more consistent than a robot. The apex painters in human form are the folks doing custom Auto painting.

So for those of you who are not currently spraying finish, but are thinking about it, this thread is for you. If you are happy with your current method, good on you. If you are thinking about a more professional finish for bows that might be marketed, hopefully this will help.

I make no claims to being a painting guru. I mostly learned in a vacuum, so most of my knowledge was acquired by trial and error. You don’t want to hire me to paint your Tesla. I know there are better, more experienced painters than me on this forum, so please feel free to add to or correct anything you see written here.

First thing to consider is the type of spray setup that will suit your needs. There are a few options.
The most common is an air compressor. A compressor setup is probably the least expensive and most versatile outfit. Everybody has a compressor, right?
The next most used setup is an HVLP turbine.
Another option is an Airless or Air assisted airless sprayer.
I'm not going to go into rattle cans or Preval. Nothing wrong with them, just not the level of finishing we are trying to achieve.

So the biggest thing we are striving for is an even, smooth layer of liquid plastic on our carefully crafted masterpieces. The way to achieve that is thru atomization. For that we need adequate pressure at the tip of the spray gun.

An HVLP turbine is rated in stages, which is the number of fans it has pushing air. The more stages, the more air pushed and more pressure at the tip. A common 3 stage turbine will get you a real world rating of 3-5psi, a 4 stage might get you close to 8-9psi and a 5 stage will get you over 10psi. They start getting expensive over three stages. If you don't get close to 10psi, you are going to need to substantially thin out your finish or its not going atomize well and you will likely spend more time than necessary sanding or rubbing out your efforts.
Tip#1  If you want an HVLP setup its easy to build one yourself. The turbine is nothing more than a vacuum motor and garden hose fittings.

This is a 3 stage motor. You can see the 3 segment at the bottom are the fans. Two and 3 stage vac motors can be had cheap if you shop around. Four and 5 stage start getting real expensive!
Here is my recommendation, buy (2) two stage or three stage  motors and hook them up in series. You won't get an increase in air flow, but you will get an increase in pressure. Make yourself a plywood enclosure, because the enclosures that come with manufactured units are too small and not adequately filtered. Plus they are way loud! A homemade 4 stage box with some insulation on all sides and a HEPA furnace filter works better than almost any stock unit and might set you back $150. A manufactured 4 stage is upwards of $1000. Save your money for a good gun. You will need 20-30' of tubing, any longer and you get too much pressure drop. You don't have to buy turbine hose, HVLP's use garden hose fittings so any light, flexible tubing that you can mount hose fitting too will be fine. There are lots of good turbine guns out there. Gravity feed is superior to pressure cup, in fact a pressure cup with HVLP is almost an oxymoron.
You don't need a monster gun with a quart cup, 4oz cup is plenty big unless you are spraying many bows at once. More on guns later.
There are some cons to the HVLP. All those impellers generate air friction and the air delivered to the gun can be quite warm. On a hot day your finish can dry in the air on the way to the bow, leaving a sandy finish. Another issue is high humidity. There is no way to inline filter with an HVLP, they rely on high flow to generate pressure. If you are in a high humidity area, its possible to get fish eyes or orange peel effect when that warm moist finish hits the cooler work surface. There are reducers to slow dry time and other additives for almost any condition, but I think less is better in this case. If I can shoot at package consistency, I’m happy not to fuss with it.
Also since hose length is limited, you will have your turbine nearby, which sucks because the are really loud, they can stir up any dust lurking around and can suck overspray back into themselves if the filtration isn’t good. The biggest advantage of the HVLP is transfer efficiency. Low pressure equals less overspray, which could be important if you are spraying $700@ gal. Auto clears like Travis (4point) but if you are only catalyzing 2oz for one bow its a non issue. I have never used a LVLP or mini gun with an HVLP turbine, could be a hot ticket.
All that said, I’ve sprayed a lot of woodwork with an HVLP and there is no reason a person can’t get an excellent finish using one with a high quality gun.
 
The air compressor setup is the tried and true spray persons outfit. You will never starve for atomizing pressure. You can spend a lot of money on a really nice 80gal intercooler compressor, a SATAjet Phaser gun, an industrial oil/water separator and all kinds of fancy fittings, but if your not shooting Maserati’s, thats not required. Lots of good examples of folks painting setups to be seen with some searching. I’m going to show mine as an example of what can be cobbled together on the cheap, but can still be highly functional.

This is a compressor I picked up free on C-list. The guy did not want to replace the piston, so he bought a new one. I’m always happy to take advantage of our throw away culture. I wired the pigtail plug into the pressure switch, so when the compressor kicks on it powers up a 12v bench supply (salvaged, modified ATX power supply from a junk PC), which turns on the cooling fan attached to an A/C condenser, both scrap from a Toyota. See the trend here?

You can get by with a smaller compressor, but its a good idea to check the SCFM rating at the pressure needed for your gun to make sure there is enough air capacity so the compressor won’t kick on during the time needed to spray your project. You can also connect multiple small compressors in parallel to get more capacity if you need that versatility. Just need a T fitting, a couple of check valves and it helps to slightly stagger the cut in/out pressure of the compressors.

Same rules apply here as with HVLP. We want cool, dry, filtered air. After the air has left the condenser, its hopefully cooled a little and when it hits the PVC precipitation pipe the water vapor will condense and there will be little moisture left when it gets to the repurposed water filter housing filled with silica gel beads. The last defense for crap in the air is 2 layers of P95 filter material in the exhaust side of the filter housing.

If you happen to have a real compressor and are crazy enough to use a setup like this, you would want to substitute Zeolite for the silica because of the oil factor. In fact when I replace the silica, I will definitely switch to Zeolite. Interesting material, that can be had cheap in the form of cat litter.
Before anyone flames me for using PVC and polycarbonate, 2”  sch40 PVC is pressure rated for 280psi. Even after its been de-rated for temperature, it’s still rated for near 200psi working pressure. I have 75psi safety valve plumbed into the pipe. I don’t need more than 50psi for any of my guns. I would not necessarily recommend anybody use plastic for pressure, but I’m not worried about getting maimed by plastic shrapnel.

That leaves the Airless pump.

 Nothing can come close to the pressure generated here, up to 3000psi! It will atomize tar. It will also make a huge cloud of finish. It’s also not practical, you would need to catalyze a quart of finish just to fill the pump and hoses. Which is too bad , because with the correct tip, you can lay down some glass. Still, its an option if you have 50 or more bows to spray.

I know that was long winded. Its even more ovbious this thread does not belong here now. Looks like this will be home for now. Hopefully I imparted some useful info and I trust if someone has something to add they will do so. I’ll try to do the subject of Spray Guns justice next installment.
 

Online Flem

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Re: How Too.....mostly
« Reply #1 on: October 30, 2020, 09:51:36 AM »
Forgot the filter pic!

Online Pat B

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Re: How Too.....mostly
« Reply #2 on: October 30, 2020, 09:59:15 AM »
Holy crap, all that for just building bows. Give me a draw knife, a good rasp and a card scraper any day. :saywhat: :dunno:  ;)
Make the most of all that comes and the least of all that goes!
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Online Roy from Pa

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Re: How Too.....mostly
« Reply #3 on: October 30, 2020, 10:06:00 AM »
What Pat said....................

That looks like a mad scientist invention:) Doesn't surprise me knowing you:)   :laughing:

Terry does not accept PM's period. He has that function blocked to everyone including moderators.

You can email him by clicking on his name in any thread then click on the email icon.

P.S. A bow shop needs a few beer cans laying around...


Online Flem

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Re: How Too.....mostly
« Reply #4 on: October 30, 2020, 10:12:59 AM »
Holy crap, all that for just building bows. Give me a draw knife, a good rasp and a card scraper any day. :saywhat: :dunno:  ;)

Funny. I know thats coming from a guy who likes to rub oil on his wood. :saywhat: But thats just the finishing part, you still have to make the bow first. Plus, I'm not done with this yet!!

Online Mad Max

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Re: How Too.....mostly
« Reply #5 on: October 30, 2020, 10:15:30 AM »
Why is a high dollar gun better than cheap gun,  what is in there that makes it better?

Nice Thread Flem :thumbsup:
I would rather fail at something above my means, than to succeed at something  beneath my means

Online Mad Max

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Re: How Too.....mostly
« Reply #6 on: October 30, 2020, 10:19:22 AM »

P.S. A bow shop needs a few beer cans laying around...

Thats why some bows turn out like my Avatar :bigsmyl:
I would rather fail at something above my means, than to succeed at something  beneath my means

Online Flem

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Re: How Too.....mostly
« Reply #7 on: October 30, 2020, 10:30:33 AM »
Why is a high dollar gun better than cheap gun,  what is in there that makes it better?

Nice Thread Flem :thumbsup:

Its all about precise machining of orifices/needles/air caps, stainless and brass fluid pathways, plus high levels of fit and finish.
I can tell you first hand that if you have a SATAjet gun and a Harbor Freight gun hanging next to each other, you are going to grab the SATA every time.

Online Mad Max

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Re: How Too.....mostly
« Reply #8 on: October 30, 2020, 11:51:11 AM »
 :thumbsup:
I would rather fail at something above my means, than to succeed at something  beneath my means

Online Pat B

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Re: How Too.....mostly
« Reply #9 on: October 30, 2020, 12:16:29 PM »
I rub oil on lots of things.  :laughing:
Make the most of all that comes and the least of all that goes!
TGMM Family of the Bow

Online Roy from Pa

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Re: How Too.....mostly
« Reply #10 on: October 30, 2020, 12:19:46 PM »
Pat  :laughing:

I have a Finnex 1000 HVLP that's a decent gun. Not top of the line but does a good job.


Online Flem

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Re: How Too.....mostly
« Reply #11 on: November 04, 2020, 09:42:05 AM »
Spray guns. Seems like there are hundreds of brands and models. I would hate to have to choose one based on the sales info provided by the manufactures. Reviews by retailers are worthless, as are snapshot evaluations on the big “A”. So good luck!
AS far as types of guns, there are a few options.

This is the least useful for spraying a couple of bows. You cannot catalyze 2 or 3ozs of finish and spray. The pickup tube won’t even find it. Even if you were to spray a quart of finish, it would not be a pleasant experience. The balance is all wrong, finish can plug the check valve in the pressure line to the cup and in the case of this gun, the HV in HVLP does not provide the necessary pressure to push the finish unless it is very thin. The one good thing about this type of gun is you can remove the cup and attach a fluid line from a 2gal pot that is pressurized by a compressor and spray for hours!

This type is your best bet. They come in different flavors. HVLP, LVLP, MINI’s, conventional, conversion, turbine, etc? They all are compressor or turbine (vacuum) powered. One thing to note, a lot of turbine HVLP guns can be used with a compressor by adding a cheap adapter. The downside of that setup is to add a regulator requires additional fittings and by the time you get all those fittings and regulator connected, you have made a boat anchor. I skip the regulator and adjust the pressure upstream.

So if you think you might want to have options, look for a gun that can convert.
HVLP guns run on a compressor do not need a lot of pressure, but do consume a lot of CFM’s, so compressor size needs to be matched acordingly.
For spraying 1 or 2 bows at a time, a mini gun is really all you need. They are easier to handle, don’t require a lot of CFM’s and hold the right amount of finish.

This one for instance holds 4ozs, needs 40-45psi, but only consumes a little over 2 CFM!! Which means you could get by with a smaller compressor or a lot less cycling on with a larger one.
Another thing to consider is if you will be spraying projects other than bows. If so, a mini gun is not your best bet. A full size gun with a smaller replacement cup and large cup might be more versatile.
Inspite of my obsession with shinny, expensive, imported spray guns, I don’t own one anymore. For spraying bows, you don’t need a top of the line unit. If you can afford one and money is no problem, by all means get one!  A midrange gun will get the job done. I would still stay away from the low end guns. Now I am sure some of you will claim to get flawless finishes with your HF gun and if its true, then you are a Master of the craft. But if you are being honest, you might recall a time or two when you spent a little extra time sanding and rubbing out your finish. I have seen some pics posted here, where the sprayed finish looked like it had been dragged thru a sandbox. I have not tested a lot of different brands and won’t venture a comparison . Roy’s gun is a good line from Graco, who has been making commercial units for a long time. I am sure there are many others. Look to see what professional Auto body painters are using. Sometimes you can find good quality in an ugly package

This Accuspray gun really atamozies well, has precise adjustments, nicely machined parts, but its ugly as hell! It lays down a nice finish. I call it the Frankengun, its chunky plastic body is held together with 15 screws! I might not spray a Lamborghini with it, but I will definetly come over and spray your Yugo. 3M bought Accuspray and they make good quality products, so that might be another brand option.
If you can be sure to add a diaphragm type regulator. Those little mini regulators have a few different style of mechanisms they use to control flow. Most are just cheater valves and work by choking off the air flow.  But some are more sophisticated and use a diaphragm to modulate pressure changes. If you don’t like having the extra fitting and valve on the end of your gun, you can fit the valve with quick releases, adjust the pressure upstream and remove the valve when you have the pressure correct. Also its best to mitigate the moisture before it gets to the gun. Get some kind of filtration upstream. Don’t rely on one of these bobbers. They remove some water droplets and particulates, but they will not stop water or oil vapor from passing.
You might get lucky and never know that you have any problems while using the “bobber”, but its a roll of the dice.

If I needed to buy one gun for spraying bows and price was no object, I would go for the bling!

I know it says Ladys edition, but who cares! Hell its got crystals built into the handle and purple anodizing!! That and its likely of one of the finest mini guns being manufactured.

Next installment will be a wet one.

Online Flem

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Re: How Too.....mostly
« Reply #12 on: November 04, 2020, 09:50:38 AM »
Forgot the inline bobber (filter) pic!

Online Roy from Pa

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Re: How Too.....mostly
« Reply #13 on: November 04, 2020, 04:54:02 PM »
I've seen better guns at Walmart:)

 :wavey:

Online Flem

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Re: How Too.....mostly
« Reply #14 on: November 06, 2020, 10:53:53 AM »
Never been in a Walmart. I do enjoy the click-bait photos of Walmart shoppers!

Online Roy from Pa

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Re: How Too.....mostly
« Reply #15 on: November 07, 2020, 08:40:19 AM »
So you are saying you use a girls spray gun?

 :laughing:


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Re: How Too.....mostly
« Reply #16 on: November 07, 2020, 09:43:39 AM »
I would, but I just don't have the matching outfit to go with the purple anodizing. :goldtooth:

Online Roy from Pa

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Re: How Too.....mostly
« Reply #17 on: November 07, 2020, 09:52:46 AM »
I can send ya my buckskin dress:)




Online Flem

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Re: How Too.....mostly
« Reply #18 on: November 07, 2020, 11:27:06 AM »
Thanks for the offer Roy, but I would have to change forum name to Pocahaunches. :saywhat:

Online Roy from Pa

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Re: How Too.....mostly
« Reply #19 on: November 08, 2020, 04:42:10 AM »
I have the ability to change your forum name to Pocahaunches.

Hang on.

LOL

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