Applying underseal - fan-shaped spray pattern?

[threadlock]

At some point soon I'll be ready to apply some underseal to bits of my 1976 Stingray. I'll be trying to replicate as closely as possible the factory finish, which means a fan-shaped pattern from an air-fed nozzle. I'm sure they did it in this way for production line speed bearing in mind the careless approach of the factory workers.

Most videos I've found of people applying underseal show a fairly circular pattern, just like a paint nozzle on an aerosol.

Can anybody tell me where I can buy a spray gun for underseal that delivers a similarly wide fan-shaped spray? I'm guessing that paint nozzles (which seem to be available in fan-shaped tips) would clog with underseal.

[buzzer]

Many years ago I wanted a nice finish on some above ground fuel tanks which we sprayed with stone chip. the normal stone chip gun gave a really poor finish so we tried a spray gun. It worked up to a point, but in the end we made the hole in the paint delivery nozzle bigger, and the air delivery hole bigger, to get a bit more suction. I think we also cut a bit off the needle so it came right back in the gun when you pulled the trigger.

This worked really well, and gave a great even finish on the tanks. If it were me, I would get a cheap gun (maybe gravity fed?) off Ebay and give it a try.

http://www.ebay.co.uk/itm/HVLP-AIR-GRAVITY-FEED-PA...

[threadlock]

Thanks buzzer. How easy it to modify a spray nozzle given that I have no experience of using them (and no machine tools)? Is it something I could do with a needle file?

[buzzer]

threadlock said:

Thanks buzzer. How easy it to modify a spray nozzle given that I have no experience of using them (and no machine tools)? Is it something I could do with a needle file?

pretty easy to modify...

in the picture below, hole 2 is the paint orifice. this needs to be made bigger, which you can do with a drill. I would modify this one first, especially on a gravity fed gun. It may be that this is all you need to do. don't go too big though! increase the size gradually.

hole 1 is the air delivery, this uses a venturi effect to "suck" the paint through. maybe go slightly bigger on this one if needed.

you may need to cut a bit off the end of the needle so it comes back a bit further, to allow more or thicker paint to come through

Hole 4 are the ones that create the fan effect.

for the price of a cheap gun I would certainly give it a go!

[Evoluzione]

A gelcoat cup gun would be the tool for the job, a bit pricey for a one off though!

[sospan]

Can you get replacement jet/needles to give more flow? That is the usual route for thicker paints/coatings?