Gelcoat Gun & Compressor combo

Foredeck Shuffle

More of a Stoic Cynic, Anarchy Sounds Exhausting
I need a recommendation on an high end amateur solution to a proper gelcoat gun and compressor combination. I want something for the backyard repair person that if I take my time can yield good results. Am familiar with the concepts of HVLP, LVLP, guns and I'm currently looking at a 10-15gal compressor with a 150 max psi, 1.5-2hp motors, I'm struggling to find CFM ratings for non-commercial compressors which seems to be critical to the selection and proper operation of a gelcoat gun. I do not want a huge compressor, aka 50gal, taking up space in the garage, thus the range above. Am I completely off here? What would be something that would provide a few good spray passes, pause for the compressor to catch up, then a few more passes, etc?

Context:
I do a lot of small repairs for myself, friends, and occasionally the mistreated club youth boat and I'm tired of applying gelcoat by hand. It's wasteful, messy, and what I'm left to work with to get to a nice finish requires more effort than I'm imagining a gelcoat spray gun would provide. I want to save time and be able to tackle small and medium sized jobs, I'm still going to stay away from structural repairs or large area repairs, though I may venture into sanding and respraying a racing dinghy bottom if I do this. Currently I repair gelcoat on about 5-10 boats per year, usually small stuff but occasionally someone flips a boat over and asks if I can tackle it, currently I say no. I've done an entire 505 bottom and V15 bottom before, they looked great but the work was much more than I have time for due to how much effort I had to put into making it look right. I often repair centerboads and rudders.

I've spent a long time searching the threads but I've not seen this question directly addressed. I've watched more professional videos than I can remember, and some backyard ones as well. The advice always seems a bit squishy from the amateurs and too high end from professionals. So any advice will be read and seriously considered.
 

SloopJonB

Super Anarchist
68,782
12,403
Great Wet North
Every compressor I've ever seen had CFM ratings for 40 & 90 PSI.

Tools are another matter - I've rarely, if ever seen a tool with it's CFM draw listed.

If you want to use a HVLP gun you are going to need major CFM at 40PSI - like 10 or more.

A small compressor won't cut it - you'll need one that runs on 220.

My Speedaire 2 horse is a high quality machine, true 2 HP on 115V via 2 capacitor start but it needs a 15 amp circuit to itself or it will pop the breaker when it cuts in on low pressure. Even a skimpy extension cord will cause it to pop on restart.

I am somewhat limited re: tools it will support - basically only intermittent tools, not D/A's and such.
 

phill_nz

Super Anarchist
3,010
954
internet atm
i didnt like it at first but in the end it became my goto
it sucked easily 8" .. i never had need to suck anything higher than that but i doubt it would have problems going quite a bit higher if needed

the finish at first wasn't great ( still better than brushed ) but with use it ended up not to much worse than commercial airless guns
i could spray a ltr in ~ a minute

advantages ..
very little solvent to clean it
on hand and usable in seconds
no air inclusion

disadvantages '
finish was a little lumpy
the setup didn't look very professional
unlikely the small company that sold it is still active and very unlikely it was ever sold outside aussie .. on the other hand any half pie decent welder / plumber ( its soldered ) could knock one up in a very short time
from memory i used it somewhere between 25-35 psi and maybe 5-8 cfm


vent1.jpg
vent2.jpg
vent3.jpg
 
Last edited:
I was in a Costco shop with my last year and got this compressor (hope the link works), it’s a Stanley 50 litre. It gets to 150psi fast like a lot of the new compressors do now. They don’t have a terrific duty cycle at that psi because they get hot if you use it all day, so I have mine backed off to 130psi, for 8 hour days.
 

longy

Overlord of Anarchy
6,820
1,154
San Diego
Hazy remembrance of some comparison article on small compressors: they cheat on the CFM numbers. IIRC by measuring the INTAKE CFM? Rent before buying to make sure your compressor will keep up with your gun & your working speed.
 

Foredeck Shuffle

More of a Stoic Cynic, Anarchy Sounds Exhausting
Phil, That's interesting, so you went with a pressurized container that is not really pushing air?

The other comments are making my humble plans seems viable? This is not by any means a pro shop, just fixing dinghies. I wouldn't expect to run this for more than an hour or two at a time as I do not have a shop and would have to build a temporary tent to work on a boat in the yard. Most of what I want to do is clean up centerboards and rudders after fixing voids with epoxy. Occasionally I may tackle a hull.

I still have some reading to do about the wax and different epoxies so that they do not interact. Still new to this. Thank you for input.
 

david r

Anarchist
586
53
pond
From my experience using gelcoat on the outside is fraught with difficulties since it is meant to be sprayed inside a mold and only cures with no air touching it. Sure you can use pva, wax or whatever to fight the air touching the curing gelcoat.
We use surfboard 2:1 epoxy with pigment mixed in. We use polyester pigment in the epoxy with good success. Just brush it on and sand out any high spots(or use polyester). You probably are sanding out the gelcoat even if sprayed on the outside anyway.
just a suggestion, feel free to ignore
 

phill_nz

Super Anarchist
3,010
954
internet atm
Phil, That's interesting, so you went with a pressurized container that is not really pushing air?

The other comments are making my humble plans seems viable? This is not by any means a pro shop, just fixing dinghies. I wouldn't expect to run this for more than an hour or two at a time as I do not have a shop and would have to build a temporary tent to work on a boat in the yard. Most of what I want to do is clean up centerboards and rudders after fixing voids with epoxy. Occasionally I may tackle a hull.

I still have some reading to do about the wax and different epoxies so that they do not interact. Still new to this. Thank you for input.
nope
it works on the venturi created by the high velocity air stream
the smaller( 90 deg ) pipe had a plastic hose on it that goes into whatever you are sucking out of .. mostly i used a plastic cup
the venturi has enough suction to draw unthinned gelcoat at least 8" ( probably a lot higher than that but 8" is about as high as i ever needed to use it )
it doesn't atomise the gelcoat into a mist ( hence air inclusion is not a problem ) it comes out as a fine(ish) splatter
it really is a useful item for anyone using gelcoats / resins ( or any thick coating that needs spraying )
the finish as i said got a lot better as i got used to using it ( as it was used a lot for lab work and testing, thinning was never an option )
next step up from this is a 2ltr pressure pot and hplv gun ( similar to this https://almax.co.nz/product/star-pp-2000-pressure-pot-kit-inc-s-770-spray-gun-1.7mm-3335.htmx )
if you need the measurements to make one just ask and i will get out the vernier
the main part is a danish made airboy ( fairly common here but anything similar would do )

( https://www.endeavourtools.com.au/124140101-BLK )









venb1.jpg
 
Last edited:

Gouvernail

Lottsa people don’t know I’m famous
38,012
5,546
Austin Texas
If all you are gelcoating is relatively small
Patches you can go old school snd fo just fine.

My ancient 2 Hp compressors like the Speedaire described sbove have served as my mobile air supply for FIFty years.

In fact, I still use a Binks model 69 to suck slightly thinned gelcoat out of a soup can.

Use about six or seven thin coats of gelcoat thinned with acetone and spray some PVA over as quickly as you can clean the gun and swap materials.

If you cannot see through the first couple coats of gelcoat you are not letting the acetone excape

If you can see the PVA after three coats you are putting it on way too fast and it will run and totally tuck up the gelcoat.

Peel off the pVA
Rinse eith copious amounts of acetone

Sand

Polish admire your fine job
 




Top