Sandblasting a beginners trials and tribulations

[cameron82]

Hi all just wanted to tell of the hardships the wins and fails of sand blasting a heavily rusted yacht .

We (still building and I) got a panblast 110 and a diesel compressor .This is the story of how we started and finally got to the stage of blasting

The compressor is a diesel 1400 cfm and looked fine it started but would konk out after going over 40 psi . We got told it was the air filter intake so we replaced the filter and put some lube in it .But still would not go over the 40psi mark with out failing .I spoke to a guy and he said it was not running on all cylinders .So after a few min of bleeding the lines she was running at 100 psi Yay finally but it was a premature celebration .The engine kept over heating and was blowing heavy smoke and would only run for about 40 min before it shut down from a over heat . The compressor was air cooled and who ever took off the panel to inspect the lines did not replace the panel which was vital to the engines cooling system .The previous owner used a self taping roofing screw to keep the panel on .So i used a block of wood to keep the metal sheet in place now the engine was running fine .

The batteries we had are sealed agms inside the compressor which didn't like the charge from the engine plus the heat inside which was about 140 c so the battery started to buldge and fail .The alternator is putting out about 15.6 volts so the mix of temp charge and human error .Such a waste of good batteries

The sand blaster

At first my logic was to fill it to the brim and this would mean less times required to fill the pot .This was a major mistake plus again we had been given bad advice we had the feeder turn to the max and it was spewing out garnet .We struggled for days wasting a lot of media .Finally I called the number on the pot and called the company .I spoke to a rep who told me what i was doing wrong after a few adjustments like not filling the hopper to the brim and only putting 50kg in the pot to make a vortex inside to help the media reach its full potential .You want the nozzle to push out a nice grey if it is pink there is to much media if its white its just air .So now we are blasting and going great .So i decided to recycle media another mistake as the humidity was 100% and the temp is 38c the blaster started making burps of clumps .I was emptying the water every 10 min but was not enough .So I mixed fresh media with recycled at a rate of 3 garnet to 1 recycled. I also used a magnet to get any bits of metal and rust out of the re used media .Finally the blaster is doing well and we are blasting away .I would be constantly walking in circles checking the compressor the water the media as Stillbuilding blasted away

Have to update computer is crashing

[cameron82]

The media we used was garnet 60 which worked great if you are just taking paint and simple rust off .But we had carbuncles that were very hard to get off at first we spent about a week with needle guns trying to dig them out this proved to be a hard task and we were getting no where. I got told to use a plate of steel and a hammer and bang the rust off after 45 min with a hammer i had taken more rust off than the week of needling .Back to the media We ordered garnet 60 and glass we decided to make a mix of glass garnet and recycled media and it worked great . At a rate of 2 bags glass 1 bag glass 1 bag recycled we had fine tuned the media and was working fine but very very slow .The rust Carbuncles are tough little suckers that don't just blast off with ease like a lot of people tell you .The paint can be done in a flash but the carbuncles take a lot .At first the idea was to go over and take off the easy stuff then return and take off the carbuncles .In theory it worked and in prac it did to but to be honest its just easy to get it all done at once .Maybe we should have spoke to the rep first but we are stubborn and think we know it all .How wrong were we

Will update some more my computer is crashing again

[KISS]

I'm very interested in the blasting process, thanks for posting, keep 'em coming.

[Pauls]

Seconded, I look forward to hearing more. I've been sandblasting pieces of steel I've been welding into my boat, with the goal of minimizing the interior blasting required for the final interior paint job. And am designing/building a custom blasting nozzle to allow me to blast on the inner side of the angles which are my longitudinals.

[boden36]

To blast at an angle, just get a bit of say 3mm flat bar, bend it at say 30 degrees,
belt it with a ball pein hammer so that it is cupped and attach it to your hand-piece with a couple of hose clamps or similar. It deflects the blast stream so you can blast under handrails etc. Used to be known as a "Centurion's helmet".

Regards,
Richard.

[Steve Bean]

What are you steel-boat people planning to use to protect the interior? I've heard cosmoline works great.

[cameron82]

Media

Garnet 60 is a great media and works great if you know what your doing .But we being the noobs that we are thought its simple .But how wrong we were our first attempts at blasting proved quite the challenge .With a mixture of bad advise and stubbornness we thought we knew it all .

So the best way to use garnet is to understand that it must reach its velocity before being really effective .DO NOT OVER FILL THE POT .You need to create a vortex inside the pressurized pot .We had a panblast 110 so that meant it holds 110 pounds of media .NOT as much as you can fit in the hopper as you want to create a vortex so with the pan blast 110 only use 50 kg .This helps so much once you realize that you have been over filling and the pot not being able to create a vortex as the vortex helps create that air media mix for optimal blasting .With the valve on the bottom of the hopper shut it off completely and slowly build up the mix rate till you get that sweet sweet grey .If it is pink turn down the feed if it is white your pumping basically air .So may take a bit of tweaking to get the mix just right .Plus Humidity is your worst nightmare if its the middle of summer and the humidity at the max you will find that your water catcher will need to be emptied a lot .Basically its a 2 man job one to blast and one to operate the machinery and fill the pot .I found myself walking around in constant circles .Going from the compressor temp to empty the water then fill the pot .Our vessel is named infinity so i walked in a infinite loop to please king Neptune

Glass media

Glass is a cheap and great media its not as tough as garnet but half the price and not as dense 1 garnet 25kg equals 1.5 glass 25kg .Glass works great it flows very nicely and it is not a fidly when it comes to humidity .Great for taking paint off and then ok for the hardcore rust carbuncles .But at half the price it is a serious contender for a replacement media for garnet if your just taking off paint and rust its great .But for the heavy duty rust its ok .Also it does not create a dust cloud like the garnet and recycles quite well

Recyling media

If you get decent media it can be recycled the glass is ok so if you do the hard bits first then use the recycled second . Garnet is claimed to be able to reused up to 3 times .But in all reality your lucky to get 2 rounds with it . Its best to mix the used media with fresh .I had a system where I would sieve it for the big parts that will end up clogging the nozzel or worse the feed at the bottom of the pot .So I would sieve and use a neodymium magnet to take out any rust metal etc then mix 2 parts new to one part used .I tried just using just recycled media but with humidity and the fact that it had just lost it density and was not doing well maybe for light paint jobs or light stuff yes .But we had hardcore rust and it didn't do much at all .So by adding new media to the used seemed to give us the power we needed .

Mixing media

We found that glass and garnet worked great it flowed well and took the carbunlces off with ease .I was using a mix of 2 bags glass and 1 bag new garnet and one bag used garnet 60 . This mix worked really well and also was much cheaper than using garnet by itself and we got the same result .Garnet 60 was about 600 a ton and glass was 340 a ton .Also the glass mix seemed to be recycled well .Remember we are new to this so experimenting was hard to work out the perfect mix .But once we had the mix right we had that rust running scared .I can't stress enough to sieve the media and use a heavy duty magnet to take out the rust /metal that might find its way into the pot and will clog the nozzle

Will post more my computer keeps crashing so quit while i'm ahead

[cameron82]

Dam I just spent ages writing and the computer crashed here it goes again but a simple quick version as i have a massage waiting and some time with the mrs before i set sail

Make sure you check all the seals its amazing how quick a little gap in the seal can eat out a coupling or the nozzle holder . We had a small crack in the coupling seal and it did not take long for it to eat its way through .This can be very dangerous as it can fly off and cause damage to anything in its path .We didn't put the seal o ring in the nozzle end and with a few days use it had eaten all the way through the holder .So being the jerry rigging king i used a coke bottle half a roll of duct tape and managed to fix it to a ok condition .By cutting the coke bottle into inch strips i strapped it round the end and duct tape the hell out of it .

Got to go and knowing my luck the computer will crash again .Please feel free to ask any questions

Also will upload some pics and video footage and explain the techniques we had evolved .

[conachair]

Originally Posted by Steve Bean

What are you steel-boat people planning to use to protect the interior? I've heard cosmoline works great.

One way...

Get as close to clean metal as you can
phosphoric acid, wash, more acid, wash again - real good scrub
blowtorch to dry straight away
Ameron sealer
lots of coats of your favorite epoxy paint

(see https://books.google.co.uk/books?id=...enance&f=false
page93

[Snowpetrel]

Good write up, lots of great info. Thanks, it sounds like one tough job in that heat. Love to see some photo's. I had all sorts of problems trying to get a little spot blaster to work well on my last steel boat without much success..

Sent from my SM-G930F using Cruisers Sailing Forum mobile app

[cameron82]

The inside will be blasted and scrubbed with a rust killer phosphoric etc maybe use cosmoline or something similar depending

[cameron82]

Hi all will post some photo's soon My friend still building has some good photos .Will continue my thread I have found a few tips for micro blasting witch would be great for engine parts

https://www.youtube.com/watch?v=QZhBQXm4yBY

[cameron82]

My friend richard is a vet surgeon and after sandblasting the deck we had hundreds of tiny holes .So with a mig he went and did every little hole a very hard task and my hat goes of to him we had sections above the gunnels that had to weld some plate steel over it .We used magnets to hold the steel in place and worked like a charm (i was below deck holding the plate with a rag witch caught fire it's amazing how you find these little tricks and you look back and think why didn't i think of that a week ago lol


Will post more about blasting and if you have any questions or are on the east coast of Australia and doing some blasting i would love to help

[Fore and Aft]

We used to use speed blast on very rusty gas pipes. With all this hassle with the blasting are you reblasting the work you did the day before? Our specs on painting gas pipes was no more than 4 hours between blasting to bare steel then painting. Not sure how that would work with a yacht?
Cheers