Keel preparation

[Hoolie]

Following on from a recent post on keel treatment and the recommendations for grit blasting or needle gun, has anyone any experience of the P*erago rotating blaster available (for example) from the Removall people ?
As an attachment to a polisher (which I have) it looks a good alternative to a needle gun scaler. The double version looks as if it would do the job pretty well.

 

[oldsaltoz]

G'day Hoolie,

Some points to ponder when planning to coat a keel.

Cast iron is porous, full of voids and can be high in moisture content as a result. Any moisture trapped will cause problems later, keels in particular must be dry prior to preparation.

The prime reason sandblasting is used is the fact that a constant flow of contaminant free grit is directed at the keel, removing all rust and contamination, it provides very good access to tiny voids that contain rust and contamination as well as surface moisture.

Cast iron will flash rust within seconds the process has started, it is most important that the raw cast surface is coated as soon a possible.

Sandblasting should be done to Class 2.5. That means no shadows in the finish, all the same shade of grey.

Any grinding method or technique that involves the re-presentation of a surface that has contacted the cast before will carry contamination, and will cause small voids to be closed without cleaning them. This results in failure or the coating as some later stage.

I hope this helps.

PS: Have a look at the treatment steel wharf pylons undergo and see how close to this practice you can get for a lasting result.

Avagoodweekend......

 

[Hoolie]

Hi oldsaltoz
I'm aware of the flash rusting effect with cast iron, but I hadn't thought of the re-contamination problem with mechanical cleaning methods which I guess also rules out needle guns for keel cleaning. Not a lot of choice if you want to do a good job /forums/images/graemlins/ooo.gif

 

[Graham66]

Not a tool for the faint hearted, have seen numerous accidents caused by this type of tool when the steel studs detach themselves.
ideal for knocking off lumps of rust and paint but certainly wouldnt use it for cast iron keel prep stick with blasting or grinding

 

[mbay]

I used the P*erago on my cast iron keel I could'nt afford to get it blasted so it was a cheap alternative for me. The keel on my boat weighs 2.5t and its was a long job but I'm happy with the results, I know I'll have to do it all over again, maybe next winter but its lasted 3 seasons upto now. I removed the paint and rust with the P*erago scraper applied a cheap rust treatment, filled the small voids with epoxy filler, primed and antifouled.

 

[Hoolie]

I think my keel weighs about 2.5 tons as well so I've a long job on if I go this route. I was interested in the P*erago as a low cost alternative to grit blasting and needle gun that needs a high flow air supply.

Grajan1 - I take your point about the safety issues with this device. I have seen a similar multi-wheel tool that comes with a steel guard, obviously with good reason.

 

[mbay]

i had no problems with it, i only bought the single version. you do not have to apply much presure and never lost any of the teeth ive also lent it out to a couple of friends at our club who were also pleased with it.
as old satz says the best route is blasting it, but im pretty sure the rust will still come through eventually

 

[misterg]

[ QUOTE ]
... needle gun that needs a high flow air supply...

[/ QUOTE ]

You can get electric needle guns now - HSS have them for hire (not sure if your boat is in the UK, though).

Andy

 

[Hoolie]

[ QUOTE ]
... electric needle guns now - HSS have them ...

[/ QUOTE ]
From what I've researched the electric needle guns don't have the power of an air gun. Tho' our boat isn't in the UK I'm sure I can hire in France - but as previously noted it's likely to be too long a job for hiring.

 

[misterg]

[ QUOTE ]
From what I've researched the electric needle guns don't have the power of an air gun

[/ QUOTE ]

Possibly so, but we hired one at work a few weeks ago, and it seemed to be quite effective.

Andy