Steel hull! 36 foot of problems!

[Adoozy Sailing]

Hi guys I have a 36 foot steel sailboat that I bought impulsivley without getting it surveyed and having littleknowledge of sailing other than the dinghy's I had as a child and my partaking as crew on a sail from falmouth in the uk down to the bay of biscay to gran canaria on a 44 foot 200 year old timber ex British navy sail transport vessel .

after stripping the paint around the bilge and inside the hull I found a rusted repair that had been done in the past and it was slowly leaking so I had it hauled out and transported it to a mates farm at great cost almost $4300 aud.

I decided to gut the interior so I could see the extent of the damage and remove all the rust to ease my mind as rust is like cancer and will spread.

I have a mate who is a welder and he wants me to sand blast before he starts the repairs but when I got in touch with paint company they said I need to prime it within four hours of the blast. When I am paying so much to have it blasted it seems a waste to spend that money if it will only flash rust again .

My idea was to sandblast up to 200mm above the real waterline and redo the antifoul and just patch and repair the few rust spots above the waterline sanding back and filling and repaint above to line and also do the same on the top of the deck. inside I have some rustisol non acidic which has ph of 7 rust converter and prime the inside of the hull with a zinc rich epoxy primer by international. I was told it would not require another coat primer would be sufficient inside. Just using a polyurethane paint on the bilge.

Am I way off?

I'd love to hear if anyone has had any experiance and might have some advice other than send the rust bucket to the scrap yard as I have already put so much into this project and it's been my dream to sail across the Pacific and I wont give up on it now even though this whole ride has been daunting to say the least.

[billknny]

Steel hulls are great in so many ways... but they have an expiration date.

They rust. Slowly if cared for well and quickly if not. But no steel hull lasts forever. A surveyor who knows steel and can bring an ultrasonic thickness measuring tool might be the best investment you can make before you spend another dollar.

Nobody can really give you a good answer based on pictures.

[Lepke]

I've built and repaired steel boats and the best coating I've found is zinc sprayed on after sandblasting. It's sprayed on with a Metco or similar gun that uses oxygen acetylene and feeds a wire thru the flame. Used guns can be found on eBay for about $500us.
The next best primer is 2 part epoxy.
I use to own a tug that was zinc coated inside and out 20 years before I bought it. There was almost no rust in the bilge or anywhere else. Only where lines and cables wore thru the coating. And Zinc coating is easy to fix with a torch and zinc rod.

[Rumpi]

Normal procedure is:
Buy ultrasonic thickness tester, test the hull in a grid pattern.
Cut and replace any obvious rusted areas and any areas that are to thin. Since this is a round bilged boat you will have to beat the replacement panels and patches to shape. You have to weld the panels butted not overlapping. Grind the welds flush.
After all obvious things are repaired, holes plugged, etc. you get on with conservation. Sandblast the hull inside and outside, prime with chosen primer like the manufacturer said. If sandblasting revealed hidden problem areas, remove primer locally, weld, grind, reprime.
Continue with chosen paint system respecting manufacturers indications. Now you have a sound hull and can proceed to the next stages, namely insulation, furniture, systems, etc.

Getting the hull sound and painted is 20% of the total work and expense. The only difference between you and someone building a new boat is that you have less welding to do and you might already have some other usable bits of the boat like engine, sails, etc.
If you are not up to what exects you then scrap her. If you are lucky she has lead ballast and you end up recouping some of your money.

Maybe she was a bargain that only needed some patches and paint when you bought her, but after gutting you reduced her to a hulk and need to start again from the beginning.

[Johnknutson]

Originally Posted by billknny

Steel hulls are great in so many ways... but they have an expiration date.

They rust. Slowly if cared for well and quickly if not. But no steel hull lasts forever. A surveyor who knows steel and can bring an ultrasonic thickness measuring tool might be the best investment you can make before you spend another dollar.

Nobody can really give you a good answer based on pictures.

I have steel boat built in 2005. Its in great shape now, but wonder how long it will remain so. With proper maintenance, what do you think is a realistic life expectancy?

[Rumpi]

Originally Posted by Johnknutson

I have steel boat built in 2005. Its in great shape now, but wonder how long it will remain so. With proper maintenance, what do you think is a realistic life expectancy?

Steel lives by it's coatings. As long as you keep them in good order the boat will outlast you and any caretaker after you.

[RaymondR]

No, you do not want to blast before you repair the thin spots. You need to follow the recommendations of the paint manufacturer.

You need at least two and maybe three coats.

The first a very thin ie. low viscosity primer, or pre primer to penetrate into the roughened surface. This forms the good bond with the steel to which the following will bond.

A high build to give a bit of durability against impacts and scrapes.

A light coloured finish coat to allow you to see where rust may be occurring so that you can get onto it as soon as possible.

The best way to fit patches is to define the area you want to remove by drilling small holes at the corners. You only want 2.5mm dia holes and you can put a piece of small wire in them to make them easier to find.

Cut your patch piece. You can use a compass to directly transfer the lengths between holes rather than measuring them if the patch is not too big and you have a big enough compass.

Tack it onto the outside and use it to guide a 1mm cutting disk to get a precisely fitting patch with a 1mm gap all around.

Cut the tacks to remove the scrap piece and tack the patch into the hole.

Then go inside and weld a bead all around the patch.

Then go back outside and using a grinding disk groove out the 1 mm crack to allow a fully penetrated weld.

Weld the groove and grind the weld back to achieve a smooth, flush surface.

The only skill required is the actual welding and you can save a lot of money by having all the patches made and the waste cut out and the edges of both hull plating and patch ground clean for about 25 mm wide beside the edges done ready for the welder (This is why he or she wants the blasting done before the patching)

Putting the patches in place and getting them fair on the outside is really a two person job and you need an auto type welders mask for yourself as well as the welder if you want to avoid flashes.

A couple of pieces of scrap flat bar tacked across opposite corners of the patch will give you something to hold onto as well as keeping the patch flush with the hull plate. If you only use 5-6 mm tacks you can quiet easily break the pieces off once you have holding tacks on the patches.

I found that triangular patches appeared to be the easiest to do and the fastest one we did took about 35 to 40 minutes of the welders time. The slowest were a couple of large rectangular ones (700 x 400 or so mm) which consumed 2.0-2.5 hours.

[boden36]

Your friend probably wants to blast it first to pick up all the rust areas.
If you were to blast the outside, and not waste too much time on fixing the holes, you could then do a quick re-blast before painting that would not take too much time.

Really, your assessment of the boat should be from the inside - if there are heaps of heavily rusted areas, forget it - the work involved will be more than the finished boat is worth. (from someone who has built and maintains a steel yacht)


Regards,
Richard.

[Michael Cobbe]

The only way to get rid of rust and stopping it coming back it to sandlblast it and paint it wth Zinc rich epoxy, as was done to my steel boat.

[ausnp84]

Every boat building material has their pro's and con's, and steel is no exception. Properly prepared, a steel boat will last just as long as a GRP boat and see you through plenty of varied conditions.

I had a similar issue with the steel ketch I bought in 2010. A HUGE learning curve that took 6 years, way too much money and a relationship, but resulted in a boat that is still going strong 10 years later without a drop of rust (other than the usual places - anywhere that had a hole drilled after initial painting and wasn't touched up soon enough).

I read all about flash rust, etc as well and that's how I started the process, but then that quickly became impossible with the shitty UK weather so in the end, we had it blasted and then within a few hours, put on three coats of Jotun epoxy primer. 2 pack poly topcoat went on thereafter. Some areas did get flash rust and were repainted with the epoxy and guess what? No rust has ever come through.

So grain of salt everything you read but as long as you give it a good blast and remove any flaky rust, you'll easily come up with a boat that outlives you.

nathan