painting the underside

[jezjez]

I might be asking the rolls royce owners about an old ford escort, but my 25-year-old marine ply boat is only a 12ft miracle dinghy and not quite a classic boat but she is pretty in my eyes with a lovely finish. This is the first time i've tried to do maintenance and i wondered if you had any advice. I've just sanded back and painted one coat of paint on the underside. This looks mostly good, but the areas which were worn (wasn't looked after for the last 3 years) still need more. How many coats of paint should i apply? Should I add more to the areas I can see need it, or should every coat be a full coat?
Secondly, I've replaced a self-bailer and one of the bolts has become cross-threaded and won't go back on (my fault i fear). Can it be saved and if not do they still sell imperial sized bolts in modern chandlers?
Thanks
Jez.

 

[jezjez]

nobody cares about my little miracle but me...

 

[Mirelle]

1. No, you will only get a metric bolt, but that should not be a problem.

2. "Underside" can mean

- under the deck

or

- under the boat.

Assuming you mean the latter, no need to do full coats; build up where you scraped back and finish with a full coat.

 

[jezjez]

Thank you.

 

[Mirelle]

The trick to a marine ply dinghy like the Miracle is to keep her lovely.

There are any number of tatty marine ply dinghies but few really well kept ones - the difference is obvious to anyone and a really well maintained boat keeps her looks and value.

Number of coats -

Varnish - bare minimum four, six or seven will make a good job and ten will produce the best result. Sand down between each coat, and try to get ideal conditions for the last coat - a fine day with overcast and very light wind. It is OK to thin varnish and it is usually advisable to do so. There is a product called Owatrol which you can get from chandlers which makes paint and varnish go on much better.

Paint - four coats of primer, first coat well thinned, second coat thinned a bit. sand lightly between coats.

Then one coat of undercoat.

Then fair up using something like Hempel's Unifiller (one tube will last you ten years at least on a dinghy)

Sand down, another undercoat mixed 50/50 with enamel.

Sand down, give one coat of pure enamel in ideal conditions (see above)

Best to do the bottom with the boat upside down.

The bit that everyone forgets is getting enough coats of varnish inside. *

Always wash down with fresh water to get grit and salt out and let her dry before you put the cover on.

* Do as I say not as I do, and don't look inside Firefly F3000! /forums/images/graemlins/laugh.gif

Good luck!

 

[mikefleetwood]

As for the imperial thread bolt, don't only look at chandlers. Look up "fasteners" etc. in Yellow pages or similar. Most places will sell whatever you want over the counter for pence. Otherwise, your nearest tool store (I don't mean B&Q) will sell special files for dressing/repairing crossed threads.

 

[jezjez]

thanks again.
When i bought the miracle she looked really smart and has been well cared for - i'm only the 2nd owner. Unfortunately I was nervous to then do any maintenance for fear of spoiling the finish and I lived a long way from where she was kept and there wasn't such an easy way to do maintenance, but now it has become necessary. As you say, Mirelle, she looks great and I'd like to continue to look after her well.
The varnish looks good, so I've only added an extra coat on what looks fine to me.
The hull looked pretty ropey after 3 years use and being kept outside. I've now moved house, so I can now finally bring her home to work on her.
If i use primer, do i only use that on the wood itself? Does that mean sanding back to wood?
I'm taking her out ON the water next week but i could feasibly start again from scratch if needs be when i get back.
Mike, thanks. There's a very good professional store, Ridgeons, nearby, i'll ask them what to do about the bolt.

 

[skipperscouse]

hi.
try a car boot for the bolt. i often see boxes of old tools which usually have old nuts and bolts at the bottom. also ,same place , you'll find old taps and dyes [dies ?]. it's very easy to make / repair your own bolts. good luck with the launch.

 

[Mirelle]

Yes, primer on bare wood, only. If you have no bare wood when you have looked carefully over her, scraped any areas where the paint is lifting and sanded back any scratches, you are unusually lucky!

 

[Mirelle]

And some more

The three sorts of paint in a "conventional" paint system for a wooden boat do different things.

The primer is the waterproofing layer, formulated to stick very well to the wood.

The undercoat is there to provide colour and "body" and to be easily sanded smooth.

The enamel is to resist ultra-violet light and to provide the shiny gloss finish which sheds dirt easily.

Fillers like trowel cement or "unifiller" should be sandwiched between coats of undercoat, and built up slowly as they shrink slightly when they dry. You can use epoxy and microballoons as an alternative, but never use car body filler on a boat (moisture collects under it).

 

[jezjez]

Re: And some more

right.
I wasn't lucky, there are definite areas where the bottom was back to the wood - or in fact a glass fibre seal over the panel edges. There were plenty of scratches and some cracking which loooked the most worrying.
As we we are going out this weekend, I'm going to slap on another coat of enamel and then when the chance arises, I'll sand back and start again from scratch. I owe the boat 3 years of work so wasting one tin of paint and starting again won't be a bother.
Primer, undercoat, filler, enamel.
As for the bolt, I got a metric replacement which is a very close fit - good enough to bite into the wood and made a proper connection, so that's sorted.
Thank you, forum. I'll let you know how i get on.