National 12 - find out more...
 

Varnish Stripping

Started by jeremyf, 04 Dec 2008, 11:03

« previous - next »

jeremyf

As my Kitchen refurbishment has gone much faster than plan I will soon have approval from SWMBO to commence a little work on Grimalkin.
As I have mentioned elsewhere she is a very pretty boat and deserves a strip and revarnish inside. However I get bored very easily and the ammount of varnished area to strip and prepare is rather significant; also there are a lot of 30 year old glued joints!
I would apreciate some advice on what is the best method to remove the varnish, Chemical stripping, Hot air gun ??  I doubt that a power sander will be of any use except on the transom and decks, and they are ok. It is the fiddly bits, knooks and crannies that will be a struggle.

Tim Gatti

Hi Jeremy - a heat gun is ok for some of the older style varnishes but watch you don't burn the wood. I tend to stick with Nitromors for most of my varnish stripping these days - the type that you use white spirit to neutralise.  It's also very good for getting into all the nooks and crannies and you can use it with wire wool to get the grain clear.  Beware power sanders!!  Belt sanders are notorious for putting grooves in your deck ply and rotary sanders will leave cross-grain scratches that look a real mess when you apply the new varnish.  Even an orbital sander can leave marks which show up in a good light. I always scrape and sand with the grain with the sandpaper on a rubber or wood block.  Once you're back to bare wood think about putting an epoxy finish on the decks before you revarnish - eg Eposeal or a low viscosity resin.  Good luck. Tim

Derek

Hi Jeremy,
It seems to me you first need to work out the varnish in question. If you have got something coated in epoxy the solution is different from that of a traditional older varnish. The older, softer stuff is more suceptable to chemical removal. The more modern material is better suited to a powered mechanical removal.
There isn't really an alternative to a bit of elbow grease if you want a nice finish. You can use an orbital or better a DA (dual action orbital / rotary) and finish off with fine paper by hand in the direction of the grain of the wood to polish out he remaining marks which should be very shallow if using fine paper as the last touch on the DA.
For coatings; beware epoxys - they bloom in UV unless suitably treated. The solution used to be to varnish with two-pot polyerathane over epoxy but I have seem professionally finished boats where that went cloudy too.
There may be more recent views but two or three coats of good two-pot is good for two or three years. You can whack on four or five coats on decks in a week with the occasional intermediate sanding to take out the bigger flies. The important thing is to leave a good enough base to do a good last fine sanding for your final coat. Leave a couple of days for the two-pot to harden rather than just go touch dry before sanding.
I suggest a 100mm foam roller and just a touch of tinners to make is flow well on this last coat.
This might sound like a lot of work but when it works and after 45 minutes of putting on the last coat you stand back to look at it and it is good - it is well worth it. What is more it will remain that good for a couple of years. If you cannot be bothered to revarnish every two or three years, you are probably not temperamentaly suited to a varnished finish - get a belt sander and paint it!
 
good luck
 
Derek - (of the painted decks) 3510
 

tonyelgar

Jeremy,
alot of the varnish is standard epifanes varnish, however under the painted non-slip sections there is some keyed in (and rock hard) epoxy based product put there by the owner before me, and it was a bit of a pig to remove and looked awful - hence the non slip. The foredeck and side deacks are again epifanes - a brand i would recommend for both varnishes and paints! The CB casing i didnt do too much to whilst i had her so it will probably need some TLC too :(
hope this helps
 
tony
ex 2760/3255

Tim Gatti

Hi Jeremy - Derek's absolutely right about the need to identify what's on the boat in the first place! But from what Tony's said it looks like you've no epoxy on the decks to worry about, just standard Epifanes.  After removing it you'll now be aware of the several options of what to replace it with.  Personally I have never had any problems with epoxy blooming.  I use two caots of MAS low viscosity resin with a slow hardener, roller applied and then 'tipped' with a foam brush.  But the wood must be dry and the temperature around 65 to 70 degrees to ensure a good cure.  I then sand off and finish with 4-5 coats of one pot - usually International Goldspar - but Epifanes is brilliant too.  Ideally if you are epoxy coating thin ply you want to do all surfaces ie under the decks as well, otherwise damp can seep through and get trapped between the top of the ply and the impermeable epoxy coating.  I suspect this also applies to using two-pot varnish as it creates a much harder, less permeable and less flexible surface finish than a traditional one pot product. For simplicity, a one pot finish applied to a well prepared surface will be the cheapest and quickest option - and if done well should last you through a number of seasons, particuarly if you have a good boat cover and you have some dry winter storage.
One final point - on older 12's that were built before epoxies became the norm, the glues used eg Aerolite, can deteriorate over time.  This can lead to weakening of joints and microscopic movement of the timbers and small cracks can open up which allow water ingress under the varnish- side decks can be susceptible to this.   One advantage of getting back to bare wood and epoxycoating is that it helps to bond the bits of the boat back together making it stiffer, stronger and less susceptible to the elements. It all comes down to how much time, money and effort you think the boat is worth - cos in the short term although it will look beautiful, it probably won't make it go any faster! Tim

Guest (Guest)

Gosh,
Thanks guys.
Yes, i have noticed slightly wobbly knees ( the boats not mine) so I guess epoxy follwed by something is the answer.
Thanks for that Tony, useful to know, I did think of just non- slipping the entire inside but there is a lot of very attractive timber and as I have a plastic boat as well it is the golden glow of varnished mahogany that excites me.
Its the hot air gun and scraper I guess then ... Tally Ho..........

ruaridh1987

Hi ive just finished a job similar to your this. 
I firstly stripped the varnish with a hot air gun and scraper. You do have to be careful not to burn the wood but providing you hold the gun a good foot away and constantly move it over it works fine.
I then sanded the bare wood with and orbital sander and rough paper before finishing it off by hand and a lighter grade paper.
I varnished using 5 coats of ordinary marine varnish and a light sanding i between.  I believe you have to be careful when using two pac on top of stripped wood as it doesnt adhere well to any areas of old varnish which hasnt been completely removed.
Hope it goes ok for you, its definately worth the effort!!!

jeremyf

Thaks for that,
It will be the hot air gun as it also warms up the garage and dries the wood!
I think I will go for epoxy, even with the additional effort as I have forund it a boon on my old Mirror for stiffening up joints etc.  I do want to ensure all the knees etc are sound as we intend to give her some stick next year !
Also if I am going to that effort I think epoxy with 2 pack over the top stand a a chance of lasting longer. My only problem will be finding a chandelry in the Midlands thats still in buisness to sell me the materials ??)
 

Lukepiewalker

Mention in passing while near the boat that you are thinking of selling the boat to me. This will make the varnish fall off swiftly regardless of how well attached it is...
If you don't want to upset your boat that much, I could come round, apply a new layer of varnish over the top, and it will be down to bare wood within two weeks.::)

angus

I take it its the hot air then luke;D
All smoke and Mirrors. N2153, 2969, 3411

Lukepiewalker


jeremyf

Joking apart,
in the mid 70's we knew some quite competitive Fireball sailors who had quite a nice Chipendale timber boat and they never bothered to paint or varnish her until she had bare wood patches. In 1977 or 78 I remember with shock and amazement seeing them srape the last vestiges of varnish and paint off her then re paint and varnish her on the beach at Saundersfoot !:o
In those days of course there was sun in the summer and I guess she dried quickly but they did keep touching her and literally as soon as the paint was dry she was back in the water.   Happy days.

Tim Gatti

Hi Jeremy - if you are worried about the reliability of the original glue you might want to consider epoxy filletting the suspect joints once she's all stripped back to bare wood.  I attach a few photos of the refurb job carried out on N3109 a while back.  Once I'd masked off and mastered the technique of applying the fillet using an icing bag (a brilliant idea nicked from a canoe building website), I did the whole interior in an afternoon.  In order to stop the mix going off in the bag I'd recommend using a slow hardener and avoid gripping the bag with warm hands if you can. Prime the areas to be filleted with unthickened epoxy - let it go tacky and then fillet. Remember to rub down the fillets before applying your epoxy coating and again before you varnish.  I think using 2-pot over 2 or 3 coats of epoxy coating is overkill and 1-pot varnish would be sufficient and cheaper. But the choice is yours.  The filleting adds a little additional weight but ensures things aren't going to fall apart if things get rough.  Check out Chinawind Yachts (see http://masepoxies.co.uk) who can send you everything you need by return mail order - or call 01205 760662 and speak to Peter, or give me a call - I'm in the book.  Cheers. Tim

jeremyf

Wow Tim That is useful.
You have done exactly what I want to and the result looks superb.
Approximately how many man hours did that take please so I can get my head around the job !
( If you have nothing to do over Christmas maybe you could show me how it was done ;))

Tim Gatti

Hi Jeremy - have just sent you an e-mail...

n12 Bottom Banner