How to work out hull area? - need more Gelsheild!

Zagato

Zagato

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LOD 24' 6"
Draft 3' 6"
Beam 8' 6"

After grit blasting last November 2.5 litres of International Gelshield was put on in March which I think is about 2 coats. Gelsheild needs at least 5 coats (may get away with 4!). Just wondering how much to get.

Will then Primocon it, boot line and Cruiser Uno it!

I would really like to do all this in the next 4 weeks whilst the weather is good as the boat will be going in next April - hopefully the anti-foul will be good for it!? May just leave the anti-foul until next year...
 
err get a tape measure and divide areas up into shapes that you can calculate area,ie oblongs or squares,allow abit or round up the multiply by two.There probably is a formular used by NA but my book is in the loft,I think
 
There is a bit of guidance in the International brochure, I expect it's on their website too!

You could sketch the underwater profile at a few points, then estimate the girth, then graph girth vs distance from bow. Area under curve is what you want.
 
If 2.5 litres did 2 coats then you need another 3.75 litres to do another three. Or am I missing something here?

Also I don't think you will need Primocon. The advice I had from International was to apply either epoxy (Gelshield) OR Primocon after removing antifoul.

By the way you have a very pretty boat!
 
Hi
I did a similar project in the winter 2010/2011 on my 23'-6" Colvic Watson.

WL: 21'-0"
Beam: 8'-9"
Draft: 3'-6"

A 2 1/2 Ltr tin of Gelshield 200, primocon or Micron Extra antifoul would do one coat with some left over to go over the rudder and keel.

I applied 5 x coats of Gelshield 200, DO NOT mix all the tin, only mix enough for a roller tray at a time, and let each mix stand about 5 minutes,
plus 1 x coat Primocon primer plus 2 x Micron Extra.

I would NOT suggest you also antifoul if you are not going 'in' until next year, leave it until nearer the time.

I stay 'in' for 2 years at a time no problem.

Hope this might help.

Mike

Gelshield200Firstcoat.jpg

FinishedApril2011.jpg
 
Thanks - nice Colvic ;)

I have ordered 2.5 litres of Gelsheild (covers 20 Sq Metres of my 12 Sq Meter hull....I'll see how it goes!) and will Primocon, boot top and antifoul next year :)

The boat was in Blagdons when I bought her, well spotted that man ;)
 
Zagato said:
Thanks - nice Colvic ;)

I have ordered 2.5 litres of Gelsheild (covers 20 Sq Metres of my 12 Sq Meter hull....I'll see how it goes!) and will Primocon, boot top and antifoul next year :)

The boat was in Blagdons when I bought her, well spotted that man ;)
Click to expand...

I reckon the area you have there is a little in excess of 21 sq m ( but thats using the LOA in the calc instead of LWL)


2.5 litres will barely do 1 coat
 
VicS said:
I reckon the area you have there is a little in excess of 21 sq m ( but thats using the LOA in the calc instead of LWL)


2.5 litres will barely do 1 coat
Click to expand...

Agreed, sadly for Zagatos' wallet !

I've gelshielded a 30' & 22' boat, by far the worst bit was getting back to the bottom gelcoats, even though eroding antifoul had been used.

I don't know if you're doing it yourself Zagato, but even with the modern stuff I'd keep a close eye on the temperature.

Have fun ! :)
 
Luckily Andy it will be Gelshield on top of Gelshield with keying, the hull was blasted before the first gelcoat was put on.

Yes I'll have to see how far it goes Vics, the boat yard put two coats on of different colours and charged for 2.5 litres. This must have been a rough estimate :confused: as they would have had to use paint from two different pots to get the two differing colours.

The guy at boatpaint.co.uk worked out the hull area as roughly 12 Sq Metres using the LOA, Beam & Draft but not sure what the calculation was :confused:

Big discrepancy between your 21 and their 12 figures - I think he was doing it from a spreadsheet programme as it kept crashing, I've got time to order more so will investigate further.

EDIT I get 15 Sq Metres using the waterline length on this programme
http://www.reactiveresins.com/boatbottomareacalculationform23.11.09.pdf


And I thought asking about hull area would be a daft question, nothing is easy it seems on boats...
 
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I used the guide on Internationals web site. Same formula that has been quoted above somewhere from Hempels website. But they are only guides!

Concerned about that big keel area mopping up the coating.

If anyone puts on 2 coats from 2.5 litres I find it hard to believe they will be doing so at the recommended WFT.
 
International also have a very informative help line.

You will find that 4 coats are recommended, if you go back to a good gelcoat or epoxy surface. Then a coat of hard white, then your erroding Micron. Hard white so that you can tell when you wash or scrape your soft AF off.

Do be careful of you timing between coats, especially the time between the 4th coat of epoxy and the coat of hard white.
 
Well the boat yard were right, 2.5 litres does two coats of Gelsheild ( four now in total) and today two coats of Primocon also 2.5 litres. All coats covered the one underneath and were a decent thickness so.... :confused:

I'll leave the anti-foul until next year.

Great weekend, nice to getaway and do a satisfying job and talk boats over a beer with other owners :D

I'm working on the Crabber stand on Wednesday at the Southampton Show if anyone wants to talk Crabbers or say hello and talk boats!
 
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