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Cobra maintenance #276447
11/30/14 03:46 AM
11/30/14 03:46 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
journeyman
Matthew Dawson  Offline OP
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Joined: Apr 2009
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Hi All

I know it's not a mozzy ... but I thought I would share my Cobra maintenance journey with you. Your feedback and advice would be appreciated.

First item - centreboards.

They are really nice timber and glass boards but need some repair. As you can see in the photo, I have sanded it back a fair bit to take off all the delaminated glass. I would like to simply seal them now - I don't really want to re-glass them. Is that possible?

I have everdure, epoxy resin and varnish on hand. What should I use?

Matthew

PS: yes I know I am a bit late ... aiming to be on the water for the nats at Christmas!


http://www.dawson.id.au/Cobra/cb1.JPG
http://www.dawson.id.au/Cobra/cb2.JPG





Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
-- Have You Seen This? --
Re: Cobra maintenance [Re: Matthew Dawson] #276448
11/30/14 04:02 AM
11/30/14 04:02 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Posts: 88
It is a plywood Cobra. Built in 1983.


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276449
11/30/14 02:43 PM
11/30/14 02:43 PM
Joined: Apr 2013
Posts: 858
Victoria Australia
Pirate Offline
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Pirate  Offline
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Joined: Apr 2013
Posts: 858
Victoria Australia
Originally Posted by Matthew Dawson
.....I know it's not a mozzy .....


we'll forgive you...... this time wink


being such a short board the glass that's delaminated wont be a huge issue strength wise

so really they probably just need sealing up

Don't use varnish, sure its easy and quick and looks good but you'll pay for it the next time the maintance schedule comes around... check TwiceShy's thread and the varnish on the rudder blades and centreboards..... took a full day to remove the varnish and polish up the glass to a usable finish for each piece.... 4 wasted days because of the varnish
mad
the other negative for varnish is future repairs, if at some stage you need to fix an issue you'll find that varnish and resin don't play well together.

So the answer your chasing in my opinion would be the epiglass-everdure treatment..... little bit more effort now but you'll appreciate it further down the track

download this and print it out..... & store with the tin wink
http://www.paintncolour.com.au/uploads/media/Everdure.pdf
(its the maximum overcoating times & drying times you'll want.... follow that and you cant go wrong)



Yar, & this ere post be done without a sin'le drop o' rum passin' me lips

Kingy
started with Impara Cadet #3 / Mosquito #245
& now Mosquitos #1182 & #1740

Re: Cobra maintenance [Re: Matthew Dawson] #276454
11/30/14 05:46 PM
11/30/14 05:46 PM
Joined: May 2006
Posts: 1,383
Kingston SE South Australia
JeffS Offline
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JeffS  Offline
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Posts: 1,383
Kingston SE South Australia
I love everdure, and did both my Mozzys with it when you do the treatment water it down with the special thinners and just keep doing coats until it won't absorb anymore, if you want to varnish over it you can but use the interluct varnish that's compatible. When using Everdure you apply each coat before the last coat sets so you have a chemical bonding reaction between layers. With varnished wood the trick is to sand and revarnish before the varnish gets old and breaks down so it always looks good so a quick light sand and thin coat every couple of years


Jeff Southall
Current boats
Nacra 5.8 1703 Animal Scanning Services
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Arrow 1576
Re: Cobra maintenance [Re: Matthew Dawson] #276588
12/05/14 05:38 PM
12/05/14 05:38 PM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Joined: Apr 2009
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Thanks Kingy and Jeff. I will give the everdure a go.


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276593
12/07/14 02:30 AM
12/07/14 02:30 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Joined: Apr 2009
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I got a lot of stainless fittings and fasteners off the two old boats I bought this year. What is the best way to clean them up?

It's mainly the screws, bolts and nuts - the threads are full of 'gunk'.

There is a fair bit of paint on screw heads and stainless saddles too.


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276596
12/07/14 05:11 PM
12/07/14 05:11 PM

S
Scarecrow
Unregistered
Scarecrow
Unregistered
S



start in a container of petrol then slowly go with more caustic products.

Re: Cobra maintenance [Re: Matthew Dawson] #276597
12/07/14 05:59 PM
12/07/14 05:59 PM
Joined: Aug 2011
Posts: 182
Grafton, NSW
Greg/Debra Offline
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Greg/Debra  Offline
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Grafton, NSW
The best way to clean the threads is with the appropriate taps and dies.


1140 Gadfly
1434 J.I.B.E.
1727 Atreus
Re: Cobra maintenance [Re: Matthew Dawson] #276600
12/08/14 02:23 AM
12/08/14 02:23 AM
Joined: May 2007
Posts: 416
Matt_Stone Offline
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Matt_Stone  Offline
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all good, but easiest way is a wire bush on a bench grinder,.... some grease don't dissolve in some cleaners, taps and dies are good but need to work out what type of thread it is... metric, with worth, BSP, imperial, ect. wire wheel is the way to go

Matt

Re: Cobra maintenance [Re: Matthew Dawson] #276601
12/08/14 05:00 AM
12/08/14 05:00 AM
Joined: Oct 2010
Posts: 92
South Oz
Phillip Offline
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Phillip  Offline
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Joined: Oct 2010
Posts: 92
South Oz
Wire wheel; PLEASE wear safety glasses/goggles. A full face shield is even better. Any loose wires launching from the wheel always seem to find soft tissue!
Hold bolt with vice grips as fingers/pliers are not sufficient holding power when those nasty little wires wrap into the threads. If you have the nut to match the thread, they are usually sufficient to clean out the remaining paint. Take care!!


Tortured ply is clearly beautiful.
Mozzie Aldebaran VI
1827
Re: Cobra maintenance [Re: Matthew Dawson] #276615
12/08/14 02:43 PM
12/08/14 02:43 PM
Joined: Apr 2013
Posts: 858
Victoria Australia
Pirate Offline
old hand
Pirate  Offline
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Joined: Apr 2013
Posts: 858
Victoria Australia
A few tips.....

there's plenty of paint stripper style products and caustic sodas to choose from, these work well to soften paint and make removal very easy.... but stainless usually has a well polished finish and paint doesn't stick that well anyway, so it will "chip" off without major effort, the strippers and caustic just speed up the operation.

wire brushes are the go for the removal of silastics/duralac etc sealers and are easily the best for removing corroded alloy that's lodged on the shanks/threads of the bolts or screws, as already stated its more a question of "holing onto" the bolt/screw as its being 'brushed'...

to make life far easier and A LOT SAFER use a wire wheel brush that you can fit to a variable speed drill and secure the drill in a vice or similar..... lower RPM wont be such a safety issue with fraying wires flying off and the chance of the bolt/screw being caught by the brush and flung into the never-to-be-seen-again region of the shed is greatly reduced...

This also has another positive with a lower spinning speed and that's one not many are familiar with....
99.9% of wire wheels are made of HIGH TENSILE MILD STEEL wires... mild steel and stainless DONT play well together and if you use a high-speed bench grinder and push a bit hard the mild steel 'can' impart some of its atoms onto the stainless and once its refitted to a boat and you get it wet it WILL rust slightly.
High grade stainless is less likely to be effected like this but can still have that mild steel transfer, lower grade stainless (316 for example) will rust stain very easily once the wire wheel imparts some of its metal onto the stainless.

If your going to wire wheel the parts then get a brush specifically to suit stainless steel smile

Also.....
its called a bench grinder..... it WILL even with a wire wheel "grind" to a certain extent, so caution is needed as to the pressure you apply with the part on the wheel, push a bit hard or for a few seconds too long and the wheel WILL remove material for the part, and it WILL impart some of its wire onto the part...


above all

its better to loose a $2.00 5/16th bolt to the never-to-be-seen-again region of the shed than it is to have a single wire removed from your now blind eye or suffer the septic healing from that wire imbedded in a soft tissue area of your body, the question then becomes, is any of it worth the effort for a handful of 2nd hand bolts/screws
Don't get me wrong, you just have to balance the risk/reward of the parts value over personal safety and well-being, in my game its always a shock as to how many people will risk injury for something that's worth less than they will make in an hour....
wink


cheers


Yar, & this ere post be done without a sin'le drop o' rum passin' me lips

Kingy
started with Impara Cadet #3 / Mosquito #245
& now Mosquitos #1182 & #1740

Re: Cobra maintenance [Re: Matthew Dawson] #276621
12/09/14 07:05 AM
12/09/14 07:05 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Joined: Apr 2009
Posts: 88
Thanks for the tips everyone. I'll try sloshing the about in some petrol first to see how I go.

I have a little dremel tool with the workstation that can mount the tool on its side. I can use that with the wire brush attachment on slow speed for the persistent bits.


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276622
12/09/14 07:08 AM
12/09/14 07:08 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Posts: 88
Anyone have any suggestions for a new mast hook?

I currently have the one in the photo below but I want to change it to a hook separate from the pulley. I want the hook a few inches below the top of the mast so I can pull up past the hook when unhooking.

Suggestions?


http://www.dawson.id.au/Cobra/masthook.JPG


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276630
12/09/14 05:34 PM
12/09/14 05:34 PM
Joined: Aug 2011
Posts: 182
Grafton, NSW
Greg/Debra Offline
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Greg/Debra  Offline
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Joined: Aug 2011
Posts: 182
Grafton, NSW
I made mine out of 3mm stainless. It's not hard to make a hook providing that you are capable of cutting, bending and drilling 3mm stainless.

The tricky bit is to get the hook dimensions and positioning on the mast just right so that the sail hooks on first go, and then also unhooks easily. I spent a lot of time considering all of that, then ended up fluking a perfect hook for 1434's mast (our other two masts already had hooks).

In designing my hook I took measurements from the other two hooks but the end result was more good fortune than good management. You've gotta be to be lucky sometimes...

Last edited by Greg/Debra; 12/10/14 03:57 AM.

1140 Gadfly
1434 J.I.B.E.
1727 Atreus
Re: Cobra maintenance [Re: Matthew Dawson] #276633
12/10/14 02:00 AM
12/10/14 02:00 AM
Joined: Apr 2013
Posts: 858
Victoria Australia
Pirate Offline
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Pirate  Offline
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Joined: Apr 2013
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Victoria Australia
I'll send you a pic shortly

wink


Yar, & this ere post be done without a sin'le drop o' rum passin' me lips

Kingy
started with Impara Cadet #3 / Mosquito #245
& now Mosquitos #1182 & #1740

Re: Cobra maintenance [Re: Greg/Debra] #276634
12/10/14 06:23 AM
12/10/14 06:23 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
journeyman
Matthew Dawson  Offline OP
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Joined: Apr 2009
Posts: 88
Originally Posted by Greg/Debra
I made mine out of 3mm stainless. It's not hard to make a hook providing that you are capable of cutting, bending and drilling 3mm stainless.


Errr ... That's beyond me I'm afraid ... smile

Hoping to buy something?

Goodall has them ... I might have to get a quote from them. Will be pricey ...


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276635
12/10/14 06:37 AM
12/10/14 06:37 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
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Matthew Dawson  Offline OP
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Joined: Apr 2009
Posts: 88
I would like to get some of my new parts anodised. Anyone know where I can get this done in Geelong or the west of Melbourne?


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276636
12/10/14 06:50 AM
12/10/14 06:50 AM
Joined: Apr 2009
Posts: 88
M
Matthew Dawson Offline OP
journeyman
Matthew Dawson  Offline OP
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Joined: Apr 2009
Posts: 88
The paper tiger system looks like a good one ... It might even work with my existing hook.

https://www.papertigercatamaran.org...;virtuemart_category_id=1&Itemid=101


Cobra 570
Cobra 581
Mosquito 126
Arafura Cadet 738
Re: Cobra maintenance [Re: Matthew Dawson] #276648
12/11/14 02:51 AM
12/11/14 02:51 AM
Joined: May 2006
Posts: 1,383
Kingston SE South Australia
JeffS Offline
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JeffS  Offline
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Joined: May 2006
Posts: 1,383
Kingston SE South Australia
If you have a halyard shackle with a ring or similar above it as in that picture your current hook should work fine as long as you tie the halyard to the shackle bit and not the top bit. as you normally only need about 10mm lift to disengage If your current hook is not quite disengaging then you can file a bit off your current hook. Some boats need to have the spanner pulled quite hard to engage or disengage the halyard can you post a photo of your current set up. Personally I think the link above shows an overly exact and complicated setup for a simple halyard lock


Jeff Southall
Current boats
Nacra 5.8 1703 Animal Scanning Services
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Arrow 1576
Re: Cobra maintenance [Re: Matthew Dawson] #276649
12/11/14 04:16 AM
12/11/14 04:16 AM
Joined: Aug 2011
Posts: 182
Grafton, NSW
Greg/Debra Offline
member
Greg/Debra  Offline
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Joined: Aug 2011
Posts: 182
Grafton, NSW
Some people call them a "parrot beak" and you can see the resemblance in that one (although it looks more like a duck to me). There is no need for a big beak like that... I agree with Jeff, you could file a bit off the beak.

Mast-top hooks are a notorious source of difficulty, but if you can get everything just right they work fine, and when that is the case you hardly need any beak at all.


1140 Gadfly
1434 J.I.B.E.
1727 Atreus
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