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19 ft G-Cat repainting HELP!

Discussion in ' Multihulls ' started by Thomas Henck , Sep 9, 2009 .

Thomas Henck New Member

Hello, I hust bought myself a 1981 19 Ft G-Cat Catamaran. I just took it out last weekend and had a great time on it...but it needs some TLC. It have some leaks/chips/dings or lose hardware or an assortment or similar issues that seem to be letting water slowly in. After about 4 hours on the lake in fairly choppy water I drained about 1-2 gallons out of each pontoon. I am planning on taking the entire boat apart this spring and replaceing hardware. The main reason for taking it apart is to repair and repaint the hulls. The gelcoat is damaged in quite a few areas in sopots all the way down to the fiberglass. I am hoping end the repairs with green pontoons. My questions is what do I want to coat the pontoons with Gelcoat or paint? What do I need to do to prepared the existing (non damaged surface) to coat? What is the process or repairing the areas with exposed fiberglass and get them ready to coat? This is the first boat I've owened personally, so please explain the repair process as step by step as possible...thanks! (previously i just used boats at the sailing center) Any articles or links would also be helpful! Also while Im asking if there any floats that are sold that go on the told of the mask to prevent the sails from sinking to far in the water if you do turtle? What is the cheapest/best place to order bungie to string up the trampoline? And ropes? I cant wait to give this fun boat the TLC it deserves and get it back out on the water!  

themanshed Senior Member

I've restored my G-Cat 5.7 several times. Here is a link to the last restore job that was a major overhaul of the boat http://themanshed.net/archived-projects/g-cat-catamaran.html The older boats like to leak in the hull seam; hard glue was used that crystallizes and cracks. I had some structural damage from a wicked capsize in 50 mph wind and an old bottom job let loose when I was getting righted. A really bad day in all but I survived being lost at sea from a nasty storm and the G-Cat faired well overall. I have the measurements written down for the tramp lines somewhere in my shop if you want them.  

Attached Files:

P1010025.jpg.

thanks for the link! if you find them id take them...if not ill just measure it when i take them off. wow what is that second jib your sporting on your g-cat...and where do I get one! question for you on your restore...did you paint gel coat over your fiberglass or did you just paint directly over it? Thanks!  

Hello Thomas, I had the spinaker made at a local sail shop. He is out of business now. A hobie 18 spinaker should fit. The pole is from Murry's http://www.murrays.com/ I can help you with the rigging if you decide to go with a spinaker. One of the earlier restores I sprayed Gel Coat, the last restore I sprayed a base coat / clear coat automotive type paint over a urathane primer. The primer was sprayed over the get coat to seal it.  

thanks, ill look into a spinnaker, they look like fun! another question for you where did you pick up the the device you use to roll up the jib...i would like to pick me up one of those.... (i appologize for not knowing the official name for it..) since I dont have a sprayer im looking to use the roll and tip method(if thats what is is called). Hmm I guess ill have to figure out if I want to put the time into gel coating before I paint if you know any good websites or other places to pick up g-cat parts(original or aftermarket) I would appreciate any info. Thanks!  

boat fan Senior Member

Roller furler The drum is a roller furler. Here is a cheap one : http://www.google.com.au/url?sa=t&s...9a1k09fAFfr2mWhxw&sig2=jqQFEqvCXG-cjA_J0BPoog  

RollerFurler.pdf

I would use West System Epoxy with 407 powder for repairs. West Marine sells small tins I am sure there are marine stores that carry the product. Get the pumps it simple. One pump epoxy resin, one pump hardner, and a spoon or so of powder. Get the batch mix down and do small batch just enough for your need as you go. No need to gel coat if you are going to paint. Use a sealer primer that is matched to your paint system. In my post above there is a hot link to Murrays website they carry about everthing you may need they are aimed at catamarans. Also try www.Catsailor.com it is a very good website for used parts or just poking about with cat sailors. Post a few pics of the boat and I can get an idea of the work you need to do.  

redreuben redreuben

Just one point, if you are going to re-apply gelcoat do not repair with epoxy resin stick to poly or vinyl-ester. If you are going to apply epoxy primer and urethane then epoxy repairs are fine.  

West System states that you can Gel Coat over epoxy not sure about other brands.  

Perhaps Thomas might like to read this thread before he decides. http://www.boatdesign.net/forums/fi...system-epoxy-incompatible-gel-coat-27544.html I have about 25yrs experience in fibreglass and composite boat building and I wouldn't. Linking type of primer, maybe if it came with a referance you can trust.  

I have used Algrip over West never had any problem but used the whole system primed and pained. In sanding I used 320 grit sand paper before 2-part primer. Pretty nasty paint must have the right equipment to use it. Here it is from my book in a nutshell: Epoxy makes better bonds, best to paint. Paint is nasty stuff. Poly is cheaper – bonds are not as good, smells really bad. Gel coat is easier not as nasty - 4 times more the work. Paint seals better, shines when sprayed. Gel coat is porous, needs sanding and buffing to shine. Paint is harder to repair but harder finish. Gel coat is softer easier to repair. I started out with Poly and gel coat - Shifted to epoxy and paint. I've used aircraft paint, boat paint, and automotive paint. Never had the best of luck with boat paint but some can be brushed. I use either aircraft paint or automotive paint. I don't leave my boats in the water. Consult with your supplier and try to stay within one brand or system for your paint and for your laminates. Remember advice is free and everybody has an opinion, even me, right or wrong. Those that are nay Sayers invite them over hand them a paintbrush, grinder, or sanding block you will enjoy the quiet.  

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redreuben said: ↑ Perhaps Thomas might like to read this thread before he decides. http://www.boatdesign.net/forums/fi...system-epoxy-incompatible-gel-coat-27544.html I have about 25yrs experience in fibreglass and composite boat building and I wouldn't. Linking type of primer, maybe if it came with a referance you can trust. Click to expand...

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• Sailboat Guide

G-Cat 5.0 is a 16 ′ 8 ″ / 5.1 m catamaran sailboat designed by Hans Geisler and built by G-Cat oultihulls starting in 1975.

Rig and Sails

Auxilary power, accomodations, calculations.

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

SA/D = SA ÷ (D ÷ 64) 2/3

• SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
• D : Displacement in pounds.

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Ballast / Displacement * 100

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

• D: Displacement of the boat in pounds.
• LWL: Waterline length in feet

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )

• D: Displacement of the boat in pounds
• LOA: Length overall in feet
• Beam: Width of boat at the widest point in feet

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

CSV = Beam ÷ ³√(D / 64)

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