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SB18 Information

Posted: Fri Jul 04, 2008 8:52 pm
by marcelo
Hello All,

I just finish the seams. :)

Reading the manual, the next steps are, to aplly glass on the Transon, them aplly two coats of epoxy and then cover the hull panels with specified cloth.

My doubts are: :doh:

1- Should I mount the transon and then cover the hull panels or I can mount it when turning the boat upright?

2- Do I need to wait the two coats of epoxy to dry first and then aplly the hull cloth?

Thank you for your help.

Marcelo
SB18Coral.

Posted: Fri Jul 04, 2008 10:47 pm
by sngatlanta
Marcelo.

Want to be more confused? :doh:
Look at the sequence on page 12 of your building plans.
The sequence is:
1. Frames on strongback
2. Hull Panels-taped on outside
3. Flip and remove strongback-Tape seams inside frames
4. Install center board case
5. Install berths and transom
6. Cockpit sole
7. Cockpit sides
8. Deck
9. Cabin Roof

My assumption has been from the start that the construction notes are somewhat generic and the Assembly Sequence is what I am following. I don’t think I could get the transom right without some of the other parts in place. It’s not unusual to leave a transom overlong and adjust it when the time comes.

On the subject of epoxy use there is some information at west systems site http://www.westsystem.com as well as this forum in the tips.

From West Systems User Manual
Recoating
Apply second and subsequent coats of epoxy following the same procedures. Make sure the previous coat has cured firmly enough to support the weight of the next coat. To avoid sanding between coats, apply all of the coats in the same day. See Special preparation-Cured epoxy. After the final coat has cured overnight, wash and sand it to prepare for the final finish.

Maybe Jacques or Evan can chime in and clarify before you move on but I’m blasting forward in the morning with my assumption. I was going to do all my fairing on the bottom before turning when I realized I would have to refair the area around the transom. The boat will need to be flipped a second time to finish the keel cut out anyway (more fairing). Which brings up a question, are you planning to go with a lifting keel or swing?

We seem to be neck and neck at this stage. I think we should plan on an on the water finish to the race. :lol:
Hope this helps.

Posted: Sat Jul 05, 2008 12:12 am
by TomW
Hint if you guys are using MarinEpoxy with slow hardener or Silvertip, there is no need to sand or wash between coats for up to 24 hours. They use a different type of hardener that prevents blushing than West uses.

Tom

Posted: Sat Jul 05, 2008 6:00 am
by marcelo
Hi Greg,

I red the manual and I missed that word (transon) :?.
Thank you for your help.
I am planning to use the lifting keel and you?
Yes we are in the same path, I think the idea to finish it on the water is very good.. :D

I am using the marine epoxy with slow hardner.

So, if I understood:

1-Apply first coat. Let it dry.
2-Apply second coat. Let it dry.
3-Apply the glass on the hull,

No more than 24 hours between the steps, otherwise, more fairing!!! :(

It will be a busy weekend,

Thank you all for your support.

Marcelo
SB18Coral.

Posted: Sat Jul 05, 2008 8:05 am
by sngatlanta
marcelo wrote:

So, if I understood:

1-Apply first coat. Let it dry.
2-Apply second coat. Let it dry.
3-Apply the glass on the hull,

No more than 24 hours between the steps, otherwise, more fairing!!! :(
Close.
It’s not a fairing issue but a secondary bonding issue. Regardless of which brand you use there are 3 stages to epoxy curing: (I’m taking this straight from west systems so don’t assume I’m a chemical engineer, ceramic engineer yes, chemical no)

1. Liquid-Open time: Open time (also working time or wet lay-up time) is the portion of the cure time, after mixing, that the resin/hardener mixture remains a liquid and is workable and suitable for application. All assembly and clamping should take place during the open time to assure a dependable bond.

2. Gel-Initial cure: The mixture passes into an initial cure phase (also called the green stage) when it begins to gel or "kick-off." The epoxy is no longer workable and will no longer feel tacky. During this do not disturb stage it progresses from a soft gel consistency to the firmness of hard rubber. You will be able to dent it with your thumbnail.

Because the mixture is only partially cured, a new application of epoxy will still chemically link with it, so the surface may still be bonded to or recoated without special preparation. However, this ability diminishes as the mixture approaches final cure.

3. Solid-Final cure: The epoxy mixture has cured to a solid state and can be dry sanded and shaped. You should not be able to dent it with your thumbnail. At this point the epoxy has reached about 90% of its ultimate strength, so clamps can be removed. It will continue to cure over the next several days at room temperature.

A new application of epoxy will no longer chemically link to it, so the surface of the epoxy must be properly prepared and sanded before recoating to achieve a good mechanical, secondary bond.

The fairing is done after all coats and glass are applied and a thickened mixture is used to level (fair) the surface to prepare for paint or finish coat.

I’m also building the lifting keel.

Got to go. Like you it’s going to be a busy day in the shop.
Greg

Posted: Sat Jul 05, 2008 10:18 pm
by marcelo
Hi Greg,

How the things are going?

I just aplied the two coats of resin today, it got a good shine. :)
Tomorrow I will work to put te glass on the hull.

Thank you one more time for your help. :)

Marcelo
SB18Coral.

Posted: Sun Jul 06, 2008 9:20 am
by sngatlanta
Marcelo,
We also got on 2 coats of epoxy today, always makes the wood look so good. We got the fiberglass laid out last night and will begin applying epoxy shortly.

You are always welcome,
Greg

Posted: Sun Jul 06, 2008 1:13 pm
by Evan_Gatehouse
Wood panels that are not going to be glassed need 2 coats of epoxy.

Wood panels that are glassed should have an initial coat of resin applied and then the glass after that. The glass + resin acts as the 2nd coat.

Sorry if you've used a bit of extra resin in doing this.

Posted: Sun Jul 06, 2008 3:22 pm
by sngatlanta
55

Posted: Sun Jul 06, 2008 3:27 pm
by sngatlanta
Wood panels that are not going to be glassed need 2 coats of epoxy.
Oops, the heck with resin I want my day back!

Marcelo,

How much epoxy did you use to lay on your glass not including the precoats?

I'll have to go back out in the shop this evening at get our totals.

Posted: Sun Jul 06, 2008 7:54 pm
by marcelo
Hi Guys,

To late, :( I applied two coats and the resin (3 coats in total).

Including the seams I used 6 gallons (4 resins + 2 hardeners)

Just for the coats (3) 2.5 gallons + 1.25 hardener (+/-).

Anyway it is done!!! :D

Question, probably we have it somewhere, but, Is there any incompatible between resins, more specific (between west system and marineepoxy?

All the best.

Marcelo
SB18Coral

Posted: Sun Jul 06, 2008 9:41 pm
by sngatlanta
Holy epoxy Marcelo that’s a truckload of epoxy. We have used to date about 3 ½ gallons for everything including bonding butt joints in the panels, seam tape, and now the cloth lay-up. For the fiberglass lay-up only we used 1.8 gallons and I felt we could have held back about 10-12 oz of that. Remeber I also used 17 oz cloth and it would take more epoxy to wet out. I’m not trying to alarm you but go easy on the stuff. Are you having the epoxy thicken on you before you get it applied resulting in a lot of wast?

Take a look at the tutorial below on this web site for information about what is referred to as resin rich.

http://bateau2.com/content/view/99/28/

I quote from the above article “Dry fiberglass is white but as the resin penetrates the fabric, it becomes transparent. Do not use more resin than what is necessary to wet the glass.
A laminate with high glass content will be stronger than one with too much resin. Too much resin makes a laminate weaker, not stronger. Resin rich is bad for strength and bad for your budget, do not waste resin.â€

Posted: Mon Jul 07, 2008 12:06 am
by marcelo
Hi Greg,

That is not good, :( .

I will be more cautious in the next steps using the resin.

Thank you very much for the information.

But, I am thinking, I just wetted that until get transparent and squeezed it.

Anyway, now, it is done, one more learning, a lot of them in this project.

I think you already have some advantage in our race...your boat will be lighter... :D

Thank you and have a great week.

Marcelo.
SB18Coral.

Posted: Mon Jul 07, 2008 7:08 pm
by sngatlanta
Learning is a good thing. You need to let the epoxy soak in before knowing if there is enough to turn it transparent and then you can add a bit if needed to the spots that are still white. Don’t worry about it.

Your boat will not necessarily weigh that much more than mine if at all. I would imagine based on the amounts you have used that the weave in your cloth is fairly full and will require less filler than mine to start fairing the outside. Granted filler will weigh less than epoxy alone but I used heaver cloth and added at least 4-5 pounds to the boat with that.

Also keep in mind the weight of the boat is nothing when compared to the competence of the crew sailing it. I never have said I was a good sailor. :lol:

When do you plan to turn your boat?

Posted: Mon Jul 07, 2008 9:54 pm
by marcelo
Hi Greg,

I will remember that when applying the inside glass.

Did you were a good Sailor? Why is not anymore?

My experience in short one, I started late and it is limited at some lakes in Brazil and some spots in the Brazilian coast. I am taking this project as a mix of pleasure and at the same time a challenge for myself, so far I am having fun. :D .

I have one week vacation in July and I am going to take my daughter to meet Mickey Mouse in Orlando. :D , so I think I will turn it last week of July, when I will be back.

And you, when are you planning to turn yours?

The best regards.

Marcelo
SB18Coral.