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marcelo
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SB18 Information

Post 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.



sngatlanta
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Post 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.

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Post 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
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marcelo
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Post 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.

sngatlanta
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Post 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

marcelo
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Post 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.

sngatlanta
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Post 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

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Post 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.
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sngatlanta
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Post by sngatlanta »

55
Last edited by sngatlanta on Sun Jul 06, 2008 3:28 pm, edited 1 time in total.

sngatlanta
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Post 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.

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