Inter 20 forward deck repair :: Catamaran Sailboats at TheBeachcats.com

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Inter 20 forward deck repair

southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 11, 2017 - 01:48 PM

We've been getting a fair amount of water in our hulls on our new-to-us Inter 20 (1999 model), which we bought in November. Particularly in the port hull - easily 2 gallons+ over 3 hours of sailing in 20kts wind. We've used the air+soap test to identify a few leaking areas (inspection hatch gaskets, bow tang), but the most concerning is the seal at the forward end of the deck, near the bow. Looks like part of the seal is old and now leaking (especially the 12'' closest to the rounded front of the deck -- the rest of the seal looks ok).

What are the best options to repair this? We're thinking of 2:
(1) Least invasive: Clean seal (without damaging it), add thin epoxy from outside and use a vacuum pump on the rear bungs to create a light vacuum so that it sucks in the epoxy into the existing seal. Cons: potentially imperfect seal, ugly cosmetically

(2) Most invasive: Remove the top deck using a putty knife to break the seal, sand the joint areas clean, and reglue the deck with thickened epoxy. Cons: more work, potentially some nasty surprises if breaking the seals is harder than we think. I looked on the forum and saw various people do this with older Nacra 5.2s, 5.7s etc, but no I20s. Any reason this would not work for an I20?

Which would you suggest? Other ideas?

Pics:
- General area:

- Damaged seal area:

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Nacra I20
Sausalito, CA

Edited by southstars2012 on Apr 12, 2017 - 12:54 PM.

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SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
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MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Dec 04, 2024

Posts: 7090
Posted: Apr 11, 2017 - 02:08 PM

I just replaced both bow tangs last fall on my mystere. the decks were no where's near that "available" for removal *required crow bars, and sledge hammers)

Those lids look like they want to pop off on their own

if i was getting gallons of water in my cat - I would rip them off, inspect all the glass and bulkheads, inspect the bow tangs for ANY signs of replacement and slap them back on
samc99us

Rank: Mate

Registered: Apr 15, 2005

Last visit: Feb 21, 2024

Posts: 574
Posted: Apr 11, 2017 - 03:41 PM

If I were doing this job, I would pull those decks off and add two layers of 5.7oz oz carbon right forward of the crossbeam for 3 feet and then tapered to one layer for the remainder further forward. I'd probably run 45/45 weave for the whole thing and uni carbon in the area forward of the beam. We're talking maybe
coolhead

Rank: Mate

Registered: Oct 04, 2013

Last visit: May 23, 2017

Posts: 141
Posted: Apr 11, 2017 - 04:24 PM

I have removed one of front the top deck on my Inter 18 last year. It was not glued properly at the front end, just like your's but less obvious. It has been fairly easy to remove. I used a thin steel blade that I was hitting on the end to make it penetrate under the deck. After, I was hitting it sideways all around the deck. Once you have separated them all around, you will have to separate them from the bulkheads. There was 2 on my Inter 18. After that you just have to clean both faces and reglue them. Before closing the deck, check the bulkhead attachment. The very first one at the bow was almost completely loose. I re-attached it with glass and epoxy resin.

Edited by coolhead on Apr 11, 2017 - 05:25 PM.

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AB
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KurtHansen

Rank: Lubber

Registered: Jul 25, 2007

Last visit: Sep 07, 2021

Posts: 9
Posted: Apr 11, 2017 - 09:33 PM

I had the same problem with my 2003 Nacra F18. After the low pressure soap test, I learned that there was a 5 inch leak in one of the seams on the top of the starboard hull. I added about 3 coats of superglue into the seam and the leak was gone. The repair is invisible and has been water tight for more than a year. Kurt
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Dec 04, 2024

Posts: 7090
Posted: Apr 12, 2017 - 10:03 AM

Quotesuperglue

for real?
samc99us

Rank: Mate

Registered: Apr 15, 2005

Last visit: Feb 21, 2024

Posts: 574
Posted: Apr 12, 2017 - 11:26 AM

Yeah do not use super glue. Marine caulking (sikaflex) would have been much better but neither are the right adhesive. These decks are a structural components of the boat. I would completely remove those decks and re-bond with a high quality epoxy resin (West is the minimum I would use, pro-set would be much better) filled with cabosil and milled fibers if you are relying on superglue to keep your boat in once piece.
southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 12, 2017 - 12:57 PM

MN3if i was getting gallons of water in my cat - I would rip them off, inspect all the glass and bulkheads, inspect the bow tangs for ANY signs of replacement and slap them back on

Thanks MN3 for that advice!

Side question - I saw you fixed the links to my [img] links so that the thumbnail picture displays in the forum. I was wondering how to get the right link since the ones I was using were not displaying -- Where did you get the .DownloadItem image links? When I go to my personal gallery I just see links like the following, which do not display a thumbnail in the forum: e.g. https://www.thebeachcats.com/pictures?g2_itemId=127231.

Still new here, and like to be able to post pics!

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
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southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 12, 2017 - 01:04 PM

Thanks everyone for the advice - sound like getting the decks off is the right way to go, plus we'll see what's going on inside. Hopefully not a can of worms!

samc99usIf I were doing this job, I would pull those decks off and add two layers of 5.7oz oz carbon right forward of the crossbeam for 3 feet and then tapered to one layer for the remainder further forward. I'd probably run 45/45 weave for the whole thing and uni carbon in the area forward of the beam.

That sounds like a fair bit of carbon - is the concern that the bows could break off? (I certainly don't want to emulate Team Philips in the run-up to The Race 2000.
Or is this more just to stiffen the platform? I haven't yet heard of Nacra I20 bow issues, but I'm new to the boat and would certainly be motivated to fix known weak points.

Edited by southstars2012 on Apr 12, 2017 - 01:07 PM.

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SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
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Dogboy

Rank: Mate

Registered: Mar 19, 2004

Last visit: Nov 21, 2024

Posts: 964
Posted: Apr 12, 2017 - 01:24 PM

Everyone seems to be recommending to remove the decks. That may be the right way to go, but if you don't suspect there are any other structural problems, that may also be a lot of extra work and as you mentioned, opening a can of worms. If the rest of the hull feels solid, why pop the top? Did you compare it to the opposite hull? Is it flexing any more than the other one?

All else being equal, I would probably just try to inject some epoxy into the void like you originally mentioned. Mask off the area really well. Fill a syringe with epoxy, and use negative air pressure at the drain plug to help pull the epoxy into the void (having a helper will make things a lot easier). Use weights or straps to help clamp the deck to the hull and wipe off any excess epoxy with an acetone dampened rag before it cures. Then after the epoxy cures, repeat the soap/bubble test and/or sail the boat and see if it is improved before you dive into pulling the whole hull apart. That would probably be my approach

sm
southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 12, 2017 - 01:26 PM

southstars2012Side question - I saw you fixed the links to my [img] links so that the thumbnail picture displays in the forum. ...Where did you get the .DownloadItem image links?
Never mind, I finally figured it out! i.e. Need to use the image link from when you right click on the source image, and choose "copy image address" instead of "copy link address" (in Chrome).

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SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
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MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Dec 04, 2024

Posts: 7090
Posted: Apr 12, 2017 - 01:26 PM

QuoteI was wondering how to get the right link since the ones I was using were not displaying

I am not exactly sure, they gave me issues too (i've only been on this site 11 years and only have 4122 posts) (lol) - it took me a few times to get them to work - not sure what was up with it. I know someone else had issues recently posting images - maybe something is up with this site currently?

I am sure Damon will chime in
dmgbear55

Rank: Mate

Registered: Jun 22, 2015

Last visit: Jul 06, 2018

Posts: 258
Posted: Apr 12, 2017 - 03:08 PM

The problem with not actually removing the deck lid is you really don't know where the problem is until you pull it off.

You can see on my deck lid that there were areas of good bonding and some areas that were either never well bonded or failed over time. The problems in at least my case were more than just at the front edge. The downside to doing the real repair is that you are never going to get that deck lid back off again easily. But while it is off you can much more closely inspect the other elements like the front of the bulkhead under the beam.

The deck lid is also structural, so the delamination from the hull that is going on is a problem that is just one more reason you need to address the whole problem.

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 12, 2017 - 09:48 PM

In terms of re-sticking the deck lid, I understand using epoxy with some filler like cabosil/milled fibers. But that will make it harder to take off the deck in the future though, if needed.

How about using 3M 4200 or 5200? I know it's more of a non-structural adhesive, but I hear 5200 in particular is pretty obstinate and strong. Looking at my current decks, the white adhesive looks visually more like 4200/5200 than epoxy.

Any idea what Nacra uses?

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SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
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dmgbear55

Rank: Mate

Registered: Jun 22, 2015

Last visit: Jul 06, 2018

Posts: 258
Posted: Apr 13, 2017 - 01:28 AM

I wondered the same thing when I was faced with this. But then I also thought that what they used didn't really work all that well either. I just decided that structural strength was more important and if I need to get in there in the future I have big saws to make big holes.

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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samc99us

Rank: Mate

Registered: Apr 15, 2005

Last visit: Feb 21, 2024

Posts: 574
Posted: Apr 13, 2017 - 09:21 AM

These decks, especially the front decks, provide a critical structure to the boat!! Take a large soda straw, grab each end and try to twist it. Now cut a slit down one side of the straw and twist. See the difference? That is what you have with the deck removed OR the deck bonded with super glue/3M 5200 or any other non-structural adhesive. The rear decks aren't as critical as the front decks, but I'm quite sure the factory intended to have these fully bonded, even if they failed to do so at times. Get in there, do some reinforcing, re-inforce your deck and bond it back on with something permanent. Do it right once and it should last for another decade.
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Dec 04, 2024

Posts: 7090
Posted: Apr 13, 2017 - 09:31 AM

I used 6 tubes of WEST SYSTEM Six10 Thickened Epoxy Adhesive when i put my lids back on

I had 2, 7' wooden 1"x1" strips on the lids that i strapped on and tightended, (and added weights too) to help keep my curved lids snug during cure

of course my images for this have disappeared :(
https://www.thebeachcats.…nc=viewtopic&topic=16179

Edited by MN3 on Apr 13, 2017 - 09:31 AM.
samc99us

Rank: Mate

Registered: Apr 15, 2005

Last visit: Feb 21, 2024

Posts: 574
Posted: Apr 13, 2017 - 10:41 AM

Good idea with the strips. Best method is to apply vacuum to the entire lip when re-attaching the deck, as this applies an even 14.7 psi of pressure to the whole joint.
southstars2012

Rank: Lubber

Registered: Oct 09, 2016

Last visit: Mar 08, 2018

Posts: 40
Posted: Apr 14, 2017 - 01:26 AM

Thanks for the additional tips -- I like the idea of applying a vacuum, and the wood strips to apply even pressure make sense. Will look into Six10, but may just use epoxy with cabosil or milled fibers (have that readily available).

MN 3- thanks for all the work documenting that repair - that's incredibly helpful. One part I didn't understand very well: you say you added tape to top of the decks (on the outside of the joint areas I presume), then "added glass to the lid lips (for a nice clean area to epoxy back on)". How exactly did these glass strips on the lid lips work?

My guess - is this correct?
1) Epoxy the glass strips onto lid lips' joint areas. These appear to stick out somewhat from the lid lips.
2) Let the epoxy holding glass strips thicken a little (but probably not too much)
3) Add joint adhesive onto the new glass strips (the new strips now allow a cleaner bond on the lid lips)
4) Add joint adhesive onto the hull's joint areas (assuming the adhesive used needs both bonding surfaces to be laid up)
4) Position the lid back on the hull joint and add pressure
5) Sand down the joint area (since the glass strips added to the lid lips now stick out from the joint)?

Edited by southstars2012 on Apr 14, 2017 - 01:27 AM.

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Dec 04, 2024

Posts: 7090
Posted: Apr 14, 2017 - 09:22 AM

the reason i used the 6:10 was - you need a good amount of epoxy for this job (3 tubes per side for me) and having to mix batch after batch after batch of west system would be problematic for me. I have found i can only mix relatively small batches because bigger ones would get too hot. this completely resolves any issues with the time of mixing up multiple batches, it is already incredibly thick and gap filling, and we already had a battery powered caulk gun (purchased by a friend for another deck lid job). we also knew how much would be needed from previews jobs - this was a sure fire way to not run out of product in the middle of the job:

as per the glass strips:
my lids did not pop off. we literal had to use little hammers, crowbars, monkey bars and then later the rum bar :) - they did not come off cleanly in many areas and needed repairs/resurfacing many places. by adding glass to the edge i was able to reconstruct a nice and flush surface to bond back to the deck's recessed area (where the deck sits/bonds)

QuoteMy guess - is this correct?
1) Epoxy the glass strips onto lid lips' joint areas. These appear to stick out somewhat from the lid lips.
2) Let the epoxy holding glass strips thicken a little (but probably not too much)
3) Add joint adhesive onto the new glass strips (the new strips now allow a cleaner bond on the lid lips)
4) Add joint adhesive onto the hull's joint areas (assuming the adhesive used needs both bonding surfaces to be laid up)
4) Position the lid back on the hull joint and add pressure
5) Sand down the joint area (since the glass strips added to the lid lips now stick out from the joint)?

not really
1 - prep the deck lid lip areas - then lay up strips of glass all allong the entire deck lid lip - let cure - grind down back to original shape and size
2 - prep the deck to receive the lid (sand, add glass in any spots that were beat up during the lid removal)
3 - lay up a big bead of 6:10 on deck
4 - put lid back on - strap down, add weights
5- pray
6 - remove straps and test for leaks/issues
7 - add lots of gelcoat and start the fairing fun

about the vacuum: that is a skill i have not yet learned & equipment i do not have but if i had both (or really just the equipment) i would have probably done that as well. I do not think a vacuum alone would come close to handling my lids. they are 95% of my deck area, and curved - something would have to be strapped down to hold it down in all spots. even w the straps, i found the corners were extra tough to sit flush... they needed weights to hold em down