Balsa Core Delamination

thataway · Posted: Sun Dec 13, 2020 9:00 pm Post subject:

The photos do show vacuum bagging for the core. No resin infusion. Just having vacuum bagging, does not have any bearing on the adherence of the core to the outer shell. If you found sunflower seed shells there, there was very poor "sanitary control". Also fiberglass work is difficult, and "dirty". The shop pictured in the series you linked to, was what I would call "dirty". I see photos of current builds and I have spent time in factories where boats were being laminated on a mass production basis (Specifically Columbia/Coronado and Cal yachts). All a lot "cleaner". Any dust, material particle (even husks) can be a nidus where there is no lamination. Also if the underlying glass has set up fully, there will be less of a bond than if it is still tacky.

A lot of water got in that core--from some place. I also suspect some freeze thaw cycles??

You are doing great work, with fantastic documentation! Thanks.

PaulNBriannaLynn · Posted: Mon Dec 14, 2020 9:42 am Post subject:

This is a great technical thread, thank you for sharing all this. Its a little scary for me with a 2007 with the same cabinet and cockpit floor.

I believe Scott hit the nail on the head earlier. The raised cockpit floor holds water, we've all determined that. When I got our boat, there was water under there. If the trailer wasn't tilted with the tongue up, or while it sits level in the water... water would creep through the bulkhead somehow and find its way into the cabinet with the water tank and puddle on the floor between the dinette and the sink cabinet. I've found standing water in that cabinet before and who knows how long its sat there. At one point I resealed the cockpit floor and that was the end of that, but now I'm going to have to check those water tank screws and bed them properly and pray I don't find anything like this while I'm doing the work. Agreed with the freeze/thaw cycles compounding the problem over time. The water is not supposed to creep that far in theory.

I'll be following along with the videos.

thataway · Posted: Mon Dec 14, 2020 3:42 pm Post subject:

I don't know exactly how these 22's were built.--but the usual way, was to tab the aft cabin bulkhead to the inner bottom of the boat all along its bottom and up the sides. I have seen several boats, including several 22's and at least 3 C Dory25's where this tabbing had either broken down or was never complete. This can also lead to water intrusion into the lower part of the aft bulkhead (which is also balsa cored). In light of this it would be prudent for any buying of these specific boats to do moisture testing on the inner cabin floor. Normally this floor should have no more moisture than the solid glass on the sides.

Persons who own these boats currently should use one of the in-expensive moisture meters to determine if there is any excess moisture trapped in the core.

In our discussion of locations of bilge pumps in different years of the boats, there are many variations of location. Some have a 'step' just inside of the cabin aft bulkhead. These also have a hole thru that bulkhead,--and often a sump there, to collect water which might pool in this area. For example my 2006 C Dory 22 had the step and sump just inside of the cabin door. It had the removable floor. Thus no water was "trapped" under it. It flowed to the sump.

I might be tempted if I owned one of the affected boats with the built in level floor in the 22, to consider putting a hole in the aft bulkhead and placing a bilge pump under a step, and "dam" of fiberglass to contain any water in a sump area.

colbysmith · Posted: Mon Dec 14, 2020 5:06 pm Post subject:

Hi Bob. Can you recommend or link to the kind of moisture meter you like to use or refer to? Thanks. Colby

thataway · Posted: Mon Dec 14, 2020 10:30 pm Post subject:

colbysmith · Posted: Mon Dec 14, 2020 11:02 pm Post subject:

Thanks. But it looks like both your links go to the same meter. I'll see if I can google to find the Ryobi. Colby

thataway · Posted: Tue Dec 15, 2020 11:27 am Post subject:

Sorry about that Colby.

Here is the proper link. It may not be in production?

The only real positive about it was it seemed a little easier to read than the General.

clayhubler · Posted: Tue Dec 15, 2020 2:15 pm Post subject:

Is anybody else getting the 404 page not found when clicking the link to the videos?
Oops, just realized the links work on my phone but not on the pc. Not sure why.

John, I'm going to have to get caught up on your videos. Looks like you are literally in the same boat as me. I too have a very expensive boat that I cannot use.

I am looking at cutting out the entire floor in the cockpit and probably the cabin on my 2003.

I just yesterday took the boat off the trailer and blocked it up with support under the chines because I was worried about the hull flexing with all the balsa removed.

Initially I was optimistic about completing this repair quickly, but I now know that will not be the case.

Blue Rose · Posted: Tue Dec 15, 2020 3:01 pm Post subject:

John-
I just finished watching video #16. It's discouraging to find isolated pockets of core rot in areas beyond the line where it the balsa appears to be solid. The more you look.... the more you find. As painful as it is, I guess you just keep going.

I'm wondering if you have tested the accuracy of using a phonic hammer and the moisture meter to predict the core rot problem areas. Maybe you could map areas using those those methods on the floor before you lift the top fiberglass layer to see how those methods relate to what you find underneath?

As you are running out of floor area to work from, you might want to use some lumber (i.e. 2 X 8's) that span the over the work area to avoid putting your weight directly on the bottom hull layer.
Jim

Brewkid · Posted: Tue Dec 15, 2020 3:56 pm Post subject:

Jim,

Thanks for following along. I haven't used a phonic hammer. The moisture readings however were just too all over the place unfortunately... I would have a hole here and a hole there and at the end of the day it looks like the most of it will just have to come out anyway...

If you noticed, I'm sitting on the outboard/thick section while I'm working and stay off the weaker middle section, but if need be I'll scaffold it up for sure! When I pull the back deck that'll be the real challenge I think. I may even need to cut it out in two sections midship.. We'll see...

R/
John
Scallywag

Brewkid · Posted: Tue Dec 15, 2020 4:05 pm Post subject:

Clay,

All I can say is I feel your pain.... I just got notification that I'm going to have to hit the road for a bit, so until then I'm just going to cut away/prep and plan on glassing when I get home.

Good luck my friend and If you need a sounding board to vent too, I'm here and will definitely understand.

R/
John
Scallywag

Blue Rose · Posted: Tue Dec 15, 2020 5:08 pm Post subject:

John,

thataway · Posted: Tue Dec 15, 2020 9:24 pm Post subject:

Brewkid · Posted: Mon Dec 21, 2020 9:01 am Post subject:

I just dropped a couple more videos.

One that covers a little detail about the raised deck to give a visual to Bobs response to Jim. (towards the end of the video)

One details my installation of V-Berth hatches and foam removal.

Enjoy.

Merry Christmas to Everyone.

R/
John

thataway · Posted: Mon Dec 21, 2020 12:09 pm Post subject:

For reference here is the link to the U Tube videos

I wonder if the small amount of moisture in the foam is from the anchor locker or the brass strip--that is where most of this comes. Also shows again, the "closed cell foam" really does absorb water.

Also not as much foam was forward as in many boats. It is not required by law in a 22' boat, but many are chock full of foam--yours was easier to clean out. I guess you gives you one plus....

It is interesting where your base stops forward. It may have varied from year to year. I would leave it alone.

The other interesting issue is the channels of water in between good and well adhered blocks of balsa core. I am guessing that it worked its way thru kerfs in the blocks and / or places where the blocks were not fully touching, and a small channel was left. The free thaw cycles probably expanded these channels.

Did you keep a record of the moisture readings. I have suggested that graph paper be used and the moisture readings can then be co-related to the areas where there is core damage.

Is the plan to finish the cabin sole, before you tackle the cockpit area?
I agree that when the floor goes back in it should be tabbed in with glass. Not directly related, but when we put the new cockpit floor in the 2003 C Dory 25, we used a roller and resin thickened with cabosil to give it the non skid, rather than trying to reproduce the factory non skid.

As always wonderful videos and explanations.