How to check for deck soft spots

KenM · Aug 28, 2016

About to drop the hammer on a 1984 Mainship 34. After reading many posts, due have some concern about soft spots in cockpit and deck. I will check on the "smile" of the sliding glass door, but is there anyway to check the rest of the decks for soft spots... i.e if the core is saturated can one tell by "bouncing" up and down on the deck? I don't have a moisture meter. Should the decks have any "give" when testing this way? Otherwise the boat seems sound, been re powered with a cummins 210, has a bow thruster, kohler geny, auto pilot etc.... Like the boat, but am a bit concerned about the deck and flybridge coring.

Thanks in advance...

Simi 60 · Aug 28, 2016

Tap with a screwdriver head shows a different sound or if like mine in spots you can see or feel it pump as you walk on it.

Thankfully I have 1 1/2 inch planks as an actual deck with you beut 3/8th F17 structural ply laid over the top which turns to weetbix when it gets wet.
Some on this forum reckon that ply has a place in a boat, I wouldn't use it in packing crates myself.

What are the decks on a mainship 34 made of?

Jeff F · Aug 28, 2016

Most of the 34s have or have had deck coring issues. not unusual in any 30+ year old boat Lots of information on the web and a few folks here that have dealt with it. Pay particular attention around stanchions and the ladder base in the cockpit, and any other deck fittings. A survey is always a good idea.

I bought a 78 with the B210 a year ago and have traveled close to 2000 miles this summer. Very happy with the boat and happy to discuss. The PO had done a lot of work to repair coring and repaint the decks.

jleonard · Aug 29, 2016

What are the decks on a mainship 34 made of?

Some are balsa core, some plywood, some foam, depends on the year and the area.
The flybridges are balsa core, foredeck balsa or plywood, cockpit and side decks balsa or plywood.
Even if they are wet they are easy to fix if you can do it yourself. If you are paying someone, then it will be pricey.
Let a surveyor tell you if the cores are wet, then price it and act accordingly.

Panacea123 · Aug 29, 2016

Simi 60 said:
Tap with a screwdriver head shows a different sound or if like mine in spots you can see or feel it pump as you walk on it.

Thankfully I have 1 1/2 inch planks as an actual deck with you beut 3/8th F17 structural ply laid over the top which turns to weetbix when it gets wet.
Some on this forum reckon that ply has a place in a boat, I wouldn't use it in packing crates myself.

What are the decks on a mainship 34 made of?

Ditto on the screwdriver
I use the largest one I have and just let it "bounce" ( large solid plastic handle (no rubber) along as I drop it through my fingers from about 4" you will hear the sound change.
When I bought my current boat, to my horror the surveyor was using a pointed hard plastic mallet to sound the deck, good news no soft spots, bad news cracked the gel coat in several places!

He also used a moisture meter which showed a spot by the windlass (windlass since replaced and leak fixed)
Sounding will only find spots that are already bad, meter will find problems likely to happen soon and leaks can be repaired before damage is done.

denverd0n · Aug 30, 2016

I got myself one of these...
http://tinyurl.com/hwmrypf

Doesn't do any damage, works perfectly, and it is benign enough looking that owners and brokers never get upset like they used to when I pulled out a phenolic hammer.

Simi 60 · Aug 30, 2016

denverd0n said:
I got myself one of these...
http://tinyurl.com/hwmrypf

Doesn't do any damage, works perfectly, and it is benign enough looking that owners and brokers never get upset like they used to when I pulled out a phenolic hammer.

Its not the brokers boat, I bet the owner would have something to say.

I have seen plenty of damage done on foam boats when clueless surveyors have been let loose with phenolic hammer .

How to check for deck soft spots

KenM

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Simi 60

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Jeff F

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jleonard

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Panacea123

Senior Member

denverd0n

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Simi 60

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