22-2 inboard rebuild

[jupitermike1]

http://s458.photobucket.com/albums/qq30 ... G_1570.jpg  
 got a good start, all below the water line hardware out, motor & trans out,
console out, bottom stripping 50%, ready to cut out floor.

[RickK]

Looking good :!:  :!:

[jupitermike1]

I read in a post about some one using nida core for a deck refit I would like to get opinions between plywood & nida core & is 5/8 thick enough for either thanks.

[71flatback]

5/8" is overkill.  3/8'"-1/2" is fine if it's glassed good. Nida-core is lighter and strong but is hard to get flat. I found the best way is to glass one layer on flat ground and the install it and add a couple more layers.

[slippery73]

If you go nida-core you definitely have to glass one side on flat ground, I would also glass ribs in it to give it some more strength. A couple pieces of pvc pipe ripped in half to give two half circles would work well, you just want enough to give the panels some strength. The nida core can be a bit of a chore if you don't have much experience working with this type of material, but they also sell panels that are already glasses both sides and made up. Then you simply install like plywood, but it never rots and is lighter.

[jupitermike1]

Speaking of lighter I cut out the deck today & removed the exposed wet foam, do you just grind the bonding compond thats left. I need to glass some spots on the stringers thats crushed after i get the wet foam out of them.I posted some more pics on photo bucket.

[LilRichard]

From my opinion, I would NOT use 3/8" ply for a deck, that is too thin.  You need at least a half, but 3/4" is better.  Go talk to some pro rebuilders - that is what a lot of them are using, including Hammerhead.  Using 1/2 vs 3/4" might save you 100lbs max.

[slippery73]

Yes just grind off the bonding agent, its a pain in the butt but its the only way  that stuff comes off. On another note, research the composites well before you choose to put plywood decks back in your boat. Its kind of silly to go through the rebuild process just to put something back in that is going to rot if not properly installed and maintained. All it takes is the tiniest of holes to let water into your plywood core for rot to begin and once its there its going to rot. Most guys on here think that there plywood decks they put in might last as long as the originals but they are sadly mistaken, a 30 yr life on a boat deck isn't bad. But when being rebuilt most guys use plywood, plywood isn't the original deck material so you can't compare the longevity of the two products since they are not the same. The original deck material was end grain balsa, some might think that balsa would be more susceptible to rot than a high grade ply, which they may be right. But in the configuration that the balsa is installed its grain runs straight up and down, perpendicular to the deck. This means when there is water intrusion into the core it takes a long time for the water to make its way through the core because the wood fibers are running the wrong direction for water to easily travel. Now plywood on the other hand are thin veneers laminated cross directionally to each previous laminate. If you have water intrusion into this type core each subsequent layer that is penetrated will let the water travel in opposing directions of the intrusion point. Basically acting like little subway tunnels of rot radiating from its original point.

Nida core is a great alternative, there are also many ridgid foam composite boards out there. Divinycell, penske board, etc. I would seriously think about going composite before investing the time and money into your boat, cost wise its not much more for the peace of mind.

[RickK]

From my opinion, I would NOT use 3/8" ply for a deck, that is too thin.  You need at least a half, but 3/4" is better.  Go talk to some pro rebuilders - that is what a lot of them are using, including Hammerhead.  Using 1/2 vs 3/4" might save you 100lbs max.

Ditto - I've heard too many people that jump into the boat after the thin stuff is used and they're pissed. 5/8 is good IMO - 3/4    - but hey, it'll be solid.  Some soles have a little crown in them for runoff, so you need some way to do that.

[LilRichard]

Bottom line, plywood is easier to work with if you're a novice builder.  I was not and am not a pro, so I went the route that allowed for the greatest margin of error.

And my boat was built with plywood, not balsa - and it lasted a long time.  I always see people talking about how wood is bad - and that's not true.  Use it right and it's a great material.  But don't take my word for it, rewad something from a pro:

http://www.yachtsurvey.com/core_materials.htm

And I quote:

"Foam Cored Decks  Foam might seem like a great replacement for balsa, since it doesn't rot. But that doesn't mean it won't deteriorate. It can and it does. By a variety of means and methods. The problem I have with foam is this: Balsa is balsa, and it doesn't come in 100 different formulations. With balsa, you know exactly how it's going to behave under all conditions. Not with foam. Try looking at a piece of foam and determining what it is. No way. All you can do press your fingernail into it and determine its density and compression strength. Or bend and break it.

You already know a lot about foams because you see lots of it used in packaging and insulation, so you know most of it is not very durable stuff. In fact, put it out in the sun for a couple of months and it will literally disappear. It evaporates. Literally. Then pour some solvents on it. Go into your paint locker and you'll find at least one that will dissolve it. Put it on the ground and step on it. Crushes pretty easy, no? Work your fingernails into it. Crumbles real nice, does it not? Now apply some heat to it. Doesn't have to be much, just bring a match near. Try to burn it with the match. Burns like crazy, right? Hot and fast. Now try the same things with a piece of balsa. In virtually every category, balsa out performs the foam. And when it comes to biodegrading (meaning rot), in many cases the balsa will still outperform the foam. Balsa, like teak, contains a toxin that fungi doesn't like. It doesn't rot until that toxin leaches away.

Another Problem: Most foams used in boat building have very low heat distortion values. Basic PVC foam Heat Distortion Temperature is around 150 degrees. That's about the temperature the white deck gets baking under the summer sun. Add some color to the surface and temperatures will begin to soar. I have measured black painted surfaces on boats as high s 237 degrees. That's why you see foam cored boats with painted dark trim, or dark gelcoat colors, that look like a checkerboard. Heat distortion is irreversible. These foams will also begin to stretch or creep when heated, resulting in the laminates loosing their design strength. Structures can actually change shape. The HDT of balsa is 360 degrees.

Shear Strength:  The shear strength of most PVC foams is around 40-60 psi; some are much lower.  Balsa is 400 psi. Not much else to say about this."

[slippery73]

With regards to the article, posted above yachtsurvey.com has a lot of good articles discussing the pitfalls of a lot of different materials and techniques. However, this article is 10 yrs old and there have been leaps and bounds in material development and construction techniques since then. The composites used 10-20 yrs ago were brand new and untested products, so as these items were put into use by manufacturers there inherent problems were found years later as the boats were used. A lot of the issues discussed in the article aren't the case anymore as the materials have been greatly improved.

As far as the balsa goes, like I said before and the article states it makes a great core material. But its just like working with nidacore, you might as well use something that will never rot if it involves the same amount of labor. I've worked with both nidacore and plywood and I personally think its probably equal labor wise, if you get the sample pack of the nidacore it should be cheaper than plywood as well, not to mention weight savings and resale value down the road.

I think a lot of the problems with the composites are just that a lot of people are afraid to use them for some reason. They really aren't any more difficult for a novice than a other materials, techniques might be different but if your a novice your just learning anyways so its not like your changing something you know how to do. Best thing to do is research an read up on things, ask questions, etc. I wouldn't take any one persons word on things as everyone has different opinions and views, just know there are pros and cons with different materials and techniques.

[Capt. Bob]

Now folks,
This is the core of what this Forum is all about. Be it decks or stringers, paint or trailer types, this is what you really come here for. Save the talk of politics, religion and the price of tea in China for all those other Forums.

To steal a quote from Bobby Duval,
"I love the smell of resin and hardener in the morning.
Smells like victory"  

Alrighty now, back to the friendly discussion.  

[LilRichard]

Now folks,
This is the core of what this Forum is all about.

Was that pun intentional, or did you get lucky?

 

[Capt. Bob]

Now folks,
This is the core of what this Forum is all about.

Was that pun intentional, or did you get lucky?

 

Well I'd rather be lucky than good  

[love2fish]

Mike- did you have foam filling the cavity on the outsides of your stringers? By the way, where are you located in Jupiter, I'm in Jensen beach, on the island. Havent seen many classic aquasports down this way...