solid versus cored hulls below the waterline

[Drifter]

New forum looks nice. Maybe it's time to get down to bizness...

It seems that some manufacturers are using cored hulls below the waterline, while others use solid fiberglass. (Some might have cored hull sides, but still use solid bottoms.)

Is there an advantage to cored hulls (below the waterline) other than lighter weight (which might mean better efficiency and faster speeds)?

Which is more costly to produce?

Which is stronger, whether it concerns sealing thru-hulls or hitting an object while running?

Any chance that modern cored hulls could hold water (adding weight to the vessel, and potentially cracking if the water freezes)?

Are there different types of cored bottoms?

Are cored hulls favored on a particular hull style, such as stepped hulls that might run differently than a traditional deep-v?

If you like a boat, but it doesn't have your preferred type of hull construction, do you mark off your list of potential purchases?

I like the thought of a thick solid glass hull below the waterline, but will admit that it's a relatively uneducated view.

Maybe we can have a discussion on advantages and disadvantages of each, and share what some of the favored manufacturers use in their construction.

I'm curious about brands such as Yellowfin, Contender, Regulator, Sea Vee, Invincible, Sea Hunter, Fountain, Wellcraft, and various other center consoles, but the discussion certainly doesn't have to be limited to these brands and styles.

Both facts and opinions would be interesting.

[swrock]

I don't really know the answer to most of the questions in your post but I talked to sundancekid one time about a fountain that I was thinking about getting. He said the fountains do have a cored bottom, and the hulls are very strong. I believe contenders are cored on the sides but solid glass on the bottom. I wouldn't be afraid of a cored hull if it was a well know builder like any of those you mentioned.

[Blue Magic]

Everybody has different tastes. The speed demons with the trips and quad want the lighter boats so they can ride on top and have the speed. Myself I want the heaviest boat possible.
I want a boat that can stomp 2 to 4 ft seas at 25 mph without the beating and pounding.
Get the popcorn ready.........this is going to be interesting.

[Kern O]

The use of coring in a hull, especially below the waterline is a subject of a lot of debate. For years, the most common coring material was end grain balsa. It has the advantage of being very light and has excellent compressive strength when used with the grain perpendicular to the structure. It is curently in use by several manufacturers, with Yellowfin and C-dory being among them. Yellowfin uses a relatively thin core (under an inch), whereas C-dory uses almost 2 inches. Balsa works very well, providing it does not get wet. Once it does get wet, it turns into a black gooey mess. Yellowfin has built a lot of boats with it and you don't hear about core problems on Yellowfins. According to Wiley of Yellowfin, every core penetration is sealed with 5200. I looked seriously at a buying a Yellowfin, but declined because of the sheer number of core penetrations. The wiring harnesses are very well tied down inside the hull, but that is done with hundreds of screws, each of which is a potential core leak. But again, they don't seem to have problems.

The other common coring materials are Divinycell and similar foam composites. While the composites are heavier than balsa, they do not break down in the presence of water. I had a Jupiter with holes bored through the transom for the rigging tubes. The holes were left just as drilled and after five years of being moored in the water, the inside of the holes looked like the day they were cut. Some composites do absorb water, albeit very slowly. The Jupiter had a ding in one of the forward hatches where an anchor had been dropped and after 4 years in the Florida rain, the ding showed moisture in about a 2 inch diameter. Ideally then, all penetrations through the composite should be sealed. Composites seal best with polyester or vinylester resin, rather than epoxy.

When a hull uses coring for added stiffness, the fiberglass is generally thinner, because there is very little point in making a normal thickness bottom and then adding a core. So, a cored bottom will have less impact resistance than a solid bottom. Coring is also compressible, so sealing a through hull is more difficult with a cored bottom. It becomes critical that the fitting to outside hull surface is sealed perfectly. Good guidelines call for the coring to be backed away from any area where a through hull will be installed.

I've spent an awful lot of time repairing soft transoms and re-bonding stringers, so I will only buy a fully composite hull. I found the Jupiter to use the most rot proof construction in their stringers. They were all fiberglass
and completely hollow. If there is nothing in them, they are not going to delaminate or absorb water.

A stepped hull, by its very nature can be stiffer, because the long surface is interrupted by vertical walls across it. I don't think coring is a variable and don't see any reason to core or not core a stepped hull.

Some builders, like Invincible, offer their hulls with or without coring. When speed is the prime consideration, you'd choose cored. For ultimate strength, solid is best.

[SKEETERMAN]

which hull cant you use a shoot through ducer? Cored or silid fib?

[Angler Systems]

Originally Posted by SKEETERMAN

which hull cant you use a shoot through ducer? Cored or silid fib?

a cored hull

[Kern O]

About shoot throughs and fiberglass. Weird as it seems, solid fiberglass looks like water to a depthsounder. The frequencies used simply don't "see" the fiberglass. But they do see air, which is why fish show up easily - they all have an air bladder and the sounder spots it instantly.

The problem with coring is that it has air in it. So, like a fiberglass hull with a void in it, the sounder sees it and the signal gets ruined.

That's why many sunken boats are not found - your sounder does not see the fiberglass boat on the bottom. It can pick the metal of the engine or hardware or maybe any air trapped in upholstery or pockets, but they are much tougher to spot than you'd think.

[SKEETERMAN]

Sounds logical.........thanks. I guess my hull is solid fiberglass then becuase i have a shoot through that i really like and performs flawlessy. Thanks for the info!!

[glen e]

Kern's right and shoot thrus are remarkable easy to install. I have both a transom mount and a shoot thru and the both work equally well....rough up the surface..acetone the surface - stick it on with silicone, and fill with non tox antifreeze....and click it into place....

[Kern O]

That sure looks like an Airmar P-79 transducer. They are super easy to mount and work very well.