Cores in hull bottoms

[jimslade]

I just finished coreing my wifes ski boat, transom and stringers with nidacore. also I fabricated a swim platform. lite and strong, I love this stuff. No more wood to rot.Still redoing the interior. I will get to the Magnum over the winter. Just wanted to learn the best way to make the coreing strong and lite. Always learning.

[SamSam]

[quote]Sportfishermen in the East Coast have been built with cored bottoms for more than thirty years. They have proven themselves in very rough weather and continuous use. I have built several of them. The normal cruising speed is 30-35Kts.
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Gonzo [quote]

Originally Posted by gonzo

Those boats are built with plywood cores. They usually have three layers with bi or tri directional glass and epoxy inside and out. Some of the boats still built by oldtimers are all juniper cores.

What kind of ply? Is the ply put on a form or molds and then glassed both sides before structure is installed or is the structure glassed over also on the inside? Was epoxy used 30 years ago or were some made with polyester? Sam

[buckknekkid]

rough weather, continuous use, 30 knots. I once did a sea trial in a hurricane, wood core, old striker mold with a pair of International diesels. That was serious crashing and bashing. wood held up though.

[gonzo]

Some of the older boats were built with polyester. However, they started using epoxy very early on. I would say about 1965. The boats are built over stations in the typical cold molded way. They are fiberglassed outside, turned over, fiberglassed inside and then the bulkheads and stringers are installed.

[Russ]

Hi Guys,
There is a new core material on the scene. The stuff is from Coosa Composites in Pelham Alibama. see at "coosacomposites.com". Chap Jackson is the owner and the materal is Glass reinforced Polyurethane. It is made into panels in huge presses and is available in many sizes and densities. I have seen the operation and they deserve some attention. He can provide data on peel, compression etc.
I found him about 5 years ago when I was with De-Comp Composites. Tell him Russ sent you. No! I won't get a commission.

[u4ea32]

I know this is late but...

Pascoe is exactly RIGHT with the idea of using carbs instead of fuel injection in boats. I am right now removing the EFI from my engines and installing carbs.

Ever notice how many cars are to the side of the road when it rains? Not many, but certainly more than when its not raining. Salt water is far more corrosive than fresh. An engine in a boat is in a very corrosive environment. The wiring harness suffers.

Consider this: On an electronic fuel injection system, many sensors feed in to the engine computer, which then runs and algorithm, and adjusts many actuators. Many temp, pressure, flow, even microphone sensors in, and many fuel injector timing, ignition timing, and flow actuators out. As I have experienced, any electronic noise in sensor OR actuator signals results in an engine that works POORLY. And the diagnistic tools show lots and lots of time varying telemetry values, but do NOT show any suggestion of what the expected values are.

I have had two of the best EFI mechanics on the West Coast working on my engines, and they cannot isolate the problem after nearly $10,000 of diagnostic work.

With a carb+distributor system its quite simple: ignition problem? check the distributor or coil. Fuel problem? check the filter, pump, or carb. Pretty darn simple.

[jimslade]

Unless your running points, your ignition uses a small computer to run it. I don't know of anyone ripping the efi off their car and putting on a carb. David P has some good points but even the engine's he recommends (crusader) now use efi. EFI is here to stay! You need to find better mechanics. Not all mechanics are cut from the same cloth. I've been in the trade for thirty years. Good Luck.

[glassr]

Hi jimslade,
Do you have any pictures of the ski boat your rebuilding.
I'm interested in how the Nidacor is working and your lay up schedule and technique.
Are you going to do this in the Magnum(awesome boat) also?
I am completely rebuilding a 30' condor cc and am interested in useing Nidacor and am looking for the best way to do it.
Thanks,
glassr

[jimslade]

The left stringer has been set in and tabbed. the transom is two layers if 3/4 nidacore with a layer of mat between them. Wherever there is a fitting or an opening that is going to have a bolt through it I use a waterproof filler around the opening. This will help with compression.I will finish off with four layers of 1810 glass to tab the stringers in and cover the transom. For the floor I will use 1/2 inch nidacore with 2 layersof 1810 glass on bothsides. I will use plexus to attach the floor to the stringers. Make sure you know where all the bolts are going first. Preparation is the key to using nidacore. Its more work but knowing that there will be no more rot is rewarding. I'm also using nidacore in my magnum. I'm compilling a album with the magnum.

[glassr]

Hi jimslade,
Nice looking work,I am wondering how Nidacor works under sheer and torsional forces. The hull that we are working on is 30',and it sees alot of punishment in 3-6' seas. We want it to last so we are trying to use the best materials possible.
glassr

[jimslade]

Nidacore is not the best in sheer strength. But the core acts like a shock absorber. I have done destruction tests and am amazed at the abuse these panels can take. Where a more ridgid core will start to break or delaminate the nida still holds together. I ran into a boatbuilder who used nida on offshore boats in the Bahamas and he swears by it.

[glassr]

Hi jimslade,
I think I've hijhacked this thread!
I'm going to email you, because I would like to discuss some other aspects of useing the Nidacor in stringers/bulkheads.
Sorry everyone about getting off topic!
glassr

[jimslade]

MY e-mail is jimslade@porchlight.ca

[Eagle Boats]

Jim, I want to use Nidacore in a 24 foot center console. I am going to build the boats with either an outboard or an i/o. What size are you using for the stringers? How easy is it to shape the Nidacore? Do you use a foam spacer between the stringers and the hull bottom? What are you using as a layup schedule to glass the stringers to the hull? Have you ever mounted an engine on Nidacore? Would you recommend using Nicacore as a core on the cockpit sole?

I appreciate any help you can give.

[jimslade]

I use 2 pieces of 3/4 nidacore glued together with resin. It's very easy to shape with moderate heat. I set it on the bottom because the core is not ridgid without glass and resin. I have used 3 to 4 layers of 1810 glass to lay the stringers into the hull. Where the mounting bolts go through, I ream out the core and use a waterproof filler, than I lay the glass on top. It take's extra prep work to know where you are putting any bolts through. For engine mounts I'm filling the core approx. 2 inches in and using 6 layers of 1810 glass. It is also great for the sole as long as you solid core any compression bolt holes.(seat bases)
I hope I have answered your questions. I built a swim platform with nidacore and I still can't believe how strong it is.