New Core for Foredeck

[Captndan714]

Also, If I am replacing with a solid piece of core, whichever I end up using, is it ill advised to glue in with 5200 instead of epoxy? Seems like it would be a cleaner job and I dont have to worry about the epoxy curing too fast over a large area since I dont have tons of experience with it.

[minaret]

Originally Posted by Captndan714

Can you recommend a good source to learn about vaccuum bagging? I know of it, but I dont know much about it.

YouTube?

[minaret]

Originally Posted by Captndan714

Also, If I am replacing with a solid piece of core, whichever I end up using, is it ill advised to glue in with 5200 instead of epoxy? Seems like it would be a cleaner job and I dont have to worry about the epoxy curing too fast over a large area since I dont have tons of experience with it.

Yep, no 5200. Use epoxy with a flexible filler or core bond, nothing brittle like colloidal silica.

[Lojanica]

Bag it. Best materials has cheap butyl tape. Buy some good quality vizqueen and you're on your way to a pro job. Remember to put a trap in your vacuum line.

I love vacuum bagging.

[s/v Jedi]

Minaret will jump in and correct me if needed, but if you are not familiar with epoxy yet, use West System to make it a bit easier to start: you're worried about fast setting... where are you, in what climate? Use a slow hardener for more time.

In West System terms, get:

- a gallon of 105 resin
- a quart of 205 regular, or 206 slow hardener or 209 extra slow hardener, decide using this: http://www.westsystem.com/ss/hardener-selection-guide/ (I'm in the tropics and always use 206)
- a 300 mini pump set
- a 20oz pack of 403 microfiber filler
- some 804 mixing sticks
- some 805 and 806 mixing pots
- a couple of 808 spreaders plus an 809 notched spreader

I have some of everything aboard, incl. their rollers, syringes,other epoxies like 5-minute and the flex one, every filler etc. some is not from the West System brand anymore: you'lle find your way once you've started. Also, just spend some epoxy on testing: mix some resin with hardener, add the microfiber untill you get peanutbutter consistency and spread some with the notched spreader onto some old plywood and press a small piece of plywood into part of it and let cure. Check if it cures good, becomes hard and tough (with microfiber it wont be brittle) andif the two pieces of plywood are joined permanently. The plywood should fail before the epoxy joint fails. Testing is a good way to spend some material, plus it provides to confidence to take on the bigger project.

Work clean, like a surgeon. A minute spent to work clean saves 10 minutes clean-up afterwards or even more in sanding. :thumbs:

[Nicholson58]

I recore by digging out the balsa, drying and re-filling the space between the skins with a mix of epoxy and microballoons. 635 THIN resin and balloons from US Composites. I have replaced about 20 sq feet of deck from inside the cabin. I also used it for core on a new rudder. The strength is about 3000 psi and it will never pass or soak water. U.S. Composites, Inc. - Fiberglass , Epoxy , Composites, Carbon Fiber

1. hole saw round plugs
2. dig out wet core
3. let dry
4. cut heavy fiberglass mat.
5. Scarify surface.
6. wet the patch in epoxy.
7. block wet glass in place with corregated cardboard, plastic release sheet and wood struts.
8. remofe struts and release materials.
9. drill/insert low fill port and high vent port
10. prepare slurry of 635 resin and microballoons. Fill re-usable calk cartridge tubes. Pump the slurry into the cavity

[Lojanica]

The nice thing about recoring from the bottom is the top skin is untouched. One way is to prep, then paint a thin layer of epoxy and let it get really sticky then roll your stitchmat between two layers of plastic to wet it out completely then peel one side of the plastic and stick it. Then squeegee tight. I've done repairs like this too on critical areas where cosmesis is of utmost import and its so clean you barely even have to mask anything. Then as mentioned either pump or vacuum the core full of epoxy filled with whatever you want. You can even add ground up foam or sawdust if microballoons are too expensive for your budget.

[minaret]

I would never replace core by filling with thickened resin. Too brittle, too heavy, too expensive. Replace like with like. This is not a pro repair method.

[Lojanica]

Originally Posted by minaret

I would never replace core by filling with thickened resin. Too brittle, too heavy, too expensive. Replace like with like. This is not a pro repair method.

Agreed. This was a response to the previous post and a method to treat but not "recore."

[Reefmagnet]

Originally Posted by Captndan714

Can you recommend a good source to learn about vaccuum bagging? I know of it, but I dont know much about it.

I'd never done it before, but I made my own vacuum unit based around an old fridge compressor when I needed to redo my cockpit floor.

I used clear builders plastic for the bag, liquid nails and gaffer tape for the seal, taffeta for the peel ply and shade cloth for the breather. Various micro irrigation fittings and hoses along with a suction cup dent puller completed the setup.

I learnt all this from youtube

[Lojanica]

Best Materials Roofing Supplies, Roofing Materials, Caulking, Sealants, Backer Rod, Waterproofing, and Rubber Roofing (look under butyl tape)

Vacuum Bagging Materials (material and book and vacuum bagging)

Pick up a cheap used vac pump.

[Nicholson58]

Originally Posted by minaret

I would never replace core by filling with thickened resin. Too brittle, too heavy, too expensive. Replace like with like. This is not a pro repair method.

Lojanica - THANKS for the inspiration. I never thought to coat the deiling and soak the glass - let get sticky and GO! I just put plastic film everywhere and we end up coated with resin.

NOT BRITTLE AT ALL

I use a mix of 3 gallons of 635 thin resin to 10 gallons of microballons to cast a new rudder. This mix has the consistancy of Kraft Marshmellow cream. Slightly soupier for pumping. The density is about on a par with foam core. It floats like styrofoam. The compressive strength is 3000 psi. The bond of the filler to the two glass skins is many times greater than balsa or foam core. Sandwiched between two layers of glass, the deck makes an impressive beam. If it did crack (in the core) the deck and core would remain totally waterproof and fully bonded. I keep a chunk in my car to amaze my friends at the boat yard. I swear, I will never use a core again that can be damaged by water.

PHOTOS: The old rudder's foam core was a disintegrated gob of black moldy muck inside the hollow, badly delaminated skins. It took 35 gallons of total volume to fill the rudder; blade 30 inches X 72 inches X 6 inches thick max. One of the advantages of US Composites 635 THIN resin is the cure is very slow. It takes 3 to 4 days in a cool basement to be sandable. This means almost no heat even in large sections. With the carbon fiber skin, it will just about bounce bullets.

[Lojanica]

Originally Posted by Nicholson58

Lojanica - THANKS for the inspiration. I never thought to coat the deiling and soak the glass - let get sticky and GO! I just put plastic film everywhere and we end up coated with resin.

NOT BRITTLE AT ALL

I use a mix of 3 gallons of 635 thin resin to 10 gallons of microballons to cast a new rudder. This mix has the consistancy of Kraft Marshmellow cream. Slightly soupier for pumping. The density is about on a par with foam core. It floats like styrofoam. The compressive strength is 3000 psi. The bond of the filler to the two glass skins is many times greater than balsa or foam core. Sandwiched between two layers of glass, the deck makes an impressive beam. If it did crack (in the core) the deck and core would remain totally waterproof and fully bonded. I keep a chunk in my car to amaze my friends at the boat yard. I swear, I will never use a core again that can be damaged by water.

PHOTOS: The old rudder's foam core was a disintegrated gob of black moldy muck inside the hollow, badly delaminated skins. It took 35 gallons of total volume to fill the rudder; blade 30 inches X 72 inches X 6 inches thick max. One of the advantages of US Composites 635 THIN resin is the cure is very slow. It takes 3 to 4 days in a cool basement to be sandable. This means almost no heat even in large sections. With the carbon fiber skin, it will just about bounce bullets.

Looks great!!! That is one tough rudder. Nice!!!

[minaret]

Originally Posted by Nicholson58

Lojanica - THANKS for the inspiration. I never thought to coat the deiling and soak the glass - let get sticky and GO! I just put plastic film everywhere and we end up coated with resin.

NOT BRITTLE AT ALL

I use a mix of 3 gallons of 635 thin resin to 10 gallons of microballons to cast a new rudder. This mix has the consistancy of Kraft Marshmellow cream. Slightly soupier for pumping. The density is about on a par with foam core. It floats like styrofoam. The compressive strength is 3000 psi. The bond of the filler to the two glass skins is many times greater than balsa or foam core. Sandwiched between two layers of glass, the deck makes an impressive beam. If it did crack (in the core) the deck and core would remain totally waterproof and fully bonded. I keep a chunk in my car to amaze my friends at the boat yard. I swear, I will never use a core again that can be damaged by water.

PHOTOS: The old rudder's foam core was a disintegrated gob of black moldy muck inside the hollow, badly delaminated skins. It took 35 gallons of total volume to fill the rudder; blade 30 inches X 72 inches X 6 inches thick max. One of the advantages of US Composites 635 THIN resin is the cure is very slow. It takes 3 to 4 days in a cool basement to be sandable. This means almost no heat even in large sections. With the carbon fiber skin, it will just about bounce bullets.

How much does it weigh? NA's design light cores for good reasons. WEST weighs close to ten lbs per gallon. That means you replaced a few pounds of flexible foam with 350 lbs of resin and filler approximately. If you recored your whole deck this way it would take at least a hundred gallons and add at least a thousand pounds to your topsides. Thickened epoxy is always brittle, it is not meant to be used structurally in thickness over about a 1/8". Ever seen a boat designed to be built this way? Wonder why not? The total lack of flexibility in the core will also cause delams much sooner, as the core can't flex with the skin like foam or balsa. Dissimilar flex rates are bad.

[Nicholson58]

Originally Posted by minaret

How much does it weigh? NA's design light cores for good reasons. WEST weighs close to ten lbs per gallon. That means you replaced a few pounds of flexible foam with 350 lbs of resin and filler approximately. If you recored your whole deck this way it would take at least a hundred gallons and add at least a thousand pounds to your topsides. Thickened epoxy is always brittle, it is not meant to be used structurally in thickness over about a 1/8". Ever seen a boat designed to be built this way? Wonder why not? The total lack of flexibility in the core will also cause delams much sooner, as the core can't flex with the skin like foam or balsa. Dissimilar flex rates are bad.

Please re-read my post. 3 gallons of resin mixed with 10 gallons of microballoons. A 5-gallon pale of micro balloons is ounces. Whipping the 13 gallons with a power mixer yields about 15 gallons of fluff. The finished mix, as I noted, is abut the density of Styrofoam. The rudder floats including the 10 foot long X 3-1/2 inch diameter SS post. This is NOT thickened epoxy in any sense that you are familiar. It is glass bead reinforced epoxy. This is known as syntactic foam and its compressive features make it flexible over large areas. It is not used in production boats because it is a heck of a lot of work. In new construction, it is really difficult to control placement and thickness. The core layer of all FRP hulls is a shear connection between the inner and outer skins. It is analogous to the web in an I-Beam connecting the two flanges. Balsa and foam have a shear connection joint on the order of 1/10th the strength of glass reinforced syntactic foam.