Core Box

A layer of denser foam around the core in the striking region used to make heavier use and larger weapons more durable and forgiving.

This is a living document and is being created, updated, and added to over time. You can reach out to me via Bluesky with comments or concerns: https://bsky.app/profile/foamdom.bsky.social

A core box is an optional feature you can include in your designs that can serve to make the foam to core lamination last longer, meaning that the foam against the core of the striking region will be almost guaranteed to outlast the foam on the exterior of the striking surface. On weapons that experience heavy use that don't have a core box, such as greatswords, the surface of the striking region can often last longer than it takes for the inner foam to become delaminated from the core or become broken down, causing the weapon to hit with more impact. Generally a stiffer and more durable foam, such as 4# XLPE, the heavier duty EVA that is in Puzzle Mats, or even 2# XLPE (as a lower weight option), is chosen, while the foam built up around it is a more typical Volara, Minicel L200, or "Blue" Foam (Ozark Camp Pads, ~2# Polyolefin).

A picture of a Core Box on a core.

A picture of a finished flat blade with a Core Box.

1. Cut the foam for your desired layup.

A Core Box can be constructed in various ways, with various levels of work involved. Go to the specific page for each layup style to get specific instructions on them.

Recommended:

• Fry

  • Requires router to make your own

  • Works well for any striking region profile

• Box

  • Can be done easily with hand tools

  • Works well for any striking region profile

• Stacked Discs

  • Can be done easily with hand tools*

  • Works well for any striking region profile

• Spiral Wrap

  • Can be done easily with hand tools

  • Only works well for round striking region profiles

* Is most easily achieved if you at least have a hand drill.

Not Recommended:

• Tube

  • Basically 2 fries glued together before you put them on the core

  • Much less likely to get even glue distribution for foam to core

• Roll Wrap

  • Starting from the small diameter of the core is a pain

  • Will need to use a very thin foam to avoid having a ridge to trim or a problematic seam

2. Make sure the core is ready.

A Core Box should not be applied to a core that hasn't been biscuited. Make sure the core is properly biscuited before applying the Core Box.

A picture of a properly biscuited core.

Note: Refer to [Biscuiting Cores] for more in-depth information on properly biscuiting cores.

3. Adhere the foam to the core.

Note: Refer to [Adhering Materials] for more in-depth information on gluing foam to cores.

4. Add reinforcement to the tip.

To help resist delamination from the strong shearing forces that are applied to the foam at the tips of weapons, it can be helpful to reinforce the last inch or so of the Core Box with a layer or two of strapping tape.

Note: Do not apply strapping tape to a surface with wet, untacked, adhesive on it and expect it to stay at the tension with which you laid it down. Allow adhesive to tack before applying any tape to any surface that it is on. The volatile chemicals that have yet to offgas can interact negatively with the adhesive on the tapes, rendering them useless. It can even be an issue just from the surface being wet and slippery, causing the tape to slide around.

This is done nearly identically to taping a biscuit onto the end of the core. Start with an "X" of strapping tape placed over tip of the weapon, with the tape laid down the sides of the Core Box, extending ~2" from the tip. Taut, not tight.

A Core Box with the first half of reinforcement tape applied.

Do a spiral wrap of strapping tape around this. Taut, not tight.

A Core Box with all reinforcement tape applied.

• If you are not using Carpet Tape to attach the rest of the foam, cover the strapping tape with a layer of fabric tape so that the adhesive has a better surface to work with.

• If you are using adhesive for most of the foam, but using Carpet Tape to affix everything above the biscuit, you only need to cover the strapping tape on the "side" surfaces.

A Core Box with the reinforcement tape covered by fabric tape.

5. Core Box complete.

Build the rest of the weapon.

If you are concerned about your foam to core not adhering as well if there is more in the way preventing the adhesive from breathing, allow the adhesive to partially cure before adding more layers of foam. This also applies if you are using adhesive to attach the Core Box to the core, but using Carpet Tape to attach the striking region foam to the Core Box. This does not apply if you are only using Carpet tape for affixing things above the biscuit.