Engineering Notebook

Objective

Confirm that adding 1¼" SPAX Power Trim screws to the leg attachment dramatically reduces leg failures (legs cracking off, pulling away, or loosening) during shipping and field use.

Method

• Apply glue + brad nails as usual for leg installation.
• Add two 1¼" SPAX Power Trim screws per leg, installed on a diagonal (caddy-corner) pattern – one high, one low.
• Repeat on all four legs for each test box.
• Send multiple boxes through standard carriers and monitor any damage reports.

Key Observations (so far)

• Legs appear to be acting as sacrificial impact structures – they take the brunt of abuse when boxes are dropped or slammed.
• With screws + glue + brads, legs feel much more rigid in tension and shear. The wood itself can still crush if severely pinched, but the legs are far less likely to separate from the box body.
• Early shipments suggest a reduction in leg-related failure claims compared to glue + brads alone.

These boxes are currently designed so that stacked units rest on the tops of the legs rather than on the lid rails. I originally built them this way to prevent the lids from getting scratched, gouged, or scuffed when boxes are stacked during use or transport. The taller legs protect the lid finish — but this also means the upper box has less surface area to rest on, which reduces overall stacking stability. A future improvement could involve designing a groove, notch, or interlocking feature on the tops (and possibly bottoms) of the legs so stacked boxes positively locate into each other. This would keep the lids protected while greatly improving stability. Alternatively, if a field-use variant is ever developed, we may revisit the idea of allowing the upper box to rest directly on the lid rails for maximum footprint and stability.

Preliminary Conclusion

For all designs using 1x2 solid-pine legs, 1¼" SPAX Power Trim screws are now considered a standard structural requirement, not an optional upgrade. This will be refined as more data and photos are collected from the field.

Background – Original Rope Handle Design

The first generation boxes used hemp rope handles passed through drilled holes in the side panels and secured with interior knots. This worked mechanically, but had two major drawbacks:

• Airtightness & climate control: through-holes and knots allowed more air exchange than desired for long-term storage and humidity control.
• Lost interior volume: the interior knots took up space, making the side zones of the box less usable. In practice, only the center area of the box was fully usable.

These issues motivated a move to a surface-mounted handle system that stayed completely outside the storage cavity.

Step 1 – Early Nylon Webbing Handles (Exposed Screw Heads)

Inspired by Cold War-era ammo boxes, the design moved to 1" nylon webbing handles. Early versions simply screwed the webbing directly to the side panel using coarse-threaded wood screws, with the screw heads exposed. This solved the interior space problem but:

• Left the screw heads exposed to impact and abrasion.
• Still relied on the screw holding in pure tension if the box was heavily loaded and yanked.

Current Design – Leg-Integrated, Enclosed Screw System

The current handle system integrates the handle hardware into the 1x2 leg assemblies and uses the legs as both a structural member and a protective shroud for the handle screw:

• The 1" nylon webbing is fastened directly to the box side with a single coarse-threaded wood screw per handle end.
• Each leg has a groove ~1⅛" wide machined into it so the 1" webbing sits embedded in the leg rather than bulging out.
• A shallow pocket is milled into the back of the leg with a Forstner bit so the screw head sits inside this recess.
• When installed, the leg fully encloses the screw head and handle attachment point, leaving only clean webbing visible exiting the leg.

Result: from the exterior you see a clean nylon handle emerging from the legs; on the interior you see no hardware, no holes, and no lost volume.

Failure Modes & Why This Is “Fail-Safe”

Because the screw head is trapped inside the leg pocket, a normal “screw backing out” failure mode is essentially eliminated. For the handle to truly fail, multiple things would need to happen:

• The leg would have to break off the box body, or
• The screw would have to rip out of the wood, and the enclosed screw head somehow clear the leg pocket, or
• The 1" nylon webbing would have to tear around the screw shank under extreme load (estimated on the order of a hundred pounds or more).

In normal use scenarios (fully loaded ammo box, carried by hand), this design behaves like a no-critical-failure system. It is dramatically stronger than the early hemp rope + interior knot design and far cleaner inside the box.

Serviceability & Field Repair

This handle system was intentionally designed to be field-serviceable:

• Each leg is attached with glue, brads, and two 1¼" SPAX Power Trim screws (see test ID FC-LEG-2025-001).
• To replace a worn handle, the owner can:
  • Remove the SPAX screws.
  • Tap the leg outward to break the glue and brads loose.
  • Access the handle screw, back it out, and swap in a new section of 1" webbing.
  • Reinstall the leg over the screw head and handle tail, and re-fasten.
• The leg groove forces the user to stick with 1" webbing (the design spec), preventing oversize handles that don’t fit correctly.

Benefits vs. Original Rope Handles

• No interior obstruction: full use of interior footprint; no knot bulges.
• Improved airtightness: no through-holes for rope; easier to control humidity.
• Cleaner interior aesthetic: nothing inside the box reveals there are handles outside.
• Higher load capacity: coarse-threaded screws into solid wood + leg enclosure significantly increase the practical weight rating.

Planned Testing – Handle Load / Shear Test

A dedicated test is planned to quantify the actual failure load of this handle system. Proposed test:

• Hang a fully built box from one handle and progressively load weight.
• Record the weight at first noticeable deformation and at ultimate failure (if any).
• Document where failure occurs: nylon tear, screw pull-out, leg failure, or panel damage.

Once completed, this entry will be updated with measured load values and any design tweaks that come out of the test.

Background

Early in production, Freedom Crate Co. used black toggle latches, but no American supplier offered black 90° latch catches. The only option was stainless 90° catches, which didn’t match the hardware finish. To keep the black hardware option, boxes were built with edge-mounted latch catches screwed into the front edge of the lid.

Method

• Install black toggles with edge-mounted latch catches on pine lids.
• Use black wood screws approx. 3/4"–1/2" long for the latch catch attachment.
• Repeatedly latch and unlatch the toggle, tightening the draw bar after each cycle to simulate a customer “cranking down” on the latch over time.
• Monitor for movement, loosening, or pull-out of the latch catch from the lid edge.

Observed Failure Mode

• Every time the latch was closed, the force was concentrated into the thin edge of the lid, directly in line with the screws.
• After roughly ~20 latch cycles (with tightening in between), the screws began to loosen and the entire latch catch started to pull out of the edge grain.
• Even when switching to 1½" black wood screws, which helped by distributing the load deeper into the lid, an over-tightened toggle could still rip the edge-mounted catch out under aggressive use.

Switch to Protex 90° Latch Catches

To eliminate the edge-mount failure mode, the design was updated to use Protex 90° black latch catches mounted down the face of the box, not into the lid edge. Protex is currently the only source for black 90° latch catches that match the toggle hardware finish.

• Unit cost: approx. $0.86 per catch at 100+ quantity (as of latest purchase).
• Shipping from the UK is ~$60 per order, plus customs and tariff fees.
• U.S. distributors (e.g., Grainger, McMaster-Carr) offered to supply similar parts but at ~3× the Protex cost, so direct import remains the most cost-effective option.

Conclusion / Design Rule

Edge-mounted latch catches are now considered a non-approved configuration for any box that will see real field use. They are only acceptable on purely decorative or light-duty boxes. For ammo and range boxes intended for trucks, ranges, and shipping, 90° Protex latch catches are mandatory to keep the hardware anchored in long-grain wood and away from the fragile lid edge.

Planned Objective

Observe how a fully loaded Rangemaster 400 behaves when dropped from approximately waist height (~3 ft / ~0.9 m) onto a hard surface. Focus on joint integrity, leg performance, lid alignment, and hardware deformation.

Planned Method

• Load the box with a realistic quantity of ammunition and/or range gear.
• Record starting weight and contents.
• Drop from waist height onto concrete, at least 3 times, varying orientation (flat bottom, corner, edge).
• Capture video and still photos for each drop and final condition.

Data to Capture

• Any cracks in panels, joints, or legs.
• Changes in lid closure (does it still latch properly?).
• Hardware bending or loosening.
• Any fastener pull-out or epoxy/liner damage.

Next Steps

Once performed, this entry will be updated with real test dates, observations, photos, and engineering changes (if required).

Objective

Validate that a penetrating epoxy flood with a formed fillet in the corners: (1) prevents moisture intrusion, (2) stiffens the lower box structure, and (3) delays or prevents panel separation over time.

Method

• Flood all interior surfaces with penetrating epoxy, allowing resin to pool slightly in corners.
• Rotate or brush as needed to form a consistent, rounded bead along the bottom interior perimeter.
• Allow full cure per manufacturer specs.
• Store boxes in real-world conditions (garage, range, truck) and periodically inspect.

Inspection Checklist

• Any visible cracking or separation at corner joints.
• Signs of water staining, swelling, or delamination.
• Changes in lid fit or box squareness.
• Surface wear of the epoxy where loose ammo or gear contacts it.

Preliminary Notes

Early indications suggest the epoxy fillet behaves like a structural radius found in marine and aerospace structures — spreading loads out instead of concentrating them at a sharp 90° seam.

Joinery Strength Comparison – Real Use vs. Theoretical Strength

The goal was to evaluate which joints are strongest when balancing build speed, repeatability, and real-world abuse.

• Dovetails: strongest as bare wood joints, but extremely slow and offer no practical benefit once the box is epoxied and used as a utility crate.
• Finger joints: strong on paper but slow to make and highly unforgiving — one bad finger weakens the entire joint.
• Half-lap joints: fastest high-strength joint. Large long-grain glue surfaces + mechanical overlap = outstanding strength. Extremely forgiving and production-friendly.
• Butt joints: adequate only with heavy reinforcement; not recommended for rugged crates.

Once penetrating epoxy is added to the interior, half-laps outperform finger or dovetail joints in drop-and-rack testing because the epoxy bonds and fillets reinforce the entire joint into a wood-epoxy composite.

Bottom Panel as the Structural Backbone

The 1/4" plywood bottom is the true shear diaphragm of the crate. Without it, any crate can be twisted by hand until failure.

• Prevents racking and torsion.
• Squares the box when installed while glue is wet.
• Distributes load across the entire structure.

Top Corner Reinforcement – Strongest Options (Ranked)

The top of the crate lacks a shear panel, making it the weak area. These methods strengthen the top from strongest → least strong:

• 1. Full 1/4" plywood interior top panel (shear diaphragm): By far the strongest improvement. Makes the top behave like the bottom — zero racking, zero twist.
• 2. Triangular wooden gussets (corner blocks): Large 3–4" blocks glued in the top corners dramatically increase torsional stiffness. Stronger than steel because of long-grain wood-to-wood bonding.
• 3. Continuous perimeter top rail (“collar”): A wraparound top frame that ties all four sides together adds major stability and keeps lid alignment perfect.
• 4. Plywood corner plates (3–4" gusset plates): Little shear panels in the corners. Cheap, light, very strong.
• 5. Heavy-gauge steel angle brackets: Stronger than small L-brackets, but limited by screw pull-out in pine.
• 6. Epoxy corner fillet (top): Gives a boat-hull-style stiffening effect. Not as strong as gussets but still effective.
• 7. Small steel corner braces (current FC1000 method): Helpful for alignment, but least structural reinforcement of all options.

Key Takeaway

Half-lap joints + a shear-locking bottom panel already produce the best strength-to-time ratio. Adding triangular gussets or an interior top diaphragm panel creates a crate that is nearly impossible to rack or deform.

Birch / “Hardwood” Plywood (3/4")

Interior-grade birch (or equivalent hardwood plywood) has consistently produced the best looking, easiest-to-work-with boxes:

• Very smooth face veneer – ideal for stenciling, logos, and clean paint lines.
• Each ply is relatively thick, so it holds screws well compared to thin, multi-ply exterior sheets.
• Panels are flat and stable out of the gate, with far less cupping/bowing than big-box solid pine boards.
• Pairs extremely well with penetrating epoxy on all edges and a full interior flood; edges seal up nicely.

Current working conclusion: for most crates that are sealed with penetrating epoxy and not left in harsh weather 24/7, 3/4" birch plywood is the premium choice for appearance, workability, and perceived quality.

Outstanding question: long-term outdoor durability vs. UTX is still unknown and will require time-in-service data.

Exterior-Grade UTX Plywood (1/2" – Rangemaster 400)

UTX exterior plywood is used on the Rangemaster 400 with the assumption that most ranges are outdoors and the box will see more weather and temperature swings.

• Exterior glue and construction – designed to handle moisture and outdoor exposure better on paper.
• Feels harder and tougher than birch ply; noticeably harder on saw blades and tooling.
• Faces are rougher and less uniform, which makes fine stenciling and detailed graphics more difficult.
• Plies are generally thinner and more numerous; the panel is solid, but individual plies don’t grip screws as “deeply” as birch’s thicker plies.
• Appears to be slightly heavier than birch of similar thickness, possibly due to adhesive content and ply composition.

For the Rangemaster 400, this plywood is: fully edge-sealed with penetrating epoxy (lid edge, box edge), the interior is flooded with epoxy, and the interior is then sprayed with Herculiner-style liner. This should significantly improve weather resistance, but actual long-term outdoor performance is still being monitored.

Solid Pine Boards

Solid pine is the classic material for ammo-style crates and has the best “real wood” feel and look:

• Visually, probably the most appealing to customers – real grain, classic crate vibe.
• Works well with stains, clear finishes, and epoxy; corners and edges look “honest” and traditional.
• Downside: boards from the store are highly variable – bow, twist, cup, knots, and density changes are common.
• Requires significant processing time: board selection, jointing, planing, flattening, and sometimes scrapping panels that won’t cooperate.
• It’s easy to lose usable material when a board moves after cutting or reveals hidden defects mid-build.

Solid pine wins on feel and aesthetics, but loses on predictability and time. It is best reserved for builds where the “real wood” character is the selling point and extra labor is acceptable.

Durability Questions (Long-Term)

Right now, several unknowns remain and are being treated as long-term tests:

• How a fully sealed birch plywood box (penetrating epoxy on all edges + interior flood) compares to a UTX exterior plywood box after years of real outdoor exposure.
• Whether the exterior-grade glue and construction of UTX truly outlasts birch once both are fully encapsulated in epoxy and liner.
• How much the rougher face of UTX continues to limit stenciling and finishing options compared to birch.

At this stage, only time and field use will definitively show which material ages best in real conditions.

Current Working Material Strategy

• For premium-looking ammo boxes with smooth finishes and stencils: prioritize 3/4" birch plywood + full epoxy edge sealing and interior flood.
• For range-focused, outdoor-heavy use (e.g., Rangemaster 400): continue with 1/2" UTX exterior plywood sealed in penetrating epoxy and liner, while monitoring long-term performance.
• For traditional solid-wood builds where the goal is “real wood crate” look and feel: use solid pine boards, accepting the extra selection and processing time as part of the build.

Why We Use Tongue-and-Groove Lids Instead of Plywood

• Strength & longevity: Solid wood doesn’t delaminate. A T&G lid is stiffer, stronger, and endures repeated opening/closing without failing.
• Self-alignment: The tongue naturally locks into the groove, keeping the lid flat and preventing shifting over time.
• Better epoxy behavior: Solid wood edges absorb penetrating epoxy and harden exceptionally well. Plywood edges always expose vulnerable plies.
• Reversible design: Each T&G board has two “top” options—smooth or decorative.
• Authentic look: A solid-wood lid gives the crate a real military-crate feel that customers strongly prefer.

Plywood vs. Solid Tongue-and-Groove – Real-World Trade-Offs

Plywood is easy to work with—always straight, always flat, always square. But the lid is the most abused part of the crate: it gets slammed, stacked on, grabbed, leaned on, and is the main mechanical hinge point. For this reason, our lids remain solid wood only.

• Plywood advantages: perfectly flat, stable, predictable, lightweight, fast machining.
• Plywood weaknesses (critical for lids):
  • Edge plies can fray or delaminate with repeated impact.
  • Screws and hinges have weaker bite over time.
  • Moisture enters at seams and ply transitions.
• Solid T&G board advantages:
  • True structural wood—no veneer layers to fail.
  • Superior hinge-screw bite.
  • Excellent edge strength when sealed with epoxy.
  • Reversible: smooth top for stencils, decorative top for multi-line aesthetics.
  • Better long-term durability under abuse.

Our side panels may alternate between plywood and solid wood depending on model and workflow, but the lid will remain tongue-and-groove solid wood—the performance difference is too significant to ignore.

Reversible Faces – Two Different Looks in One Board

One of the strongest advantages of tongue-and-groove boards is that they're fully reversible, giving two possible “top” faces for the crate lid:

• Face A — Smooth, flat surface: Best for large stencils, stars, logos, insignias, and wide graphics. Downside: the seam between boards is more visible due to the 0.38–0.53" taper gap.
• Face B — Decorative multi-groove surface: Gives the appearance of multiple narrow boards. The central seam blends seamlessly into the decorative groove pattern, making the seam nearly invisible. Downside: only text stencils work on this side—fine shapes like stars won’t lay cleanly.

In short: Smooth side = graphic/stencil side. Decorative side = aesthetic side with a hidden seam.

Profile A – Wide, Softer Board (Preferred for Lids)

• Overall width: 5.44"
• Board thickness: 0.72"
• Groove depth: 0.30"
• Tongue length (horizontal): 0.30"
• Tongue height (vertical): ~0.22"
• Shoulder / taper length: 0.29"
• Joined taper gap: 0.53"
• Species feel: lighter, softer pine-type; planes smoother; less tension; better machining.

Profile B – Narrow, Denser Board

• Overall width: 5.33"
• Board thickness: 0.69"
• Groove depth: 0.31"
• Tongue length: 0.24"
• Tongue height: 0.25"
• Shoulder length: 0.27"
• Joined taper gap: 0.38"
• Species feel: heavier, denser pine; harder on blades; tighter seam fit.

Joined-Seam Behavior & Internal Taper Gap

The underside of the tongue includes a milled taper, and the interior of the groove includes a matching taper. When joined, these tapers form a V-shaped interior gap:

• Wide board seam gap: 0.53" (looser, more forgiving joint).
• Narrow board seam gap: 0.38" (tighter, more restrictive joint).

The larger taper gap of the wide board reduces internal stress, producing a flatter, more stable lid after planing. The narrow boards, while usable, tend to bind more and resist flattening.

Why the Wide Profile Is Preferred in Our Shop

• Slightly wider lid: ~0.22–0.25" additional total width when two boards are joined.
• Smoother joint behavior: Longer tongue + larger taper gap = less tension = cleaner seams.
• Easier to machine: Softer species, fewer chip-outs, cleaner cutting.
• Flatter finished lids: Lower internal resistance makes planing and joining more consistent.

System Overview – Two Layers Working Together

The approved interior coating system is intentionally split into two different jobs:

• Stage 1 – Penetrating epoxy flood: ultra-low-viscosity resin that soaks deeply into the grain, seals end grain, and forms a continuous fillet in the corners.
• Stage 2 – Elasto-polymer hard-coat spray: a very tough, textured, bed-liner-style coating that bonds to the cured epoxy and creates a thick impact- and abrasion-resistant shell.

Stage 1 turns the interior into a wood–epoxy composite; Stage 2 armors that composite against loose ammo, metal mags, cleaning gear, and hard field use.

Stage 1 – Penetrating Epoxy Flood (Armor Core Concept)

• Very thin – “water-like” viscosity: flows into joints, panel seams, and end grain instead of sitting on top. Excellent for saturating tongue-and-groove edges and plywood edges.
• Long pot life / working time: plenty of time to pour, tilt, and brush so every interior surface and corner is coated before the resin starts to thicken.
• Forms a continuous interior fillet where the bottom panel meets the side walls; behaves like a mini boat-hull radius and spreads impact loads across the corner.
• Greatly reduces moisture movement into and out of the panels, stabilizing the box long-term.

After flooding, boxes are left to cure for at least a couple of days before any secondary coating is applied. This avoids trapping solvents and gives the liner a fully hardened surface to bite into.

Stage 2 – Elasto-Polymer Hard-Coat Spray (Bed-Liner Style)

Over the cured epoxy, we spray a high-abrasion elasto-polymer hard-coat – essentially a truck-bed-liner-style product without naming the brand. Key characteristics:

• Extremely tough, gritty texture that shrugs off loose ammo, mags, and gear.
• Solvent resistant: holds up to typical gun-cleaning solvents and oils without bubbling or softening.
• Waterproof and moisture-proof: combined with the epoxy, makes the interior effectively sealed.
• Impact-resistant shell: turns the interior into something that feels almost indestructible in normal use.

Current limitation: most readily available products are only offered in black. For now, black is the standard, but we are actively watching for alternative colors with the same toughness.

Known Downsides & Future Improvements

• Odor: freshly sprayed liner has a strong smell for a while. Boxes are allowed to off-gas before shipment, but we’re still exploring ways to reduce or shorten the odor window.
• Color options: current system is locked to black. Long-term goal is to identify tan/green/gray equivalents without losing the abrasion and solvent resistance we get now.

Dragon Skin Silicone Experiment – Why We Rejected It

We tested a two-part pourable silicone system (marketed under the name “Dragon Skin”) as a potential interior liner. The idea was to create a soft, shock-absorbing insert inside the box.

• Too soft for ammo boxes: the cured silicone felt more like a removable insert than a bonded liner. It did cushion impact well, but it didn’t behave like a permanent structural coating.
• Poor adhesion to wood: the silicone never really “bit” into the interior. Once cured, you could almost peel the entire interior out like a rubber glove.
• Solvent compatibility issues: when exposed to common solvents/cleaners, sections of the silicone would bubble and react, which is a non-starter for anything that might see gun cleaner or oil.
• Shorter working time & thicker mix: compared to penetrating epoxy, the silicone had a shorter pot life and a thicker body, making it harder to chase into corners, grooves, and tight areas before it started to set up.

Verdict: the Dragon Skin-style silicone might be useful in other applications where a removable, soft insert is desirable (delicate instruments, electronics, shock-mounted containers, etc.), but it is not approved for Freedom Crate Co. ammo and range boxes.

Current Conclusion – Best System So Far

As of now, the combination of penetrating epoxy flood + elasto-polymer hard-coat spray is the strongest, most practical interior system we’ve tested:

• Excellent solvent and moisture resistance.
• High impact and abrasion toughness for loose ammo and metal gear.
• Realistic shop process: long epoxy pot life and a simple spray step vs. complex multi-layer systems.

This entry will be updated as more long-term data comes in and as we experiment with lower-odor formulas and additional liner colors that meet the same performance bar.