What chain actually does in a combination rode
Even a short length of chain at the anchor end of an otherwise rope rode adds weight right where it matters most — close to the anchor itself. That weight helps the rode lie flatter along the bottom near the anchor, improving the pull angle exactly where the anchor needs a shallow angle to set and hold. A common setup on smaller fishing boats is somewhere in the range of 4 to 10 feet of chain ahead of the rope, scaled up with boat size and anchor weight.
Why rope dominates the rest of the rode
Rope is lighter, easier to handle, cheaper per foot, and stores far more compactly than chain for the same length. For most recreational fishing boats under about 25 feet, running the bulk of your rode as rope with a chain leader is the practical choice — all-chain rode at the lengths a 7:1 or 10:1 scope calls for in anything beyond shallow water gets heavy fast, both to store and to physically haul back in by hand.
When all-chain actually makes sense
All-chain rode shows up mostly on larger boats with a windlass to do the hauling, where the weight isn't a hand-fatigue problem, and where the flatter lay and abrasion resistance against a rocky or coral bottom are worth the cost and complexity. For most lake and river fishing applications, this isn't the boat you're running.
Rope type matters too
Three-strand nylon is the standard choice for anchor rode because it stretches under load, absorbing shock from waves and current rather than transmitting a hard jerk straight to the anchor and your bow fitting. Braided or low-stretch lines, which are great for other boating uses, are a poor choice specifically for anchor rode because they don't offer that same shock absorption.
Sizing rope diameter to your boat
Rope diameter should scale with boat size, independent of scope ratio. A small jon boat or aluminum fishing boat is typically fine with 3/8-inch nylon rode; boats in the 20-25 foot range often step up to 1/2-inch for the added strength and a better grip in hand. Going thicker than necessary mostly costs you storage space and weight without adding meaningful holding power for a boat that size.
Putting scope and rode type together
Rode material affects the details, but scope ratio is still the dominant factor in whether your anchor holds. Get scope right first using the anchor scope calculator, then choose chain length and rope diameter appropriate to your boat size and typical anchoring conditions.