The big advantage of heel straps is that the feet don't drop off the pedals. This might be particularly useful for someone with edema (heavy legs) or limited use of one leg (stroke). Here's what they look like:
I've been using these exclusively for a couple of years and have even raced with them. My wife prefers them as well -- the adjustable length makes it practical for one strap to fit a variety of shoe sizes.
These are made out of sheet neoprene -- it flexes with the foot, can be cut to any length, holds its position on the heel, is quickly adjustable for length, is durable and has good strength. It is commonly available through gasket suppliers.
This next picture shows the material, preferable tools and slot jig,
General notes:
1. The material is cut on a bias to accommodate the length of the strap. I use 20" finished length for up to size 11 (US) shoe.
2. Slot intervals are 1.5" on the inboard side and 1" on the outboard side. The more slots, the more adjustable the strap.
3. These straps are cut 1.5" wide, trimmed down to 1 1/8" width plus 3/8" for the heel cup. As an alternative, the straps can be cut straight without heel cups.
4. Get enough material to practice on, make mistakes on and make an extra pair or two. I used 1/8" sheet neoprene.
Procedure:
1. Lay-out the desired length and width using a white (pencil or comparable).
2. Cut the gross strap size with a straight edge and box knife.
3. Trim to create heel cup (optional).
4. Round off corners with round chisel and mallet (optional)
5. Make jig for slots as shown above using Hobie toe strap for slot template, centered on strap and angled at about 20 degrees.
5. Use a leather punch to create appropriate size hole at each end of slot; use box knife to remove remaining material. Trial fit each slot on pedal tab; adjust as necessary.
Here's what the straps look like finished:
This is a close-up showing fitment on the inboard pedal tab:
Note that the angle on the slot allows it to: 1) to clear the pedal shaft and 2) allow the heel to drop straight in without slipping off (like the raised back of a sandal). Note also, the pedal now hangs correctly without the need for counterbalancing weights or bungees.
One should always be mindful of having your body fully clear the boat in case of capsize. I've capsized twice with these and had no problems:
Note, heel and toe straps should not be used together, as they can trap the foot in case of capsize.
Heel straps are a great alternative to the factory toe straps for many users.
