55' x 60 Tons
24-Ft. Dia. Sea Anchor
Force 8-9 Conditions
File S/P-5, obtained from Captain Dennis Crosby, Youngstown, FL. - Vessel name Ashly G, hailing port Panama City, FL, Thompson trawler, LOA 55' x LWL 50' x Beam 18' x Draft 10' x 60 Tons - Sea anchor: 24-ft. Diameter Para-Tech on 400' x 3/4" nylon three strand rode, with 3/4" galvanized swivel - Partial trip line - Deployed in low system in deep water about 150 miles south of Mobile, Alabama, with winds of 35-45 knots and seas of 15 ft. - Vessel's bow yawed 10° - Drift was estimated to be 4-5 n.m. during 24 hours at sea anchor.
Ashly G's partially torn sea anchor came back for repairs a number of years ago. Upon inspection the first thing Victor Shane noticed was that the canopy was inside out! The skipper of the boat could not recall how this came about. Most sea anchors and parachutes have a heavier, skeletal, web framework that cradles and reinforce the lighter canopy material. If the parachute is used inside out high loads may tear the canopy away from the radial basket, which is probably what had happened here.
Upon further inspection Shane also noticed heavy damage in the vent-hole area.
The vent-hole is the discharge orifice incorporated into the top of the canopy to afford stability and shock absorption. This is a very critical area where there is tremendous water pressure trying to squeeze through a small hole. The nylon cloth of the parachute is not strong enough to withstand the pressure, so the vent-hole has to be heavily reinforced with webbing - it is the strong webbing that takes up the strain, and not the lighter canopy material. And indeed, in this case it had been redundantly reinforced.
So what could have happened?
Further investigation revealed the culprit: CHAFE! The trip line has to be tied off to something. Usually that something is the webbing that reinforces the vent-hole. In daily use the trip line rubs and pulls against the webbing. Chafe does the rest. Once the reinforcing webbing has chafed through the high loads have to be born by the lighter canopy itself, usually resulting in failure of major proportions.
Shane was quick to bring the matter to the attention of Para-Tech's Don Whilldin. A master parachute rigger and veteran skydiver (more than 1000 jumps), Whilldin went to work and redesigned the critical vent-hole area.
All Para-Tech sea anchors now have a separate recovery bridle, to which the trip line may be attached independently of the critical webbing that reinforces the vent-hole.