Spherachutes Anchor Recommendations
Our recommendations are based on years of input to the Drag Device Database by Victor Shane. We have made changes to our products and recommended components because of this input. Our general rule of thumb is when in doubt, go to the larger size – Sea Anchor, rode, hardware, etc. We look at the LOA of the boat first then the weight or displacement then the type of boat (S/V, P/V, multihull, etc.) for offshore use in potential heavy weather with breaking seas the minimum size we recommend, regardless of boat size, is 12 feet. Any smaller Sea Anchor would likely be caught in the crest of a breaking wave and be completely tumbled and collapsed.
The following chart illustrates the "holding power" of Spherachutes Anchors. There is no way any Sea Anchor could take these kind of loads and the displacement numbers are best viewed strictly with respect to the amount of water a Para-Anchor displaces – they have no bearing as to the strength of the Sea Anchor.
Sizing is first based on length overall with weight, keel configuration and windage taken into account next. Note that generally the greater windage of power boats equals the greater draft (wetted surface) of sailing craft, hence the same size “Sea Anchor.” When in doubt, go to the larger size. General recommendations are as follows:
Para-Anchor Sizing
Sea Anchor Sizing Considerations
Offshore Storm Conditions
The minimum size Sea Anchor we recommend for this application is our 12-foot, for the reason noted below.
Wave Crest Capture
In confused or breaking seas, the breaking part of the wave can extend 8 feet deep or more. A Sea Anchor smaller than 12 feet caught in this breaking crest will be fully captured and tumbled causing the Sea Anchor to completely lose its grip on the sea. With the Sea Anchor no longer holding, the boat will fall off and be in danger of being rolled.
By using a large diameter parachute Sea Anchor of at least 12 feet in diameter, if the seas are breaking 8 feet deep, the lower 4 feet of the Sea Anchor will remain in the non-breaking part of the sea and will maintain its grip on the sea. Once the breaking wave passes, the Sea Anchor is then able to reset itself and fully hold the boat. This is the reason we advocate the use of large diameter parachute Sea Anchors.
Note: All Sea Anchors, when under load in storm conditions, will ride right at the surface. Anyone who says otherwise is not being accurate.
Offshore in Moderate Conditions
For overnight layovers when fishing, you can follow the sizing guidelines on the Sea Anchor page.
The Drag Device Database
Following a successful solo crossing from Santa Barbara to Honolulu and back in 1979, aboard his 24 Foot trimaran Providence, and aided by a surplus parachute as a Sea Anchor, Victor Shane set out to catalog and disseminate accurate information about the use of Sea Anchors and drogues. Thus was born the Drag Device Database. An added impetus was the 1979 FASTEN tragedy where several boats and lives were lost - lives and boats that could have been saved had they been aware of modern drag devices.
Now in its fourth edition, completely revised and updated, we consider the database to be the best work available on the subject of offshore drag devices – Sea Anchors and drogues. Because of the real world contributions from drag device users to the database, we have made refinements in our Sea Anchors to make them more user friendly, and have also refined our sizing and rigging recommendations.
The DAB is an ongoing work and we are constantly in touch with the author to swap information. Every Spherachutes drag device goes out with a response form; we want to know what works the best and where improvements can be made. The database can be viewed online here.
Supplemental Instructions
These instructions are for times when you’re using your Spherachutes Anchor for overnight layovers – fishing trips and the like.
Rode Length
For storm use, we recommend a length of at least 10 times the LOA of the boat. This length is to mitigate the effects of being out of phase with respect to the Hazards of Wave Particle Rotation (see pg. 13 of the instruction manual). In confused seas, the phase will not remain constant, which would make it necessary to constantly adjust the rode length. But the strain on the rode in such conditions so high that it is virtually impossible to make such adjustments, so adjusting the scope is generally done because of chafe. This is not the case in moderate conditions where the strain on the rode is much lower. In any case, it is easiest to let our additional rode to get “in phase.”
On overnight layovers in moderate conditions, a much shorter rode can be used. However, you must pay particular attention to the hazards of wave particle rotation and make sure the Sea Anchor and boat are "in phase." If conditions deteriorate and a longer rode is necessary, you need to be prepared to let out as much as 10 times the LOA of your boat, or more. This may entail shackling a second or third rode to the primary rode.
Trip Lines
The use of a full trip line (all the way back to the boat) for overnight layovers will make recovery much easier. Extra care should be taken during deployment to keep from getting the trip line wrapped around the Sea Anchor. The full trip line should be ¼” nylon and at least the length of the rode, plus the size of the Sea Anchor. Once the Sea Anchor is set, excess slack should be taken out of the trip line, but it should not be tight.
Recovery With a Full Trip Line
The easiest way to recover your Sea Anchor with a full trip line is to take all the slack out of the trip line and cleat it off. Next, let out the anchor rode. As the rode is let out the Sea Anchor will "trip" (turn upside down) and collapse on itself. It is then a simple matter to pull the Sea Anchor in via the trip line.