The September double issue contained the first of three articles on radar antenna mounting choices. That first report was on mast mounts. This one is about what may be the fast-becoming-popular gimbaled backstay mounts.
In conjunction with this radar mount project, we made a small survey of Practical Sailors neighbors at East Passage Yachting Center and Ted Hoods Little Harbor in Portsmouth, Rhode Island.
An even 100 survey sheets were placed on sailboats that had radar. There were 39 replies. The number is not large, but it probably is a fair indicator of the way in which most boat owners handle the placement of the radar antenna.
Of the 39 who replied, 22 have mast mounts. Eight carry the antenna on a pole. Only six are on backstays. (There also were one mizzen mount, one arch and one custom frame.)
Mast mounts currently are the overwhelming choice. However, when specifically asked, Do you wish you had chosen a different location or kind of mount or that it was gimbaled? five of the 22 with fixed mast mounts (and one with a pole mount) said they wish they had gimbaled mounts.
So, instead of a mast-pole-backstay ratio of 22-8-6 bias, the score (counting the wish I had votes) would have been 17-7-12.
Its not just that mast-mounted radar antennas can be damaged by the flailing leech of a jib and that, even with a guard (off-the-shelf or custom made), the sail will develop a frayed edge.
The real allure of a gimbaled mount stems from a radar antennas vertical beam width of 25, which means that if the boat is heeled more than about 15, signal loss sets in. How bad is the loss? As part of this series, well be testing that, too.
In our survey, about a half dozen of the 39 who replied said they did not care about gimbaling because the boat is almost always under power and level when the radar is used-such as when motoring into harbors, in fog or at night. The value of gimbaling seems to depend somewhat on whether the radar is used when sailing, especially as a collision avoidance instrument.
The hooker in gimbaling is how to prevent the device and the antenna from swinging freely. A sailboat is an engineering laboratory devoted to controlling movement. Anything loose is dangerous. Another detail that must not be overlooked is the loop in the electrical cable, to prevent breaking the cables extremely fine wires through continual flexing. (See a discussion in the June issue on the proper routing and size of the loop required.)
There are on the market but three kinds of gimbaled antenna mounts. The three represent extraordinarily interesting entrepreneurial pursuit. At the heart of these mounts are devices that severely dampen movement as the boat heels. Two are hydraulic; the third uses mechanical friction. An interesting question, we thought, was whether the dampeners would handle rolling. Some boats, particularly modern fin keelers, have rapid rolling motions.
The Questus
The gimbaled backstay mount was developed in 1989 by a Marblehead, Massachusetts, sailor who, as is often the case, wanted something better than a fixed mast or pole mount on his 1974 Tartan 41.
Allen DeFatnick has the means to do it right. He owns a successful company that makes surgical instruments and equipment, including implants. A 54-year-old engineer educated at the Massachusetts Institute of Technology, he knows and has high regard for precision work.
His Questus antenna mount, a very technical and finely made piece of equipment, hit the market in 1990. Since then, 3,000 have been sold through Pompanette, Inc., which owns Bomar, Hood Yacht Systems and several other marine companies.
The Questus is made to high standards, the quality is tightly controlled and, in DeFatnicks words, The engineering is probably overkill.
The torque loads are transmitted through the hydraulic unit, down the pole to the deck. The cast base plate has a hole to carry the electrical cable through the deck. The hydraulic cylinder even has a thermal expansion chamber to compensate for temperature changes…for use in the tropics.
The object, said DeFatnick, is to assure that the antenna platform always stays level. It may be slow in reacting to a fast roll, but there is no oscillation. And I expect it to work virtually forever, without fail.
The Questus comes in two models with mounting options and adjustments to fit any imaginable installation (including a mast or pole). Assembly, using the extensive installation manual, requires some meticulousness. For the record, the backstay options are: radome forward, pole forward of the stay; radome forward, pole aft of the stay; radome aft, pole forward; radome aft, pole aft; radome foreword, stay inside support tube; and radome aft, stay inside the tube.
Questus is the only maker with models that enclose the backstay, which requires some special lower-end tubing if you have a hydraulic backstay adjuster. It also is the heaviest of the three. The two-arm model (a version of which, with other attachments, is shown on the cover of this issue) weighs 18.2 pounds. The two sizes sell for $990 and $1,475, but are discounted by Defender for $800 and $1,275.
The Waltz RLS
Seeing the success of the Questus, a 44-year-old Oregon engineer who specializes in cost-conscious simplicity, brought out in 1993 a gimbaled mount called a Waltz RLS (radar leveling system).
Keep it simple, said Tom Betts of Performance Marine Technologies, Inc. If you do, itll be easier, cheaper and last longer.
Much simpler and less expensive than the Questus, the Waltz (named for Betts friend, Dr. Roger Waltz, who first drew the plans) uses a smaller stainless support tube and a small non-adjustable top end that enables Betts to boast of the Waltzs light weight. Betts said about 800 to a 1,000 have been sold.
Where the Questus gets its universality (to fit over or parallel to any backstay in any fore-or-aft position) from a large and somewhat complicated top unit that has a number of Allen head machine screws, the Waltz has a new head-a simple welded stainless unit with big grooved nylon washers to grab the backstay and a leveling device that is a simple block of high-grade aluminum machined to accommodate the hydraulic innards.
Adjustments to bring the antenna parallel with the waterline must be done with washers.
The base plate for the pole is three pieces of stainless and a clevis pin. The base has no hole for the electrical cable.
Early Waltz mounts used an off-the-shelf hydraulic dampener, but Betz now makes the unit himself. Compensation for heavy radomes or temperature extremes involves dismantling the unit to fill with lighter or heavier oil. Its an easy job and, if the seals wear, they are standard automotive stock.
The Waltz also avoids some price and manufacturing complications by not offering a model that fits over the backstay. The Waltz can be mounted in any of the usual four positions. Level tuning fore-and-aft requires spacers or washers on the radome platform. Almost as heavy as the Questus, the two-arm model weighs 17.6 pounds.
The two Waltz models, for 18″ and 24″ radomes, list for $727 and $883, but discount to $549 and $699.
The Radar On The Level
Most recently, Michael W. Donoian, who owns Marine Services and Salvage, Inc., in Bellingham, Washington, also thought it odd that antenna mounts were getting to cost about as much or more than the radar itself.
His gimbaled backstay mount is called a Radar On The Level. He went into production last February with a split backstay model that requires no pole and another, for a single backstay, that uses a pole to support the weight and transfer the torque to the deck.
Donoian took an entirely different cut at the problem of controlling the swinging movement. To avoid the expensive hydraulic dampener, he suspends the R.O.T.L. on a 1/2″ stainless bolt equipped with two 1-7/8″ x 3/16″ Delrin washers, a Delrin sleeve and four stainless washers the same size as the washers. By tightening a nylon-lined nut, the sleeve (which actually fattens under the load) and nylon washers compress to provide controllable friction. As it wears, the nut is tightened further.
Donoian says he has had the prototype on his boat for more than a year and it still works perfectly-no wear, no adjustment needed. There is no stop on the movement, other than a piece of shock cord.
Attachment to a split backstay is very straightforward, with a triangular plate that substitutes for the plate that comes on split backstays.
For a single backstay, Donoian uses two grooved nylon sheaves mounted in the otherwise all-stainless head to secure the mount to the backstay. The R.O.T.L. is mounted on an aluminum pole greater in diameter than either the Questus or the Waltz. The pole model is admirably lightweight at 11.25 pounds.
The split backstay model sells for $500. The single backstay version is $1,100.
The Test
Except for the split backstay R.O.T.L. model, all of these mounts require room on deck, adjacent to the backstays chainplate, for a fitting where the bottom of the support tube is firmly secured with a backing plate. When the boat heels, considerable twisting force is exerted at that point. The pole is, in effect, a torsion bar. A custom fitting often is required if the deck is cluttered or the boat has a reverse transom.
We attempted, with a big geometric jig, to test the gimbaling characteristics of these three units. However, we did not get significantly different results. The only thing proved by our measurements was that one model was quicker to level, which means nothing. All three kept the radome platform, to which was attached a 10-pound weight, perfectly level.
When swung repeatedly through 60, as though the boat had gone from a 30 heel on one tack to a 30 tack on the other, the Questus and R.O.T.L. remained level and accomplished the swing in 1.5 seconds. The Waltz also remained level and completed the swing in 1 second. All three came to abrupt stops at the end of the swing, which means there was no backlash or oscillation.
How about our question about a boat under power being rolled quickly by chop? Because no boat has a roll moment anywhere near a second and a half, these mounts obviously would have no trouble keeping up with the movement.
The Bottom Line
If youre looking for the tried and true, proven performer, the choice would be the Questus…except that for many buyers its price is a choker. (The numbers are very small, but in our mini-survey, of the six boats equipped with gimbaled backstay mounts, five had Questus and one had a Waltz.)
Only time will tell whether the new R.O.T.L. friction-operated mount wears at a slow enough rate to make it practical. Considering that no expensive hydraulic dampener is involved, the price for the pole version is not as low as might be hoped for. We expected it would sell for less than the Waltz, but that is not the case. However, its light (11.25 pounds) and is very attractive. But if it wears too much or too fast, it would be annoying.
Its not nearly as jewel-like as the Questus, but the lightweight, soundly engineered Waltz, with a hydraulic dampener its maker says is as foolproof as that used in the Questus, wins hands-down as the Best Buy.
Contacts- Questus, Hood Yacht Systems (Pompanette, Inc.), Box W, Charlestown, NH 03603; 603/826-4125. Radar On The Level, Marine Services and Salvage, Inc., Box 791, Bellingham, WA 98227; 360/671-6381. Waltz, Performance Marine Specialties, Inc., 21785 SW TV Hwy., Beaverton, Oregon 97006; 503/642-5200.
