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Tuning a Dolphin Mast (updated May 11, 2013)  

June 25, 2012. The question of how to 'tune' a Dolphin mast came in over the transom a couple of days ago. There is a lot of technical stuff on the Internet - much specific to certain boats - nothing I could find on the Dolphin. Number 1 on the Google Search engine is http://www.ballengerspars.com/mtguide5-97.html. Its general, reasonably brief, and I like it. Others must too.

Our Dolphin masts are not all the same, and therefore there are more than the usual variables that impact this discussion. A few are 1) racer or cruiser? 2) typical sailing conditions 3) your sailmaker recommendations, One important variable is that early Dolphins had 'telephone pole" masts. Sparkman and Stephens had a well deserved reputation for being conservative - to the point that S&S specified masts were called, in some quarters, 'bridge breakers'. Dolphins were raced a lot in early days and owners made lots of modifications - including specifying lighter, bendy masts, adjustable back stays, baby stays, and rig systems designed to shape the sails. Another important variable is that design changes for the Yankee Yachts built Dolphin resulted in a double set of lower shrouds vs O'Day's single lowers. (Interestingly, the original design for the Dolphin 24 had double lowers - click here to see it.)

I think the majority of our masts are not bendy types, and Marionette's mast probably represents the standard - a telephone pole. So we'll start this off with what I do to 'set up/tune Marionette's mast. Hopefully, we will get input from others.

I use a Loo's Model B tension gauge and a 50' steel tape. Marionette's shrouds are 3/16" diameter, a single pair of lowers, a single pair of uppers, a backstay with a an old fashion double flip handle adjustable turnbuckle, and a forestay.

Marionette's Old Fashioned Backstay Adjuster

Loos Tension Gauge - Model B
What's the Ring for? See Below

1) the mast is set up more or less straight with turnbuckles hand tight. The boom is not set up, halyards are loosely tied off on the mast. In the early days I set up the mast with 3' of prebend and fairly stiff shroud tension - as she and I have gotten older, I have dispensed with the prebend, maybe just a touch, and the rig is a lot looser. I only tighten things up if we are going to face a lot of hard breeze - and I'm better now at avoiding those conditions than I used to be. Anyway, she seems to like our current set up.

2) My mast has 2 large diameter, internal, side by side sheaves at the top - the stbd side is for the main halyard, port side for the jib halyard. I tie the end of the 50' tape to the main halyard shackle, and a spinnaker sheet as a safety line. I raise the halyard to the top and take measurements side to side to the chainplates, the back edge of the transom and the stem head fitting.

By measurement, and by sight, I soft adjust/hand tighten the shroud turnbuckles as necessary to make sure the top of the mast is centered side to side.

I hang a heavy turning block on the spinnaker sheet and sight up the mast to check if the mast is straight fore and aft - and soft adjust the back and forestay as necessary - maybe a touch of rake in some years.... I try not to look at the little kink in the aft starboard edge of the mast maybe 8ft from the top - an incident that must have happened before I owned her.

I actually recorded these measurements in the past, but don't any longer - I just measure to be sure side to side the mast is straight. I sight up the mast groove and make sure it is straight - no curves!

NOTE! Adjust your spreader tips so that they have that characteristic Dolphin up tilt....I use my fully extended whisker pole and tap up, or with a piece of tape holding in the locking pin, fit the clip over the end of the spreader and pull down an over exuberant spreader.

3) I start with the upper shroud turnbuckles and give them each 3-4 turns and go back and look up the mast groove - no waves/curves. I clip on the tension gauge and check the loads - then adjust the turnbuckle on the softer side, if there is one, to make them the same. I tighten the turnbuckes, 1-2 complete turns at a time, the same amount on each side, until I get to 30 on the gauge, checking up the mast to see if it looks good side to side. Don't twist the shrouds, just the turnbuckles.

4) Then I repeat the procedure on the single set of lower shrouds - mine go to the same chainplate fitting as the uppers. This gets a little trickier as, sometimes the top of the mast will kick over a bit to one side as you tighten the lowers, and you get a 'wave' in the mast. Trial and error, and patience. Take off some of the hard tension on the suspect lower and take another look, then start again. Eventually.... I tighten the lower shrouds to 32 on the tension gauge.

5) If you are into a bit of prebend, tighten the backstay to get the desired amount. I tighten both fore and backstay turnbuckles the same number of turns, visually checking the mast to make sure nothing weird is happening, until I reach 30 on the forestay. If I need more forestay tension while sailing in a breeze, I use the handles on my old fashion backstay adjuster to tighten the forestay.

6) check all the shroud tensions to see if anything has changed. Look up the mast groove and make sure its still straight.

Try and get forward of the boat - next dock over or ashore and see how it looks (especially the spreader angles (tilted up and even - very important - there are spreader angle watchers and they'll whisper behind your back....

7) rig the boom, bend on the main, finish rigging and go sailing - watch out for excessively loose lower shrouds on the leeward side going up wind. When you get back, if all is ok, put the cotter pins in your turnbuckles and tape them. If not call Harry, or post a question on the Forum, or contact your webmaster's attorney.




Because we knew you'd ask - the ring on the back stay in the picture above has 2 purposes. It will hold the bottom end of a man overboard pole, or snap shackles that clip a lifeline wire from the ring to the top of the last lifeline stanchions on either side. When single handing, or racing, we use it since Marionette does not have a stern pulpit (ok, pushpit)


May 11, 2013. A recent email asked for what we had on different kinds adjustable backstays on Dolphins. Here's three more....

Abbie Burgess' backstay adjuster wheel

Carlos Vergas's Yankee, #107 - backstay to adjustable block system







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