DN NA Class

I am considering building a composite mast. I came across a interesting article by Paul Goodwin in the IDNIYRA reprints number one. It focused on quantifying mast stiffness in fore/aft and side/side conditions below and above the mast hound. I have not come across any updates for composite masts.

I am interested in knowing the current state of thinking regarding the proper level of stiffness for a good general purpose mast. I am a heavy skipper at 250, but one of the boats I am building will be for lighter people at 180 and the third for my girls at 120 with all their accessories.

I currently have an old Sherry mast I was told was his original race mast when I bought the boat. the boat was supposed to be the master to the clone series, but who knows for sure. To the other extreme, I have some Kenyon masts.

Any guide lines on what I should target for good all round masts for each application is appreciated. Also, info on the sail characteristics will be helpful. If any of these were to race, it would be the two heavier setups. The light weight will be purely recreational.

Thank you

   One of our top sailors has been evaluating and measuring a number of the best composite masts.  What he's found is that for the typical 170-200 pound sailor a mast that measures 58-60 pound per inch spring rate for the first 11' and 18-20 #/in for 15 1/2 ft seems to work well. The fore and aft measurement for 15 1/2 ft is typically a little less then the 11' spring rate.  A 250 lb. sailor would probably need a mast in the 63/21 lb/in range. That said, I'd really think twice about building your own mast. The hardware from Sarns alone is around $170 and glass and epoxy isn't cheap. Then you have to build a mould and figure out the proper glass lay up schedule. A friend of mine who builds masts said it took him 5 tries before he got a decent spar. The masts that are being built fit the standard FO1 sail. If you build one that doesn't fit this sail you are not going to be happy with your mast since it's going to be hard to find the proper sail. Several years ago while composite masts were being developed, several of us built wood cored composite masts. They went okay but didn't really match the fiberglass masts of the day and most all of them eventually broke. I hate to discourage a guy who wants to build stuff for his boat but finding a decent used mast is probably the best way for you to go. Good luck. Bob

Thanks for the info Bob. There is a group of 5 of us getting together an evening or two each week to build/rebuild boats. Between us we have access to enough equipment to make most of the hardware ourselves. I have access to a lot of prepregs from JD Lincoln and can probably even manage some FEA modeling. We decided tonight that we will get the old boats rebuilt and the 2 hulls I started complete along with inserts, planks, ect. and have as many boats ice ready as we can before we start on this. For now I will accumulate equipment, materials, do the modeling, ect. and plan on maybe gearing up next year. I am thinking of sticking with glass and making them a little heavier so it won't be too much $$. We should have 6 boats to the ice next winter along with a 4 boat enclosed trailer so we can get out of the snow belt...we get around 300" a year here and boating days are slim.

Do you think I can use one of my Kenyon blanks for the mold pattern?

  I'm not that familiar with Kenyon masts but you probably could. Bob

Aluminum masts are not tapered.  Composite masts, at least the fast ones, are. So find a composite mast and use that as a master.

Contact Bob Rast for excellent advice.  He has developed the tools and materials and skills.  It only took seven years or so. Bob may share his layup schedule, or not.  Lou Loeneke had a mold for sale last fall at the swap meet, and it may still be available, for a jump start.  Both were built from Kent masts as masters, I believe.

Believe me, once you take the time to build a mold and wood pressure vessel (to hold the mold closed while the internal bladder is inflated to 25-30 pounds), and find the material for the bladder, buy the epoxy and glass and parting compound, and the building table, and the post-cure oven, and the pressure regulator for the bladder, and the luff tube material, and do the mold prep and epoxy drain holes, and actually build one, fit it and sail it,  only then will you start to evaluate exactly how good or bad the masts are.  Oh, that is after you figure out how to cut the bolt-rope tunnel and mount the hound and mast base and halyard and pulley and halyard stops.  A little carbon is a trivial price. 

Oh, I watched my Polish friends measuring masts.  They support the mast at the base and hound and measure deflection at 200 pounds at the mid point.  Then they move the mast down until the tip is on the horse and measure again. 

Based on my experience, the proper bend is not very skipper weight dependent.  The mast will bend or not in light air based on its stiffness and tuning, regardless of the skipper weight.  The mast must bend to point and go fast.  Most of the time, we sail in wind conditions less than the maximum that most skippers can handle, meaning less than what causes uncontrolled hiking or extreme mast bending.  A heavier skipper will need to tune differently for heavier air, with more power available than a lighter skipper. 

The above is NOT true for very light skippers, say less than 120 pounds.  It has to bend to keep the boat in control in heavy air. 

The tip stiffness is a preference.  A sherry rocket and a sherry ugly stick and a sherry whip all bend differently.   Skippers sailing all three were faster than I at the worlds.  Usually.  A mast with soft fore-aft bend is a mast that doesn't want to rotate.  A soft tip looks odd, but seems to still go fast except at the very top end of the skipper skill levels.

Ken,

I have a Sherry mast, from what I have seen on his site, I'd say it is a whip. It does have trouble rotating at times, I have to coax it over, but it seems fine. I wasn't going to use that because it was molded with a little bow to one side.

From what you are saying, it will probably be a good starting point for us. As all say, it's not really less expensive to make vs buy, it's the fun in the effort to make one we are after. A couple of us have technical backgrounds, one is a construction guy, and we have a couple of salesmen to keep us motivated!!! For the 2-3 days a year we get to sail around here, most of the fun will be in getting together to build. I do hope to get the trailer on the road after we get the group's boats up to snuff.

   Most of the new masts have a problem rotating to the next tack that's why most sailors with these masts are using Matt Struble's about 6" wide hound attach fixture. It works great.   Bob