Sloop Mast Location ?

Is there any set rules on the location of the mast verses it's position along the designed waterline. In the many books i've read and scaled measurments of say 50 drawings i've come up with the following. Most technical books on rigging and masts say nothing--A few recommend around 25% of the waterline length, back from the stem(i'm assuming where the waterline intersects the stem) The scaled measurements i have taken of the numerious sloop plan drawings show most at 30% but many at 35% and a few bordering 35% plus. I'm presently in the fortunate position that my mold for the keel and the resultant glass keel shell is adjustable until I finally bond it to the hull. I can still slide it along the present keel to alter the CLP(CLR) location. This being the case i have an option here to place the mast anywhere from 25% to 35% plus along the waterline length. I've also come across an article which stated that Sparkman& Stephens were playing around with sloop mast location up to 40% of the waterline length but am not sure how this panned out. I know I'm in over my non design head here and things can get pretty technical but given I'm installing a long modified long foil keel/skeg combination that is probably closer to a flat sided full keel than any foil chacteristics i just need a better to go this % than that % type of answer. This is just an old man having fun building his own boat trying to improve on his last build--Tnx. Geo.

P.S. If any of the hulls hydrostatics, sail area,(main 400sq.ft)(fore tiangle ?) are needed to better the answer i can provide such.

A yacht is not defined by the vessel but by the care and love of her owner--

 

In a typical masthead sloop the mast is at station 4 (waterline divided into 10 equal stations with zero at the stem/waterline intersection). In a 7/8ths sloop the mast is about at station 3, also in a ketch the main is at station 3 and mizzen at station 8. And a schooner has the foremast at station 2 and main at station 6......of course there are many exceptions to these guidelines....but they do work for many boats.

More importantly get the CE between 28 and 34% of waterline length from station zero.

I thought I told you this before and sure enough I have....http://www.boatdesign.net/forums/boat-design/forward-keel-location-angle-questions-37563.html

 

400 sq ft of main is considered a handful to reef for one person.

300 is a snooze.

 

TAD and sure enough you did -- man getting old --as a matter of fact looking back in my notes i did position the leading edge of the keel mold based on that info --The 60's were fun but possibly paying the price now Thanks for the second time --Geo.

 

Fast Fred--oops two dam oversights today, now i'm really getting worried, that should be 200sq.ft and you'll know what i did wrong . Fred It should also be a breeze to shorten sail, it is equipped with Dutch slab reefing. Sorry guys I'm swamped with work and need funds for boat and retirement, Getting a little wacky in the head because I can't get time on my own build. Soon have to set up stadium lights around her and do night shift. ---Geo.

 

Viking,

There are no hard and fast rules. There will be a preponderance within a certain range, but it all comes down to balance between the CE and the CLP (which has been discussed exhaustively on this forum) and the geometry of the rig. Don't worry where the mast is located along the length of the Lwl--it doesn't matter--only the balance of CE/CLP matters. The mast will fall where it will in the design.

Eric

 

Thanks Eric and Tad-- I got a much better idea now-- set up a rough location for the mast approx. say 40 % of the DWL back from the stem intersect and it will produce a given CE location. As recommended by TAD a CE between 28 to 34% of DWL for a masthead sloop from station 0. I've also read a 2002 post by Stephen Ditmore recommending basically the same tho a little higher percentage, regardless this gives me a good reference point to set up the keel to properly balance it's CLP with that CE (CE leading CLP(CLR) by approx 14 to 19% of DWL.(Skenes) Can't believe I just posted this and actually have a good understanding of what it's all about Tnx.-- Geo.

 

Before signing off on this thread- and after searching out and reading the all the related threads on forum( for the past 4 hrs. from 2002 to present), in addition to those I researched prior to opening the thread with my query. I would like to repeat my thank you for your patience in once again replying to this most common subject posted over the years. While I did do my research both on and off the forum prior to, had I run the extra mile I would have gathered more than enough info to answer my opening post. However by doing so it has pleased me to learn that given the fact, I am working with a pre designed and built hull (conversion project) the approach of mast location first(CE) and keel location second (CLR) to attain an approx. correct Lead was by luck on my part the correct approach. One important tid bit I picked up is the effect of the aft sections on the amount of lead. Since my somewhat narrow hull (7ft 6 in. on 28ft) has a fine exit (canoe stern) i will set the Lead on the lower end of the 14% to 19 % range. This whole effect of the aft section shape on Lead, windward ability, drag and so on is quite an interesting part of hull design tagged for future study and possible questions . For now I am armed to move forward with the task at hand.(get this thing built and enjoyed) Thanks once again Forum---Geo.

A yacht is not defined by the vessel but by the care and love of her owner--