Free Standing Mast Loading

[brian eiland]

Eric are you fully retired now or still puttering about? Most of us find retirement just proves that, your golf game can't justify all the extra time on your hands, so you're back to doing something pretty quickly.

Speaking of golf, I recently picked this little item up at a flea market.


I figure it would make a great 'gag' gift for the frustrated golfer.

 

[LP]

LP, the paper is attached. This was presented at the 6th Chesapeake Sailing Yacht Symposium in 1983. Pay particular attention to the Addendum at the end of the paper, it has some corrections and additional advice. You may circulate this paper to anyone who is interested. A few years ago, I gave copies to The Landing School and to Westlawn so that all their students could study it.

Good luck,

Eric

Wow! Thanks,Eric. I'll be chewing on this one for a while.

 

[Chuck Losness]

LP
If you are not an engineer you will be chewing on it for a long time. Then you have your spread sheets to create which will give you even more to chew on. It was a challenging process for me.

 

[LP]

Chuck,

I have some engineering background so it's more a matter of pulling out my texts if I run across something I've forgotten. I'll also be applying Eric's information to the wooden masts I plan to build.

I've already written a spreadsheet to develope my masts based on my own understanding of the mechanics of the forces in a mast. I'm hoping Eric's paper will confirm what I have already calculated. Most likely though, I'll be getting additional insights into the design process and may need to make changes accordingly.

Thanks for your concern.

Greg.

 

[Eric Sponberg]

Chuck,

I have some engineering background so it's more a matter of pulling out my texts if I run across something I've forgotten. I'll also be applying Eric's information to the wooden masts I plan to build.

I've already written a spreadsheet to develope my masts based on my own understanding of the mechanics of the forces in a mast. I'm hoping Eric's paper will confirm what I have already calculated. Most likely though, I'll be getting additional insights into the design process and may need to make changes accordingly.

Thanks for your concern.

Greg.

If you haven't found it already, Hasler and MacLeod's book Practical Junk Rig is quite good for designing wood free-standing masts.

Eric

 

[Kamelisko]

Stub mast all over the top?

Hi. Sorry for replying this old(ish) thread, there is one thing I still haven't found anywhere answered:

How it is made that stubmast actually goes all over the top of the mast to install wind meter, lights etc. at the mast top? Is there "stiff" stub with bearings and then there is just some kind of flexible pole attached to that which stays still as the wingmast rotates around it?

 

[Eric Sponberg]

Hi. Sorry for replying this old(ish) thread, there is one thing I still haven't found anywhere answered:

How it is made that stubmast actually goes all over the top of the mast to install wind meter, lights etc. at the mast top? Is there "stiff" stub with bearings and then there is just some kind of flexible pole attached to that which stays still as the wingmast rotates around it?

Kamelisko, The way that I do a wingmast/stubmast design is that I have a lightweight wood form, a mandrel, that creates the shape of the mast. Onto this mandrel I lay up the carbon fiber laminate. In the designing the mandrel, which has a shear web and various stations in it to help form the shape, I also include plastic conduits to house electrical wires, halyards, and a lightning ground wire. These conduits are built permanently into the wingmast which slips down over the stubmast. The conduits do not move and they are not really flexible. The lower ends of these conduits are situated just above the top of the stubmast when the two mast parts are assembled. As the wingmast turns, the wires and halyards are free to twist slightly through the length of the stubmast.

The stubmast is made similarly to the wingmast in that there is a lightweight wood mandrel to start the shape with carbon fiber lay-up over. However, there are no conduits in the stubmast, but rather a central opening where the wires can go all the way down to the bottom of the stubmast and come out there inside the boat. I usually try to make the halyards come out of the stubmast at deck level. This means that the hole where the wires go through has to have a standpipe of sorts so that any water on deck won't get back up into the halyard openings and go down into the boat through the wire hole.

It may sound a bit complicated, and it is, so that is why detailed drawings are necessary to plan the precise routes of where all the conduits for the wires and halyards. It can get to be pretty tricky geometry that requires careful planning.

I hope that helps.

Eric

 

[Kamelisko]

Hi, thanks for the answer. I just want to make sure: so there is no place at the top of the mast which does _not_ rotate? How is the mast light and such things aligned? Wouldn't they turn to wrong direction with the mast? Or you just simply don't put those things up there with wingmast...?

 

[Eric Sponberg]

Hi, thanks for the answer. I just want to make sure: so there is no place at the top of the mast which does _not_ rotate? How is the mast light and such things aligned? Wouldn't they turn to wrong direction with the mast? Or you just simply don't put those things up there with wingmast...?

Correct, you cannot put rotation specific items, like a tri-color navigation light at the top of a mast. An all-around white light and radio antennae can go up there. You can put a wind anemometer at the top of the wingmast and then have a mast rotation sensor at the base of the wingmast. Brookes & Gatehouse used to make such a sensor, perhaps still do, which can feed into your electronics to give you the proper wind direction to the center of the boat.

Eric

 

[BobBill]

Chuck Losness wrote: "...Your life will now become busier then you can imagine and you will wonder how you found the time to work in the past."

+1 to that...and this retired klutz dodger also appreciates the wondrous information herein.

Life is good, even when I mess up!