Anonymous wrote:

Anonymous wrote:

My apologies for violating convention..... I deleted the post in question and spent a few minutes in the privacy section, then logged out to see how I appeared to non members.  I had not realized that things appeared differently to members than non members, though I should have, as people who showed up as anonymous before I joined no longer.

The essence of my deleted post was that pushing the dinghy sideways at different points should quickly resolve where the CLR actually is.... a simple and low tech solution that I will use on my own project when it reaches that stage.   On a dinghy, this could be done from the dock or standing in the water, etc... with a person seated in it or a weight to simulate loaded condition.

     I'm also planning to build a junk rigged sailing dinghy.... later, and am currently working on a 15' trimaran built from a fiberglass canoe and fabric covered amas  for use on local lakes... weekending...side decks will make it useable for camping out. I hope to play with Paul McKay's Aerojunk design, as I like the potential to achieve variable camber from  flat sail, and building batten cages is more up my alley than lofting a sail....I have bigger ideas I'm pursuing, but starting small is usually a good idea in my experience.

                                                      H.W.

Ok, so what was the original post? I’m intrigued by using a body in the dinghy while it’s in the water,  to discover CLR but you’ve not given enough detail for me to understand. 

I feel teased

please elaborate. 

I'm not sure what's left out... the body in the dinghy creates a realistic CLR, because things change as you shift weight.  In the PJR Hassler and McLeod describe making an outline of the underwater shape of a boat out of construction paper, and finding the balance point of that to determine the CLR... that would yield the same result as pushing the loaded dinghy sideways in the water until you find the zero yaw point.    It's pretty simplistic, but so is the PJR method.  A better representation would be for the person in the boat to hike out until you have a moderate heel, and then do it....  The underwater profile changes with heel on most boats... and then there are hydrodynamic forces generated by moving through the water.  When the CLR really matters is when you have side forces, and that means when you are heeled over.  

                                                       H.W.

My apologies for violating convention..... I deleted the post in question and spent a few minutes in the privacy section, then logged out to see how I appeared to non members.  I had not realized that things appeared differently to members than non members, though I should have, as people who showed up as anonymous before I joined no longer.

The essence of my deleted post was that pushing the dinghy sideways at different points should quickly resolve where the CLR actually is.... a simple and low tech solution that I will use on my own project when it reaches that stage.   On a dinghy, this could be done from the dock or standing in the water, etc... with a person seated in it or a weight to simulate loaded condition.

     I'm also planning to build a junk rigged sailing dinghy.... later, and am currently working on a 15' trimaran built from a fiberglass canoe and fabric covered amas  for use on local lakes... weekending...side decks will make it useable for camping out. I hope to play with Paul McKay's Aerojunk design, as I like the potential to achieve variable camber from  flat sail, and building batten cages is more up my alley than lofting a sail....I have bigger ideas I'm pursuing, but starting small is usually a good idea in my experience.

                                                      H.W.

Great thread! I'm about to do the same thing Nicholass. I have a nice little dingy as a tender we could row, sail or power from our larger vessel i'm preparing to Junk rig over the next year or so. Thinking a quicky junk rig on the tender will be invaluable for learning the way of the junk rig under way. 

I like how you, Martin, talk about doing it and figuring it out as you go. I'm more that kinda guy, although I had my larger vessel's JR designed by Alan Boswell. I also like Martin that you used a windsurfer mast! There are loads of masts sitting around the boat yard where I'm based, so might be able to procure one cheaply.

My dingy is also an unknown make, from Donegal, Ireland not far from me. They were built to have a small sailing rig if requested, so hopefully will be ideal.

My calculations for my project dinghy (a 14' Wanderer; approx 120kg) indicate that the biggest righting moment is the crew hiking out. I understand that the Finn dinghy is designed for large men who will be hiking a long way out in windy conditions.

From the pictures, your dinghy doesn't seem to have side decks so I assume you are not planning on hiking out as part of normal sailing? Thus you won't break the mast unless you plan on sailing your dinghy in windy conditions with a couple of large crew hiked out.

I found the class rules on the Finn dinghy here: http://www.sailing.org/tools/documents/FINNCR110618-[24058].pdf. This gives the max section as 60mm side-to-side and 100mm fore-and-aft. This is big enough given its design load.

A Finn mast looks ideal for my Wanderer; however getting hold of one at a cheap price doesn't appear to be very easy in the UK. If you can get hold of one I suggest you try it and report back :-)

I do have some notes on my design process for my Wanderer mast on my blog. There are some tables on Aluminium tube strengths you might find useful. TBH mast material selection seems to be mostly a question of "what can you get hold of cheaply where you live?".

It probably depends on how you intend to use your boat. My dinghy mast is extremely flexible (it is an aluminium windsurf mast in a heavyweight 12' GRP hull) but this works fine. I'm not looking to go fast and I'd rather have a forgiving response to gusts.

Do you know the section of the proposed mast at the partners?