Greetings folks, from the wilds of Northern California USA.
I'm new here and very excited to read all the good information I've already seen. I am actualizing my dream to build a land sailer from recycled materials. (very California. The hull is a very aerodynamically slippery river kayak, shortened and reinforced. The front wheel and forks are from a 50 cc pocket bike. There is a very sexy looking 4" disc brake which I fancy because in the hull I can't brake with me feet when returning to camp. Rear wheels are Dunlop "mags" and tires at 3.50 x 8; beach wheels from a Zodiac inflatable. The rear axles are made from laminated downhill racing skis. The tips are removed and the tails cut off to provide two four foot units which are springy yet quite stable and only slightly heavier than optimum.
I"ll power the boat with a wind surf rig working against a "hound post", guyed three ways.

So, questions.

The deeply reclining position and requirement to cantilever the axles creates a space conflict. I'm considering angling the axles FORWARD, the opposite of the arrangement of a Fed 5 or Pac. Magic. The axles would mount under my head rest, and extend forward. Are there any physical (as in physics) demons that immediately come to the minds of the experts? Where does the real benefit come from angling the wheels like on a PM?

I have the choice to mimic the physical dimensions of either a Manta twin, or a Pac. Magic. Can anyone share anything about the proper location of the mast and support post? This is the basic configuration of an Ice Flyer except in my case the pilot is in the rear.

I hope this gets something started. I'll check back regularly to dialog. Thanks in advance. I'm excited that I have the opportunity for technical advice from the land of OZ! Way cool!

Graybeard...(Perry)

Welcome Perry, ditto on what Joe said.

Also under news/articles Promogirl has loaded the plans for the pacific magic. Even though you're not building one you can still get the measurments from it about where the mast is positioned etc.

Looking forward to seeing pics of your project progress!!

Howdy Paul:

Thanks for your response. To answer your first question, I tip the scales at 15 stone, or 95.2543977 kilos. (210 lbs.) That will change next time I pee!

I'm not too concerned about racing classes. Where I sail, the most boats I've ever seen at one time was about nine. I want to go relatively fast, but light air sailing is even more inportant in that we travel seven hours to the playa, and it is too much of an investment to sit around in moderate wind waiting for it to get up to 12-15 mph. (19.3121-24.1402 kph) Where the PM's and Manta's get started.

I'm curious to know how many skis were laminated to form the axle which you thought would not be effective. I have found that to be similar to the flex in the Manta twin axle, three skis are required.

Relative to the question about angling the axles forward or rearward and the toe-in/out question: Is there a component of axle flex that contributes to instability in the forward design when bicycling? I can't see how rotating either of these tricycle designs on their long axis would create toe-in/out.

My main interest in angling the axles forward is to get my body weight over the contact point of the rear wheels to avoid the constant "crabbing" and regular "twitchiness" that I get with the Manta in the 80 kph range.

I'm going to attempt to add a couple of images. The Manta Twinjammer has been modified to change the canvas twin seat to a rotomolded bucket, it is otherwise box stock. I now call it a "Twingle". It was moving in the high 70 kph range in this photo.

If you go to Google Earth and navigate to 42 degrees 30' 25.61" N and 118 degrees 31' 48.66 W you will have arrived at our normal campsite. You can then scan around for views of the playa, the hot springs etc.

Here is a little slide show made with a free site I found: http://www.photoshow.com/watch/WG5Nc6ii




Enough for now. Hey...Good on 'ya for a GREAT competition in Olympic swimming!

Perry

since you weigh in the plus 85kg range I would have the axles at 90degrees and move your body weight forward of the rear axle. Now I realize that your going to laminate the skis i say do it , photograph it an let us know how it goes. .I would build the chassis to the lefroy mini dimensions and wack a 5-5.5m sail on in the light wind dropping to a 4m when the wind gets up. most importantly keep it light. Throw away the brakes and learn to stop without them. Build your mini as a simple torsional frame ,leaving off all those extra bars. the skis are going to take all the shock loads and allow you to carry a bigger rig.
cheers paul

Cisco: Those speeds were achieved in in winds of 25-30 mph. Pretty near the safe limit for the five meter sail. Personally I've only been clocked at 50 mph by a pick up truck running along side. The manufacturer claims the Manta twin is capable of 70 mph. Here's the shot from the pick up.

cisco said...

Please don't tell us that. It will start a designing and building frenzy of ultra light aircraft convertible into land yachts.

Hmmm, now there's a thought, although surely it would be a glider!

www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=37931
this topic was on the conversion of a glass mast( no carbon ) to mini yacht use.
the important bit for you is that we simply put a piece of wood up the lowest section at the base . It is important to have a short mast step if building the lefroy minis as a torsional frame. this allows the mast to bend and take away a focal point for stresses. the mast tube on the minis is only 250mm.
On the PROMO cl 5 yachts the mast step is also 250mm and they are carrying 5.5m of sail AND a heavy stiff Alloy mast.
. It is important t set up your sheetingso that the boom IS NOT pushing into the mast when loaded up, This was always a problem with the manta type yachts

here is some photos of the boom set up and sheeting I use on the minis sail is 4m but could be 5

heres the front of the boom showing the hieght of the mast step.

Hey Landy...

What about the issue of the tapering mast in a cylindrical step? Isn't there slop at the top, or does this slight movement just play into the overall sail design as it "looks like" the angle of the mast when board sailing?

More later. (You can count on it) Perry