runin2dson said...
I do like the simplicity of the Manta design and will draw up some new plans based on that. It should save on weight and be a bit cheaper to build as well (though I do like the solid structure of the sirocco type frame)

The Manta setup is actually quite complex with lots of nuts, Hi tensile bolts, washers and needs plastic supports to stop the tube crushing.

Here is my updated twin design - Anyone have new concerns on the design?

- Saves on weight, takes out a couple bends
- Moved mast step forward
- designed for integrated seat
- breaks into pieces for easy transport

dont go with the purple option , failed in 1984
If you are sticking to that style of front fork i would stand it up a bit, the 30degree steering gizmo is talking about is completely different again.
by standing up the steering it will not tend to become stiff and unresponsive when a big load ( like 2 adults under sail) goes on it. If possible move the point at which you bend the front pipe back towards the base of the mast, this will reduce the leverage the front wheel puts on the frame.
( maybe a photo of gizmos Ancient class5 would demontrate this)

Ok, couple thoughts for redesign...

- Moving the bend in the front pipe towards the mast is a great idea! Not sure why the front mast support is bad though... the front of the frame needs more flexibility for rough conditions = a better, smoother ride?

- I like having the bends in the pipe at the seat because then the seat is much easier to make and I can attach the rear axle to the frame easier (90 deg joint). I will probably cut and weld those "bends".

- According to the picture below and how I have designed the front steering fork, I have a Head angle of 60 deg which I thought gave me a "rake angle" of 30 deg. With a small offset/rake on the fork, this gives me around a 2 inch trail.

good?

OK! So I may as well put in my Two Bobs Worth (20cents).
Why are you insisting on such a complicated Frame Structure?? I can see no reason why a Simple "T" Frame unit can't be modified to twin seat.. Constructed with or with out Shallow "V" Axle.. Talk to Landyacht (Paul), he is a man with a lot of experience. Constructed on a Spine "T" from a Drill Tube or heavy 3" Pipe it will be strong and resist twisting and get rid of all that superfluous Super Structure making it easier to enter for both Driver and Passenger and should you drop it on it's side there will be less for Bodies to bounce off of.
As for Seat construction, over glassing Ply with Fiber Glass or Carbon Fiber makes for a strong light seat..
Steering; Try the 30deg from horizontal Flop Over type steering you will be surprised at how effective it is. Look at the LLF Mini for inspiration I used a hybrid using a bicycle Steering Head modified to give the inside neck strength and Built a heavier Front Fork..
Think about it carefully

Ron
PS; Stick with the KISS Principle. The Simpler the less can go wrong. You should also keep Murphy's Law in mind as well

I get your drift Paul.. I was thinking Glassed Wood and Flop over steering like the Mini or Pac' mag'. Horses for Courses I guess.
Ron