Hi David,

I was feeling quite smug with myself at having excluded the mast in my MK III rig and felt that i would consequently have less error/  turbulence to mess with the flow, but of course in real life we still have to have masts - sadly, so yes to your suggestion i will experiment with a mast of similar scale held both above and below the battens at the  luffs as you suggest.

Weather forecasts tonight suggest the jet stream will be coming south over UK this weekend heralding the start of unsettled weather and strong winds.

It will be too soon for me to use, but good to know that it's coming. I have never looked forward to winter so much.

Ash

Cheers Arne, Ash

I made a  mistake in my MK II  Test Rig as  posted on Technical Forum - Illustrations, it won't work, got it wrong - sorry. 

But the good news is - I have now designed a MK III that will work ok and is capable of measuring LIFT and DRAG,  so in a moment i will describe it in more detail, but first i should briefly reply to Arne's post above (3104043) in which he ends with "What have i missed"?

"Nothing Arne", what you say is spot on.  Mark also makes a similar point re a  windsurfer. I agree a very good 'feel' can be achieved in flying the panels as you describe, and i can see how a video will be able to record the batten angles against the horizon. But i think the flow of tell- tales and the actual loads of drag and lift would not be easily remembered by me for accurate comparison over a period of several days.

Yes impressions could be gained, but i want to try to obtain something that is more accurate, less subjective and provides data that I can consider long after the test rig has bitten the dust.

I enjoy the process and will learn a lot even if is a total cock up, the materials are scrap or readily available. The  Junk rig is so user friendly and relatively easy to make as compared to a Bermudian sail so I feel it is worthwhile having a go.

Realistically - this is likely to be the last boat and sail I will construct, i want to know that within reason that it has been my best shot, not to be sitting in the cockpit thinking 'now if only i had done...x, y and z'!

How I hope to set up and use the MK III test rig.

1. With sail and battens pointing head to wind and spilling, DRAG will be generated, caused by friction. With no 'Horizontal Mast', as in the Mk I design to provide an anchor, the sail and battens will be pushed downwind, tugging and swaying whilst held up on their vertical rope supports. Water is then added to Bucket "D" (drag) to oppose the drag and start to settle things down.

2. Simultaenously gravity will be pulling the sail cloth and battens downwards so a little water added to Buckets "LA" (lift aft) and "LF" (lift Fwd) until they hold the rig level, so balancing out the force of Gravity.

3. The 3 buckets and their water contents will hopefully by now be holding the panel fairly steady, each will be weighed (without detaching them from their rope). These initial weights will provide a zero starting point ; and they will be deducted from any weights of water found during subsequent tests. That is to say: only the additional weights will be used as they represent the subsequent forces generated.

4. The interesting part can now begin as we 'sheet in' - by adding water to bucket "LA". The leech will be raised and wind deflected, applying a downward force to the sail and battens. This downward force is LIFT.
We will also need to add water to bucket "LF" to maintain our required Sheeting Angle, the weights at "LF" and "LA" reflect the total LIFT generated and is being delivered via the Luff and Leech ropes.
As we are now deflecting the wind, a greater DRAG will be created - consequently more water will be added to bucket "D" until it stops the rig being dragged downwind. The stabilized sail panel can now 'sail' quietly, hopefully generating measurable LIFT and DRAG, corroborated by tell-tales which will indicate the moments when : the starved, attached and stalled air flows.
These comparisons will take place at varying sheeting angles from horizontal up to about 30 degrees or more until DRAG  outweighs LIFT.

5. I hope to be able to mount a total of 3 panels at a time, side by side, to fly in the same wind conditions and record their data at varying sheeting angles. There will be a total of 4 Test Panels: Flat, Arne's Cambered Panel ARNE'S, Slieve's Split Junk Slieve's and David's Swing Wing with a hinged batten.David's 

6. I aim to be able to obtain a LIFT vs DRAG Ratio of each panel's performance for comparison and to be able to make changes to panels in order to find the optimum shape for each one. Trying out different ideas - maybe varying the amount of camber, the position of that camber, the entry angle, the size of a slot, or the sheeting angle of a jiblet. I will also watch the effect of clipping 2 meter long x 30mm wide pieces of ply vertically to the battens to see if they limit the escape of pressure from the high to low pressure sides and what effect they cause. No doubt anomilies will occur and further tests may need to be carried out for clarification.

Lastly I just want to comment that my quest is to enable me to decide which design of sail to make, and is peculiar to me, 'very peculiar' I know! 

In no way am I wishing to set up competition or to judge a winner. We all have different requirements so my eventual selection may not be yours. I think it's very much 'Horses for Courses'.

I do appreciate all the fantastic info available on JRA and the unselfish and honest help I have had from many of you since posting this subject a few days ago.
In particular to David Tyler, Arne Kverneland and Slieve McGalliard, their encouragement and advice has prompted me to rethink this all through again and has, I hope, resulted in the my MK III being a more realistic test rig.

I am really enjoying the process in any event, so fingers crossed that half reasonable results can be obtained.

I have managed on this occasion to post an illustration of the MKIII Rig in Technical Forum Illustrations and also hopefully as a link Here

Thanks again, Ash

Sketches of Ash's proposed test rigs are now on the Technical Forum illustrations page. 

Encouraged by Roy to air this thought:

Whenever I've daydreamed about this sort of thing, I've envisaged a Tug Of War trial.

Picture if you will a kind of land-going proa. A triangular frame with a bicycle wheel and a mast at each of the leeside corners, and some ballast and a further bicycle wheel at the windward corner. Tether it so that it doesn't travel but you can see which way it wants to travel. Rig two test pieces, one  on each mast, opposing each other. By adjusting their sheets, get each one pulling at its best, and may the best rig win. Conduct a series of round-robin or knockout trials.

This compares the lift, but not the drag of two test pieces. You would have to add a load measuring device somehow, to measure the drag.