High Performance MPX Foil/Self-righting Trimaran-The Test Model

From the looks of it Doug it seems that

Is the only change from the last update. Is that correct?

 

MPX Test Model

MPX ama foil compared to Flying Phantom main foil: (not an accurate comparison because the Flying Phantom foil is not fully deployed and is at zero degrees whereas the MPX foil is at about 10 degrees-interesting nonetheless)
Picture on right shows the "L" portion of the TNZ foil with the slight curve similar to the "L" portion of the MPX foil(far left) :

 

I came up with this device accidently: it changes the tension on the gaff control line as a function of the rotation of the gaff and as a function of the offset the point of attachment of the gaff control line is from the "no-tension" axis of the gaff. The gaff control line is adjusted relative to the fore and aft position of the control device tip. So the effect is that the rotation of the gaff relative to the fore and aft centerline of the mast can be controlled to this extent: the "springiness" of the upper sail gust response is affected by the fore and aft position of the tip of the device. I built a small test model that convinced me of the viability of the idea so it will be included on the Test Model.
Note- the control device does not change the angle of the gaff when the tip moves fore and aft: the control line is eased(or tightened) to keep the gaff in it's proper position.
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UPDATE- Made the device today from carbon dragon plate with a little uni added. Came up with the attachment system as well.(See upper right illustration and lower left picture)

Pictures-L to R: Top Left=original concept drawing,12/17/13, Top Center= final design,12/18/13, Top Right=Mounting System,12/19/13-Note: pivot and retaining fasteners are not shown, Bottom Left=Gaff Control Device finished except for trimming edges and drilling three holes. Using Dragon Plate allows a mold finish on a one off part,using carbon keeps the part light and very strong------

Click and expand for best view:

 

So that's more weight aloft... thereby reducing RM even more. correct? So is the reduced RM made up for by the gust response?

 

MPX Test Model

I made the Control Device mount today and installed it and the mast extention today as well. Cosmetics required on both ends for the reinforcing at the top of the mast(for the Control Device retaining and pivot pins) and for the extention which is made up of 4 perfectly sized carbon tubes epoxied in place. Added 12.625" to the mast for an overall length of 8.56'.( equivalent to just under 31' on the full size boat)
Next job: cosmetics and installing the micro carbon tubes that support the luff wire of the main,the gaff "gooseneck"/attachment point, installing the Gaff Control Device, the noggle/gooseneck and "rail",the boom, vang and main. Getting closer every day.

 

given the spec similarities and the fact that he phantom require very active crew work to fly stably, I suspect this bodes poorly for the bucket seat idea

 

MPX Test Model

Two out of three of these pictures have a slight blur. My stablilized camera is
not stabilizing or I shook too much. At any rate this gives and idea of the actual movement of the Gaff Control device installed in the mast. This is merely an illustration of the total range of movement, not necessarily the range that will eventually be found to be effective:


pictures-left is the neutral position-no change in the gaff control line tension as the gaff rotates, the other two pictures represent increasing tension with rotation-

 

Why not just use batten tensioners and full length battens in the top of the sail? Skiffs manage to control depth of draft that way very effectively and with less weight aloft and with less aero drag than a gaff generates.

 

MPX Test Model

I got the mast mods complete today. Next is installing the gaff goosneck, luff wire retaining tubes, single mast tang, noggle/gooseneck rail, noggle + main boom, vang and mast rotation pin.

click-

 

MPX Test Model-The Curved Piece

I've had some questions about the "curved piece"-see pictures below.
This piece allows high dihedral angle to the cross beams while placing the ama hull in exactly the right place*. The shape allows the effective buoyancy
of the ama + curved piece to be over double that of the ama hull alone which helps to prevent a knockdown/capsize. Viewed from forward the curved piece
buoyancy is vertically higher than the ama which increases stability further in the worst case situation.
* this means that the ama is quite far forward- in its ideal position for this design to keep dynamic lift from the planing ama forward as well as allowing
placement of the ama foil in the best position relative to the CG of the boat. Note that on the MPX Test model the planing ama is designed for intermittent water contact after take off. On the smaller version the planing ama is designed to lift about 50% of the boat weight with a small t-foil providing foil assist.

Pictures,L to R-1&2 are the curved piece for the MPX Test Model, 3&4 are of the MPX 12** a concept model of a smaller version of the curved piece+ planing ama. Also see the planing ama used on Hydroptere(picture 5 below) and hydroptere.ch(posts below)-these are two of the fastest multihulls on the planet. Hydroptere uses hers after takeoff for intermittent contact only-which is exactly what the MPX Test model will do.
**See posts 740 and 750 for more pictures and technical detail on the MPX 12 and the planing ama
click-

 

None of that makes sense Doug. You could have gone with a square angled joint as well as a more extended ama - one that meets the empirically derived 22:1 aspect ratio and still have gotten all the same benefits. Nor is it clear in any logical sense whatsoever why the ama is this odd dart shape when the experiments done by the Gougeon bros showed a long time ago that a slender 22:1 driven shape is faster than a planning shape for sailboats once you get over about 15knots of relative wind speed at full scale.

so its a bit confusing as to why you have abandoned this principle.

furthermore by the time that part of the ama is in the water contributing to buoyancy, the CoMass is going to be well to leeward of it (given the mast and spars are a nontrivial part of the weight and will have a long lever arm while the aka will be largely overhead contributing almost no RM.

So the whole explanation is just confusing.

 

Merry Christmas.

 

Makes perfect sense to me, but then again I have no hidden agenda or Doug Lord obsession Keep up the good work Doug

 

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Merry Christmas and Happy New Year to you too! Enjoying the funnies?!

 

MPX Test Model

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Thanks, my friend! It oughta make sense since planing amas are used on two of the fastest multihulls anywhere.....