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

Well your form of grammer Hoyte was in the imperitive. that to me is an instruction, a command or an order.

Now as to civility, I don't see why asking questions - albeit inconvenient ones is incivil. And I don't see how attacking someone personally is civil. Nor do I see how defending such an attack is civil.

So I'm not sure how anything you posted is related to civility. I don't see how you seeming to feel the need to protect an adult like Doug is "civil" either

Again, I've asked the moderator to delete or move this whole subthread I think that speaks to my desire to maintain civility.

 

BB,

You question Doug's math, and then provide the discussion above.

I believe the above was in reference to Doug's:

Single handed MPX-
a. crew 175 @ 11'= 1925ft.lb
b. boat 400lb @ 8'= 3200ft.lb
Subtotal = 5125ft.lb (almost equal to Flying Phatom with one crew!)
c. Downforce= 440.6lb@ 8'(from center of lift of lee foil)= 3524.8ft.lb
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Doug is clearly stating that he is getting most RM from weight over specified distances. For max RM from weight alone the main foil load is 0 lbs and the rudder lift is 0 lbs. For this condition the ama foil is loaded to boat (400 lbs) + crew (he used 175 lbs to show what is available even with a smaller guy, but for this boat, your 200 lbs might be better). He then goes on add in 440.6 lbs of main foil downforce. With this addition, ama foil lift + rudder foil lift (rudder can be plus, minus or nothing) are only boat + crew + 440 lbs or say 1040 lbs.

Your statement "lifting 6200 Ft lbs" and "your main foil has to generate almost three tons of vertical lift" are mixing force (lifting) and torque (6200 ft-lbs).

Although Doug may fudge numbers (like many of us, he does seem to have rose tinted lenses at times), I did not see any basic method errors in his RM calcs. I can not say the same of your statements.

 

Great back on track. Torque is angular force.

My look at the RM calcs was intended to delve into an aspect I've not seen analyzed - namely how much lift the main foil has to generate in the light air conditions that Doug is looking for it to lift and fly the main hull.

This is an area where a scale model is something you cannot extrapolate from because the scale factors on the materials are not linear, while the force scaling is linear (well volumetrically it wouldn't be, but Doug says that his current model is scaled at a weight level to match the full scale model).

so while its not hard to build a scaled down foil that is strong enough to generate 54# of lift, building one that can counteract the full RM of the hull and crew at full scale is a different matter

One of the common failures of moth foils is in that T joint and they are more lightly loaded than this foil will be. And High On Carbon in an interview about the C class V foils (also more lightly loaded) talked about having to go to solid carbon and in some cases milled titanium to carry those loads

 

Actually...
(1) torque is a moment, not any kind of force
(2) angular force, a term associated with panetary motion, is a poor synonym for centripetal force and doesn't seem to fit in the discussion

If you define your own terms it make it very difficult to understand you, try Google once in a while or ask here for help maybe you'll find someone that knows and is willing to help you.

 

I was being sloppy - my bad. I should have used "force couple" and I got sloppy and used the colloquial notion of "torqueing" a structure.

Torque is the moment of the force couple. and in this case we have a fairly large force couple.

that said I was thinking about the maths and realized I had made an error. Though the analysis gets a lot more complicated because we have potentially varying axis off rotation:

While the leeward ama is in the water (regardless of how much lift the foil is generating - the rotation of the structure will be around the Ama and the force-couple distances need to be calculated from there

But if the leeward hull lifts off and foils, its possible that the aka becomes the axis of rotation of the two amas - and its very hard to tell what's going to happen because of the dynamics of the center hull.

So the safe thing from a design perspective is to calculate worst case loads for both configurations and take the max of the two for your design loads.

 

MPX Test Model

Glassed(not carbonated) the mast in way of the single tang for the shrouds and forestay. Wasn't going to do it but looked at it real carefully and decided that the wall thix is just two thin to not reinforce it.
Also considered a set of diamond spreaders but nixed that idea because the mast is so stiff.
Still--carbon tubes for luff wire, noggle plates, rail for noggle(and carbonation) vang, gaff and boom....

 

Except that since the leeward foil is lifting vertically with a lever arm of 11' (3.4m) you have a force couple essentially driving the weather and center hull into the water.

Since the leeward foil is supposed to be able to support 100% of the weight of the hull "at speed" and according to you Doug, that will be after takeoff when speed doubles, the lift generated at 1/2 speed is 1/4 the weight of the boat.

That works out to be roughly 150# but with a lever arm of 11'. So that's adding 1500# of rotational down force on your main hull

Its an error Doug to call something "designed" when you haven't actually run the full set of numbers. What you hope the configuration will do is very different than what the design numbers say.

 

Adding a lower modulus material only marginally increases strength Doug. Because the lower modulus material will give and the load will transfer to the higher modulus material. This is the problem with carbon rigging for example, you have to pre-load all the fibers uniformly and individually, otherwise the one most in tension in the matrix will take 80% of the load, fail - and transfer it to the next strand which will also fail and you get a creeping failure.

so you need to use a carbon reinforcement if you are worried about material failure

 

so Tom.151... what do you think of the word "carbonization"?

 

Hey Doug, how long till seeing it all in action?

 

MPX Test Model

No telling, Slavi. Best I can say is "when it's done". Lots going on in Real Life at the moment-slowing me down again.

 

Hmm how about another approach. How many man-hours of work left before she can be sailed?

 

BB ----You may as well ask "How long is a piece of string".

 

How long is the whole string?

 

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Hoyt will that be followed by an instruction, command or order ? Huh?

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Happy New year to you and Paddy!