MPX-11 Very Small High Power Trimaran

MPX-12-----design modification:ama + SA

My friend the windsurfer designer helped do an analysis of the planing area required for each ama again today. It appears that 2 sq.ft. is not going to be enough to support the full load at 15 knots boat speed. We have tentatively decided to double the area and increase the wetted aspect ratio to 3/1 as compared to the 1/1(approxmately) it is now. That means the planing surface at 15 knots will tentatively be three times as wide as it is long(F&A). The amas on the model may be re-shaped to test this geometry. The amas,should the test boat be built, will be designed to allow easy addition or subtraction of area as mentioned before during testing. In addition, there will be a change in SA of approx. 16 sq' additional to maintain the SA/ws numbers in comparison to a Moth. There will be very little increase in weight,if any. As before the numbers reflect a crew weight of 240lb which is likely to be at least 20lb less in reality-as a maximum.
I will update the spec sheet to version 5 when I can.


See page 13

 

MPX-12-- Version 5 Specifications

Version 5 and updates*-start 11/8/10

Note: Moved to page 13. Thanks

 

A DOUBLING of the planing surface? Really? After all these sessions with the running of numbers on every tiny little element of the boat, followed by the pasting of another redundant set of figures, and you now need to DOUBLE the surface to get it in the ballpark? Based on your previously bullet-proof assumptions what sort of gross miscalculation was made to yield this kind of error?

 

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ostlind: every element of this design is reveiwed as often as possible and where I/we see a problem we act to correct it. My friend had not had enough time to look at this closely before the last two days and I appreciate his help.
Until the design is complete everything is open to reveiw and even then changes as a result of testing will surely happen. I'm not afraid of changes, improvements, mistakes etc. since I hope I have a system that will allow/catch each and every one.
Everything will be looked at again and again as the process goes forward. This is a unique design which has never been done before at this size and our review process will help to get the basics as close as possible prior to on the water testing, should the boat be built.
Its a tribute to my good friend that he took the time to look at this carefully and then be able to explain what he thought was wrong and right and why,in detail. I'm very gratefull!

 

I don't really know how you view this function, but it seems to me, after reading all the lengthy posts that have been put-up here, that the planing capability of the amas is critical to overall boat performance. The process of leaving such an integral component of the design to this late in the game (this will be the 170th post since July) calls into question each and every one of the estimations and calculations derived so far.

Making a mistake that requires a doubling of the ama size to correct, is of the gross error variety and not some some minor correction that fits within a typical prototype process.

Some time back, Munter suggested that your weight calcs, among several other fundamental component elements of the design process, were likely flawed and that base design elements such as weight, on a weight sensitive boat, would be big trouble. You argued with him and suggested that he didn't know of what he spoke. You chose, instead, to post another long list of numbers with colorful additions and big type face insertions as the answer to a truly important observation by a trained engineer.

Now, we arrive at this very uncomfortable place where it is revealed that the planing ama is so poorly conceived that it creates a condition in which the boat would never work as claimed. This is a Come to Jesus moment that will allow you to scrap the whole thing, rethink the boat's purpose and get rid of all the extraneous technology so that the design can breath.

 

Angle of heel is relative to the surface of the water - and the surface of the water isn't flat - it is moving all the time. Depending on where you are in the wave train, you can have changes of 20 degrees or more in heel - with the wand system working perfectly. This is the issue I was pointing out. Gravity works relative to the earth, not the surface of the water, therefore heel changes due to positioning on a wave DO affect how the benches work. It is perfectly possible for the boat to be operating exactly as designed using wands and STILL have a sharp downhill heel affecting the benches. Draw a wave train and then draw a boat at different positions on it - you'll quickly see what I mean.

My comments about the Trapwing technology were not in jest - combining the two ideas could be far more revolutionary than using the two benches - and less complex as well as easier on the operator. The simple movement of the Trapwing would provide a more adaptable interconnection to the canting T-foil than two independent benches. And the positive, self locking positioning of the Trapwing makes the location of the crew and canting T-foil much more predictable.

Your attempts at provocation by calling me ignorant and silly are direct evidence of your failing to open your mind to new ideas. I'm not interested in conflict with you - but I am interested in the performance potential of this multi-hull foiler.

I don't understand why you are so paranoid and defensive that you could not see my contribution as worth consideration - it is just a new combination of two of YOUR ideas - and it might be a way to get two of your revolutionary concepts built in one go and on the water.

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CutOnce

 

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???: you don't understand one or both concepts-there is absolutely NOTHING that one would add to the other. Suggesting such a thing is evidence-on its face- that you have no clue about either one of the two concepts.

 

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Chris #2: that is just plain BS- the only thing that changes is the size of the planing surface-the ama "size" remains 95% the same. You must not understand the design process at all. The constant review of all design decisions is critical as is the utilization of help from people with greater expertise in certain areas than I have. This process will continue and, as is obvious, it works. Further, I have no qualms about presenting these considerations in the same way as I have presented every design discussion throughout the very public design of the MPX-11 and 12.
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You characterize this as late in the game-what nonsense! You could not possibly know what stage of "the game" this is!! I don't even know! The design is not complete and no decision to build a prototype has been made.
The important thing about this design ,as mentioned in post 166, is that this boat-with the modifications- exceeds the comparative statistics of the Moth and is therefore in exactly the configuration it needs to be to meet my design goals.

 

Mr. Lord:

My name is NOT Chris. Perhaps I don't understand your concepts, but this is no reason to get personal about this. I've tried very hard to be friendly and non-judgmental, but you persist in attacking.

I like the idea of the Trapwing, and I like the idea of this multihull foiler - I do think the dual sliding bench concept needs a little more refinement to be able to control the canting, gybing T-foil as well as provide a reliable place for the helmsman to augment righting moment. I thought people post on these forums looking for feedback - so don't get personal and mad when I do just that.

Are you the moderator of this forum? I read the posting rules quite clearly, and there was nothing indicating a person who starts a thread gets to decide who can post and what they can say (as long as it is polite and to the point). I think multihull foilers are a more interesting platform than monohulls - they bring the foiling experience to a lot more people than trying to balance a 10" wide Moth hull - so I want to follow the ideas here.

I think you are getting closer to the people's foiler every day by looking at multihull foiling platforms. Keep it up!

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CutOnce

 

Parsing words, ignoring reality, tossing out a few more smokescreens; amusing to be sure, but it won't help this boat become a working example.

Unless you plan to make this DOUBLED planing surface from neutrally buoyant, wafer thin, non-structural material, it will increase the bouyancy of the ama, add weight, change the dynamics of the boat, increase wind resistance and alter all the other calculations accordingly.

When you say, "You could not possibly know what stage of "the game" this is!! I don't even know!" , you make a statement that I truly do believe. You don't even know.

What I do not know, is that you seem to enjoy attacking good people for asking questions and making reasoned suggestions. This has been driven even further home with this latest revelation about the crude ama calculations that were made. Rather than listen to reason, you have gone off the ranch in a series of personal attacks to blunt the criticism.

When you say, "is therefore in exactly the configuration it needs to be to meet my design goals." I can only wonder. You have been implying this very thing from the outset, yet more complexity is getting added with regularity. That's not an "exact configuration". You blew the planing surface calculation by an enormous margin and that is not an "exact configuration". It is also a dynamic adjustment to the design which will force changes in several other areas of the structure in order to accept the added loads being generated. That is also not an "exact configuration".

 

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Mr. Once, as I said in my PM anonymous posters who post about technical stuff without sharing their name or any of their own work are viewed with reservations on this forum-at least by me. I apologise if you turn out not to be the evil one.
However, describing me as "attacking" when I post my reaction to your suggestion of combining the Trapwing with the MPX-12 is false. I simply pointed out the FACT that to even make such a suggestion shows that you have not read the material on either concept enough to understand it. That is not attacking or being defensive-it is merely pointing out the reality of such an unfounded suggestion. The two concepts have NOTHING in common,zero, nada. If I am blunt it is because it is annoying to be confronted with this kind of poorly researched "suggestion" when, if you had read the material, you would know better. In light of all the work and detail I have posted on both subjects I think the least I could expect is that someone making a suggestion has read the material and understood it. I think I am entitled to assume that if someone didn't understand either system that they would ask a question.
The last few times you have asked questions I have taken the time to answer point for point. But then there is your post 155 and the Bradfield post
which cross the line and raise many questions about your, shall we say, "sincerity".
Again, if you are just the typical anonymous poster and not something else I apologize for getting your name wrong.

 

Apology accepted. Perhaps I am cautious, but I do not blindly trust the Internet, website owners and do not want every advertiser, stalker and foreign government to be able to associate my name with an IP address, therefore I consciously choose NOT to broadcast my name to the world. I value my identity far too much to broadcast it on a public, non-SSL insecure Internet forum. If that disqualifies me from commenting here, so be it.

I'm not a professional naval designer or builder - I'm just a guy who has built a few boats in my garage and I'm looking at this market as a possible activity for later in life.

I've participated in design work, and I would say I'm very computer literate, so working with CAD tools and the science behind this isn't frightening at all. I've been sailing performance boats for over thirty years, so my opinions are based on experience.

My comments regarding Dr. Bradfield were due to the very clear website representation he gave regarding his firm's design of the F3 (designs from 56" foiler ...) - it was clear from their website they gave the appearance of having been the designer. Perhaps it is worth having them clear this up on their website so no one else reaches the conclusion I did. His web site does not acknowledge you as the designer of the F3 at all.

Regarding post 155 - you must admit there is a very large gap between your time spent discussing concepts, time in the shop and proving them on the water. By what reading I've done it appears you do not actively sail at all, and your last build was in the 90's - but there is no evidence you actually enjoyed the boat "aeroSKIFF" enough to sail it more than a couple times before destroying it. If I had put that much money and time into a build, it would have got a lot more love than that. My last build is visible in videos on Youtube, and it was displayed in Woodenboat magazine as well. I just can't get my head around how a foiling enthusiast like you could kill their own design that quickly.

Your work is fascinating and brave in the sense that you do not appear to bother with small, incremental steps - you go "all-in" on every hand. From a poker perspective you are setting up for big failures - or - a huge win of an epic pot.

There is a very clear bias you present for the things you believe in, and perhaps too quickly dismissing all arguments against - I don't get a feeling of any objectivity from your threads except when you appear to highly respect the person posting.

To be honest, there doesn't appear to be a huge amount of real world activity here at boatdesign.net in the areas I'm interested in - not enough actual building, build blogging and actual on-the-water design reviews.

Thanks again for rescinding your labeling me as Chris.

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CutOnce

 

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1) You apparently missed the fact that my microSAIL! website was linked on the same page -and when it was up told the story as it happened and just the way I told you. And the rest of the story does not seem to have gotten thru,either.
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2) You seem to draw conclusions frequently without all the facts and with no attempt, apparently to ascertain the facts. In response to one of your questions I' m sure I linked to the Trapwing thread and that tells the whole story of the aeroskiff which will serve as the Trapwing prototype. You missed that thread?
In addition, I have sailed well over a hundred hours over the last few years on a Rave and yet you feel comfortable saying "you do not actively sail at all"??! And thats just one boat out of several over the last 5 years, that by the way, includes the aeroSKIFF(becoming the Trapwing proto).
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You seem comfortable jumping to conclusions or actually inventing "facts" if you can't find any info. Thats a shame and likely to be an unproductive course of action on a forum like this.

 

As you well know, I'm relatively new here. I can't review a website that was taken down by you two years ago (I think that's what you said). I tried following the link from Hydrosail's website and your site was gone. So I did try to verify things, and by your removal of the site was unable.

Mr. Lord:

I don't draw conclusions - read through what I've said and it is carefully written to qualify opinions as different from your own public statements. "It appears you do not actively sail" was said instead of "you do not actively sail". I don't know if you do or not, but you certainly do not ever talk about having a great day on the water sailing last weekend. You never mention boat ownership, club membership, races participate in, regattas traveled to, recent swims from capsize, beers consumed during beer can races, club bars in which lies were told etc.

Reading through your past posts about your Rave experience, there appears to be a lot of variance on how much actual time, where and when you sailed. I don't think many of the posts match at all. There are a wide variety of posts and claims made about your aeroSKIFF sailing as well. There just isn't a lot of consistency and historical continuity regarding these topics. It is as if the events as they occurred get dimmed over time and misremembered.

All this does not matter in the slightest anyway. I'm more than willing to accept all the points you stipulate and start from a fresh page.

I can't wait to see the new Trapwing prototype hit the water!

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CutOnce

 

MPX-12--FLASH TRItm featuring the "Devils Tail(tm)" ama*


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The Theory behind the MPX-12(based on proven performance) :
1) The hydrofoils' principal job is pitch control. Pitch control is critical as is a well controlled heel angle for the planing ama to be effective and at the same time to be low to no drag in light air and minimal drag when planing at the most efficient planing angle which is 100% maintained by the hydrofoils(and adjustable as well).
2) The foils are designed to lift the boat off between 6 and 8 knots of boat speed-about 5 knots of wind. With the 16.5' beam without the foils the thing wouldn't fly the main hull until over 15 knots of wind or so. Most people sail in 10 or less so it is essential to have the boat perform exceedingly well in those conditions. In up to 10 knots of wind there is no need for the amas to touch the water-after that the leeward ama gradually loads up until it is carrying most of the weight. As that is happening the foils unload reducing their drag considerably. The reserve "power" of the foils is always there for pitch control. This allows the wetted surface of the main hull to disappear early and the drag of the foils to drastically diminish as speed picks up. The beam is necessary to generate the tremendous righting moment required to sail fast in a breeze.
3) A side benefit of a wand controlled main foil is that not only will it lift vertically but once the boat starts to heel beyond the "set" altitude(heel angle of 10 degrees) the wand causes the flap on the main foil to go up generating downforce(extra RM) as necessary. This allows a very wide crew range since a 120lb kid would be able to sail with the same maximum wind pressure as the heavy crew because of the extra RM from the downforce of the foil.
Response of the altitude control system is virtually instantaneous. Some of the early posts in this thread discuss other boats that use an altitude control system for VERTICAL Lift and DOWNFORCE-like the Rave and Hobie Trifoiler.
4) This system is critical for the performance of the boat-without it in light air or heavy air it would be a dog. All of it works together and is inter-related-without one part of the system the whole thing is useless.

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