High Power Very Small Tri(s)-10'-14'-why not?

=================
Sure you do. About the sail weight: I have a very sophisticated set of sails here-a main and jib of 182 sq.ft..
Expensive sails with ultralight foam carbon battens-the ones on the boat in my avatar. Together they weigh 14 lbs;divide that by 182 and you have
.07692. Multiply that by 130(sail area of MPX-11) and you get:9.9999 or gee,guess what: 10lbs!

 

------------------------------
Thats ridiculous since I have shown precise detail including a laminate and hull weight based on the actual areas with a laminate I have used before on a 16 footer!(with a thinner foam core on this boat and without the mat used on the original each side of the foam) I have compared those weights with those of a Moth showing that the main hull is 1.3 times as heavy as a Moth with less total skin area. Same with the ama: almost three quarters the weight of a Moth and less than 50% of the skin area. That adds up to light weight strength.
--The mast I specified is 1.3 times as heavy as a Weta mast for virtually the same upwind sail area and the MPX-11 has a lower CE(center of effort).
Thats because of the high max pressure this boat can sail in and because the sail is a bit unique and requires a stiff mast.
--The cross beams are substantially bigger than the Weta cross beams even though the MPX-11 has only a little more than half the maximum design RM(righting moment) of the Weta-I want great stiffness here.
--The foil weights are from actual Moth foils+vertical fin that I have here and a Dotan rudder modified for a lifting hydrofoil.
The weight estimates for the folding system are just estimates based on an experimental design-they could change-as a matter of fact IF they change they are likely to get lighter.
---The boat uses a foil that pulls down at some times similar to the windward foil of a Rave hydrofoil(or any other foiler that uses a foil or foils to generate RM). As shown(and detailed) in the specifications post the maximum pressure this boat can sail in is 2lb per sq.ft.-11% higher than an F 18 cat. Like the Rave at a certain point sail area will have to be reduced to avoid structural damage. The Rave posted a warning in the cockpit to remind the "pilot" of this. This boat-if ever built- will be tested to find the exact apparent wind speed or boat speed that reefing should take place-but I can say it will be somewhere over 25 knots. This is a minor drawback to major
advantages provided by foil assist: (already detailed in the spec sheet on page 5)
1) early takeoff of the main hull
2) the ability to sail at maximum RM(righting moment) regardless of crew weight in the range of 120lb-to 243lb.,
3) the automatic control via the wand of the boats heel angle when flying the main hull.,
4) Drastically increased pitch resistance compared to a similar design w/o the foil.
===========
The so-called questions and doubt expressed here about my specifications are insincere, inaccurate, uninformed and designed to cast aspersions because of the agenda of two or three individuals. I have PROVED the accuracy of my specifications as best I can at this point in the development of the design.
The one thing that puts the lie to the so-called good faith "questions" that are asked(even though previously answered in detail ) is that I have repeatedly stressed that these are preliminary specifications and that there is a lot of built in leeway for increasing weight should that happen as the design progresses. This boat as shown here is based on a max crew weight of 243lb! How many other 11 footers are designed to sail at their best with that much weight aboard??! None,period. The weight of the boat could increase 50% and still allow a 180lb single crew or two 90lb kids to sail. This fact has been ignored by "munter" and "ostlind" repeatedly!
-----
"ostlind" uses the term "respectfully" above to describe how my "failings"(made up horsemanure) have been pointed out by himself and munter. What a joke: it doesn't take a rocket scientist to go back and read the disrespectful tone in many of their posts. munter even admitted that he had directed a condescending attitude my way. Even so, for a time, I still tried to answer his questions in detail-until ,that is, I realized the game he was playing. Answering these guys as if their questions and interest was legitimate and in good faith is a farce. I did this post to help any who are genuinely interested in learning more. I will not engage any further with "munter" or "ostlind" and allow this thread to become another s**t fight-not going to happen!
I look forward to any comments and questions from the readers of this forum minus two........

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In terms of the increasing use of lifting hydrofoils in multihull design-don't take my word for it-just read Martin Fischers interview
http://catsailingnews.blogspot.com/2010/05/cs-interview-martin-fischer.html

 

A typical Moth sail can weigh anywhere between 3 and 4 kilos, depending on fitment at the loft. That same Moth sail is 8 meters (86 sq. ft.) in area and weighs .09 pounds per square foot on average. Multiplying that .09 figure times 130 gives a sail weight of.... 12 lbs!!. Remarkable how that matches the figures given by the Italian guys and their rigs for 10' boats.

Now, if you are planning to slam an ultra exotic and ultra expensive rig on a 10 foot, untried boat, I'll just get out of your way and we'll all pull up comfy chairs and watch it happen.

So, that covers the post on sail weights. This last post, though. Whew!! There's just nothing to say about all that anger and the tone contained within the writing. You started sounding just like this last year when you got yourself banned from Sailing Anarchy's Forum.

You are being asked civil questions and you are responding in an uncivil manner. I guess the only thing left here, is for you to go build the boat and prove to us all that it actually works. I have my doubts for a number of reasons, but you seem to find value in the pursuit of the project, so get on out there and start building.

Good luck to you.

 

Hi Doug,
Your continued strenuous assertions of detailed proofs are nothing of the sort.

Re hull weight. You quote a panel weight and surface area, multiply the two and add a little for reinforcement and arrive at a mass figure. How have you calculated the hull surface areas? There isn't even a sketch on this thread and yet somehow you say you accurately know the area? If you have the details then why not share them? I could check them for you if you like.

Then there is the panel weight. You helpfully advise that you have used such a panel weight before (on a 16 footer). I presume this is the 16ft a-skiff? Your published weight for the a-skiff is 68 kg for hull only. Assuming the surface area is simply a double sided rectangle 4.8m x 0.91m, the approximate hull surface area is 8.7m2 - lets be generous and say 10m2. If you divide the mass of the hull by this surface area you end up with a panel weight of 6.8kg/m2 even though you say it was built using a specification of .47lb/sqft. (2.1kg/m2). Panel weights don't tell the whole story on boat mass. Your own past projects show that there is a world of difference between simple choosing a panel weight and calculating the hull mass. Based on your own craft's history it appears you should put a multiple of approximately 3 on the panel weights if you're going to use these to arrive at the actual finished hull weights. What are the resultant masses of the floats and main hull when this factor is applied? Why have you ignored the lessons from the a-skiff and yet quote it as a reference to substantiate your predicted mass?

I see you are now noting a maximum wind strength and claim that the maximum will be in excess of 25 kts and that structural failure will result beyond this. You also assert that this is a relatively minor problem compare with the benefits of the foils. How is structural failure a minor problem? What will happen when sailing in 20kts and a 25kt gust rolls through? It isn't possible to reef for each gust so what happens when a gust comes in and the sheet is cleated? Most boats capsize, you acknowledge that yours will break apart (but that the occupant will have a warning sticker). Hmm - how about making it stronger so that the owner gets a second chance? I'm not saying abandon the design - just make it realistic. Where did this 25kt figure come from anyway? How will the RM be magically limited to ensure that it isn't exceeded until 25kts windspeed? Will there be a load cell in the foil to trigger an alarm? I suspect you have made up this figure because it sounds good but you actually have no basis for it - there is certainly no basis presented in your previous posts (though I see you are editing them as we progress).

I also see your comments on the stiffness of the cross beams. You advise you have increased the diameter because you want them to be stiff. Have you any idea of the wall thickness? How is it that a Weta float and beams weighs 18kg and you only have an allowance of 5.5kg (float) and 3kg (beams) per side? Your beams are longer and support greater load (as your tri flies on one hull) and yet somehow you believe they will come in at less than half the weight of the Weta equivalent. Yes, I acknowledge the float is shorter but you must acknowledge that the beam length is greater and the load it supports is also more. Why did the Weta guys not go with a larger diameter, lighter weight beam?

With respect to your comment regarding your numbers being preliminary/target/proposed - obviously they are (you've not even shown a sketch on which they are based) but exactly how much have your numbers changed since they were first put forward? Minimally from what I can tell. You are not open to any kind of suggestion that your design needs further development before it could be called anything like a success. You claim the figures are preliminary and flexible but then reject any suggestion that they should change when presented with multiple arguments. Is it your pride that is limiting your ability to move on from the first miraculous walk down the deserted beach?

I see you have understood my comments on the Weta not flying the main hull. Do you understand that this affects the way you should calculate RM for this craft and will you now go back and re-calculate? Your use of the incorrect Weta RM in comparison to your craft now need to be re-assessed.

 

Doug - I notice that you are retrospectively amending your posts but not acknowledging all the amendments. At least be upfront about it and address the changes you are making in a new post instead of trying to sneak it back into the previous text.
Do I need to quote your original posts to maintain the integrity of the discussion?

 

------------------------
Alex, thanks again for the link and for your comments. The little tri that I have proposed in this thread is not a "full-flying foiler" like the Rave, Moth or Hobie trifoiler. It is a "foil assist" design that uses a foil on the daggerboard and one on the rudder to control pitch, primarily, and to aid in flying the main hull earlier than it might otherwise fly. Side benefits include the ability to use the "wand"(surface sensing component of the altitude control system), to set the angle of heel of the boat when flying the main hull and to be able to sail the boat at MAX RM regardless of crew weight within the range of 120lbs to 243lbs up to a max pressure of about 2lb. per sq.ft.- after which it would be reefed.
Using foils in this way makes it possible to power up a small boat like this-without them it would not work.
--
Examples of "foil assist":


Catri trimarans
Stealth beachcats
M20
Nacra 20
Some new A Class cats--"Curved daggerboards in the A Class" from SA: http://forums.sailinganarchy.com/index.php?showtopic=108776&st=0
(see pix below of A Class cat using curved lifting foils)
ORMA 60's
New One Design 70's
Sodebo(90+' tri)
Banque Populaire(100'+ tri)
Groupama (about 100')
Americas Cup winner USA-first boat to use lifting foils(foil assist) in an Americas Cup
Steve Clarks 2010 C Class Cat---- see here for more pictures and comments by the man himself: http://www.boatdesign.net/forums/multihulls/little-americas-cup-2010-c-class-real-one-32301-4.html
Yves Parlier 60' L'Hydraplaneur(rudder t-foils)
And more all the time....
---
And monohulls using foil assist:
International 14
National 12
Brace-Wellbourn 25 DSS
40(?) Wellbourn DSS cruiser-racer
"W152" New Disabled dinghy/rudder foil
"Flying Canting keel" boat

---All these boats use foils to reduce wetted surface, improve pitch characteristics or both.

-------------------
The Future of foils on multihulls:

While this is about catamarans from an interveiw with Martin Fischer(top multihull designer and guru), I think it applies to ALL multihulls-most particularly a trimaran that could accomplish the challenge of this thread:

CS- Is it possible to see in the future an established racing class of foiling beachcats ?
MF: Yes, I am absolutely convinced that foiling multihulls are the next step. The challenge is to make them reliable and easy to handle. I am currently working on putting an A-Class on foils. First tests are very promising. I start flying the boat, also it is not very stable yet, but I think we will get there.

CS- I've heard from Landy in the A-Class, from M20 pics and reports and from Macca in the Nacra F20 how they are flying with curved boards, so slowly we are going in that direction, not full hydrofoils of course, but is the future in your view (flying beachcats Moth style)?
MF: Yes, I have here in New Caledonia an A-Class with curved foils. The boat works nicely but it is not yet fully air-borne. If everything works according to plans I’ll have a flying A-Cat before the end of the year.
The full interview is here: http://catsailingnews.blogspot.com/2010/05/cs-interview-martin-fischer.html
----------------

from Gino Morrelli(famed multihull designer with Morelli and Melvin):

"Foils are definitely the way to go: it's an instant turbo".

 

Doug...

Read carefully.

By deleting and shuffling around already posted segments, as if what you are doing is some clever strategy that nobody notices, you are quickly turning this thread into a cartoon, rather than a discussion of properly supported merits.

This type of action is, very clearly, an indication that you have nothing fresh to offer on the thread topic.

If you are not going to engage with some sort of order that fits with reasonable forum expectations, then please let his thread die and try to do it right the next time.

 

The Weta looks like a skiff with training wheels.

 

---------------------
Thanks for your post and welcome to the thread. The "training wheels" allow the thing to be modified to carry the same upwind SA(200sq.ft.) as an International 14 yet be sailed singlehanded....
In a way you're right: using Bethwaites SCP/Total weight the Weta is above
70% which puts it in the same category as a lot of skiffs. The planing
main hull gives it a lot of speed even with the "normal" rig. I've seen it up close and it is an impressive boat.

 

Sorry for the gaff, no insult intended to the Weta. I was trying to express what I saw from mmy mainly "MONO" backround.

 

=================
Briggs, I didn't see it as any kind of insult. It's great to have the feedback!
I think that as time goes by there will be a lot more boats that might not fit traditional definitions or that fit more than one definition.

 

Briggs,

Training wheels it is, even though I would not have chosen those words to describe a very cool boat in a brand new niche.

If you are even giving a sideways thought about a Weta as a fun boat for yourself and possibly family (as I don't know your circumstance) do keep in mind that the complete boat, as you see it, was carefully created by the company owners and a qualified boat designer to remain in the configuration as it has been presented.

If these very smart guys had intended the boat to be something more, they would have created a bigger version (which they have considered) Altering the boat according to a much different paradigm would place it in a different, really tough to sail, category and that takes the original design brief well out of its thoughtfully crafted envelope of being a great boat for a family, or exciting solo sailing.

Want a bigger, faster version? Then the Montage and the Collage designs would fit your interests accordingly. http://www.lunadadesign.com/index.php?s=Montage

 

Doug - by going back and editing all the posts you have indeed made this thread a little nonsensical. I see you have moved the discussion to a new thread here:
http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686.html

btw - nice rendering Chris. I wish I had the time to build the 18 footer but can't see there being any window any time soon...

 

----
The Weta falls into this thread from a LOA standpoint but not from a high powered standpoint. This is one great boat- as I've been able to see first hand lately.It has a planing main hull so is not speed limited in the same way some of the smaller displacement trimarans presented earlier. It will not fly the main hull but is nevertheless a fast boat-see the video of the Pacific Coast Championship.
What I'll do in this post is figure out some of the design ratios of this boat and then see exactly what it would take to fly the main hull with one or two crew. A Turbo Weta will be described and and detailed.
--
Weta Specs(most supplied by Weta Canada):

Length - 14 Feet 5 Inches (4.4 m)
Beam - Rigged 12 feet 2 inches (3.7 m)
Beam - De-rigged 4 feet 11 inches (1.5 m)
Main hull-beam at waterline- 2.71'
Main Hull L/B at wl- 5.3/1 (planing hull)
Ama length -11'(est)
Ama beam - .625'(7.5")
Ama L/B -17.6/1
Sail Area - Main 8.3 sqm (89 Sq Ft)
Sail Area - Jib 3.2 sqm (34 Sq Ft)
Sail Area - Gennaker 8 sqm (86 Sq Ft)
Total Sail Area- 209 sq.ft.
Weight - Main Hull 123 lbs (56 kg)
Weight - Float with Beam Frame 37 lbs (17 kg)
Weight - Mast 9 lbs (4 kg)
Weight - Rigged Total 220 lbs (100 kg)
Mast - Length 21 feet 4 inches (5.6 m)
Mast - Height above Water 24 feet (7.3m)??
---------
Design Ratios-"normal" boat:
Normal boat is defined as boat with one 175lb crew

--SA/D=36.6/1
--SA/WS=2.66/1(optimum immersion of ama for lowest wetted surface and max RM)
--W/SA= 3.29
--SCP/Total weight= 73%( Note since the normal Weta has a planing main hull this ratio is particularly interesting since boats with a ratio above 30% should be able to plane upwind)
----------------
--Max RM-based on company reported capacity of 440lb and max buoyancy of ama-340lb.-(not a normal sailing configuration but one that must be used to engineer the boat or there could be product liability problems)-4815 ft.lb.
--Max "normal RM" -with one 175lb crew in hiking position and lowest wetted surface of ama for the best RM= 3048 ft. lb.
====================================================
====================================================
TURBO WETA

-----
Changes to the specs are listed below: (Note: there is talk among some Weta dealers of a Turbo version of this boat. Also the possibility of a completely new boat. This is the result of my exploration of the possibilities in "turboing" a "normal" Weta with the least changes possible-enjoy!)
--
Upwind Sail Area: 200 sq.ft
VERY IMPORTANT: This sail area will require a new max capacity of 350lb so as to not overload the EXISTING structure. Weight increases will be very limited(main foil, rudder foil, ama foil , larger mast). Estimate for total additional weight: 9lb (3 hydrofoils), 7lb mast, 6lb sail for a total of 22lb.
It is imperative that crew position when sailing at max capacity(350lb) is limited to 8' from the CB of the ama. If a foolproof way of doing this can't be devised ,max capacity for the Turbo will have to be lowered further. This is important so as to keep the boat within the structural boundaries of the design.
The Turbo, with 200 sq.ft. SA(same as an International 14) can be sailed singlehanded in the same breeze as an F18 cat. Or it can be sailed with two 175lb crew . It will fly the main hull in as little as 6-7 knots breeze.
--The boat uses a foil that pulls down at some times similar to the windward foil of a Rave hydrofoil(or any other foiler that uses a foil or foils to generate RM). As shown(and detailed) in the specifications post the maximum pressure this boat can sail in is 2lb per sq.ft.-11% higher than an F 18 cat. Like the Rave at a certain point sail area will have to be reduced to avoid structural damage. The Rave posted a warning in the cockpit to remind the "pilot" of this. This boat-if ever built- will be tested to find the exact apparent wind speed or boat speed that reefing should take place-but I can say it will be somewhere over 25 knots. This is a minor drawback to major
advantages provided by foil assist: (already detailed in the spec sheet on page 5)
1) early takeoff of the main hull
2) the ability to sail at maximum RM(righting moment) regardless of crew weight in the range of 140-350lb.,
3) the automatic control via the wand of the boats heel angle when flying the main hull.,
4) Drastically increased pitch resistance compared to a similar design w/o the foil.

--The beauty of the choices described here is that the boat does not have to be changed structurally at all!( may require strengthening here and there-Roger Kitchen would decide that) Even in the worst case scenario the max RM barely approaches the the designed maximum RM. The same limitations in very strong wind-over 25 knots-will have to be tested and considered as with any boat that can use a hydrofoil for righting moment. The max speed of the boat will increase dramatically especially in light to moderate wind.
The modifications will include a new mast, new boom new sail, new daggerboard /foil combo and the installation of the retractable ama foil. There is a distinct possibility that after more research and testing that the Turbo version and original version could be interchangeable-keeping costs down. With the proviso, of course, that the max capacity of the Turbo version is limited to 350lb(see above) rather than the 440 of the "normal" version.
---
Turbo Design Ratios-only the ones that changed:
--
SA/WS=20/1-dramatic change
W/SA= 1.975(single crew)
= 2.85 (double crew-same as Moth with Gulari)
TURBO max capacity limited to 350lb( or less)!
Max RM ,single= 3365 ft.lb.
------------------------
from Gino Morrelli(famed multihull designer with Morelli and Melvin):

"Foils are definitely the way to go: it's an instant turbo".

------------------------

Weta West Coast Championships- Great video of the main hull planing: http://www.youtube.com/watch?v=LKpiVZvu-a8&feature=player_embedded
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post edited 7/14/10 to add pictures

 

I've moved the MPX-11 to its own thread because it seems to me it is worth exploring in more detail than is possible in this thread. There is still a bunch worth considering here including references to numerous other boats in this size range like the Weta and proposed Turbo Weta as well as John Marples and Kurt Hughes boats.

MPX-11 thread: http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686.html