Crossbow fl

"the concept has merit" is minor encouragement. Because it talks only about concept. But there is strong criticism in Bethwaite's comment as well - namely about the pods and not being able to shift ballast fast enough.

This issue of speed of ballast shifting has been something that has been raised over and over again and something Doug has consistently dismissed by using unrealistic numbers.

For example, he uses a tacking time of 7 seconds. Which is about how long a 49er or a 5oh that is in clear air and on flat water in moderate winds uses to tack for optimal VMG. However When doug has been presented with video of 5ohs gybing in 3 seconds or 49ers tacking in 3 seconds, he has basically attacked the person presenting the video. I can tell you from personal experience sailing a variety of high performance skiffs, that when things go pear shaped (which is when your really test your system) you need to be able to go from max weight to Max weight in the order of 2 seconds (I've had a screwed up tack saved by my crew literally diving across from full trap to freehand trapping wing to wing as I dangled against the main, fouled in my trap hook, and that was much less than 3 seconds).

and the problem that this poses is the same one that Bethwaite aims at Cayard's idea -- that of a lot of weight hurtling across the boat at quite high speed.

pFlados - "proving" the trapwing at the model level really doesn't tell us much. why? because

• the power densities of model batteries and motors vs "full scale" are significantly different (function of x² scaling)
• the strength of the materials is increased by either square or cubed power functions
• the absolute velocities involved are much slower and thus catastrophic loads much lower

now as to DSS being a "proven technology -- itst not. Not at the dinghy level. It has been shown that on a diesel powered maxi it adds 3% performance. We have anecdotal evidence of it working in 30' lake racers and 25' ocean racers but no real comparative side-by-side data on identical platforms. (the Quant 28 doesn't have a sister ship that lacks DSS nor does it have a large data set of sailing with and without)

we have zero evidence of it working on a dinghy. Remember that according to the designer, the DSS has to be immersed a minimum of 1 chord length below the surface to be effective. A high performance dinghy typically draws about 3" of water. so that means EITHER

1. your dss foil has a 1" chord
2. your dinghy gets bastardized to draw a lot more water and hence loses its performance
3. your DSS is operating in 3" of water - in which case it basically is just like dragging your weather wing through the water
4. your DSS is inserted at a steep angle in which case the 3% RM is reduced to even less benefit and a significant leeway component is generated fighting your CB

Now #3 is an important thing to think about because as anyone who has sailed a 49er knows - that if you dip your wing at speed in breeze, there is a damned good chance you are headed for a cartwheel. Its why the 18s and 14's both carry their racks well up above the water - much more so than the 49er.

So adding DSS into any sort of scaled up build


Now Doug's clarification of the order in which the "technologies" get added is brand new information. In fact it is contrary to pretty much everything he has posted on this subject before.

When it was pointed out to him that the cheapest way to prove this out would be to get something like an old Laser II for say $1000, get a cheap PLC controller for about $300 and some used actuators for around another $200 - his response was that this was not the way it would be done because that did not include DSS.


So now he has embraced an iterative engineering approach. Great. But frankly given where he lives, he could easily prove out this concept on a Laser II with no increase in the "workshop" he has. After all, assembling the motor and driving mechanism only takes the size of the Laser II hull which is not much bigger than his current MPX project.

And then building the trapwing itself can be done in three pieces (its how you would do it anyway) and tthat too can fit into a std apt living room.

And assembling it out on the lawn is not a deal breaking limit

 

Paul, for your information: this is to counter some of the deliberate mis-information of the previous post. The poster has proven that he is not knowledgeable about the Crossbow fl or the systems it uses. However, apparently(as proved in this post), he will make up data that serves his purpose in denigrating my efforts. I don't believe anybody is entitled to make up information in order to attack the work of others as this person has been proved to do in this thread. That's the reason for this post:

--1) The quoted post below(from page 1, post #7) refutes paragraph three of the previous post which appears to be 100% fiction-just plain made up!
--
--2)As is paragraph 5 regarding testing models-bears no resemblance at all to the facts! The model version of the Trapwing isn't testing motors or batteries, or materials strength-it is testing function for which it is ideally suited. Since the system speed relative to the model is much faster than the system speed relative to the full size boat, the controllability of the system is also tested and requires even better reactions from the RC skipper than does the full size version. RC model testing of fullsize boats has been done by some of the top designers for years and years-and if you know what the testing limitations are it is an excellent method.
--
--3) The final example of egregious mis-information is most of paragraph 7 and it's "supporting" info--again with made up from thin air words used to inaccurately describe the Crossbow system illustrated in the sketch below(at the bottom of the page). Since the Crossbow fl is a new boat that has not been built yet there is no "proof" of it sailing or of it's DSS foils working. Except that the design has been aided by the inventor of DSS, including the use of one of his proven DSS foil sections. The design has been and will be refined by the whole Team(see post 144) as building and testing takes place, but the groundwork has been laid for a succesful small DSS sailboat. And the bit about draft may be true on boats the poster is familiar with but the 15.5' Windmill that I grew up racing has a hull draft of 6" and a waterline a bit shorter than the Crossbow fl! So, the conclusions drawn in paragraph 7 of the previous post are absolutely baseless with no relevance whatsoever to the Crossbow fl.

=================================
Tacking Speed Summary: (Crew timed max out to max out except on the Canoe)
PS-Paul, please check the timing on these if you get a chance-thanks dl.

=======================
Contender- http://www.youtube.com/watch?v=Pzrb-HYrxPM

5-7 seconds full out to full out* in good weather for the trapeze movable ballast system on the Contender
=============================
Flying Dutchman- http://www.youtube.com/watch?v=dHsa0bUdFOM
6-8 seconds for the trapeze movable ballast system from full out to full out*

=============================
505- http://www.youtube.com/watch?v=YqEhY...eature=related (video dead)
6-7 seconds for the trapeze movable ballast system from full out to full out*

=============================
12' skiff- http://www.youtube.com/watch?v=k2PvV820Qpk (toward end of video-7:58 min into video)
7-8 seconds for the trapeze movable ballast from full out to full out*

=============================
International Sailing Canoe- http://www.youtube.com/watch?v=Exb6i3E3r-4&feature=related (first example 35 seconds into video)
5 sec 50% out to 50% out;estimate 7 seconds full out to full out (very hard to find IC videos that show a boat tacking!)

=======================
* full out to full out= max outboard movable ballast CG on one tack to the same position on the other tack.Measurement starts at first instant of the begining of a tack. Note that not only will the Trapwing system be faster that a crew on a Trapeze, it also move's it's ballast a much greater distance than the crew moves.
=================

Crossbow fl hull section at foil-use picture of upside down hull to understand what that means.
There is some camera distortion of the lines and I don't know why:

 

Doug, leave off with the personal attacks and perhaps read what is written. As I pointed out, a crew can go from max out to max out in 2 seconds or so if they don't bother to hook in (which is what mine did when I got tangled in my trap). So 3.5- 4 seconds is SLOWER THAN SIMILARLY MOVING CREW. The videos Doug you are providing are exactly what I described before: strategic optimized VmG tacks. its curious that you avoid reposting any of the videos of 5ohs and Contenders tacking in tactical or panic modes.

I strongly suspect it is because they have consistently shown your claims of timings to be false.


Secondly, unless you put a latching clutch into the system - which slows response time - your motor is what is holding the weight in place. This is one of the areas where RC models do not scale well to full scale. In an RC model the mechanical inertia (gearing resistance etc) dramatically reduces the load on the stalled/positioned servo motor.

In the real world a positioning motor like the one you describe is actually running in a stalled motor state when "not moving". This is counter intuitive but unlike with gas motors, electric motors draw max power when stalled, not when running at full speed. So what you need to calculate for is your stalled power draw, not your moving power draw.

And then you have to assume that the stalled power draw is continuous to give you some reserve capacity.

 

BTW doug, here is a 5oh in breeze where 75% of weight transition happens in under 3 seconds, and its not a crash gybe, its a strategic, fully controlled normal gybe
https://www.youtube.com/watch?v=0IkeEz0D4lA (1:49 seconds in)

3Heres a series of skiffs with 3 or so second tacks https://www.youtube.com/watch?v=pMtr6pZn3hk
none of which are crash or wire to wire tacks

here is a slow speed wire to wire in a musto that is 3 seconds https://www.youtube.com/watch?v=GSm2-ytrorQ

You really are being an ostrich here doug - and its going to bite you

 

While you make some decent points BB, I think you're too dismissive of doing development using RC models. It's something Doug has some real familiarity with, and on the whole I see no reason he shouldn't continue down the road he's going. Greg Ketterman proved out his hydrfoil's complex dynamics using RC models, and attributes much of its success to his having done so.

 

Concerning the need to lock the extended ballast in place without running an electric motor continually, can't this be accomplished with a simple ratchet? Or with a power-off clutch? Or in probably three or four other ways?

 

---------------
Yes-for sure. The full size system will work in a very similar way to the RC version.

 

I know it's far from ideal, but some great boats have been built inside houses. I think it was the Comet class in which a pair of brothers managed to build boat in the attic without their mother knowing. Gold medallist and 'world' 18 Footer champ Peter Mander designed his living room windows so he could build Sharpies, 18s and Rs inside, and I think the first title-winning lightweight ply 16 Foot Skiff was built in my living room.

Tough? Yep. Doable? Yep.

 

For keeping the weight in place, the simplest would be what is called a self locking gear set. A worm gear is at the far end of gears that have sliding surfaces. These are very self locking. Gears can be engineered with less sliding than a worm gear, but just enough friction to not allow motion when torque is applied to the driven end.

Automatic breaking when the motor is not on is also not difficult. My cordless drills and saws have these.

BB, you have posted about this before. The various options to not rely holding the weight in place using power to the motor are kind of obvious. It would seem that some of the "bash Doug regardless of facts" mode that we have seen at SA are bleeding over to BDN.

 

no pFlados its not a "bash doug" approach to point out that if you need a Lock to Lock transition time of 2-3 seconds, you don't have time to run a ratchet mechanism or a clutch. The only way you get that sort of speed is by being "on standby". Remember, this thing is also trimming the boat which is a skiff.

Now I dunno how many of you have sailed a trapeze skiff, but to get the speeds Doug seeks to get your power/RM ratio has to be very high, and you are constantly moving your weight in and out. Sure its not Lock-to-Lock on each move - but that's actually WORSE. See if I am running a motor that starts a weight from stop to speed and back to stop 3 times a second - because if you are crossing 3 waves a second that's what you are doing - then I've got SIX "start/stop" cycles, which are essentially short-circuit/max current draw load points every second.

So the notion that the motor can shut down ignores the practicalities of a trapeze boat. Secondly the auto-brakig on a drill and a saw are not sufficient for this. Remember you need to have precise positioning of the weight, this isn't a "coast down faster" - this is a "lock it in place".

So in fact PFlados, I think your personal attack on me is out of line.

Secondly, on my dismissing RC boats as inadequate models - I challenge anyone to point me to where I have said that.

What I have said is that doing something at an RC scale is not proof of the concept at scale.

• your test first off needs to do as much as possible to simulate real world conditions as possible. In Doug's model of the trapwing we don't see that. he put it on a keelboat model, not an unballasted dinghy model. This means that
  • we have no evidence that an operator controlled via joystick response time is adequate
  • that the new lateral gyradius the ballast introduces does not cause problems
  • that such a configuration is self righting
• you also have to make meaningful measurements such as power consumption and calculate out loading factors
• you then have to scale these values to full scale taking into consideration the changes in energy densities and material deflection properties

Now if you don't do these things, then you haven't even shown that the RC model is a "proof of concept". After all, I can build an RC 3D "stunter" out of sheets of 1/8" paper covered foam and some carbon pushrods. and it will hover on its prop, tumble when I reverse the prop direction in mid run and all the other cool 3D stunt flight capabilities

Now who here is going to put up their hand to go up in a 16' version of my 2' stunter? lets see that show of hands of who will trust their life to a 16' airplane made out of paper covered foam and glued together with superglue....

And who here thinks that there are real-world full scale batteries that can delver enough power to have a 15minute all electric flight doing 3D stunts?


Note BTW that Doug's response to steven Ditmore indicates he has not really thought through the scaling issues. So Steven - ready to go up in my 16' foam and paper airplane?

 

Doug those aren't specs. Those are wish list items. "specs" is short for "specifications" which derives from the term "specific" so

"from 90+ degree knockdown" is not specific. because it does not SPECIFY the point at which you fail recovery
"has buoyancy much greater than required to float the ballast" is not specific because it does not SPECIFY the amount of reserve buoyancy.

So this is a list of what at most generous can be called "features".

and lest this sound like a nit pick its not. Specifications are specific so that they can be validated and designed for or refuted. And without specifications you do not have a design.

so what you end up with are things like #4c which is a feature that may or may not be necessary, and may or may not work the way you assert. Now if you wanted to SPECIFY the functionality, you would actually write something more general such as
4c - Leeward ballast articulates to lift lee side wing out of the water.
And while #3 is "specific" in terms of what mast it uses, it is completely unspecific in terms of the strength loads, rigidity, reserve buoyancy necessary for the purposes of specifying actually what the structural properties of the mast are. Without that it cannot be validated that such a mast can be built. For example, here is an A-Class Mast. weighs roughly 1kg/m of section and has a cross section of roughly 0.002 m². this means that each 1m section has 0.002m³ displacement and weighs 1kg. 1kg of water is 1 liter ie 1000cc. or roughly 0.001m³. so you get roughly 1kg of buoyancy per meter of immersed mast. Now the masts are roughly 9 meters in length, so with a fully immersed mast you would get 9kg of buoyancy.

But weight you say (pun intended) you aren't including RM. true. but lets look at that. When a boat capsizes, typically only about a meter of the mast is in the water. and the mast never actually fully goes in the water until the boat is turtle. Now this boat is designed to be safe for a 250# physically handicapped crew. So we really cannot allow it to capsize more than 15 degrees beyond 90. OK. and the mast is going to be roughly 1 meter off centerline. So this lets us do some rough SPECIFIC calcs. sin(15) is 0.26. and assume that the hull floats about 1/3 of a meter down when on its side. So the dif between 0.66 vertical distance between mastbase and water and 1 meter is the distance you get the mast tip in the water. so you at MOST have 3 meters of mast in the water providing reserve buoyancy of 3kg operating with a lever arm of 8 meters so you get 24kgm of righting moment from the sealed mast.

That's not much. particularly since your "specifications" include a 114kg person sitting in the hull. Now that person is offset from the hull's center of lateral floatation by say a generous (ie making this look as good as possible) 0.5 meters. so that's an inversion moment arm of 55kgm. Now since they are sitting in this fancy 180 degree rotatating powered seat, that's really more like 60kgm of inversion moment. And this is BEFORE adding the weight of the unimmersed mast, which is 6kg operating at a moment arm of 3m for a negative RM of 18 kg (essentially reducing your masts contribution of RM to a whopping 6kgm

So right here we see that the "Feature" from #3 gives us a SPECIFICATION of some 10kg-15kg of buoyancy at the mast tip. that's 15 liters of volume. of air. Now the lightest foam weighs roughly 20kg/m³ http://www.foamonline.com/types.php?cartID=c1b5e3eb832637baf8a28253af55a770
so 15l of foam weighs 0.3kg roughly so you have to add another 2 liters of foam. So you are looking at almost 20 liters of foam at the mast head. Essentially that's a 5 gallon hunk of foam at the mast tip.


But this gets more interesting:
an A class cat mast is designed for the loads associated with an A class captsize. which is a single crew of no more than 100 kg + the 75kg weight of the boat. Here we now have a 114kg crew, plus seat, plus the batteries to power the trapwing plus the motor for the trapwing, PLUS THE TRAPWING and its rotational momentum. So now our mast has to basically be MORE THAN twice as strong, because we are subjecting it to almost 4x the force (accel/decal is a quadratic function) and it has to fail LESS THAN A-class masts do (since if it fails the handicapped sailor drowns). Therefor this idea of a mast that weighs 1kg/m just went away. its weight now is closer to double that. which pretty much not only eliminates any reserve buoyancy you get out of it by sealing it (and if you've ever sailed any boat, sealed masts... are not.) in fact the mast now is starting to contribute negative RM (6kg of displaced RM at 8 m - 18kg of negative RM at 4.5m => -33kgm ). So that now adds another 2 liters to the foam ball at the mast tip.

nd this is a SPECIFICATIONS analysis of just ONE of the "Features" we have in the list. from this we can see why Specifications are very important and "features" less so. Particularly "features" dressed up to sound like they are specifications when in reality they are not.

And we can go through most of that list and see that
#2a is a desired feature, not a specification
#2b is a desired feature, not a spec since there is no definition of what "faster than a crew" is (and we know from the videos that doug has cherry picked that his notion of "faster than a crew" is not accurate)
#3 is not a specification
#4a is not a specification (it doesn't spec trailering requirements)
#4b is not a spec since there is no hull design to show that pivoting is required or works
#4c is not a spec since there is no hull design to show this is necessary
#6 is not a spec since you can float a grounded freighter "off the beach"
#7 is curious since someone who is too handicapped to be able to manage boat weight with their body will not have the strength to hoist or douse a socked kite
#8 is not a spec since it doesn't give us RM impacs
#9 is not a spec at all, since there is no measure of what defines a "dry ride"
#10 is not a spec since the Swift Solo's "collective" is very specifically designed for certain hull dimensions and does not actually move easily to other boats.
#11 is not a specification since
a) DSS has never been demonstrated as working on a dinghy
b) DSS has no track record of increasing sail carrying on a shallow draft boat
#12 is meaning less since there is no calculations of RM and SA that allows these numbers to be meaningful
#13 is not a specification since it doesn't give us anything in the way of RM or stability numbers


So what we have is a grab bag of wishlist items. Not specs. And a retired engineer who built wind turbine blades and now does contract for hire work is not going to tell you what's wrong in a skiff, nor is a lawn gnome designer going to shape you much of a high performance hull.

 

Ok I'll start doing the same delta summaries I was doing in the trimaran thread for readability

 

Thanks for the summary of what you are trying to do. I still have some questions:

About the shifting balast
-to control all the movement you are showing I think you will need at least 3 lines going to each side of the wing -one from the mast, one from the bow, one from the stern -and each is independent (the amount it must retract is not equal to what any other extends). So it would take three motors per side to move the way you are proposing. I didn't see fore-aft lines on your models but I don't think that is viable to control 80# hanging 12ft away from the hull. How many motors do you plan to have to control the beam?

-You don't say how the beam is attached to the main hull but based on your movement it has to be a linear bearing on a ball. Are you leaving this detail out intentionally?

-You say the ballast is sealed in the beam -is the motor that moves the ballast sealed inside also? I see no functional reason to seal ballast inside and it makes the design more difficult.

-Comment -this shifting ballast is pretty unique. I think it would be possible for you to make a full size demonstrator you could break down to store in your apartment. This is what we call a test mule and I think it would be very convincing for investors/supporters.

About the rest of the boat

You list some weights that are reasonable for state of the art build, but I don't see any of the electrical components -motors, sealed electronics, batteries, sensors....and you have a lot of automatic stuff here. You also list a tilting seat -automated?

You seem to indicate you have made some full size parts -foils & mast Is this true?

A cat mast is 9M -your drawings show something shorter. How tall will your mast be?

About all the expert names you list contributing, they mean something here but in crowdfunding... not so much. I think it would be VERY beneficial if you had a handicapped sailors association on board with your project. It would also be good to give the boating professionals you list a heads-up before you go for funding -advice they give to friends for free, endorsements cost money.

Finally about funding, do you have a project plan with estimated costs? I think you need to at least know how much it will take to reach each milestone and it will tell contributors what they are getting.

 

Here are the answers to your questions:

Picture shows athwartship pivot mentioned above. Completely adjustable and automatic. When weight is centered shock cord automatically levels the wing:

 

again this highlights that this is a wishlist not a design

Lets see we need 5fps speed minimum so with a thread pitch of 45 degrees (which is incredibly aggressive) we need the power to drive this magical shaft which bends along its length without wobbling at 7fps. plus all the added friction.

if there is a line, then there is water ingress and egress. which means you now have something that in case of captsize fills with water and resists being righted.

that's going to be interesting to see because if you look at the videos of the Acat sailors or of a Musto skiff sailor etc. the forward hand is MORE than fully occupied with just the sheet - periodically having to move bring the aft hand in for help. So I'm not sure where the dexterity comes from to control the wing.

Note also Doug - if you have a bad back, you are not going to be able to sheet on the main. One of the nice things about a trapeze is that you can and do use your legs to get that last 1/2 meter to meter of sheet pulled on. Something you don't have when sitting upright. And once sheeted on, the load of the sheet passes up your arm, into your shoulder, down your spine and down your legs. Thus you don't need that much muscle to hold it. whereas sitting up you have no structure to help. Its all about how strong your core muscles (abs and lower back) are. So if you have back problems, this won't work

please stop with the silly "carbonated" fizzy term. Its a carbon mast. But an A class mast won't be up for the kinds of crash mpact loads you are talking about. remember that even one crew is enough to break an A class mast. but you are talking about the momentum of well over 2 crew (the trapwing, plus the motor, plus the batteries plus the chair) So I recommend you look at a much stronger (albeit heavier) secton lest you drown someone when that fails

Again leave off the "carbonated'" fizziness. It obscures what you are doing in this case. Carbon is the hull, wood or foam are the core. Foam core hulls in dinghies tend to fail. Wester Red Cedar holds up well other wood cores less so But to give you a build cost estimate A Swift Solo costs about $27,000 to build from exsiting plans with existing build processes.

So to do a build from scratch without mechanics you are looking at double that. Add in the machinery and you re looking at double that again.

So that's $100k you need. And there are two ways that crowd source funding works:

a) folks prebuy at a discount. when volume gets high enough you have enough to do the tooling and then build. So this won't work for this boat.

b) you throw it out there and folks invest because they think your business plan is viable, and they now own a share of your company. Given that you don't have a business plan, this isn't a viable path either.

You need to sit down and rethink this. BTW if you go for crowd funding and keep using the term "carbonated" you will reduce the likelihood of investment significantly since folks won't understand what you are talking abou