Dream Flyer fl-an 18' daysailing trimaran

Doug,

Good for you. I hope you find more time then I can to work on your boat, then I can find for mine these days!

 

Dream Flyer fl

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Thanks! Just sent the check for the carbon tubes-and I asked them to wait one week before starting my order so I'll have a little time to review any design errors I haven't found yet. Added one 6' X 2" tube for a traveller mount. The Forte guys are first class to deal with!

 

Dream Flyer fl, a daysailing trimaran

Rough sketch to scale of final tube and DSSM arrangement:

click on image-

 

Dream Flyer fl, an 18' daysailing trimaran

Good news from Eric Sponberg: using the original 165 sq.ft. rig, at this point there does not appear to be a need for waterstays( wire from the crossarm to the hull). If I soup the boat up in a year with a 250sq.ft. upwind rig things may change.
Took the ama plan to Sharon today for her to cut out of styrofoam. When she is done the styro pieces go to Matt McDonald at Falcon Marine, LLC to be carbonated. The carbonation will also include the mounting of two vertical tubes and one 4'X 6" DSSM(DSS for multihulls) foil in each ama.
I talked to Matt about doing the final assembly as my idea of renting a 20 X 20 shop and hiring a helper was impractical. We're going to meet Thursday morning to go over it in detail. I may still do the bow but we'll discuss that ,too.


Dream Flyer Ama-click on image:

 

Nice going Doug, good luck!

 

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Thank you!

 

Dream Flyer fl, an 18' daysailing trimaran

Just met with Matt McDonald at Falcon Marine,LLC. He doesn't want to do the project one piece at a time and since it is going to be a few weeks for some parts-foils, styro and carbon tubes we are shooting for 4 weeks to 6 weeks to have everything at his shop.
He and his team are going to:
1) carbonate the amas,
2) carbon the verticals into the main hull,
3) carbonate the ama vertical/main cross arm joints(4),
4) carbonate the main cross tubes at the proper dihedral(2),
5) carbon on the hinges and lower latches(4 of each),
6) carbonate the main cross arms to the main hull verticals(4),
7) fix the bow from the "windsurfer/scow" type it is now to a sharp bow,
8) carbonate the seat tubes in place, and bucket seats,
9) carbon the push/pull rod to the ferrule(2),
10) limited "cosmetization"(painting)
Matt is a pleasure to deal with and does first class work not only on his production cats but on special projects like Dr. Bradfields Osprey-all of which I have seen up close and personal.
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As of today all the major components are on order-starting to get a bit exciting.....

 

How much lateral resistance are you going to have with this design doug? seems like not much with the foils at only 7.5 degrees? you sure its going to work?

 

Dream Flyer fl

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Groper, you must have missed the picture of the daggerboard in post #1. I redid the illustration below to show the daggerboard. For all practical purposes, these foils contribute nothing to lateral resistance-they are there for lift only and are not designed to be effective when the boat is upright. The nominal angle of heel for which the lee foil is most effective is 7.5 degrees, as shown by the red waterline.

click on image for better detail:

 

Dream Flyer fl-spinnaker system

I've been going back and forth a lot on whether to go with a Weta style system where the asy spin is carried upwind on a furler or with some way to douse it on deck. Tonight, I think I've devised a way to douse it on deck w/o interfereing with the jib using a system similar to a cat system but with a retracting pole. Most likely going with a custom made spin about the size of an F16 sail(188sq.ft.)-if I can be satisfied that I can handle it singlehanded.


Weta spin furled(upwind) and set and flying. In each case the spinnaker pole is,in essence, a bowsprit since it is not retractable.:

 

Dream Flyer fl- an 18' daysailing trimaran

For future reference here are a couple more pictures of the original boat sailing in light air:
( thats my sailmaker sailing the boat)

 

Dream Flyer fl-the experiments

I'm doing this boat mainly to have fun and part of that fun is testing new ideas:
1) The first configuration of the boat is a relatively low powered daysailer with an all up sailing(and boat) weight less than an F18 cat. I'm using lifting foils attached to each ama just forward of the forward crossarm. These foils are based on the theory behind Hugh Welbourn's Dynamic Stability System which is being used successfully on a couple of sport boats with more boats coming along including a new lake racer in Europe and and a cruiser/racer in the UK. The system has been tested for years on rc models, test tanks and on prototypes in addition to the new Quant 28 and slightly older Brace,Brace, Brace and has proven very successful in creating enourmous extra righting moment for these monohulls. In my own study of DSS, I've found that the RM increase can easily be the equivalent of a canting keel canted 90 degrees!
One of the interesting elements of this system is that the foil is designed to function as close to the surface as one chord and to function at a reduced rate right at the surface.
When I found out I could do this boat, the first thing that occurred to me design wise was to use a version of DSS in combination with very low buoyancy amas. Each ama is capable of supporting just 55% of the total weight of the boat fully immersed. At the design waterline the ama will support only 28% of the total sailing weight with buoyancy. That is 162.4lbs.
This design, being a daysailer, will not fly the main hull-the main hull provides the pitch control for the boat. So the max pressure before depowering will be
1.25lb/sq.ft which equals a heeling moment of 2578ft.lb. and a load of 368lb on the ama/foil combo. Since the ama buoyancy at its designed waterline is
162.4lb, that means that the DSSM foil will have to provide a vertical lift of
205.6 lb.( plus gust response). It will do this at about 9.46 knots with a one chord immersion. I fully expect that the maximum design sail pressure will occur at a speed substantially in excess of the 9.46 knots above(especially downwind). What is interesting here is what happens next: theoretically, as the boat accelerates the foil lift will increase. If it increases beyond the load it has on it it will get closer to the surface. The closer to the surface it gets the less efficient it is until at the surface its efficiency is about one third or less than when it is fully submerged. The reduced efficiency could be a self-limiting feature of the foil-which might be good. That is the main thing I want to document with this configuration.
Questions that I will attempt to answer:
1) how does the foil behave when its lift is greater than the load on it?
2) how does the ama/foil combo behave throughout the speed range?
3) when and how does the foil ventilate?
4) does the foil produce lift when fully ventilated?
5) how does the foil and ama/foil combo behaviour change upwind vs downwind?
If this thing works well it can provide an ideal shallow water hydrofoil that would allow trimaran designers to reduce ama size/weight/cost significantly w/o drawing virtually any water-at optimimum immersion the ama/foil combo draws 6".
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2) Depending on the results of the first configuration the boat may be souped up to more SA and possibly more beam. SA may be increased to 250-280 sq.ft. upwind. Two additional foils will be added to the main hull-similar to a Moth-daggerboard main foil and rudder t-foil with a wand altitude control system on the main foil. This will allow the boat to fly the main hull in light air while the main hull foils will start to unload soon after flying the main hull. Effective dihedral would be changed to allow the outboard ama foil to be level when the main hull is flying. Whereas on configuration 1 above the main hull provides pitch control on this version the two main foils will control the pitch of the boat and angle of attack of the ama and ama foil. This system allows for a dramatic increase in performance both in light air and heavy air.
If the first foil configuration(1 above) doesn't work well the ama foil will change to a curved lifting foil.
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This will be fun and very interesting to learn how to use these foils most effectively.

 

Interesting idea regulating the DSSM foils lift with proximity to surface. If the functions of the foils are to be separate, DSSM foils in amas for vertical lift and increased RM , and the dagger board for lateral resistance and lift to windward, with the main hull always in contact with the surface providing passive pitch control, then could you not ditch the dagger board ,load up the rudder and adjust the CE accordingly?

 

Another question. How important is the dynamic relationship between the DSSM foils the COB THE COG and the CE?

 

Dream Flyer fl

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Timothy, I don't see ditching the daggerboard at all-the boat would have massive lee helm because it would not balance w/o the daggerboard. Moving the rig aft is not possible or desirable on this boat.