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

Thanks for the great comment!

 

I got google to goggle the noggle.

 

I toggled between browsers to get google to goggle the noggle and was boggled.

 

When I was just browsing BDN and SA, it seemed like Paul was overly common in the areas I was interested in.

Kind of hard to get me mixed up with someone else when I use my first initial and last name.

At work, I probably get referred to by my last name only more than by my first name or both names combined.

 

From Eric Sponberg: "The noggle has been used as far back as Capt Nat Herreshoff in the latter part of the 19th or early 20th Century" Eric has used it on a few designs.
The idea is that the noggle automatically restricts the angle of the boom to the mast-once set you don't have to fool with it. I'm going to make an adjustable version. This may eliminate the need for a separate mast rotation control as seen on many cats.
Haven't figured out what to make it out of.....

Click on rough sketch for clarity:

 

I have been continuing to play around with XFLR5 to get a better feel for how to achieve the different objectives that we face in sailing.

For best possible Cl/Cd, a given wingmast will probably have an optimum mast rotation. Setting up a noggle seems like a good choice for this objective.

With a mast like Doug is using, a separation bubble on both sides is pretty much a given.

If on the other hand you are using a mast with a section more resembling a NACA profile, I am not sure the optimum for Cl/Cd will be with a bubble on both sides. Trimming for a smooth transition from hard to soft on the top (lee) side seems to work pretty good for some stuff that I tried. I noticed this most in the high wind situation with the sail adjusted to a very low curvature configuration.

For max lift, you may find that a noggle with only one setting does not let you get max grunt for accelerating or for that downwind run.

Again, I am suspicious that the mast foil shape can make a big difference on whether you can get one setting to provide a reasonable compromise.

When I posted earlier, I was really more interested in discussing the pros and cons of different foil sections, not in the mast rotation question.

 

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You might want to talk to Eric-he's done an awful lot of work on rotating wing masts.

 

MPX: The Test Model

Every thing is ordered except the sails and they should be by Friday.
1) McMaster-Carr-miscel items to make the dual wands("extruded" in a silicone tube), reefing system velcro discs, 2 sealed SS bearings, Kevlar thread.
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2) Goodwinds-these guys have a lot of kite gear. I got 150lb spectra line and 500lb spectra line, miniature shock cord, carbon rod.
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3) Dragon plate-in addition to many different carbon sheets these guys have some really cool bondable fasteners.
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4) Alsa-specialists in wild paints and the only"real" chrome paint-which I didn't order. They come in spray aerosol cans:
a. One can of black base coat,
b. One can of Crimson red-crazer style*,
c. One can of Mirror clear
* they tell me you spray on the black, let it dry thoroughly then spray on the Crimson red(and heres the fun part which I've never tried before) then you take saran wrap and lay it on the fresh crimson, move it around, then remove it. Let it dry and then spray on the clear. Now, I may never get to the crimson because I have a feeling I may really like the black.
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5) Rockwest carbon tubes-ordered the tubes to make the retractable rudder gantry. They have a very wide selection of tubes-from small up to 4".
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6) WM Berg-specialists in small mechanical components. I ordered the mainfoil push rod, the wand axle, and a few miscel. components for the wand system.

 

SRT/MPX test model

Some interesting, nearly final specs, that reflect some changes. More changes are sure to be made when I get sailing:

1) Fairly accurate final sailing weight=13.5lb
2) Sail area @ 200sq.in per pound(proven on F3 for light air foiling)= 2700sq.in..(18.75 sq.ft)(Actual incl mast 2/17/13=2838sq.in(210 sq.in per lb.)
3) Main foil at .188lb per sq. in.(proven on F3 for light air foiling). Main foil lifts 80% of the total weight at main hull take off= 10.8lb.. 10.8/ .188= 57.44sq.in.
Rectangular dimensions of main foil 2.75" chord 20.73" span, 7.5/1 aspect ratio. That is just to get an idea of foil size-span will probably be greater.
Foil will have a 30% flap actuated by dual wands on the main hull.
4) Rudder foil at take off lifts 20% of the load but to improve performance we're going with half the main foil area(28.5 sq.in) with a .095lb per sq. in load. So 50% of the main foil area and 50% of the load per sq.in.
Load =2.7 lb / 28.5=.095lb/sq.in. Area may be reduced during testing.
5) Ama foil will lift the whole boat(nominally) at approximately 10mph boat speed).
Using Vellinga's simplified formula for finding area: S= L/ (v^2 X Cl)=
13.5/ 215 X .5) = .1256 sq.ft. or 18 sq. in.
As explained elsewhere, as soon as the main hull lifts off, the main foils begin to unload and the ama foil loads up until it is carrying all the weight. The main foils then are devoted to controlling pitch and heave of the main hull and running angle of the ama and ama foil.
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The ama foil configuration is changed from the "bent T-foil" shown in post 231 to a curved "L" foil similar to TNZ mainfoil on their 72. Also inspired a bit by Gary Baigents straight angled "L" foil and Greg Kettermans "L"(or "J") foil on the trifoiler. The "L" foil will be built in one piece-all carbon.
The essence of what I'm trying to achieve is an "L" foil with some of the characteristics of a surface piercing foil so that it will have automatic altitude control. At some point the angle of incidence of the lifting portion of the foil may be adjustable by radio for testing. May also try a "normal" T foil close to the ama so that it would not need an altitude control system-sort of a variation of the "DSS for multihulls" idea in the Dream Flyer thread that would work with the planing ama.
One of the drawbacks of the curved "L" foil vs the "bent T-foil" or a normal T foil is slight reduction in maximum RM of 7-15%. It's a judgement call that this will work just fine.
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Foil illustration tomorrow....

 

Doug, get a free account at photobucket.com and upload your pictures to it. Then go to your library, and click on the one you want. A larger version of the picture will come up, with a menu of image links to the right. Go down to 'IMG code' and click on the box; it'll say 'copied.'

Then go to the post you're writing at boatdesign.net. Hit 'ctrl V', and it'll paste the link into the post. Or you can just go to Edit at the top of the screen, and click on 'paste.' eEther way will insert a link to your picture, so it'll come up automatically whenever someone reads your post.

I lost track of this thread somehow, so I had some catching up to do. Glad to see the project is still coming together.

 

Thanks, Troy! Hope all is well....

 

Doug, get Photoshop or something similar, plenty out there, store your shots, then you can size to whatever dimensions you want, high definition or low, high or low memory usage, sharpen or contrast, ctrl plus c, ctrl plus v, very simple.

 

I'll check it out ,Gary, thanks!

 

Another photo editing program is paintnet which is free, with most of the same features. The only thing I have noticed that is missing is an air brush feature and being able to store the photos with in the program.

 

Thank you!