CNC Plans not Included

This setup gives rotation plus flips up. I think I would use something similar for the rudder. The only problem with asymmetric is you need one for each side. These are self stayed though I think I overkilled it, they are pretty small but you can get more lift out of them. I still need to add the trailing edge foil.

I know I will catch some flack on the flange but that an engineer can figure out pretty easy. The flange makes it easy for me to try out different variations and replace a board when/if one breaks. The flange is also below the waterline to interrupt the flow of air down the low pressure side... It might have to be further down which would be stronger anyway.

 

Jorge - KISS

Your above drawings dont acheive any structural benefit by bracing it from the bearing attachment- the load is still on the bearing bracket!
Rob Denny was referring to staying it out wide near the hulls to a point exactly the same height as the center of the bearing so they maintain the same tension throughout the pivot range...

 

Yeah I understood him but that version was symmetrical and didn't rotate. This version uses rotation to adjust angle of attack, it has to be braced off whatever is rotating. Not shown is the rotating shaft continues up the other side in a pocket like a mast.

I will finish the drawing and separate the parts for better visual. It's the simplest way I could think of.

 

Bracing it off the bracket like that doesnt make it any stronger - the weakest part is still the bracket which is what youve braced it to so the loads are still on the bracket!

Comon Jorge - rotating, leading edge slats and trailing edge slats....seriously?

It doesnt need to rotate if you have slats... All this is sounding like a nightmare on steriods... stuff like this is what stalls projects, it all sounds easy in theory but in reality its a PITA getting it all working and ironing out all the bugs you didnt see in the initial design... And its all for probably half a knot improved VMG... worth it? IMHO Nup...

 

JP, before you get too much into rotating/flaps etc, stand back and look at the basic problems.
Here is a useful analysis by Martin Schöön, Dec. 2004 of the loads and designs needed for dagger boards. It assumes the boards are hull mounted but all you need are the basic formulas to determine loads.
Plug in your righting moment and dimensions and calculate the loads that the board will experience.
multiple the board load by the lever arm (board COE to pivot axis) and divide by the radius of the pivot. Given your air gap (1m?) and immersion depth (3m?) the loads on the pivot are going to need Americas Cup levels of engineering.
If your board COE is 2.5 m from the pivot and pivot arm is 10 cm the load multiplication factor is 25 times. Actually its a bit more complex than this but the results should give you some feel for loads involved
If the experts find some discrepancy or omission in the analysis let me know -

 

I don't think the dagger attitude should be tied to where you point the boat, however if one has a rotating mast that might be enough, so you guys could be right.

But it's not complex and heck of alot easier to build and maintain than a conventional dagger and case. This stuff can all be machined and fab'd pretty cheap with std bearing szies and the whole unit just drops in... as for strength, this is way stronger than a regular dagger which is not nearly as precise a fit.

I don't see the problem with slats? It doubles the lift capability of a wing without substantially increasing drag like flaps do. The trailing edge by the way is a slat too, it doesn't rotate like the first version I drew. I took that idea from Short Take Off and Land (STOL) light aircraft. They use fixed slats to reduce complexity cost and weight. The venturi effect sucks the flow around wing back to the wing so the angle of attack can be greater and it also helps to reduce stall on shorter chords or at slow speeds which means the entire dagger can be smaller. The flange lets me switch things out so I can inexpensively try out different variations.

In light winds you won't be able to point the daggers as aggressively so maybe you want them inline with the boat, but in decent or high winds you might be able to reap the full benefits of the slats. I don't think it's complex at all, I think it's easier than a standard dagger and case for sure! Now whether it only gets you an extra knot, can't say. My gut feeling is if you can produce double the lift over a standard foil then you should be able to tweak things to gain more than a knot.

All said though, it's still easier to build than a regular dagger and probably not anymore expensive.

 

Not engineered, so not to scale.
1. Axial Bearings attached to blocks on main beam
2. Main Shaft slides through bearings and abuts the Thrust Bearing
3. Flange is bolted on to Main Shaft and Pivot Bracket to that.
4. Extension assembly is slipped into Pivot Bracket
5. Add daggerboard of choice.

I would just let a machine shop fabricate it. All I need to do is pay a mechanical engineer to design it properly and as light as possible. Then I drop it through the hole and tighten some bolts, attach the rotation mechanism (probably hydraulic) and build the daggers. I don't think it would even need stays, even with a couple of tons of side force I can't see that pivot or the extension assembly bending.

 

BTW - Thanks for the Board Strength Paper! Here is another one in case it helps somebody, way over my head!!!!

 

All that fabricated in 316 stainless? How much $$$ do you think all that would cost?
I dunno about over there, but over here i doubt you would see any change from $10k a peice not including the daggerboards, considering the thickness of material and size of those bearings etc...

 

We pay about $400 for SS 316 - 8' long by 4 in dia by 1/4 in wall ... But the engineers have to spec it all out, no need to over build. My drawing is not accurate with regards to tube size, I drew big just to see my clearances with rest of boat. Both shafts are behind main beam completely out of the way. I would be surprise if it goes over $20k including daggers and engineering.

If this works I will be kicking my heels in joy because I just lopped off another ton of work. One thing I am thinking, is if the slatted boards don't work as planned, I can still use the mechanism as dagger rudders like the proahs.

 

Perfect for the boat )) -

 

This is inspiring ... would love my beams to as light! The truss weighs 14 pounds, that is 2800 lbs of weight on it with no sign of flex, they say. Pics are form the Dragonplate website.

 

Nice looking PR photos but I call a technical foul. The guys on the extreme left and extreme right could weigh a couple tons each with breaking anything other than the concrete support blocks. A naval architect will draw you a compound beam that will more than match the truss shown while handling the 3D racking loads of a catamaran that the truss is unable to handle. Will not be cheap or easy to build however.

the 505 board design doc is good at explaining the intricacies of racing board design and hydrodynamic effects. thanks for sharing

 

lol but the bags of concrete?? That is pretty impressive for a 14 lb truss. Given, it's only meant to take a static load in one direction but I think they have examples of box trusses too.

Here is a better pic of the main components that would make up the dagger mechanism. Most of it is pretty straight forward. The tubes I could buy or since they are short, I could possibly make them without much complication, the forks would be easy to make a mold of, the pivot pin and bushing I would just buy.

But what interests me is the daggerboard. I think it would have to be built with framing like a rudder. The end that ties in would have the framing extending into pockets of an adjoining flange. This is where it gets tricky for me as I don't have experience bonding CF.

The frame members are all flat table infused and cnc cut so quick and easy ... skins are easy too, they would be infuse in a mold and bonded to the frame, the leading and trailing edges bond to the lighter colored frame members. A real wing )))

 

In thinking about the tubes I think I have figured out a great way to make high tolerance cylinders. It builds on Gropers mast process.

1. Lay out prepreg fabric on a flexible substrate such as the laminate used on cabinets.
2. Tape a bag around the back edge of the laminate and suck it down. the vac port would be located on the extra length of the laminate.
3. Roll into an informal cylinder shape with the fabric facing out not in
3. Drop into a pipe that has been turned to the exact diameter plus thickness of bag
4. Let it spread out, it should be a bit short of perfect so no overlaps, and then insert a baffle tube, like a kiteboarding baffle, and pump it up so it's pressing the skin tight up into the tube and put it in a cheap home made autoclave.
5. Finish off by gluing the ends together with an insert on the inside of your new pipe, fair the gap and ...
6. For really perfect finish, don't think it's needed but ... turn on lathe and remove a few thousands of material.

PS you could also do it on a male mold once you know how many layers of cloth to get to a certain thickness. Wrap around mandrel with skin facing mandrel and use a second vac bag to pull it tight.