Nacra 15 FCS for fun

[Stanno]

Hi Riley!
Nice to have you aboard. Yes with a light crew anything is probably possible as that was what the boat was originally designed for, no question it can certainly can surprise you at times performance wise. At those wind speeds given our crew weight, wave and tidal conditions in our area we arnt going to get there. We use the Vakaros Atlas 2 fixed to the front crossbar when we sail and find a difference of 1 - 1.5 knts at times between the GoPro and the Atlas (the latter being more conservative and likely more accurate given its higher sampling rate). No matter getting up into the higher teens in those conditions is impressive @Stanno's lads and Martin and his son might be able to give you an idea of their performance numbers in those conditions.

We sail only on the FCS foils these days so Martin and @Stanno's guys can probably give you solid information with regard to the difference between sailing on the FCS Foils and the C Foils

Sounds like you have an exciting season ahead of you, good luck ... keep the videos coming and post a few here now and then so we can see how you are making out

R

My son Rohan knows Riley well - they've raced each other in Catamaran heaven of Hervey Bay Queensland just a year ago!!! Ro hasn't sailed his C boarder since April, and has been spending time on a 49er, ILCA 7 and various yachts ... and is off to university this weekend so won't be flying any hulls or foiling for a bit ...

Good luck Riley - hope those WA foils stay in one piece, unlike RO's!!

 

[PitPater]

Hey Martin

Keep us posted on how you are making out at Worlds, should be lots of fun

R

 

[martin 'hoff]

Hey Martin

Keep us posted on how you are making out at Worlds, should be lots of fun

Thanks! Good times so far. Just got here. A bit of a bad surprise that the _lower_ gudgeons are different for having the rudders in-board. The top ones you just shift inboard. The bottom ones are a different piece, and we don't have it. We're having a bit of a moment over that.

Crowd is great. Not as big as Garda (85+ boats, vs 25+).

After Worlds, I think FLL + Miami we'll have 5 FCSs – some FLL boats get converted right after, and two loaner boats from US Sailing that live in Miami will also get converted, plus us. Not sure if there'll be enough ppl to sail them, but damn we won't be short on toys.

 

[PitPater]

Dont ever remember seeing anything in the conversion literature that indicated that the lower one was different ... in the end the boat came configured for FCS so I never had to do the conversion myself and no extra parts were provided with the boat...guess that could be a measurement issue?

Would be cool if you could actually find enough folks to actually crew those boats and be able to race regularly in FCS mode...here is hoping

Good Luck Racing!

R

 

[PitPater]

N17 Raking mechanism, gudgeons and other parts just arrived from Nacra (7 Days!!!! from confirmation of the order from the Nacra Store way better than I was expecting)....they are physically larger (hefty) than I imagined them, guess thats why they can use them on the F20 as well

Committed now! First step will to mock up the F15 transoms and see how it all fits and how much raking movement there is with the L rudders in place ... (including the currently installed rubber shim)

R

 

[martin 'hoff]

Brief report from N15 Worlds in FLL. Great regatta, lots of fun, hard work. Location is grand, and they put a good show. But launching and navigating to the race course was challenging. Volunteers at the ramp/dock and tow through most of the way were a hard requirement.

We had a mildly stressful measurement process bc our main crossbeam didn't have enough bend (and didn't want to bend to it), and because the lower gudgeons are different for proper C foil configuration. Top gudgeons are just same, moved inboard. Not so for lowers. Mad scramble to get the correct lower gudgeons and the metal flaps, which we secured just in the nick of time.

First couple days in 10-14kt very wavy-choppy, we placed 16th of 25, best finish was 10th and we were proud. Last 3 days were fickle light winds from the East – each day a bit less chop but always way too much chop relative to the wind.

Upwind in light and fickle, with chop, is the realm of constant gear changes in response to subtle condition changes, and we aren't yet on the pace there. We get some, we miss some. So we'd nail the start, run top pack for the first 100 meters, then arrive at the back of the pack at the top mark. Gain some places downwind, but lose them again on the 2nd upwind.

We shrank the gap every time, learned a ton, and scored some incredible team and process goals. Our final overall score is 22nd but we're incredibly happy and proud of the outcome.

We are way over early in this picture – you can see the pin boat and the flag coming down. We got UDF, but scored the best picture...

Hoisting in light-ish air (8kt?) – you can see I'm slightly cross-eyed, trying to get the spin halyard tension just right for light winds (lining up the splice point to a mark on the mast).

 

[martin 'hoff]

Here's a bad quality video from the RC boat, showing the start of the last race (race 19). Skip to 1 minute in, and you can see us (USA 156) come in with speed, right at the dot, tight on the RC boat.

 

[PitPater]

If you had fun and learned something about the boat then its sounds like it was a great experience and worth doing ... and if you are not over the line at least once early then you are not trying hard enough! ... great pics ... Id imagine it was a good father son bonding experience to boot

R

 

[martin 'hoff]

If you had fun and learned something about the boat then its sounds like it was a great experience and worth doing ... and if you are not over the line at least once early then you are not trying hard enough! ... great pics ... Id imagine it was a good father son bonding experience to boot

R

All of those are true, and more. We booked a huge swank regatta house with the Red Gear Racing gang, with its own dock, so we'd prep over breakfast, then debrief with 3 teams at the end of the day. Jacuzzi, pool, billiards table, pranks. Being semi-local, I lugged my espresso machine and caffeinated the squad (+parents) up in the morning.

We hosted a big bbq inviting some of the out of town teams one evening. Helped folks across the boat park with our big toolbox, got help and advise in return. The event photographer was hosted in the house as well – we all befriended her and got the best pictures of the fleet.

I'm sure I'm forgetting some important parts.

It was a rollicking affair.

 

[PitPater]

Definitely sounds like a good time ... jealous ... just got 2 feet of snow in the last couple of days, apparently 6" more on its way tonite .... I blame the groundhog!

 

[Stanno]

All of those are true, and more. We booked a huge swank regatta house with the Red Gear Racing gang, with its own dock, so we'd prep over breakfast, then debrief with 3 teams at the end of the day. Jacuzzi, pool, billiards table, pranks. Being semi-local, I lugged my espresso machine and caffeinated the squad (+parents) up in the morning.

We hosted a big bbq inviting some of the out of town teams one evening. Helped folks across the boat park with our big toolbox, got help and advise in return. The event photographer was hosted in the house as well – we all befriended her and got the best pictures of the fleet.

I'm sure I'm forgetting some important parts.

It was a rollicking affair.

Regatta done properly!!! Bravo!!

 

[martin 'hoff]

Put the FCS boards for a few days, but changed back to C boards for a mixed fleet regatta that routed over some shallows. Video of the race below.

From the PoV of crew and kite handling downwind, changing back to the foiling kit... in light air it was easy to transition back. In heavy air, however, it was not: when it gets hairy in a big downwind with C boards, you ease the kite to pull the bows up and avoid a pitchpole. On FCS boards easing the kite pops the boat out of the water – foils higher and super unstable, crazy stressful – as it gets hairier you trim tight, even overtrim, to control height.

Anyway - C boards, long distance race:

-

 

[PitPater]

So started fitting up the rudder raking assembly for the F15 on the transom mock ups. Fit looks like it will be a bit better than expected, was thinking I might have to move the rudders inboard a bit (green line is the current centerline location), but if I do it wont be by much. Rudder standoff from transoms (distance from pintle centerline to transom surface) will go from 1" (current) to 3.25" which was as expected. Will finalize the the raking assembly position on the mock up transoms once I have the rudder to rudder centerline fixed.

After that the next step will be to zero the rudder rake and calibrate the movement range. Does anybody know how this is done? Nothing in Nacra's manual indicates as to how to go about doing this (aside from using the physical adjustment mechanism to do the positioning)..... I have never seen anything put out by the N17 folks to how they do this either

What is zero rudder rake? More to the point what is considered the zero datum? Is against true vertical or the back of the transoms (I think the transoms may have a slight slope to them, I may be wrong but I dont think they are perfectly vertical, but I have never leveled the boat to check and see so I dont know for sure?). Does the boat need to be leveled in order to zero the rudders the first time around (I assume once you know where zero rake is you can just do a differential with the transoms and the rudder leading edge in the future and adjust accordingly) We also want to document what our current rudder rake is with the 1/8" rubber shims that were factory installed on the bottom of the rudder casting so we can duplicate our current settings starting out....so knowing what the zero datum is important. I would guess the process would be similar as on the A Class cats as well. Anyway it would be nice to get our hands on a procedure if such an animal exists ... or maybe we are over thinking it

R

 

[Kshack]

Gat an RC helicopter digital pitch gage. Pick a spot on one transom and zero. Use the same spot for both rudders. Now slide the gage over the winglet. The rudders must be pointing straight and the gage needs to be parallel to the hulls.

 

[martin 'hoff]

That looks super @PitPater . Couple comments

- Don't forget the inside of the transom. It's not flat, unfortunately. I would plan to get a couple of G10 plates for backing, and for "absorbing" any irregularities of the transom insides as needed

- Can you put the boat on sawhorses or equiv, high enough that you can lock the rudders down (with the standard kit)? With that, use your phone or the pitch gage that @Kshack suggests, take the transom vertical as the zero pitch. I've been told to use the foil horizontal, but tbh to horizontal is far from flat, so you'd need a 3D printed profile to lock in the angle. Instead, the leading edge of the vertical I think is 'true' vertical. That's what I'd use.



- My understanding is that the standard rudder rake/AoA is either 2 or 3 degrees. Which sounds about right to me, and matches what we feel/find in our N15. (The relationship between rudder AoA and mainfoil is what makes it go, and it's at 2-3 of mainfoil vertical that we get the best foiling – in high wind, high speed, ~2 of mainfoil rake gives us a slight bow down, which at the right speed gets us fast and locked in).

- What will you do with the rudder heads? How do you plan to fit with the (I understand) thinner rod?

- Actually if you are planning to use the standard rudder heads, what you _really_ need is to match the gudgeon positions. Or the rudder head pitch. This will be a lot easier to measure IMHO. No sawhorses needed.

 

[PitPater]

Gat an RC helicopter digital pitch gage. Pick a spot on one transom and zero. Use the same spot for both rudders. Now slide the gage over the winglet. The rudders must be pointing straight and the gage needs to be parallel to the hulls.

Thanks Ken ... so if I read this correctly you are basically you are zeroing the rake against the transom (See Attached)... in much the same way you measure you mast rake angle .... so in a nutshell

1) Zero Pitch Gage (Inclinometer) against a documented transom location (to be able to replicate future zeroing)
2) Set Pitch Gage on winglet with calibration gage edge facing and parallel to the transom face, this value would give you the current rudder rake
3) Adjust rudder rake angle (using adjusment mechanism on top gudgeon assembly) until Pitch Gage value goes to zero

HI MARTIN .....I THINK THIS IS WHAT KEN IS GETTING AT, IT IS EASY TO OVER THINK THIS ... SINCE THERE IS NOTHING SIMILAR TO COMPARE THE F15 TO AT THIS POINT (I.E., N17S AND A CLASS CATS HAVE T RUDDERS AND ITS LIKELY THE AMOUNT OF RUDDER RAKE USED AT ANY GIVEN TIME WILL BE SPECIFIC TO THOSE TYPE OF FOILS AND BOATS). GIVEN THAT, WHAT WE REALLY NEED TO DO IS TO BE ABLE TO SET THE RUDDER RAKE INITIALLY TO WHAT WE HAVE CURRENTLY (AND FOR THE HELL OF IT CALL IT -1 DEGREE), AS WE KNOW WHAT THAT DOES FOR US NOW. ONCE WE HAVE THAT BASELINED WE CAN SCALE OUR AMOUNT OF RUDDER RAKE OFF OF THAT ACCORDINGLY SUCH THAT WE CAN CHANGE THE RUDDER RAKE ON THE FLY BY A KNOWN AMOUNT AND DOCUMENT HOW THAT CHANGES THE PERFORMANCE OF THE BOAT .... AT LEAST THATS THE PLAN ... THINK WHAT KEN IS DESCRIBING IS A METHODOLOGY TO EASILY CHECK AND SET THE BOAT UP THE SAME EVERYTIME ...THE AMOUNT OF RAKE USED WILL REALLY ONLY BE SPECIFIC TO US AND OUR DATUM ... BUT I WOULD EXPECT THE DEGREE OF CHANGE SHOULD BE SIMILAR TO OTHER BOATS

- Don't forget the inside of the transom. It's not flat, unfortunately. I would plan to get a couple of G10 plates for backing, and for "absorbing" any irregularities of the transom insides as needed. YES PLAN IS TO INSTALL BACKING PLATES INTERNALLY (G10 OR ALUMINUM) ... THERE IS CURRENTLY G10 INSIDE THE TRANSOM I ASSUME THEY ADDED THIS TO STRENGTHEN THE TRANSOMS WHEN THEY CHANGED THE BOAT TO A FOILER (SEE PHOTO) OR MAYBE IT WAS STANDARD. MAY ALSO ADD A THIN EXTERNAL ALUMINUM BEARING PLATE ON THE OUTSIDE OF THE TRANSOM AS WELL

- Can you put the boat on sawhorses or equiv, high enough that you can lock the rudders down (with the standard kit)? With that, use your phone or the pitch gage that @Kshack suggests, take the transom vertical as the zero pitch. I've been told to use the foil horizontal, but tbh to horizontal is far from flat, so you'd need a 3D printed profile to lock in the angle. Instead, the leading edge of the vertical I think is 'true' vertical. That's what I'd use. WE WILL PROBABLY DO THIS AND TRY AND LEVEL THE BOAT AS BEST AS POSSIBLE. I DO THINK YOU ARE CORRECT THERE IS A SLIGHT SLOPE TO THE TRANSOM BUT THE ONLY WAY TO DETERMINE THIS IS TO GET THE BOAT AS LEVEL AS POSSIBLE (BE INTERESTING TO PUT THE LEVEL ON THE BOAT WHEN ITS SITTING IN FLAT WATER AND SEE HOW LEVEL IT IS AND WHAT THE TRANSOM ANGLES ARE IN THOSE CONDITIONS ... AS YOU SAY THERE ARE A COUPLE OF COMPLICATIONS AS THE LEADING EDGE OF THE RUDDERS ARE PER SE NOT STRAIGHT (THEY HAVE A SLIGHT TOP TO BOTTOM CURVE ON THEM) AND THE WINGLETS ARE NOT FLAT THEY ARE ROUNDED AND MAY ALREADY HAVE A SLIGHT PITCH TO THEM



- My understanding is that the standard rudder rake/AoA is either 2 or 3 degrees. Which sounds about right to me, and matches what we feel/find in our N15. (The relationship between rudder AoA and mainfoil is what makes it go, and it's at 2-3 of mainfoil vertical that we get the best foiling – in high wind, high speed, ~2 of mainfoil rake gives us a slight bow down, which at the right speed gets us fast and locked in). GEOMETRICALLY SPEAKING ONLY, WITH RESPECT TO THE TRANSOMS THE RUDDERS (WITH THE 1/8" THICK SHIMS) WOULD HAVE APPROXIMATELY -1 DEGREE OF RAKE (AT LEAST ON THIS BOAT) IN THIS CONFIGURATION...BE INTERESTING TO SEE IF THIS IS THE ACTUAL MEASURED AMOUNT....THATS BASED ON THE ASSUMPTION THE RUDDERS WERE VERTICAL (TO THE TRANSOMS) PRIOR TO THE INSTALLATION OF THE RUBBER SHIMS ... AND THATS NOT NECESSARILY THE CASE.

- What will you do with the rudder heads? How do you plan to fit with the (I understand) thinner rod? YES EXISTING RUDDER HEADS WILL REST ON TOP OF THE NEW GUDGEONS AT THEIR CURRENT BOTTOM FACE TO BOTTOM FACE VALUE OF ABOUT 8". THEY WILL BE LOOSELY RESTRAINED FROM MOVING VERTICALLY USING NUTS LOCATED AT THREADED PORTIONS OF THE ROD IN THE GUDGEONS ARE (SIMILAR TO THE CURRENT PINTLE GUDGEON CONFIGURATION). I HAVE TO ORDER NEW BUSHINGS FOR THE RUDDER SIDE GUDGEONS AS THE ROSE BEARING DIAMETER AND THUS THE ROD DIAMETER IS ONLY 1/4" DIAMETER COMPARED TO THE EXISTING PINTLES THAT ARE APPROXIMATELY 3/8" DIAMETER

- Actually if you are planning to use the standard rudder heads, what you _really_ need is to match the gudgeon positions. Or the rudder head pitch. This will be a lot easier to measure IMHO. No sawhorses needed. YES THAT IS EXACTLY THE PLAN

I THINK THIS WHAT KEN IS GETTING AT, IT IS EASY TO OVER THINK THIS ... SINCE THERE IS NOTHING SIMILAR TO COMPARE THE F15 TO AT THIS POINT (IE N17S AND A CLASS CATS HAVE T RUDDERS AND ITS LIKELY THE AMOUNT OF RUDDER RAKE USED AT ANY GIVEN TIME WILL BE SPECIFIC TO THOSE TYPE OF FOILS AND BOATS). GIVEN THAT, WHAT WE REALLY NEED TO DO IS TO BE ABLE TO SET THE RUDDER RAKE INITIALLY TO WHAT WE HAVE CURRENTLY (AND FOR THE HELL OF IT CALL IT -1 DEGREE), AS WE KNOW WHAT THAT DOES FOR US NOW. ONCE WE HAVE THAT BASELINED WE CAN SCALE OUR AMOUNT OF RUDDER RAKE OF THAT ACCORDINGLY SUCH THAT WE CAN CHANGE THE RUDDER RAKE ON THE FLY BY A KNOWN AMOUNT AND DOCUMENT HOW THAT CHANGES THE PERFORMANCE OF THE BOAT .... AT LEAST THATS THE PLAN

 

[PitPater]

I guess technically you dont need to adjust the rake angle to zero in Step 3, but adjust it so it matches the same angle as the existing non raking set up (essentially putting the rudders back to their "Factory Settings"

 

[martin 'hoff]

@PitPater 100% with you – but I do suggest call thecurrent rake "+2". And it matters because the N17 brackets have, I believe, 6 degrees of range.

And the overall goal – beyond rigidity and strength – is to get the N17 brackets to

1 - reproduce that +2 point
2 - AIUI, N17 and a-cats have -2 to +4, so from the standard baseline we need to match that range.

(If we consider the current rudder rake to be "0", then whatwe need from the adjustment system is -4 to +2).

 

[martin 'hoff]

@PitPater the other bits I'm interested are around the rudderhead mounting:

- bushings
- vertical rod - are you going to keep that threaded rod?
- how will you control for up-down slide of the rudder-head? the double nuts on the standard setup basically should be able hold the weight of the boat + rig forces - various foilers have different setups for this. if you use a threaded rod, you can add double nuts in places as you see fit

 

[PitPater]

Hi Martin

I agree, important to know where we want to be range wise so we can set up accordingly, once I get the brackets on I can check the actual full movement range of the N17 assembly and then mark the on the water range accordingly.

Do we know whether the rake response range for the T Foils will be the same for the L Foils? I believe the A Class Cats had L's before they went to the T's ... wonder if they found the response range different for the Ts?

Yes plan is to thread a portion of the rod (not all) probably just above and below the gudgeons to allow me to double nut (and teflon washers) top and bottom if necessary. Should be able to determine the threading areas using the ready rod for the mock up, as indicated looking at 17-4PH Stainless for the rod material ... looks like rose bearing diameter is slight less than 1/4", must be metric..I have some 1/4 steel rod but it wouldnt go through, ready rod just slides through...will put a vernier on it

Sam passed along some names with regard to bushing suppliers and material, so I will track them down once I know exactly what I am looking for.