Anyone have plans or ideas on how to add racks to a Nacra 20? Setting the boat up for another Everglades Challenge next year (March 2018) and would really like to have the convenience of siting on a rack instead of a harness for 300 miles.

sure - get some smart fabricator to make you a set

both my mystere's are set up for my wings (i have set that i can swap on and off boats with 4 bolts

my beams were drilled (horizontally), a tube was welded into the beam that the wings pivot in for transit - when down they "rest/sit" with a pin on the beam caps - the front wing arms have a custom "1/2 cup" that rests over 80% of the beam cap and a pin goes through the wing "cup" and beam.

seanhawes5

Anyone have plans or ideas on how to add racks to a Nacra 20? Setting the boat up for another Everglades Challenge next year (March 2018) and would really like to have the convenience of siting on a rack instead of a harness for 300 miles.

Lee W. had them on his 20 for the GT300. He has moved up to the Carbon20. PM me and I will put you in touch.

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Philip
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MN3

sure - get some smart fabricator to make you a set

both my mystere's are set up for my wings (i have set that i can swap on and off boats with 4 bolts

my beams were drilled (horizontally), a tube was welded into the beam that the wings pivot in for transit - when down they "rest/sit" with a pin on the beam caps - the front wing arms have a custom "1/2 cup" that rests over 80% of the beam cap and a pin goes through the wing "cup" and beam.

MN3

Do you have any plans or close up pictures you could share? Thanks Sean

Sean,
Got the PM. Sending you a text with his contact info.

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Philip
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I had wings on a Mystere 6.0XL,(20' x 10' beam, basically a modern Tornado). They made the boat 13.5' wide.
They were modified Hobie 21 wings. My wife liked them so much she made me buy an H18 Magnum & won't get on the Nacra now.
It is easy to get the Hobie far enough up that the wing drags in the water. That was not the case with these. If you tipped far enough to dunk a wing you were going swimming.
One other thing I noticed. When in rough water, sitting on the wings, there is not much weight on your feet. At speed, boarding waves want to rip your lower legs off. The Mystere has big hulls, you are well off the water, but still, it was surprising how often the bows would cut a wave which then yanked your feet off the hull.
Whatever you build, make sure the tubes are sealed, otherwise, if you do flip, they will hold a ton of water. Hobie inserts a foam plug into the small bracing tubes, the large tubes are sealed, with no drains.
Not sure if this will help you, but I took some close ups of how they were mounted & put them in this album
https://www.thebeachcats.…387f59d3370a231a8fe1718c



Edited by Edchris177 on Apr 29, 2017 - 12:18 AM.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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Edchris177 - so the only way to remove the wings for transport was to remove the end caps, remove the bolts and take the wings 100% off?

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Do you have any plans or close up pictures you could share? Thanks Sean

I plan to drink rum and sail often... hope that helps :)


Oh ... nevermind - here are some pics


















Edited by MN3 on May 01, 2017 - 11:40 AM.

Thanks MN3. Looks great

Quote

Edchris177 - so the only way to remove the wings for transport was to remove the end caps, remove the bolts and take the wings 100% off?

Not quite. I only took the end caps off in order to take the photo, to show how they were anchored inside the beam. The plate with the SS locknuts is captive inside the beam, so you just set the wing in place, hand started the bolts, then tightened with an allen key. I put them on solo, hooking the trap handle under the middle of the seating beam to hold them mostly in plcae while I did the bolts.
Yes, you had to remove the 4 bolts/wing, however, the upper wing could stay installed while on the tilt trailer, so in reality it was 4 bolt, lift the wing off & go. It is not as handy for a trailer sailor as the folding Hobie wings, but I keep mine in the backyard, fully rigged all season.
IIRRC they were 10'3" long, they came off a Hobie 21 I believe. The H21 set them into a pocket on the hull, so there was no pivot point, or small brace tube AKA H18 Magnum. In some ways they were better than the magnum wings. The geometry was such that if you ever drug a wing in the water, you were past the point of no return. The H18 wings drag pretty easy.
Original on H21 looked like this;




Edited by Edchris177 on May 01, 2017 - 08:48 PM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

Quote

Thanks MN3. Looks great

yw/ glad to help!
they are expertly made (and i keep scratching them and messing them up)
want to warn you about adding them - it changes your CE and changes the handling of the boat - it makes weight placement even more important (for my boat at least)

If i was to "order" them to be built custom - i would remove the back 1/4 or 1/3 of them. I NEVER sit there and it's just added weight and windage. I think i may use a bigger mesh on the wings when i replace the current tramp material (less windage)

feel free to ask any other questions

Quote

the upper wing could stay installed while on the tilt trailer,

oh yea, due to the 10' beam it sits on a tilt trailer = gotcha
they look great

PS my pivoting ones mean i don't have to remove (def a 2 person job for me) but securing them in the upright pos is a PITA - i made a pvc brace to prevent them from folding IN any more but they require a lot of rigging to ensure they can't move around during my 5 mile drive. adds 15 - 20 min of rigging / break down time

everything on a boat has it's pros and cons

I looked at making some made for my I20 years ago. It looked straight forward enough to me. I have the abilities to build them but it was not going to be a cheap endeavor. I think you would pay $1-1.5K for a fab shop to build a set. Shouldn't be any real problem for them.



Edited by bacho on May 02, 2017 - 08:03 PM.

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Greenville SC

Offering sails and other go fast parts for A-class catamarans
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I think you would pay $1-1.5K for a fab shop to build a set. Shouldn't be any real problem for them.

I think the most challenging part is fabricating a working attachment system - and this "fab shop" better have a good idea of the forces and the directions of these forces.

I think you would be doing Very well if you get a set made for under $2000

$1300 - for these - wow pretty crappy looking - http://www.sitnsail.com/ (what stops the forward /backward sway of these?)

Quote

$1300 - for these - wow pretty crappy looking - http://www.sitnsail.com/ (what stops the forward /backward sway of these?)

Not crappy at all: http://www.sitnsail.com/SitnSail_Manual.pdf
At least take the time to review the documentation and educate yourself before making assumptions.

Hairfarm

Quote

$1300 - for these - wow pretty crappy looking - http://www.sitnsail.com/ (what stops the forward /backward sway of these?)

Not crappy at all: http://www.sitnsail.com/SitnSail_Manual.pdf
At least take the time to review the documentation and educate yourself before making assumptions.

What makes you think i didn't look at your manual? OH you assumed i hadn't......
i saw it

To me:
This equipment does not look robust enough for my needs, nor does it look comfortable nor does it look safe

the seat width is way too narrow for me,
plus it is a solid bench - i would only fabricate / purchase a mesh wing (tramp material) seat - for comfort and reduced windage both upright and capsized

the lip on the bottom of the bench looks like it could decapitate or delimb someone in a pitch pole


this design looks like it will suffer failure in a common way - lack of sway support both forward and aft and up and down)

the support arms look like they are parallel to the front and rear beams (hard to tell from the images)but without any angle to them, there is nothing preventing forward and aft sway (except the attachment points). any time anyone does a hobie style beaching ... or pitch pole ... there are lots of stresses trying to sway that bench (i.e. rip off the attachment or bend the arms)


Hope i am wrong and your product is great and has many happy customers








Edited by MN3 on Nov 10, 2017 - 05:16 PM.

What about this solution? M32 style studs in the rear and wires from the mast hound in the front. Though a little to wide in this case.



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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

https://www.facebook.com/groups/1192604934176635
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revintage

What about this solution? M32 style studs in the rear and wires from the mast hound in the front. Though a little to wide in this case.

looks good to me

but i would still prefer regular wings over this i think



Edited by MN3 on Nov 12, 2017 - 08:36 AM.

Since Revintage brought up a picture of our Inter 20 wings on Team Ketch Me if you Can for the 2017 Race to Alaska (facebook team page here), I figured I owed some more details on our wings and the research we did -- I had promised to do this a while ago but didn't get to it since the race in June...

First off, it's fair to say there are many ways to skin this cat, both looking at production and custom designs. Below are just some of the inspirations we used - I thought it would help to have them all referenced in one place.

(1) Hobie has various styles: see descriptions here and here (don't miss p2). Good pictures of a "Classic" Hobie 18SX wing assembly here. Note: this is older Hobie wings from Hobie sailing heyday, pre-Hobie Getaway era (short stubby wings).

(2) Nacra/Prindle wings: see on CatSailor here and here -- these look pretty flimsy to me (unsupported fore & aft, no upwards support via halyard, all loads concentrated in beam ends)

(3) Mystere 6.0 custom wings: see discussion on CatSailor (good info on Hobie wings too) and pics on this forum here

(4) M32 wings: see pics here and here

If you google "wings" on TheBeachCats, CatSailor and HobieForums, you get a lot more details, but it helps to know what to look for. The above cover a lot of the most common styles.



Edited by southstars2012 on Nov 15, 2017 - 03:50 AM.

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SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Now in terms of the custom wings we built, here were the key parameters of our design:

- Seat style: we went broadly with a Hobie Comfort seat style

- Beam/hull supports: we went with M32-style supports, as revintage pointed out. These are similar to Hobie 18SX wing supports in terms of overall load distribution (a compression/downwards load on the beam end + a tension/upwards load 6-12'' inwards from the beam end). The M32 style seemed easier to make, and sturdier overall vs. the slim support strut tabs and attachments on the Hobie 18SX wings (though admittedly the later are battle-proven). A critical consideration in favor of both styles was the ability to swing the wings up (at dock or if beating upwind in heavy airs where we wouldn't want the leeward wing dragging).

- Mast wire support: to distribute loads further, we reused old trapeze wires to support the wings from the top in two places (near the front beam, and and about 2/3 between the front beam and the aft beam). We tried to distribute the loads about 50:50 between the beam/hull supports and mast wire support. Perhaps we should have put more load on the mast, because we still broke one of the rear beam connection points... (but were able to jury rig it and continue using the wing, though more gingerly)

- Fore-aft support: we had none. That is not uncommon (see M32 wings, and early H18SX wings for example), and felt ok for our use case (one time race). But I would agree that for long duration uses/cycles it would help to support the wings fore-aft. Hobie later added this to the H18SX with a small strut going from about 6''-12'' behind the rear beam and then going forward to the primary wing support strut (see picture here)

- Primary support struts: these are the large posts that go from the beam to the wing itself, and incur most of the loads. The main decision here is whether to go straight (as we did, also mostly on the M32) or with a curved beam (as on Hobies). A curved beam enables a fully-flat seat, while the straight struts mean the seat is always inclined (and more so if you're lifting a hull). While flat may be best for beer can sailing, the inclined seat felts very safe (little change of you falling backwards out of the seat!).

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Finally, I'll go through a few of the materials decisions we made. Probably more to detail I can share later if people are interested, since the devil is in the details (as often). Keep in mind these wings were not battle tested over time, so better material choices could probably be made with more testing.

You can see more pictures of our wings on our FB photos album here, and in this YouTube video here.

- Main wing outer tubes and primary support struts: aluminum 6061 T6, 1.75'' OD, 1.50'' ID (0.125'' wall thickness), weight 7.5lbs/10ft, estimated section modulus 0.242 inches^3 (higher is better). That was what we could get from a local metal wholesaler.

We used 2x 12ft for the outer tubes, and 4x 3ft (approx) for the primary support struts.

Note: Hobie wings are same alloy, but 1.875'' OD, 1.71'' ID (0.083'' wall thickness) (according to this thread), weight 5.5lbs/10ft, estimated section modulus 0.200 inches^3. So ours were heavier but sturdier than Hobie wings, which felt reasonable given the I20 beam to beam distance is longer so the wing tubes need to carry more load (8.6ft vs. 7.1ft on a Hobie 18).

- Wing inner tube (inboard seat tube): a bit smaller/thiner than outer tube to save on weight, 1.50'' OD, 1.37'' ID (0.065'' wall thickness), weight 3.5lbs/10ft, estimated section modulus 0.101 inches^3. This doesn't take a lot of point loads (the netting distributes the loads nicely, and most of our weight was on the outer tubes anyways), so maybe could have even been downsized further. In contrast, Hobie 18SX wings have the same size for inner/outer tubes.

We used 2x 10ft for the inner tubes, cut down to size (approx 8.5ft each).

- Wing fittings: we used off-the-shelf "Hollaender" (aka SpeedRail) aluminum railing fittings wherever possible.

Specifically:
*4x model 41-8 flanges (here) for connecting each primary support strut to its beam. The flange swivels, allowing the wing to be raised.
*4x model 5Ext-8 tees (here) for connecting each primary support strut to the main wing outer tube. In hindsight, we could have tried the similar but lighter weight 5-8 or 5E-8 tee models (we chose the EXT model because it would better distribute the point loads at the end of the support strut)
*4x model 17-8 adjustable tees (here) for connecting each secondary support strut to the primary support strut
*4x model 5-7 tees (here) for connecting each wing inner tube end to the primary support strut

In hindsight, we could have gone with -7 models (Schedule 40 1.25'' pipe, i.e 1.72'' OD) rather than -8 models (Sched 40 1.5'' pipe, i.e. 1.94'' OD), to save on weight. With the -08 models we had to custom machine some metal rings to bridge the gap between our 1.75'' OD tubes and the 1.94'' fitting sizes, whereas with the -07 models we just needed to shave off a bit from the fittings in the workshop to get the 1.75'' OD tube to fit the 1.72'' fitting sizes.

- Custom beam plates: to attach the primary support strut to each beam, we custom-made and riveted 1x flat metal plates into the beams about 5-6'' from the beam end to distribute the loads, and then screwed in the 41-8 flange into each plate. This would allow us to remove the wings, while keeping the riveted piece in place. Because the rear beam's main track creates a protuberance, we had to work around that (see here). The rivets on one of the rear beam plates did let go, so we clearly didn't get everything right (it seems one of the secondary support strut slipped, transferring all the load onto the primary).

- Secondary support strut "feet": we made some rubberized pads to help the secondary support struts distribute the loads on the beam ends (and to prevent them from moving). We probably should have found a way to pin these struts in a fixed position to avoid them slipping at all.

- Wing seat nets: we used some old Corsair F31 trimaran nets and cut them down to size by hand, lashed with dyneema.

- Additional "safety" nets (lifeline netting): we added these to make sure nothing could be dropped overboard between the hull and wing.

Total cost: $500-600
- $190 for aluminum tubes
- $210 for aluminum railing fittings (those add up fast, $12-15 a piece)
- $40 for lifeline netting
- Some miscellaneous parts amounts for custom beam plates, screws, metal rings, dyneema, etc
- Wing nets were free
- Labor was free (access to metal workshop)

Total weight: approx 50-54 lbs (vs. 58lbs for Hobie 18SX?)
- 33lbs for aluminum tubes (cut to size)
- 13lbs for aluminum railing fittings

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Thanks much for posting up the details - the 1.72/1.75 fit and off-the shelf brackets position this well for home-brew. a flapper wheel inside the bracket or emery cloth outside the tube would clear .03 quickly and still leave a tight fit.

Randii

Hi Southstars2012,

Nice and ingenious build, together with great info. This is how we did it this summer, for us retired guys to get rid of the trapezes. This winter we are shortening the wings a little, moving the fittings to the inner of the hull and widening the beams. Will also go M32 at the rear(great minds think alike) keeping the lines at the front. Not as wide as yours, but we are not heading for Alaska . We are very pleased with the system lifting the leeward wing automatically when sitting on the windward. Will take my time and read all your info, maybe I could loan some of your ideas. You can follow this winters build and our other Frankencat/boat builds at: https://www.facebook.com/groups/1792963567605832/ . Would appreciate you as a group member.

https://www.thebeachcats.…opic/topic/16946/start/0



Edited by revintage on Nov 22, 2017 - 07:14 AM.

--
Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

https://www.facebook.com/groups/1192604934176635
--

Revintage -- I liked the pictures in your BeachCats thread. Thanks for sharing those -- it helps to see the details.
Looks like a great setup, I actually think it's as wide as ours...? (based on how you are sitting -- when we sat our feet touched the hull a bit) I definitely don't think ours replicated a full double-trapeze, which is why we kept the ability to trapeze further out.

The PVC tee fittings you used to connect the different pieces of the wing seem interesting -- might shave a bit of weight (ours were ~0.6 LBS). The fitting weights add-up...!

I also really like the metric 50 OD x2 ID mm tubes, that's very close to the Hobie sizes (50x2mm is approx 1.97'' x 0.079'', vs. Hobie tubes are supposed to be 1.875'' x 0.083'' -- by my math they're about the same weight, and the metric section would be a bit stronger than the Hobie one).

Our wings seem marginally lighter (58-62lbs vs. ~65lbs with yours if I take your 15kg/wing measurement), despite being a bit longer (12ft on the outside). Note I revised upwards our wing weight as I realized I had underestimated the weight of our smaller sections (1.5'' x 0.125'' not 1.5'' x 0.065''). I think you may actually have overestimated your weights a bit:
- The extra tube you use by your feet definitely adds weight (~9-10lbs by my guess, assuming ~9ft per side). Since that's not that structural, I could envision eliminating it or downsizing it to a much smaller tube...
- However our wings would have been ~9 lbs lighter if we had used Hobie or 50x2mm metric sections like yours, instead of the heavy 0.125'' ID sections we had locally.

So net-net they should weigh about the same!

I could see getting the wings down to ~45-49lbs in our design if we used your sections and also removed the forward M32 style supports so the wing was supported up-front by the trapeze wires (using M32 supports only on the back). That would be a very nice weight gain!



Edited by southstars2012 on Nov 22, 2017 - 10:27 PM.

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Correcting some mistakes in my prior post containing the technical details of the R2AK I20 wings. I quoted our wing inner tube sections wrong, and overall weight wrong as a result.

southstars2012

- Wing inner tube (inboard seat tube): a bit smaller than outer tube to save on weight, 1.50'' OD, 1.25'' ID (0.125'' wall thickness), weight 6.4lbs/10ft, estimated section modulus 0.172 inches^3...

Total weight: approx 58-62 lbs (vs. 58lbs for Hobie 18SX?)
- 41lbs for aluminum tubes (cut to size)...

Edited by southstars2012 on Nov 22, 2017 - 10:25 PM.

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Revintage -- One more thing: while I do like your automatic lifting setup (we had considered something similar, again great minds think alike!), in the end we decided we didn't want to force lifting of the downwind side, and found it quite useful to be able keep the downwind wing down. For example, we could split our weights sitting on the downwind wing and upwind wings in light airs, to help the windward hull skim. On the other hand, we lost out on the advantage in heavy air of moving the leeward wing weight further inboard to increase righting moment... (we could manually clip the leeward wing up if we really wanted it, as we did while docking, but this would be hard to do quickly in heavy airs tacking).

I think the ideal solution would be a 'best of both worlds' approach -- using your lifting setup, one could add a secondary adjustment that allows shortening or lengthening the dyneema line between the two wings. In 'short' mode (medium/heavy airs), the weight on the windward wing then lifts up the leeward wing automatically (as in your current setup), while in 'long' mode (light airs) the line is long enough for both wings effectively stay down (as in ours)...

--
SL
Nacra Inter 20 (sold)
2017 Race to Alaska "Team Ketch me if u can"
- Facebook: https://www.facebook.com/TeamKetch/
- Race video highlights: https://www.youtube.com/watch?v=YTWp4DP0VcA
Sausalito CA
--

Southstars,
Will just give a short reply now, will come back when I have consider all your valuable input.
1 You designed your setup for open sea, I designed for lake sailing. This might explain some of the differences on our basically alike designs.
2 You mention weight and this is something to really look into. Have calculated the weight of PVC-tubing to use in some places and it is 0,66kg/m while the alu tube is 0,81kg/m. Not very much to gain there. But the T-fittings are really something, will compare weight with the alu pieces.

--
Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

https://www.facebook.com/groups/1192604934176635
--