5.5 low wings :: Catamaran Sailboats at TheBeachcats.com

5.5 low wings

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revintage

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Posted: Sep 28, 2017 - 05:40 AM

Trying out new low wings on the old nacra 5.5 on Swedish lake Malaren in 8-16knt on this nice autumn day. The leeward wing lifts, using a pair of small blocks and a 3mm Dyneema rope, when you sit on the windward one, making it possible to set them so much lower than the commercial high, sofa like racks. The slim hulls aren´t really capable to bear three persons, still we logged 17knts.

http://racerdirekt.com/0927.mov

Brgds
Lars

Edited by revintage on Sep 28, 2017 - 07:50 AM.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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MN3

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Posted: Sep 28, 2017 - 09:43 AM

looks neat
how does it pivot ?

What makes "low" better than another wing?

are you out further from the boat?

Edited by MN3 on Sep 28, 2017 - 03:18 PM.
tominpa

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Posted: Sep 28, 2017 - 10:01 AM

Looks like it uses the trap wire to support raising and lowering on the front corner, and there may be a second eye midway along the wing? Can't see where that line terminates or cleats. How is this mounted to the crossbars? That is a lot of leverage.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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dmgbear55

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Posted: Sep 28, 2017 - 01:30 PM

This is very interesting. I would like to see more details of how the wing tubes are joined or mate to the beams.
These kinds of aluminum castings to join the tubes are very common for whitewater raft frames, so readily available at NRS and other providers.

An example:
https://www.nrs.com/produ…nrs-lopro-frame-fittings

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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nofearofflying

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Posted: Sep 28, 2017 - 03:50 PM

fantastic,i too would love to see diagrams/plans for construction installation-sailing mate Joe lost 1 bench in nacra 570 capsize, and I lost pair of factory benches with prindle 16 theft. Do you think i could modify so they affixed to Dart 18?(Have 2,lost 1 Dart to hurricane Irma) What benefit to low close to water bench/wing? Great video, Looks like summer over in Sweden
revintage

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Posted: Sep 28, 2017 - 04:40 PM

Mating to the beams are made very simple using 60x40mm U-beams and 6mm bolts. Tubes are 50x2mm. The dark grey joints are made of sturdy PVC used for water piping while I found the aluminium ones in Germany http://www.brinck-rohrverbinder.de/shop/Rohrverbinder/-Oslash;-50-mm/T-Verbinder-5540::2713.html.

I am using both trapeze wires, one in each corner of the wings, with lifting and lowering only at the front. As the leeward wing lifts, there is slack in the leeward rear wire, ie it will not get in the way of the mainsail even on a broad reach.

Lowering the center-of-effort of the ballast is a no-brainer .

Pic below is from the first try. Clic the pic for details.

At the beach:

No summer in Sweden, just a few sunny days with 15-18 C air temp.

About Dart I guess you will have to place the "hinges" on top of the beams but inside of the hull fittings. Will actually place the next version on top of the inner beam straps. Will come back about that when tested.

Brgds
Lars

Edited by revintage on Sep 28, 2017 - 04:55 PM.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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Dogboy

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Posted: Sep 28, 2017 - 10:08 PM

It is an interesting idea, but it also seems like having the wings only held down by gravity could be a fairly major liability during a capsize. Not sure how much fun it would be to be sitting out on the wing as the boat goes over and then having the entire wing fold in and dump you off. I could also see there being potential (safety) issues with the wings being unsecured with the boat on its side or the wings slamming back down when the boat comes upright.

sm
Andinista

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Posted: Sep 29, 2017 - 08:39 AM

QuoteLowering the center-of-effort of the ballast is a no-brainer icon_wink .

The factor between tilted and horizontal wing is cos(angle), assuming it's the same length
When it's about man on the trapeze, length can't be extended, only angle can be adjusted, therefore trap systems are adjustable. But with the wings, you could make longer ones to compensate for cos(angle) and forget about it. So I would question if it's really worth the effort to make them adjustable.

Actually the math is not that simple, the above is valid only with the boat horizontal, as the boat heels, the tilted wings would be less and less effective compared to ones aligned to the beams. But on one side I think this effect is not so relevant and on the other, if the hull can't be kept low it means it's time to adjust something else
revintage

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Posted: Sep 29, 2017 - 08:47 AM

Good thinking sm,

Actually got the foldable idea from M32 and they seem to accept full fold when capsizing .

If one wants to prevent a total fold when turning over, a stop could easily be adapted to prevent the wings to fold more than the leeward lift.

The wings are fairly light at 15kg/side(no prob as we are both fairly light) so another solution is to add a elastic line in parallell with the 3mm Dyneema "lift line" to keep the wings down/unfolded when not loaded by the crew.

Will rebuild this winter as I have a pair of 18SQ beams on their way from Holland. Will then be able to shorten the wings ca 30cm/side.

The reason for adding wings is that we are retired, without the acrobatic skills to trapeze any longer .

Edited by revintage on Sep 29, 2017 - 08:49 AM.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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MN3

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Posted: Sep 29, 2017 - 09:00 AM

interesting

Edited by MN3 on Sep 29, 2017 - 09:03 AM.
revintage

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Posted: Sep 29, 2017 - 11:46 AM

Andinista

The factor between tilted and horizontal wing is cos(angle), assuming it's the same length

Hi Andinista,

You are right about that, but to be picky it is not only about cos when you tilt the wing. If going for an extremely steep tilt like 45 degree, which is typical of the beachcats with fixed wings, compared to horizontal, you loose 1-0.707 times the wing width in righting arm. On a horizontal(or just above) wing you can also change your body CoE more easily by hiking with your back more to windward like with a trapeze, ie the the more tilted the more upright you sit with your back.

My idea was to mimic the position you get when using trapeze. But also get some righting arm. In the position I sit on the first image I get about 20cm more leverage compared to trapeze.

Having tried angles from to horizontal I have found just above 10 degrees works best. When going horizontal it´s a pain to rise up from your comfy position even though I have left the trapeze handles on the the wires .

In purely mathematical terms the differencies might not be big, but you get the feeling of a more stable and balanced ride the lower you get.

Edited by revintage on Sep 29, 2017 - 11:55 AM.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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Andinista

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Posted: Sep 29, 2017 - 03:14 PM

OK. So it's more about functional factors, and you have been experimenting, now it makes more sense to me. Interesting
Andinista

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Posted: Sep 29, 2017 - 03:26 PM

Your beachwheels also called my attention. I had thought of something like that but separate sets for each hull, would that work too? Not needing wheels today but who knows in the future..
revintage

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Posted: Sep 29, 2017 - 04:22 PM

It would absolutely work. About the wheels it is also my intention to remove the tube between, it isn´t even bolted. Probably one should add an elastic strap to keep them in place on each hull. Will go for that when I add the wider beams.

Another idea stolen from M32, that uses 4 sets .

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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Andinista

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Posted: Sep 29, 2017 - 04:33 PM

Cool. Yes, I thought of a strap too. It wouldn't work aft of the front beam, but it's about enough on that boat (same as mine)
revintage

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Posted: Sep 29, 2017 - 04:53 PM

Hmm, didn´t think about that. I usually have to place the wheels just behind the front beam. Might be able to sneak the strap in the corner just aft of the beam, before the trampoline.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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Andinista

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Posted: Sep 29, 2017 - 05:24 PM

maybe one line only. It would also be hard to grab the other end
dmgbear55

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Posted: Sep 29, 2017 - 07:16 PM

Are the cradles laminated wood, or a composite construction? Your wheels look like they are similar to wheelbarrow wheels, did you snitch some hardware from your wife's garden shed?

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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revintage

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Posted: Sep 30, 2017 - 07:10 AM

Haha, no it´s actually the cheapest 8" wheels I could find, had to drill them for 1" axle though.

Still I am not satisfied with the wheels, need something with a flat profile. Wonder if 6" width and 11" diameter is enough? Guess 16" diameter would be better but they are awfully expensive

Cradles seems to be GRP clad with carpet, got them together with the boat and seems to be made for beachcat trolleys.

Will test without centeraxle next week, might take a snapshot.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

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Andinista

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Posted: Sep 30, 2017 - 10:21 AM

An idea: Put two lines on each set, with some sort of quick attachment at each end, one end attached at the shroud and the other at the front beam or maybe at the forestay bridle. Both starting from the center of the cradle to avoid rotating it. A long line towards the bridle may seem too much but it would probably be handy to retrieve the wheel from the bow on the water. All this just to avoid that the cradle slides along hull, i'm assuming that would be enough to keep them there.
Sorry for the off topic...

Edited by Andinista on Sep 30, 2017 - 10:22 AM.