Dear Mr. Sidecar

[Sidecar]

Has any proa put a lifting foil on the outside of the short side? I know you don't normally heel enough to have it be useful, but since proa folks tend to try stuff "normal" people wouldn't...

Yes

John Pizzey tried it, see photo. Theory being that it becomes a self levelling device making flying a hull easier and “safer”. It was bi directional.

Sidecar originally had a canting bi directional foil. Canted 45 deg to windward, it did lift the ama early, at around 7.5 knots, as opposed to 9.0 knots without. Canted to leeward, theoretically, it gave you extra RM and lift to windward. But you ran the risk of popping it and suddenly having much less RM, just when you need it most. The forces and loads involved were huge, I could never engineer the controls well enough, the hinge took 3 iterations before it was man enough. Dragging the foil through the water slowed the boat by a knot, so was hard to see any benefit overall. I took it off, with no regrets.

PS

Photo: You can just make out foil in retracted position. Another risk was “catching” it retracted in big seas going downwind.

 

[SkipJ]

"Sidecar originally had a canting bi directional foil. Canted 45 deg to windward, it did lift the ama early, at around 7.5 knots, as opposed to 9.0 knots without. Canted to leeward, theoretically, it gave you extra RM and lift to windward. But you ran the risk of popping it and suddenly having much less RM, just when you need it most. The forces and loads involved were huge, I could never engineer the controls well enough, the hinge took 3 iterations before it was man enough. Dragging the foil through the water slowed the boat by a knot, so was hard to see any benefit overall. I took it off, with no regrets."

Apparently canted foils just don't mix with proas. There was a short article in AYRS 121 by Pierre-Yves regarding his 8m pacific proa which started with a canted float but had a tendency to bury the thing coming off a wave downwind resulting in a slow motion diagonal capsize.

 

[Sidecar]

Apparently canted foils just don't mix with proas. There was a short article in AYRS 121 by Pierre-Yves regarding his 8m pacific proa which started with a canted float but had a tendency to bury the thing coming off a wave downwind resulting in a slow motion diagonal capsize.

Hard to see how a (canted) foil could drive you under, I can see how a (long) canted ama could drive you under, especially if there was sufficient differential flex in the cross beams encouraging it to do so.

Sidecar’s (aka) wing has some torsional flex, and I have changed the bridle attachment of the outer shroud and boom to single point, because the aft part of the bridle was taking all the tension and twisting the aft wing end up, imperceptibly turning the nose down. I could sail Sidecar even upwind in bad chop with water coming over the ama. Never a danger, just disconcerting. With single point (no chance of twist transferrance) and sheeting the windward jib 2:1 onto the front strut, I can twist the wing so that the nose now rides imperceptibly high and keeps it there. The greater the sheet tension, the greater the nose lift. I could make the wing stiffer with a layer of carbon all round on the outer half, but FTB, am happy to experiment.

Watch the flexible ama section in the video:

 

[munt]

Someone with a brain explain the function of that ama???

 

[patzefran]

Ballasted keel above the water !

 

[Sidecar]

Someone with a brain explain the function of that ama???

I can’t claim to have a brain, but the “Equilibre” ama is designed to be articulated, looking for a smoother ama ride over/ through waves, with less resistance. It is not an uncommon feature in many traditional proas. If you look at their aka beam systems, there are many which are setup to act as a compound spring. Ditto small amas. Provided they provide the requisite RM and sufficient reserve buoyancy for being caught aback, there is less drag and pitching with them.

Regarding suspension systems, the Gougeon brothers also tried something similar:

Document sans titre

I didn’t design Sidecar to specifically have ama shock absorption, but it inherent to a certain extent with the use of a wing. If I stand on the end of my ama and bounce, you can see the wing twist a little and the other ama bow go up and down around 100mm. I did design Sidecar to have a small ama for the reasons above, and it helped to keep wing twist down.

 

[munt]

It seems like that ama is so small and light it can't be doing anything..?

 

[Sidecar]

Depends on how heavy it is…… many traditional proas have/had solid logs for amas. I don’t know ”Equilibre’s“ details, but the oversized main hull helps makes the ama look small as well.

Sidecar’s ama has batteries in it, and space for drinking water, 2nd anchor and chain, plus any other gear which is handy to have, but don’t use often. And you don’t have to shift any of it when you “tack”.

And the ama is the balance provider for the weight of the akas plus anything carried in or on them. Sidecar carries the main anchor and chain, mooring warps, spare sheets, fenders, boat hook, etc, all in the wing, outboard of the cockpit. Out of the way, but still easy to get at from the cockpit. Anything which doesn’t need to be in the main hull, isn’t stored in the main hull. Saves space in the main hull too. And you don’t have to shift any of it when you “tack”.

 

[don54321]

My factory built Tremolino, a Newick design, uses mast sections for akas / beams which in practice are very flexible. The waterstays, contribute the load bearing strength, and rather than being parallel with the beams, extend from the corners of the tramp to a point in the center of the boat (near the waterline. By virtue of the angle, it does not totally constrain the rise and fall of the corners of the tramp and rocking of the floats. It delivers an incredibly smooth ride. (comfort is one of the best features of the boat). The guy who sold it to me, bought the folding version of the Tremolino which has rigid I beam like beams. It rides nowhere near as smoothly, despite identical hulls. The flexing does not exude an appearance of strength, though 32 seasons later, I guess it proves the soundness of engineering.

 

[Hell-Bent]

Not shunting, but gently rounding up:

View attachment 554550

Apologies, video is too big. I will post again when it is sorted…..

I managed to compress that down to a size that could be uploaded. Unfortunately, because SA's file size limitations are more useless than its home page, most of the video quality (which was already lacking) was demolished in the process. Let's all enjoy this 480i video clip of Sidecar cruising past which apparently was more interesting than the fish on the line at the time.

Headphone users beware...

 

[munt]

Very great!

 

[Sidecar]

Sorry to bump the thread, but for those of you who would like to know more about Sidecar, there is now a lot of information on Proafile:

Proafile - multihull design concepts and review

Proafile - multihull design concepts and review

proafile.com

 

[SkipJ]

Yes a lot more in depth info, thanks for posting.
FWIW a few additional data points for Lateral area/Sail area P52; 9% Trivial obsession; 17% Current projec; 10.6% Trivial Obsession probably shouldn't be included since it was primarily a trial horse built with materials at hand and under canvased.
I hadn't considered total lateral/sail area before but always shoot for having the static lateral area if the float (ama) at $% of sail area.

 

[Sidecar]

Proafile has a lot more info, drawings and pictures than what was published, so hopefully they will use some of it for a couple more articles soon……

 

[Hell-Bent]

Great to finally see an article on there about Sidecar! I agree that they should do a followup with the remaining documents, although it was pretty thorough with the explanation. I'm too busy building and flying drones to work on my own designs at the moment, but this might have just inspired me to give them another pass...

 

[Sidecar]

Sorry to bump the thread, but for those of you who would like to know more about Sidecar, there is now a lot of information on Proafile:

Proafile - multihull design concepts and review

Proafile - multihull design concepts and review

proafile.com

The Proafile article now contains some drawings and I know now, that there will be at least 2 more articles with more photos etc, coming soon, which may be of interest to proa fans and open minded multihull enthusiasts……

 

[Ocean View]

Great article Bob.

This thread and the Profile article is excellent info.

Glad to see your design and build skills came to fruition and worked as planned.

 

[Sidecar]

Just published on ProaFile:

Proafile - multihull design concepts and review

Proafile - multihull design concepts and review

proafile.com

There will be another article to come next week on Bi plane rigs.

Much of what I have said in these articles is the same or similar to the many bits and pieces on this thread and elsewhere all over SA. I thought it best, for those that would like to refer to it and explore more easily, to get them into one place, and not buried everwhere in multiple threads, conversations and thread drift.