Yrvind

sharpii2 I'm with you on this one, your points are valid and well thought out, good post. I believe, preach and always advise KISS - keep it simple and stupid. This rig is overtly complicated and the structural engineering challenges are so huge that failure becomes a given. Now that my boat is finally finished and I can play and experiment with it, the KISS principle shows it self once again as the only way forward.

http://www.boatdesign.net/forums/boat-building/manies-microcruiser-27869-69.html#post700872

more updates soon

 

Thanks for the kind words, Manie.

I have never been out of sight of land on a boat in my life, but I do read a lot.

I also like to play with design ideas, as I have just enough knowledge of engineering and design principles to be dangerous.

I like your mini cruiser design, but I haven't quite figured out the sail. Is is a balanced lug?

What I like most about it is the retractable awning.

Anyone who has any experience at all out doors will certainly see its merit, its necessity.

Being that I'm quite poor, the likely hood of me owning any kind of a boat seems remote. I have no place to keep it.

Lately, I have taken an interest in "raid" races and cruises, where the travel is coastal or inland and the boats are very small. At least owning a boat that can do that is at least conceivable if not entirely possible at his point.

Here's an example of one I have designed (see attachment).

The main thing I've done is moved the skipper out of the stern and into the middle of the boat, where his weight will be the least harmful and do the most good.

To do this, I had to have remote steering, as a five or six foot tiller on a boat with a three foot beam just isn't practical.

The mast had to moved out of the way too, and securely stepped. So I divided the rig, with one mast stepped against the forward bulkhead and the aft mast stepped against the aft one.

This is a good set up for a boom tent for sleeping on board.

The two sails, with their Center of Areas separated by some distance, can be used to help with self steering.

The rudder kicks back much the way an outboard engine does. It has an elastic strap to pull it back down.

At least somewhat dry storage is to be had with the two compartments, fore and aft, which also serve as emergency flotation.

 

yes it is a balanced lug sail and it works FANTASTICALLY !!!

I will post more pics of it soon on the water

 

I see. Interesting set up. Seems the boom is always well under control, as it has a double gallows. Or are those lazy jacks?

 

Well as for a spirited reply Sven certainly makes his point loud and clear!

http://www.yrvind.com/present_project/

It goes to show that the old saying of "different strokes for different folks" always holds true, and one thing that is always very important in any healthy debate is that we can amicably "agree to disagree"

I suppose that in certain aspects I am very fortunate to have a good understanding of engines and computers, therefore an outboard motor is not a problem for me at all - and electronics on a boat does not worry me much. So what I see as complicated you probably wont, and what you may see a complicated I may not mind at all.

This is a bit off topic but I rebuild compactor / rammer / tamper engines (Robin EH12) and here are some pics that may be of interest to some readers. So an outboard motor is easy for me, no problem at all.

And as always I wish Sven well and the best of luck.
Sven you have taught me a lot, thanks.

 

Sven indeed made his point about the KISS principle LOL !!
I'm an advocate of A. Einstein who said that things need to be as simple as possible but....not simpler.
Sven has the "habbit" of change during this design/built but it seldom get's simpler. Change is only usefull if it is an improvement over the existing.
Comparing a living creature,even something as basic as a cel, in terms of complexity with a boat is something only Sven can come up with to "justify" that complicating things isn't that bad LOL !!!

He is an extremely experienced sailor but to he's dead wrong about the KISS principle for me....but who cares about that

 

I’ve been studying Sven’s latest post.

I do agree with him that there is definitely a scale factor that goes
with the Square: Cube law.

But I think there is one thing he is not considering.

That the YRVIN 10 is much more dense than his original BRIS, which had close to the same design displacement.

To get an idea of how much more dense one is over the other, I use my
Heft factor (Hf) system to compare.

IIRC, the original BRIS was about 6.1 m long and about 1.8 m wide and she displaced about 1.5 mt.

To find her Hf, I use the following formula:

20 * Vol./((Beam ^ 2) * Length

So the Hf for BRIS is: 20 * 1.5/((1.8 ^ 2) * 6.10) which equals 1.52

Now for the YRVIN 10.

As far as I know, the YRVIN 10 has a Beam of about 1.7 m and, of course, a Length of 3.05 m. Now, assuming the displacement is about the same for both boats, I’ll find the Hf for the YRVIN 10.

20 * 1.5/ ((1.7 ^ 2) * 3.05) which comes to a Hf of 3.40.

Now, that’s assuming the Hull Depths are roughly the same. If anything
the YRVIN 10 probably has a lower Hull Depth, which would make her even more dense.

The consequence of this is that the YRVIN 10 will be hit much harder by
advancing breakers than the old BRIS was.

This is because there was much more of the old BRIS for the breaker to hit than there will be for the new YERVIN 10. For this reason, the old
BRIS could be driven before the breaker, as the denser YRVIN 10, which is more than twice as hard to get moving, will take a much harder hit.

To demonstrate this, I suggest Sven’s old walnut demonstration.

In it, he takes a walnut, puts it on a hard surface, and smashes with a
hammer. Then he takes another walnut, holds it in one hand, and tries to smash it with a hammer.

I suggest a variation on this demonstration. I suggest he takes a walnut, glues it to a block of wood, that weighs about as much as his hand, then holds the block of wood, in one hand, while again trying to smash the walnut with a hammer. This is a crude representation of what I see as the situation.

Naturally, the Hull itself will most certainly be strong enough.

It’s the Rig that is most vulnerable.

An advancing breaker could come on deck and just take the Rig with it, as it departs. As an added consideration, it could also rip out Mast
attachment points and other Deck fittings, leaving holes in the Deck.

For this reason, the Rig has to be very strong and securely mounted on
the boat. For a boat this size and this dense, it needs to be nearly
ridiculously massive. It needs to be at least strong enough to capsize
the boat. And that just gets us to the ball park.

The two sketches, I have attached below, give some idea of what I think is called for.

I took Sven’s idea, of bracing the raised mast, to its ultimate
conclusion.

I drew an asymmetrical “A” frame Mast, which can pivot fore and aft.
To allow this I drew double pivot plates, which I call “Shoes”. These
Shoes have only a large diameter pivot pin and no locking pin.

The locking pin was eliminated because I think it will be worse than
useless. This is because there will be some stretch with the fore and aft
stays, especially if the lanyards shown are used. This will put all the
load on the locking pin and the shoe itself, if the locking pin doesn’t
fail first. This load, especially if it’s a shock load, from a sudden
gust, or breaker hit, may be sufficient to rip the shoe attachment bolts
right out of the deck.

With no locking pins, the stretch of the stays may give the rig an added
advantage of some fore and aft resilience, where it will be needed the
most.

I don’t think laying the Mast down in a storm is a good idea, especially
if it is left attached to the Shoes. Too much of it will trail aft, in
the happy hunting grounds of the breakers.

By raking it aft, there is a good chance that the boat will heave too,
especially if there is a ’Board down. This is an old trick used by the
Scots, with their famous Zulu fishing boats.

Raking the mast forward, with no sail, will certainly cause the boat to
run well before the wind.

I’m not sure the asymmetrical mast will clear the cabin, when it is laid
down on the deck. It might need some kind of a crutch to hold it up just
enough to clear it.

As for the ‘Board, I suggest a fore and aft pivoting “Lee Board”, which
is really a “Side Center Board” (as much of a mutilation of the English
language, that term is, it does get the point across) (see third
attachment). It is held to the side of the boat with a massive pivot pin,
with a large diameter, thick, washer like Bushing, on the outside. It
would probably be nearly 2.0 m long and nearly half that in width. The
structure would be so massive that the same ‘Board can be used on both tacks.

 

sharpii2 a very good post !!!!!
Lots of things to think about there.

I'll stay with KISS

 

Flap on Leeboard​

Flaps seems to work well on the relatively small rudders of big ships, so the idea to put a flap on a leeboard in the described conditions looks promising . .

Flap Rudder --- Images --- YouTube​

 

I think Sven possibly underestimates the power needed to make the flaps or slotted flaps work.
It's not for jokes that on take off, with full application of the flaps that an airplane needs a LOT more power than while cruising when the flaps are not in use.
There hasn't been a one sided medal invented yet, it still has two sides.....

I'm not an expert by all means but to me it looks that the drag on this set up can cause the opposite outcome of what Sven is expecting......but there's no evolution without experimenting.

He's adding complexity at a big rate, but that's only my opinion.

"It's difficult to keep non moving parts in one piece on a boat, moving parts constantly trying to get away from that damn boat as quickly as possible......" LOL

 

Sven is talking about deploying the flap while fighting gales head on at an estimated speed of half a knot through the water. I don't think the flap consumes a lot of power at that speed. However, it's the question whether the flap increases the efficacy of the leeboard sufficiently at such a low speed, only way to know for sure is testing I think.

 

An interesting idea for sure. I wish Sven the best of luck, if he uses it.

But I seriously doubt it will do him much good.

He plans on resisting fierce winds and associated near surface current with a boat with less than a 10 ft waterline.

Originally, the "lee boards" were supposed to be a kind of go with the flow device, meaning that they were to be retracted in stormy weather, so they don't trip the boat when it's hit by a breaker. The rudders too were to be retractable, IIRC.

Now they're supposed to hold the boat against such a storm, so it won't move too far in the wrong direction during it.

Seems to me he would have done just as well with a long, fixed keel.

With the long keel, he could heave to in stormy conditions to reduce his wrong way drift. Since the long keel would likely have considerably more area than the proposed lee boards, and it acts more like snow plow than a wing, it would be quite effective in this regard.

The risk in doing this will be capsize, of course, but that might be acceptable.

He could also set up the lee boards, now that he has committed himself to them, to act as side centerboards. This way, he could have one or both down at the same time. With both down, he has effectively doubled his lateral area.

I think even a tubby, heavy boat like his could quite comfortably do 3 kts, and average 2, when being driven back by storms is factored in.

The real problem I see with the flap idea is it produces much higher lift, but at a much higher drag/lift ratio. My father's Cessna had flaps. To use them required full power, or nearly so. He certainly could not use them in an engine out glide, except, maybe, for the last few seconds before landing. This would be to stall the plane's lift, once it was near the ground. More likely he wouldn't try that unless he had a very short landing space, as the risk of applying them too soon, and having the plane drop from the sky, would be too great.

Looking at his 1/8 scale model, the lee boards seem quite weakly mounted, in that the whetted area has a tremendous amount of leverage against the narrow surface they pivot against. I can imagine one good breaker hit breaking the board, the pivot axle, or the narrow strip of hull it all is attached to. Adding the proposed flap, which seems to attach only to the lee board, only seems to heighten this risk, even though the high density of the boat will certainly mitigate that to some degree (see my earlier post).

 

Angélique,
If the flap doesn't consume much power than it doesn't deliver much work....
you only can get out of flaps what you put into it and not at the same rate.
The good thing is that Sven keep's looking for ways to increase the chance of making the circumnavigation a succes.

Adding a flap to what probably is the weakest point of an airfoil, the trailing edge, calls for good structural engineering in order to avoid loosing both ,flap and leeboard.
A non-engineer like myself tends to replace knowledge with weight/bulk to get the job done, rather than light weight structures situated in the right positions.For this case, I think Sven is fishing in the same murky water as I do.......but at least he's trying.

I think that those flaps will cause him much more trouble than benefit, that's my opinion.

 

Agree, hence the question in my previous post.

 

the Ten

Well folks it's all official now. I have started building my "ten"

http://www.boatdesign.net/forums/boat-building/manies-ten-51428.html