Howard Fund

[AlexQ23]

Hello! I have a great project that I want to propose to Howard Fund. Is-it still active? Can we still submit some lines? If yes, will it be better to send it by mail or e-mai? Let me know. Thank you.

[AYRSwebadmin]

Definitely by email! or you can post the bones of it here.
Regards
AYRS Web Admin

[AlexQ23]

Designing a small boat is not an easy task. The principal difficulty encountered comes from the weight of the crew members that could totalise almost half the entire mass of the boat it-self. The mobility of this weight compromised greatly boat lines and stability. So, imagine now, that you want to design a performing, easy towable, seaworthy family micro-cruiser. There, you will hit a real challenge.
The boat should be as light as possible to be easily towable behind a small car but, in the mean time, it should be well ballasted to own the suitable stability when sailing on rough sea. It should be small enough to keep the ballast weight as low as possible and still be efficient and roomy to accommodate a small family aboard. To be fast, we need to maximize the flotation length and minimize wetted surface and drag of hull and appendages. Resolving this equation looks practically impossible to accomplish.
The development of a new rig named “roto-duplex”, will help to solve, at least partially, this paradoxical assessment. But we have also to design and build a different type of craft especially dedicated to this kind of rig. That’s how Kasala project was born.
Kasala is a double chine plywood hull of 5,5m /18’ length, a beam of 2,3 m/7’ 8’’ and a minimum draft of 0,315 m / 12”. With a STIX of nearly 19, it has a great stability and can carry 23 m² divided in two main sails.
Despite this new kind of rig, several other features were investigate and included in this design:
- High hull and appendages efficiency
- Oscillating single rudder
- Shock proof keel arrangement
- Impact resistant lower plywood panels
- Singular accommodation configuration
- Ergonomic cockpit
- Permanently mount crutches
- Insubmersibility through the help of closed cell foam mattresses
- Innovative main-sail hook
- Powerful sculling oar
- Efficient anchor
Kasala looks to me to be a perfect candidate to the Howard Fund grant. I will send by mail a complete documentation to the subject to the AYRS editor for future investigation. If some of you are interested, feel free to ask for more information.

[Fredthecharlie]

Sounds interesting, I look forward to seeing the full details but what is meant by oscillating rudder?
FCB

[AlexQ23]

Rather than words, a picture will show you what I call an oscillating rudder. But if you want to rename it, feel free! And here is the explanation I give in the presentation:
“I decided to use a single rudder, even if the hull shape, from a plan view, looks like a wedge. With this kind of hull, when the boat reaches important heeling angles, a large surface of the rudder will pull out of the water. In response to this, KASALA’s rudder assembly will be able to swing from one side to the other on a circular sector bolted onto the transom. Handy ropes will operate its movements. By using a single rudder, we reduce weight, wetted surface and keep a lively tiller.
Despite this, one can find a NACA 0010 profile compensate rudder that could be lifted completely out of the water when beaching.”
But,sorry I don't know how to insert a pic! Alex.

[Fredthecharlie]

Thank you for the explanation, if I understand it properly it means that th rudder mout swings to the leward side of the boat and offers the benefit of twin rudders using only one.
FCB

[AlexQ23]

Hello! Here are the pictures of the oscillating rudder.

[Robert Biegler]

One of Dashew's books has a picture of an Open 60 (or possibly a predecessor to that design rule) with such a rudder. I think it was called a tilting rudder there. I also saw it on Mudskipper, a steel cruising boat from Australia that came to Trondheim. There are pictures in one of the Junk rig Association Newsletters.

What advantage do you see compared to double rudders? A drawback I can see is having to shift the rudder during a tack or gybe, possibly quite quickly, while other events demand attention. A double rudder would seem to have the advantage that swinging up the windward rudder can wait until everything else is done, and lowering it again can happen before things get busy.

[AlexQ23]

A boat is a choice of parameters and you have to keep in mind that Kasala is a laboratory. I'm the kind of helsman who like to sail with a long stick up to my shoulder and between two fingers! You can not do that with twin rudders. The tiller is often tough and not really pleasant to handle.
Minimizing wetted surface and load is what drive me to go for a single rudder. But you are right, it could be questionable when tacking. But there again, before the tack the rudder can be swinged in central position and replaced proprely to leeward well after, when the boat sail on the new head.
With the roto-duplex rig, the rudder is almost useless. Sooner, I will unveiled some highlights to this kind of rig and it will surely be more comprehensive.

[AlexQ23]

Roto-duplex rig.
Duplex rig also called twin cat rig or bi-plan rig consist of 2 masts lying side by side symmetrically at sheer line or mainly on each hull of a catamaran. This rig is rarely used on monohull due to the fact that, on close or beam reach, the windward sail shade the leeward one.
With the roto-duplex as shown on pictures of Kasala model, the mast assembly can rotate and both sails can be exposed to “clear” or “fresh” wind. On closed reach for example, the leeward sail is moved forward. Before wind, or on broad reach, the two sails are wide open like butterfly wings.
I find several benefit but also few drawback to this device.
Benefit:
- Large sail area with lower center of pressure
- Only two identical main sail (no jib or spi)
- Large possibility of sail reduction with only 2 reefing lines per sail
- When furled the sails stay on the boom (no sails in cab)
- Ease for jibbing one sail at a time
Drawback:
- Tacking is more complex and time consuming
- Restricted access to front deck
To be proved:
- Better efficiency.
Eventually, with rotating small mast section, sail efficiency should be greater. Also, heading on beat should be better due to rig configuration and sails specifications.

[Robert Biegler]

Have you decided how to attach the masts to the circular track? I suppose that connection must cope with compression as well as upwards pull. And I think sail forces will always push the whole kaboodle to lee, so you must actively control the angle of the mast assembly to the wind?
Rotation of the mast assembly trades off gap against stagger. You might be interested in two papers on "Gap and stagger effects on biplanes with end plates": https://arc.aiaa.org/doi/10.2514/6.2009-1085 and https://arc.aiaa.org/doi/abs/10.2514/6.2009-1086

[AlexQ23]

Well notice! Yes there is some pressure (or traction) on side mast base. This pressure could be estimated at 5000 N (1100 lbs) per side including an appropriate safety factor. In fact the rail is a hight quality grade aluminium "U" shape channel, perfectly bend and lay on his side on deck. Originaly,it was an UHMWPE shoe that slides in between the channel branch. This slide receive the pressure directly from the mast. But it's hard to operate at full pressure, and in the future, four Nylatron rollers will be added to each shoes and attached with a semi-elastic manner. You don't want any play or gap there but they still have to rotate freely. A tricky design, for sure!
I know the papers you mentionned. Unfortunately they are not free accessible. So, I use more older references as the one of Prandlt or Munk. Also, a 2D CFD basic configuration shows that some sails arrangments could be relevant. But thank's.

[Robert Biegler]

I'm the kind of helsman who like to sail with a long stick up to my shoulder and between two fingers! You can not do that with twin rudders.

Me, too, but back when I sailed a Hobie 14, that's how I had it set up, and with much of the lateral resistance being provided by the rudders, they saw some load. So fingertip control can be achieved with some twin rudders. What do you expect to prevent this on your boat?

With the roto-duplex rig, the rudder is almost useless.

Why is that?

[AlexQ23]

On most catamaran the rudders are vertical. By contrast on beam transom monohull, the rudders are angling about 15 or 20°. This create some friction in mechanical linkage and increase the stiffness of the tiller. Diabolo rubber are often use to realize those attachment.
With a duplex rig, like with a bi-plan airplane, the cell is more stable. Numerous studies confirm that and it's also confirm by experience. With Kasala, the model shows that the rudder is not really loaded and that the unit can stay straight on a steady course just with sails adjustment. We still have to prove that with the full size model.

[AlexQ23]

Few words again on roto-duplex rig:
It doesn’t seem that this rig arouse much enthusiasm. But we all know that sailors are conservative and are allergic to drastic change. Wind is a free energy and trying to improve efficiency of a sailing arrangement is for poor interest for a great majority of us. This is true! But we have to look forward and the benefit of such rig will, maybe one day, serve a most universal cause like freight ship propulsion, for example.
When describing this kind of rig, I don’t want to use the word biplane. For most people, biplane is a reference to an early flying machine equipped with two pairs of wings. And then the comparison between monoplane and biplane is never far. This is not our case! Don’t forget that a sloop rig is also a biplane where the wings are much more in tandem configuration rather than standing side by side; but there is still a pair of sails! With the roto-duplex rig we will be able to trim the sails from “biplane” configuration to “tandem” one. It should be, somewhere in between this adjustment range, a practical arrangement that will deliver the maximum efficiency out the sails. The theory tells us that it could happen. But, a sailboat is not a flying machine; we are not operating at the same speed or with the same wing (or sail) shape or profile. So it’s quite difficult to extract a true prediction out of the different studies that are realized for airplanes. I really think that we have to try this on a real sailing model. That’s why the Kasala project is born. There is a time where experimentation should happen, most of the time to prove the soundness of an idea that will lead to new theory or a new vision of an existing theory. That’s how the science can grow.
So I hope that why my project will be published, it will received some consideration.

[Fredthecharlie]

Hello
The photos seem to suggest you have built the boat itself but the rig appears to be a model, I find your project very interesting but feel that the boat ought to be sailed with a conventional rig to establish its performance before moving on to the new rig.
There are lots of novel features described in the hull which need to be proven before attempting the rig.
FCB

[AlexQ23]

I'm glad that you find the boat interesting! Unfortunately, the rig is integrally part of the project and another type of rig can not be fixed on those hull without affecting balance, stability and efficiency . But sails performances can be demonstrated with polar curves. Also, competing with other similar units like Aviator or Sailart18 can demonstrate rig performance. I'm sure that active members of AYRS could give me relevant advice to help me in this matter. Actually, the rig is completed too; I'm now working on booms that are also quiet unusual.

[Robert Biegler]

Actually, the rig is completed too; I'm now working on booms that are also quiet unusual.

That was going to be my next question. I noticed the model has conventional booms and no apparent control over twist. There doesn't seem enough leverage for a vang, and a traveller might have problems with masts moving fore and aft. I would use wishbone booms. What solution have you come to, after a lot more thought?

[AlexQ23]

Hello Robert,

For sure a wishbone could surely do the work too! But...
- Some are not so effective for fine tuning the sails.
- The reefing is not as simple as it looks
- With a rigid mast and a square top sails they are not particularly recommended
- When the sail is furled you can’t leave it on post (or on the boom)
So I prefer to go with a boom. The boom is a half 6 inches thin aluminum pipe, rigidified in the bottom with a full length rail. The main sheet traveller slides on this rail. There is a 20:1 cascade pulley boomvang and a gas spring that can keep the boom up. When reefing or furling the sail fall easily into the boom. This wide boom will also minimized the air mixing between intrados and extrados of the sail (pressure side and less pressure side).
A small rope and a bungee cord keep the sheet traveller automatically at the same vertical position, no matter if the sail is going forward or backward.
Keep in mind also that the mast rotates. Hope the 2D drawing will help you to understand how everything works!

[Robert Biegler]

For sure a wishbone could surely do the work too! But...
- Some are not so effective for fine tuning the sails.

Because you can't separate outhaul from leach tension? I think that could be done if you have a vang to regulate the vertical position of the end of the boom, and you attach the clew to a ring sliding on a short horizontal tube, with an outhaul attached to the ring. And the lever arm of that vang would be a lot more advantageous, so you wouldn't need to put so much compression load on the boom, and a lower point load where the vang attaches. Then again, Rob Denney uses simply a rigid boom, with bearings separated by a similar distance as your goose neck and vang, and it seems to work.

- The reefing is not as simple as it looks

Probably not.

There is an alternative that has not, to my knowledge, been tried yet: use rigid, curved battens that rotate around the chord, like a Bierig camber spar, and sheet each batten like in a junk rig. In theory, that should give you good control over twist, low loads on the rig, and good reefing. And in theory, theory and practice are the same...

- With a rigid mast and a square top sails they are not particularly recommended

Why is that?

[AlexQ23]

I’m sorry, but I never use a junk rig and I don’t know anything about it. But, what I know is that I never see any winning racing sailboat equipped with such a rig. Bernard Moitessier sails with such rig when young but he never keeps it on her later craft.
A square top sail is quite specific. The top of the sail should be able to twist in gust. It will act like a relief valve. When the top is flexing, the induced drag will collapse or at least diminish. It’s all a question of leech tension, flexion of sail battens and flexion of mast top. So it’s really not an easy process to design a sail for such consideration and it’s more than often a try an error process. So, if somebody can help me there, it will be well appreciate. You will find here enclosed what I propose to do with Kasala sails. Can we improve the profile or curvature or batten arrangement?

[AlexQ23]

Select the right keel profile.
A few weeks ago I complete installation of Kasala keel inside his trunk. Everything was going fine and the simple lifting system I adopt, allows a 10 years old boy to raise or lower the keel. It’s a 6:1 pulley system install on top of the cab, completed with an external small winch with a 10:1 handle. So it’s easy and simple to control the 330 lbs keel from cockpit.
But it could be interesting to share with all of you, how I choose the right keel profile. As you surely known, we are looking to have a profile that can give us the maximum lift for the minimal drag. But the maximum lift at an angle of attack of around 4° is not a real problem, because all the profile we are looking for, deliver about the same amount of lift at this angle. So, limiting the drag is the issue. And the drag is directly proportional to the thickness of the profile. So, limiting the thickness of the profile is critical. With Kasala we can come with a 7.5 % of the cord, thanks to the two layers of carbon fibre that stiffen and encapsulate the hard wood core. We have also to keep in mind that we will have to cut the tip of the trailing edge and that, also, will add drag. But now, we will have to choose between several profiles. The most useful for us where design by NACA and more specifically, the four digit series, the 63 series, the 64 series or the 65 series. In a real interesting paper presented by David Vacanti, “Keel and rudder design”, easily found on the net, in fig 9, we can find at table 3, for each profile, the drag coefficient at maximum lift in regard to the foil thickness. And we can see that for about 7% thickness, the minimum drag occurs with the 63 series. So we adopt this profile for Kasala.

[John Perry]

Hi Alex - your workmanship, as evidenced by your photographs, looks superb!

One point I would make with regard to keel section is that I think you need to consider the situation when the wind is strong, the boat is trying to go to windward so keel loading is high but speed through the water is very low due to the effect of rough water and windage. Might this require a different keel section to that which gives minimum drag under more favourable sailing conditions?
John

[AlexQ23]

Hi John!
Thanks’ for your compliments.
It’s an interesting topic you bring here. For sure, that when we select a keel profile we assume that it works in a laminar flow. But it’s true that it is rarely the case. However, I don’t think that the choice of a keel profile has something to do with the situation you describe.
The lift of a keel is proportional to the lift coefficient, the speed squared and the area. A fin keel operates at high lift coefficient. But, when speed drop, as per your example, the keel can stall.
It is a reason why the keel area is often more large than what it should do. Generally, we adopt a ratio between sail area and keel of 3% and 1% for the rudder. So you should have an appropriate keel area. But you should have also an appropriate Keel aspect ratio. A long keel for example with a low aspect ratio will never experience the same problem in this situation.
You have to keep in mind that the lifting force of the centerboard, when the boat is close to the wind is directly opposed to the lifting force of the sails. The speed factor is also quite important. If you pay attention to sailing models, you will notice that the keel area looks larger than what it should be in real. It’s not rare to see a keel/sail area ratio of 20% on sailing models!
So, when you boat is slow, proportionally, you need more keel area. The faster you go, the less “wing” you need. If we go back to the early days of airplanes, multiplans were the rule. As soon as we increase the speed, the lift will be provides by a single set of wings. And on a high speed missile, few winglets will do the job. The speed of our displacement boats will not vary much from one boat to another. With my 5,5 m I can reach 6 knots. A 9 meter will reach 7,5 knots. So for an increase in length of 63%, the increase in speed will be only 25%!
Obviously, the keel is a complex matter and there again the choice of right parameters are critical.

[AlexQ23]

Kasala latest news!
The boat is now fully completed and we make our first trial with the sails on, a few days ago. It was a light air test, around 6 to 8 km/h. However the boat react admiralty well. He is well balanced, lively and performed better than expected especially up wind. I was really surprise by the rig and how by rotating the mast we gain in performance. It was expected that when you slide the leeward sail before the windward one you should have a better efficiency of the rig. But that makes all the difference! There are some tiny bits to correct like to stiffen the top of the mast but nothing major.
So next year I will be able to collect all the required data and brings a complete analysis of the boat in all sailing condition.

[Fredthecharlie]

Does the winch work both ways ie. allow a controlled drop of the keel rather than having to ease the tail of the rope from the tackle?

[AlexQ23]

The purpose of the winch is triple: As you mentioned, it helps to hoist the keel, but also to raise the mast and finally it could help to raise the sails. But it never serve to handle the sails. As I mentioned earlier I have design and install a hook that locked the halyard when sails up. An interresting feature with this hook is that it can work also with the reefing lines. I will be please to show how this hook is working but I will have to figure how to insert picture now (Tynipic is out of business).

[AYRSwebadmin]

If you use the Full Editor instead of the Quick Reply, you will see below the message box a tab labelled Attachments. That allows you to insert files either inline or as links.

If all else fails, email them to webadmin@ayrs.org and I will insert them.

[salvage]

hi its me sav

I would like to apply for the Howard fund

do I need to send it by e-mail or in the post ?

I have some photos that I have tried to post on the AYRS facebook page but they dont seem to appear?

not sure why everything needs to be so complicated .. normally facebook is so straight forward

perhaps you could look into simplifying things so that us who are not computer experts but still have a brain can operate them.

just a thought..a bit wound up over it all

cheers sav

[John Perry]

Hi Sav - I have replied privately with more detail, but if people want to apply for the Howard fund they should follow guidlines on this website (About AYRS>Howard fund). The email for sending an application to the AYRS Secretary is office@ayrs.org

I am also confused about the AYRS Facebook page - it seems that someone has set up a second AYRS page on Facebook. I am sure we dont need two AYRS Facebook pages, but I am not much of a Facebook person so I am not the best person to sort this out.

John

[AlexQ23]

Kasala latest news
Let’s say first of all that the boat is a wonder!! She is sailing really well with her roto-duplex rig! A new rig is born! With only two sails, we can reach the same speed (around 5 kn with a 10/12 kn wind), no matter the sector the wind is blowing. 30/40° beating the wind depending on how strong he is blowing! I will try soon to complete a more detailed report that could be incorporated in a future Catalyst. But in the mean time, I want to share some pictures with all you and also to thank everybody for the support you give me during those past years.

[John Perry]

Well done getting to this stage - your boat looks good, sails appear to set well. Of course our Editor will be pleased to receive anything you can write about it! Are you planing to do more testing this year, or will it wait to Springtime now?

[AlexQ23]

No, it's time to go sleeping for winter! it's already snowing here! And it's also time to put data and words together to complete a report !

[AlexQ23]

2020-12-03_160344.pdf

(236.15 KiB) Downloaded 2297 times

2020-12-03_160344.pdf

(236.15 KiB) Downloaded 2297 times

I still not have enough time to complete my report. But in the mean time I can unveil the polar diagram of the duplex rig. It shows everything and how efficient this rig ! I wish happy holydays to all of you!

[Robert Biegler]

Nice data, but how did you derive the polar for the hypothetical sloop?

I have a suggestion for getting real data: in the next season, generate another set of polars with the two masts of your Duplex rig always on the centreline. I expect the sheeting won't let you simulate sailing wing and wing then, but for all courses on which a sloop would keep both jib and main on the same side, this should be the best approximation for an actual sloop. In fact, when it comes to finding out whether controlling gap and stagger independent of course has an advantage, this would be better than comparing to a sloop, because you keep everything else constant, such as sail profile and planform. And I actually expect that giving up some stagger for a greater gap would give you an advantage over the sloop when hard on the wind.

What do you think?

[AlexQ23]

Hi Robert!
Yes, it’s a great idea, but... In fact, I’m not able to put one sail directly behind the other one, with my rig. If one sail sits in the boat axis, the other one lays on windward or leeward side. So, on close reach, close hauled and let’s say, beam reach the comparison with a sloop should be identical. But then, on broad reach and even in running, we cannot compare both rigs. On broad reach, for example, the windward sail mask completely the leeward one if placed like we will do on a sloop. That’s exactly what happened on a simple Duplex rig where the two sails are parallel. One sail shade the other one. On the roto-duplex, I have to bring the leeward main sail astern and to put the other one pass the wind’s eye on the front. I now, it’s a bit difficult to imagine and even more difficult to explain. But it’s easy done in practice!
So the curve I extrapolate for a sloop come from a curve from an old ACC ( Marchaj), when they still have a unique and non planning hull. Knowing both hull speeds we can easily deduct the right profile. Also, I have some polar from a Fareast 18, and they look quite similar. But, definitely we have to do more and better comparison.

[Robert Biegler]

I forgot that the masts are a bit ahead of the rotation axis.

Even so, can the rig be rotated so far that the forward and aft sails are along a line parallel to the centreline? Could the forward sail be sheeted in far enough for upwind work? That should still be the closest comparison to a sloop.

[AlexQ23]

Unfortunately I’m not able to do that due to the location of main sheet holding point.
But it’s not so important afterward. But, what is surprising with this boat, is that he is faster before wind! And that’s incredible! So I try to figure how and I find that the drag coefficient of the sails configuration should be way above what we normally take in to account ( a bit above 1 or 1,17). I had a chance to carefully measure the drag of the hull and I know that at a speed of 5.5 knts we found 310 N. So it’s easy to calculate the drag coefficient of the sails. Cz = Fvx /( rho/2*Vap²*S) where Fvx is normally the force induce by the sails that we can now replace by the drag coefficient of the hull; rho/2 is half the density of the air and in metric we replace it by 0,65; Vap² is the apparent wind speed square, so at a 12 knts reel wind speed we deduct boat speed (5,5 knts) and we found 6,5 knts or 3,34 m/s square it becomes 11,15. And S is the area of the sails plus the area of the hull section hit by the wind and that comes to 24 m². So Cz becomes now 310/ 0,65*11,15*24 equal 1,78!! So it seems that the area between the two open sails react as well as an effective drag area! Going before wind is not easy with a sloop rig but it becomes so natural for a roto-duplex rig that the boat keeps the cape and goes fast!!

[TheoSchmidt]

Hi Alex,
This thread stopped just before Christmas 2020. Any more news or did you post it elsewhere? Did you now write it up as a submission for the Howard Fund?