Hi Alan,
you are very close to.
In accordance with my consultant, once the boat is fully centered, I shall adds some lead at the bow and adjust the bulb to reestablish the longitudinal balance.
In view of that I should drill another hole in the bulb !
Of course recessing the Rig and Fin/Bulb, should help so far the Hull dynamic balance is not corrupted.
Cheers
ClaudioD
PS :
another simple example of damping is the ice skater. Once he want to increase the rotational speed is bringing his arms close to the chest and when he want to slow down he will open the arms until he stop.
Claudio - while at the very extreme of my thoughts, and with the obvious need to slightly refine the deck to hull connections to a more rounded “chine” concept, (as well as relocated waterline) I am thinking of using the 123 cd6 - but upside down - and retain your foam bow concept previously pictured. Also, by shifting everything rearward, the difference between mast and keel lead would remain the same - providing similar helm control, while greatly extending the bows for the forward displacement you are seeking. Surely a wide “flair” on the bows would contribute to a “quick stop” as the bow came down on a wave?
I do not infer the design change to be taken at face value - only a thought as to how it would work as a monohull design. Something to consider is all -
Increasing the rotational inertia will certainly help damping the pitching oscillation, especially with a piercing designed bow.
But why start by adding lead in the bow. Isn’t there some “free” gain to be made first by moving foward the battery pack up to the bow, and even the sails servo(s) in front of the mast? By free I mean that this won’t add to the total weight. With this optimized, we may then consider adding some lead for extra damping.
P.S. Won’t any pitching damping attempt affects yaw damping, asking for a bigger rudder or slower manoeuver? Or do we consider that the water friction is way more important that this added inertia?
Hi Dick,
very particular approach indeed and as say often an architect, friend of mines, when I’m asking some questions, make it, try it and do not forget to tel me how it work !!
Cheers
ClaudioD
Glad to hear I’m on the right track Claudio, still heaps to learn and it’s a lot of fun learning !
Sylian, we are on the same page, one boat where I had no free ballast I moved the winch in front of the mast and it sails much better in rough water.
On another boat where have 300 grams free ballast I left the winch behind the mast and crept the free ballast forward until it sailed with minimum pitching.
In both cases the bulb was last item that was fixed into position after the best hull balance was found.
From what I can deduct, the more buoyancy in the bow, the more ballast you can move forward to help stabilise the hull heading up wind ?
The downside is when running the leverage from the sails in a blow can bury the bow much easier, the only way to minimise this problem is to run slightly off the wind (not square)
since I like experimenting, and as St Thomas, I just made a little rudimentary jig as in the drawing below and picture :
From that it is clear that adding ballast at the extreme help a lot in damping the oscillations.
It could be the battery, the sail servo, additional ballast.
Obviously the hull design and dimensioning shall consider the options taken. As Alan says the bulb is the last to be mounted as such to obtain the balance .
Cheers
ClaudioD
Great stuff Claudio ! your rudimentary jig test proves the seesaw principle … the question I struggled with the theory was how to apply it in practice & I would like to share what I did.
In the workshop set up the boat (fully rigged ready to sail) to balance the it on the designed C.B point (marked on the hull) then using the ballast/C.G I moved these until the hull was balance along DWL.
I wanted to keep the ballast just in front mast base (to minimise nose diving tendency when running) so when positioning the ballast in the hull if I thought the ballast was too far forward, I then moved the Bulb (C.G) aft until the balance was found again, so far I’m happy with the results.
The next thing I would like to do is take the mathematical C.F position and try and find it in practice … any ideas ?
Claudio, now I cannot sleep thinking about C.F:rolleyes:
Am I right in thinking that C.F is fixed part of hull design that is transferred into construction ? or in other words once the hull is constructed there is no way you can change the C.F as it the result of the distribution of hull volumes along the DWL.
I’m thinking about how one can physically measure C.F, and wondering if I reverse C.B balance at the hull and looking at balancing the hull using bulb C.G as reference to extreme points of DWL to find C.F ? (e.g the C.F should be in middle of DWL)
I understand ideally the C.F should be in-line with C.B or maximum 1% forward of DWL, and that having C.F behind the C.B is not good, why I’m really not sure, maybe you can explain ?
Hi Alan,
The LCF is the geometrical center of the water plan area and cannot be modified once the hull is constructed like the LCB.
Is correct to say that LCF as well the LCB should not move each other statically by more then 1% when the boat is tilted within 25°/30°. Closer tolerance, better is.
Now I know it’s different but since there are expert boat designers and builders here what about a completely different type of bow design like the Mini 6.50 747. A completely different approach and it works in this class with obviously faster speed downwind as the boat start surfing much earlier than the others and it seems to also work upwind too (that’s more amazing). Have a look at this video //youtu.be/AgBxZDaKnQ4
Little OT and nothing new, simply higher on the water to cross the ocean. See American Scow Class created long time ago : http://layc.net/sailing/c-scow/
ClaudioD
Call it laziness or just because the place where I shall carry the tests is some 50miles from home.
Strange enough in Nice, where I’m living, there is no calm place where to put the model boat in the water !
Since I’m very patient person I wait the arrival of Alan to organize a trip together in less the 10 days from now.
This give me time to study the future development on the same model.
She really does look stunning & I’m sure her sailing abilities will reflect the time and effort that have gone into the design & build stages. I’m guessing that age and experience give wisdom and above all, patience - I’m sure that I and many other contributers wouldn’t be able to wait quite as long before the maiden voyage!! Speaking of maiden voyages, I’ll certainly be interested to hear how you get on with the constant control of 2 winches and whether or not you feel a new channel allocation would be beneficial.
Once again, many congratulations on a superb looking yacht & I look forward to reading your and Alan’s comments on her performance.
+1 She does look fantastic- she even looks fast on her boat stand ! test on the water will tell if she’s up to her expectation - one thing for sure there was a lot of work put into her. Can’t wait to see pics or video of her in the water with other boats…
Hi everybody, I hope me too that the nice looking will maintain the promises !
This footage show the ponds where we will go to test the 1.2.3.
Is a natural protected area and RC sail models can use only a limited authorized place.
Definitely a fabulous venue for RC Yachting but my goodness, what a drive from Nice. Is there really nothing on your doorstep that’s suitable? When ‘Enterprise’ is finished (!!) I’ll only need to drive 15-20 minutes (about 15 km) to reach a usable/suitable site - and I begrudge that - I’d much rather it was literally on my doorstep, even better would be in the back garden!
