Boat balance?????

[Crag Cay]

I'm afraid I must second Jehardiman's words of caution.

Bilge keels, shallow (looking) draft, steel, 3.5 tons of lead in 20 tons displacement, adding bulkheads and generators which have a weight component above the wl, 'beefing' up the rigging which is weight with an enormous lever arm, removing lead....... Any one of these is food for thought. Together they signal that some informed investigation is needed.

Don't be comforted by her stiffness when moving around on board or under sail. There are several factors which can contribute to initial stability 'stiffness'. However at larger angles of heel and in ultimate stability, the height of the CofG becomes of primary importance. Nothing you have said so far would enable anyone to give an informed opinion about whether this has been compromised in any significant way. Jehardiman's recommendation of having someone investigate further is to be endorsed. However it's not a small job and would involve several man-days of costs.

To return to the original trim question: Is her original interior essentially back in its original positions? If so, it's probably worth investigating further with a long-ish spirit level, when she is afloat. Remember she will have been built level to the designer's plans and although the sole (floor) isn't guaranteed horizontal (although often is), any bulkheads will have been plumbed upright. Check them all out, including the ends of bunks, etc. See if any variance from vertical is consistent in mm/metre. If it is, work out what that corresponds to over her overall length.

[mallo]

Hi Crag Cay
Thanks for your input, the interior is as close as it was, the levels are not far out to be noticeable as we are probably only talking 25mm over the whole length of the boat. All apart from the bulkhead (aluminium) are low down it the boat, well below the waterline, as in my last reply the next boat the designer went on to design and built didn’t have a centre keel filled with lead, only the bilge keels (I am not sure if the designer had the confidence to do away with the centre keel at that time) she crossed the Atlantic on several occasions and crossed the Pacific (she is currently on the North West American coast) on one trip in the Atlantic they got caught out in a hurricane they had some damage but the hull behaved well, this boat had a dog house with a lot of things even higher up (some of the windows were smashed and they had to board them up, she is a similar length, breath and draft) they went on to build another 20 years on, this one had an aluminium dog house(she is in Austria).
Surely with a bilge keel boat when she is upright the weight of the two keels are counteracting each other as the boat heels one keel is being lifted up and the other being pushed under the boat, as she heels more the keel being lifted must be acting more and more trying to right the boat, more so the a traditional keeled boat (due to the angle of the bilge keels being offset as apposed to one centre keel) I understand that a traditional keeled boat would have a longer (deeper) keel to counteract this. Everything is very low down, when we took the original engine out this had a day tank end exhaust box all above the engine and waterline, the engine is about 12-18” below the waterline, the steel fuel tank top about 24” again below the waterline. With regards to the rigging, the original galvanized rigging was larger than the current one; we haven’t added much weight up the mast, we have added weight but low down in the hull (as much as possible).
I can’t feel that we have changed things that much as surely their would be a noticeable change in the heeling moment and sailing performance???
I wish the original designer was still alive; I could try and find out his thoughts on his design. She is not a standard/traditional bilge keel boat; she is a cross from a traditional keeled boat to a bilge keeled boat and has a lot weight low down.
The original enquiry was how is the righting moment worked out, is it done from the plans or is the boat tested and then it worked out from there?
Thanks again for your help/advise its appreciated
Michael Allo

[jehardiman]

Originally Posted by mallo

Hi jehardiman

What is involved to do a set of righting moment curves? What would be the cost and how do they do them (from plans or the actual hull)?

Right now, the hard part is getting the lines, either from a plan, which you said you do not have, or lifting them directly from the hull. If she was up on the hard, it would be a few days work to get enough to rough in the lines (maybe a little more with the bilge keels). After you have the lines in a format that will go into a form calculator program it is a few hours to spit out the curves of form and cross curves of stability. Next comes the inclining experiment to determine actual KG which is waterborne and about a days work to do. So all total say 5 to 7 days chargable time plus rental of the lasers and levels if any.

Don't know what the going dayrate is in your location for a small boat NA to take on an inclining is over there. But a quick google show that one company (Ace Marine http://www.acemarine.co.uk/html/stability.html ) will do one up for 1250 GBP which jives with my off the cuff estimate of 7 days with a dayrate of $300.00 to $400.00 to give $2100.00 to $2800.00 (1071 to 1428 GBP). If you do pay for one, make sure that you get all the documents signed and in compliance with the current EU specs. That will come in handy down the road.

Edit: I forgot to add this little gem :

Note: I have no commerical association with the company(s) cited above and recommend doing design research before selection of any product or service.

[tri - star]

To mallo:
The advice from jihardiman is VERY practical and to the point.
" ....lifting them (the lines) directly from the hull." will answer
most of your questions.
Like; " .....is she more tender ? "
Of course she is !
Given: almost everything done recently, by your account,
to the vessel - is all ABOVE it's C.of G.
The boat, in a stiff gust - WILL heel more now. For sure!
The only debate is - how much?

If you acquaint your self, in depth, with only one designer's term
- I suggest it be - Craig Cay's reference to:
"........an enourmous LEVER ARM......"
Fishermen drown every year, off our coast, not fully understanding
why - putting a new 300 lb piece of equipment high up on
their boat - and greatly adding to the LEVER ARM, is so dangerous.

Increasing the mast height - adds rigging/mast weight and
raises the Center of Effort of the sails.
This ALL adds to said - LEVER ARM.
Most people - even experienced sailors - are very suprised to learn
how only few hundred lbs of force, becomes
so powerful - when it's way up high.

Some us are getting concerned about the present situation
re: your boat and your future intentions.

This is not a time to be: Penny WISE and pound FOOLISH.
It is difficult to give you specific advice - as we, at best can
only receive - info. in general.
So before any more money and time is spent:
Get some " As BUILT lines." by a hands on guy, who lives
close by.

[mallo]

Hi Jehardiman
Thanks for answering the question on how to find out the righting curves, that it’s taken from the lines, we have some basic plans somewhere, I will look them out and see what information can be got from them.
It looks as if we will have to take the boat to the UK (she is currently laid up with a cover over and masts in dry storage) and get someone to take a look at her and "bite the bullet".
Thanks for your help
Best wishes
Michael

[mallo]

Hi Tri-Star
Getting someone to look at the lines and comment on the righting moments is probably the way forward, unfortunately there isn’t anyone here capable of doing so.

I understand what you are all saying but we haven’t put gear up high at all, if anything its as low down in the boat as possible and probably below the centre of gravity, we have also take some weight out of the mast (replaced a load of wire halyards to rope, a tenth of the weight of the originals) this is going the other way to what you suggest.

Also she isn’t tender as in one of my previous posts I mentioned that we are reefing in the same amount of wind so to me this signals that we haven’t changed the righting moment…she doesn’t heel more in a stiff gust at all.

I don’t know where you got the idea that we have increased the mast height, this hasn’t happened at all, we still have the original 1939 one if I was to change the mast I would put one of the same height back.

We have had some fast/successful trips last year since we have changed things around, including sailing in the UK in 45kts of wind without any problems, (we don’t usually go out in these conditions but it was in fairly sheltered water up the Solent and Southampton water.

As I mentioned in my previous post there isn’t anyone with the experience here to help with the subject, unfortunately I only have a very limited set of plans, It might be enough.

Thanks for your help
Best wishes
Michael

[Tim B]

A lot of the info here is based on initial stability premises, which are fine upto about 10 degrees, but are not vastly useful after that.

Tanks are considered in initial stability using:

GMeff = GM - ( Ixx[fluid surface] / fluid volume )

GZ=GM*sin( heel angle )

However, for stability at large angles, a full tank can be considered as a solid mass without too much inaccuracy.

If you can post a few drawings, I MIGHT be able to have a quick look before next week.

If you have a section shape forward, middle and aft on one drawing, and sheer, waterline and profile view, then I can definitely draw something that resembles your yacht pretty closely. I'll also need to know the displacement.

I can then give you a "GEOMETRIC GZ" ie. assuming that the CG is on the origin and it is reasonably easy to work out the true GZ from there. By adjusting it based on the movement of the CG.

Cheers,

Tim B.

[mallo]

Hi Tim
Thanks for your reply, I would be very interested in your input and comments, I will try and find the drawings we have, however I am unsure if I can find this information out before next week, (have a very busy weekend coming up) we are based in the Channel Islands and have been over to the Southampton Boat show with the boat for the last few years, would it help to see the boat or has it all got to be done from the plans? We will probably be over for the next show later on in the year.
Thanks again for your help
Michael Allo

[Tim B]

I can't guarantee that what I draw will be an exact drawing of your yacht. However, It should be pretty close.

Unfortunately I'll probably be moving to Glasgow in June, but with luck I'll be back for Cowes Week (not a business engagement, honest!!!).

I'll try to get it done reasonably quickly, but I've got quite a bit of work on at the moment.

Cheers,

Tim B.

[tri - star]

To mallo:
The new information from you - indicates that there is less
to be concerned about - than was initialy presumed.
We can, after all, only make "educated guesses" from the
often sketchy generalities people give us.
So I stand corrected re: rigging/mast weight.
However, you stated,
" ....we now have a larger sail area than before..."
A common way to increase said, sail area, is to increase mast
height. So this was a reasonable presumption.
Also you state that you, ".....leave things the way they
are and see how we get on...."
So one might infer, that you WERE considering,
increasing the mast height.
You have also stated:
"......Dad decided to remove .......ballast."
( How much - is left to our imagination.)
"......this is higher in the hull...."
"......with a different engine....."
( Most likly a HEAVIER lump of iron.)
" I am sure we have more gear onboard than ever."
"......fitting an Onan gen....160 Kgs..."
"......if I have taken too much ballast out."

All the above statements - indicate a reduction in the
stability of the vessel.

The aforementioned, deceased fishermen, did not
consider that their new, heavier gen. were very
high up.
However, my "high" is a lot lower than their "high".
You will be suprised how little an increase
in height - is required for a increase in weight or increase
in Force, to decrease stability - significantly.
Tug boats roll over all the time. Often right at the dock.
And these vessels, are hardly to be considered "high"
off the water.
Allthough, your new gen. and main engine are relatively
low down - the fact that ballast has been removed -
means that their weight MIGHT contribute more to
reducing stability than the original designer's intent.

In conclusion,
we are glad to hear that you are taking jehardiman's advice
and it sounds like you will be in good hands with Tim B.

P.S.
My uncle came from the Channel Islands and my father was
born in Devonshire. All so, legend has it that I'm related to that
infamous family - the Doones.
" T'wasnt smugling lad......more like...reacting to market forces."
".....taking advantage of the difference in the price of Brandy
....'tween France and England."

Cheers and good luck in your project !!

[mallo]

Hi Tim
Thanks for that, sorry for not getting back to you before now, I will see what I can find and will Post/E-Mail it to next week, hope this is OK, I would very much appreciate your input into the uncertainty I have. I will be in touch soon
Thanks again
Michael

[mallo]

Hi tri-star
Thanks for your input, when I mentioned a larger sail area, we had a larger (more overlap) jib cut 20 years ago, and that’s been fine, the biggest increase is I was given a large second hand cruising chute (for helping a friend out), I wanted to replace the original 1939 cotton spinnaker that was past its best (it was getting a bit rotten, one of the last times we set it the wind got progressively stronger and in the end we decided it was **** or bust, and it held out. The problem was it wasn’t big enough for the boat it was only big enough for blowing your nose…..)I wanted something for light winds and those sunny days (hopefully soon). This chute is a bit on the big size but brilliant in any less than 13Kts of wind, anymore and its too much, I watch the wind instruments like a hawk when we have it up, and I drop it if there is any hint of the wind picking up or black clouds forming. As commented on the last reply to you we haven’t increased the mast height at all.
The amount of ballast removed is about 250Kgs as we worked out what weight would be in the fuel tank and the extra plate to make the tank.
The engine was changed 30 years ago, from an all cast iron heavy Gardiner to a Ford (with a certain amount of alloys in it, probably not a huge increase in weight).
The fitting of the generator couldn’t be any lower in the boat without building on a capsule on the outside/underneath the boat…..
Sorry if I had mislead you previously.
Where about in Vancouver are you based, it’s a long story but I did some research to try and find out where the other boats that were build/designed by Robin Riverdale in Hull the UK and eventually found the third it has turned up in your part of the world, Lopez Island, I have managed to track down the owner.
My family have owned our boat since 1973 and after an accident in 2003(won’t go into details) we stripped the boat completely repaired her and had her sand blasted and re-painted inside and out and then totally re-built the inside ourselves (not sure if I would do it again…..) the only part we didn’t do was the sand blasting and the painting, we didn’t have the equipment and experience to do it and get a proper job done, most important in a steel hull…..
It took two years of very hard work and a lot of man hours (I dread to think) but we are very pleased with the result, it has been a bigger project that you probably thought.
Which of the Channel Islands did your uncle come from?
Thanks again for all your help
Michael Allo