TimW
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Posts posted by TimW
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I find it funny after a great days sailing like on saturday everyone talks about there top speed, timberwolf sailed 60nm in around 6 hours 10knot adverage, we sailed on boarderline and finished 19 minutes behind TW, our top speed was no more that 20 knots if TW topped out at 30 odd either there was alot of slow times or back the speedo back a few.
The speedo is calibrated correctly as this photo shows (speed set by ken ormandy across the harbour in November last year).
The Nexus gear was set up by Woolfy and Gappy from Kiwi Yachting.
Although in the instant of 30.86 on the speedo the GPS is not as impressive I'd suggest that is due to adverse tide (probably 2 knots or so?) and also unashamedly we were not pointing straight at the finish but more like pointing at Takapuna or Narrow neck trying to get a new top speed across the face of the swells.
Whether you believe it or not this is genuine.
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Really nice photo taken on the way to Mahurangi, Thanks Bill
Was a really great weekend.
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021795826
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Awesome. There goes my record!
This was in more wind and a Code 0 on.
Yours is still good with a Jib only !
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We got 4 good bursts last night after Orakei, was a really good ride.
I suspect this was just after the bridge in very flat water, we got a nice little gust and really took off.
I think if we had that same breeze for a bit longer we could go faster still.
The boat was pretty dodgy up by Bean Rock though in much more heinous waves where we had to keep backing off a bit.
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Or no Main hull
I think that could work but it then means no Coastal....
Or a Pod in the middle kinda like on 888,
So then by the time you get the Tubular structure in place plus the pod maybe you can build a trimaran main hull not that much heavier.
My opinion is that the AC45 and AC72 are both cats only to save money.
I thought the last AC kinda proved that the ultimate multihull weapon is probably still a tri in most conditions ?
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Disappointing last night.
He felt our foils don't give us enough lift.
sounds like nice way of saying he thought your boat was a bit heavy
that is exactly how i interpret it as well.
Heavy and slow because of it.
Two ways to fix that.
Lighter main hull or bigger rig or both.
Need a sponsor to do that though.
As to altering the foil angles to increase lift, yes we can do that but that increases drag.
My opinion is that on an underpowered boat foils don't get used that much anyway and increasing drag is just
mean that you are going to use them even less.
I'm not that sure that the way the SL33 rears up in the air is that great of a thing anyway?
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Disappointing last night.
We had been looking forward to having Dean Barker aboard Timberwolf.
(they were filming an ad for Nexus)
I'm not sure how much footage they got, it seemed the Camera was always under water and the Chase boat could never keep up.
Although we hit 26.75 knots I guess for Dean it was nothing special. He felt our foils don't give us enough lift.
By the way, the Nexus Windgear is just awesome ever since Woolfy set it up just the way we wanted.
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Actually that speed was just effortless, we were zooming between two other boats, I think MRX's with Ken on the helm.
There is more to come from the boat, I am quite certain of that.
We need the right breeze direction and less waves.
Its gonna be even more fun than Friday... And that is saying a lot!
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Its just a magic little boat on days like that.
I'm not too sure when we got the Top speed, were also going fast at Orakei and in towards Torpedo.
I don't think it is at all "hectic' on the boat, it really felt very very safe yesterday, it probably looks scarier and more nose dive prone from off the boat.
I know if you are to leeward it feels pretty dodgy at times, but safe as houses to windward at the back, but what ever you do, don't over sheet the sails, you can lose control pretty quickly.
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Although this is not a very big improvement since Wednesday night, this is the new Top Speed set in a Rum Race with just a Self Tacking Jib and a single reef in the Main.
Was a really great day to be out there and we had on Board Pete Geary the owner of Akatea. It was a really good day to get him out there on a Multi.
There are a bunch of guys out there planning a 10m Racing Cat quite similar to the SL33's of Team NZ and as well a smaller cousin of the AC45 cats.
These boats will have plenty of sail and be very light so should really fly.
The recent development around the 10m size is great for the local multihull scene.
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New Official Top speed achieved with new low drag foil.
Was very exciting to drag off the mighty Vodafone after the start like that !
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So NACA 63014 is six series NACA? max thickness located 30% of total chord aft from leading edge and 14% of total chord is the maximum thickness?
And that's a pretty middle of the road, all purpose foil? or optimised for higher speeds i.e. a trimaran?
Send it/Tim - what do you think for an Elliott 7.4, gonna bulb her and loose the hydraulic lifting + new foils. Recomendations of a NACA profile? Plus the ram down the gutts makes it way fat...!
EE
the 63014 has its maximum thickness at 35%.
The Old AC boats around the Mid 90's also used this section.
I've used it a lot on Skiffs as well.
It suits a Faster boat as Laminar Flow sections are about trying to reduce drag at speed.
My literature has it as being ideal on a Trimaran.
They do not perform as well as a Standard 00 section at Low speed.
For your boat I'd start by talking to Kevin Dibley, he worked his magic on Nosaka the White 40, and it is definitely going a heck of a lot better with a new Bulb keel.
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The camera angle is probably a little deceptive.
The only differences are:
Old board was NACA 63014 but when it got glued together the glue was a little thick and it ended up about 1 or 2mm thicker than it should have.
On the new board I scaled the measurements back to 13.9% to help ensure it fitted in the new case, and by using a much thinner glue brew it actually came out a very small amount thinner than it should have.
It still needs a little fairing which will rectify this.
It is also designed so that at a later date I can put a trim tab on the back of it, which I would like to do one day as it is a very good idea.
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So as I had said a lot of people get bogged down.
Tim,
The Core Density is not the Bare Timber.
We have vacuumed the cedar, the Resin really soaks in around the edges, unlike with HD foam.
This affects the Density of the Core, it affects the Compressive properties and as well it affects the shear properties quite markedly.
You can see from the above numbers quoted from Martin out of the Gougeons book that the properties aren't too dissimilar
But
Tim, the Core and its properties might be completely irrelevant if you have thick enough skins.
A shear Web is just one way to skin a cat.
You can have a Hollow board if you use enough laminate, and its thick enough.
10 years ago all the Big French Wing masts used Shear webs in them.
My mast has a type of Shear Web at the fitting locations, but Both Borderline and Deeds masts, which are essentially the same section don't have any shear web in them, they are just made with a thicker wall.
The Net result weight wise can be quite similar.
In the Photo you can see the new Board has the 120mm Wide cedar laminated in blocks (6 of) with the Grain boxed.
The Foam is also 130 density for the new and 80 for the old.
New laminate is 5mm thick at the cedar for 120mm wide, compared with only 3.2mm thick at 100mm wide for the old.
The new board however is only 60mm thick compared to 64mm for the old.
As the Old board lasted 5 seasons I figured it must be pretty close to strong enough.
The new one is way stronger.
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The Old and the New
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The Offensive Timber has been covered over by the layers of Carbon Uni.
To ensure we maintain an accurate shape we have skimmed in some Filler, in most cases there is less than half a mm, and in many places you can see the carbon.
now the foil is ready for its outside skin.
So back to High density foam at 200 kg versus Long Grain Cedar (at around 550 kg density).
I reckon for compressability they are much the same, perhaps HD foam is slightly better.
But HD foam is very hard to glue to, the Resin doesn't penetrate the surface as it does with Cedar so the Peel/Shear properties of the Skins are compromised.
The Cedar in the Board cost me $140.
200 HD Foam for the Same Quantity Costs $718. (And you have to buy HD foam by the sheet, so can't get the exact amount you need)
For me the two have similar properties, the Cedar is definitely the Heavier option.
End grain Cedar would be way better but no CNC machinist will touch it as it is nasty to machine and very time consuming to produce.
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Yes, End grain Cedar would be better but really no one sells it and it takes ages to cut it into blocks and is very hard to machine.
The density of the Cedar run long grain is still higher than High Density Foam and it is still less comp[ressable, especially with 5mm of Carbon laminate on it.
The Cedar is definitely a compromise, a Carbon reinforced Girder would be better, but this way it has to be easy to machine and strong enough to do the job.
Cost is also a big issue. The wood is a cheap option that has a number of good things going for it.
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[THANKS Tim. Very important information you are sharing here. TNX
What sections are being used in the c/b's & rudders of the AC 45's - or is that knowledge not available??
Does the section you have chosen to use have its maximum cord farther aft at the bottom than the top?? Is the section thinner as a % at bottom than the top (at the hull exit point)?
Does anyone wedge the board to windward by say 7 or 9 degrees when going to windward?? ie - tack the board in the case. Could ask the same question about a 'trim-tab' on back 1/3 of the rudder blades - thus creating more - lift to windward of the rudders?? Bennell, Miller, Locki & others did that with radio controlled model yachts (that's where 'funny' keel was developed). I've always wondered if it would work on fast multihulls as it's done on slow monohull keels? Thanks for taking the time to be bothered with the questions. We're all learning lots - at your cost though. Ciao, james
Out of all the areas of sailing I think foils are the one area I see a lot of people getting bogged down.
take a look at the Top multi's sailing in Auckland, Many have very average foils that would not merit the level of discussion going on here.
Yet despite everything being wrong about these foils the boats still have a habit of kicking everyones arse on the race course.
My view is that all the theory is fine but the real world is that there are just so many compromises you should just get a nice set of foils that work for you and ignore the boffins who tell you they are no good.
The AC45 centreboards look similar to me to NACA 63412 and are assymmetric.
The rudders appear to be a similar section to a Standard NACA 0013 (or there abouts).
The section we use has the maximum chord at 30%, I think 40% works better on slower boats ?
The Section is just constant,not thinner at the waterline.
We use Dagger cases for both Centreboard and Rudder that are an exact fit to the foil.
Section changes just leaves gaps between the foil and the case that can fill with water (water spouting out the case).
The gybing board idea is used in Int 14's.
But I'd rather not have the extra drag of the case filling up with water.
The Trim Tab is a great idea, I would love to have one on. Vodafone does.
I decided against a trim tab only because of the complexity of the build process (including additional cost).
Also in our current configuration with our big Centreboard, Timberwolf is a very high winded boat, No one really Out points us.
And with the curved foils down we have some real upwind pace through the water.
So I'm sceptical of the need for trim tabs.
Like the curved foils I'm sure they are great when they are great but you can do without them, especially when you consider you are just racing different designs in handicap racing.
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So we started with a layer of Carbon cloth onto which we glued the Cedar and foam.
After it was CNC'd that is the photo you see.
where the cedar is there is a rebate, 3.2 mm for the Top 1300mm and tapering to a 2mm rebate at the bottom.
This allows us to put 110mm wide Carbon Uni strips that fill the Rebate.
The laminating is mostly done in two halves.
The Outside of the board is then covered in a further laminate of 1.8mm thickness. It is not DB on the outside but rather is made up of around 65% of the laminate in Unis at zero degrees, 28% in CDB at 45 degrees, and the remainder at 90 degrees.
The Central Carbon layer is basically there to form the central part of the trailing edge and to keep the trailing edge sharp and straight for joining purposes.
You will also see there are 3 dowel holes in the board to keep it straight when the two halves are glued (under vacuum) together.
After the board is joined there is a DB tape applied down the front only (approx 60mm wide).
The board will need very little fairing and I rate it certain to fit in the case !
Yes, the process can be done other way round in a Female Mould (as I do with my Rudders).
I never bought a Centreboard Mould so this is the next best option.
Does result in more fairing this way but saves the cost of the mould.
The Coastal reports were wrong.
We just broke the Centreboard in the main hull.
It fell down around 150mm lower than usual (it had 150mm more out the bottom and 150mm less in the case) and when we landing after launching off a wave it snapped.
We continued to sail after it broke with just the curve foils down but we were going sideways pretty fast, and only making a VMG of around 2-3 knots while tacking through 110-120 degrees.
I decided to withdraw and Motor home because at that stage it seemed pointless continuing (to me) and as the broken piece of board was crashing into the bottom of the boat (it was still attached) I didn't want to risk it puncturing the hull.
Later under motor it eventually broke off and no damage was done.
At no stage were we in any danger at all, however.
It was a very disappointing way for our Coastal to end as at times we had been going very well and would have been confident of doing well on the final beat in those conditions.
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The curved foils lift the boat up out of the water and when it lands again it comes down sideways, as in a lot of leeway.
i think that that is where the extra load that the foils must be seeing is coming from.
As the foils that have broken, 1 cb and 1 rudder have been on the boat for over 5 seasons.
The foil section we use on the cb, Pedro is 425mm fore/aft and 60mm thick.
It weighs around 20 kg and it is not an area I am going to try to save weight in.
Foil design is complicated, and the 63014 section we use is a nice all round section with a forgiving angle of attack that combines quite low drag properties at speed but hardly ever lets go (stalls) at lower speeds.
Have been using this section for years on both skiffs and the tri.
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The section we use on both Centreboard and Rudder is NACA 63014. It is a laminar flow section ideally suited to a High Speed Trimaran.
The Core Density is very important as the two most likely modes of failure in a foil are in Buckling, either outward buckling caused by Core Sheer Failure (very common in Centreboards) or Inwards buckling, alleviated greatly by a Higher Density Core.
The Core sheer properties are most governed by the choice of Foam, in our case a Structural Airex PVC core.
While the Carbon Laminate (5mm thick where it exits the boat) does most of the work (in compression and tension) the Core has a vital role to play.
Our rudder that broke failed because the core compressed.
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Here is the Blank for the new Centreboard.
Started by Laying Up the Carbon , on which a Cedar Stringer forms the centre with 130 kg density foam either side.
This is the machined by Styrotech to the same section as the Old board to make sure it fits in the same case.
Thank you so much to Russell (of Absolute CNC) for Modelling the blank so that Styrotech could machine it !
The new board has a little more laminate than the Old one, with a Much Higher density core (up from 80 kg).
But the main change will be that it will be tied in so the top of the board can't fall down too low in the case.
timberwolf
in MarineTalk
Posted
In those conditions we can push the boat quite hard, it is safe and fast.
In its original format it would have been a real handful and certainly no where near as fast as that.
As has been pointed out we struggle upwind in sloppy waves like those with the foils down. The new centreboard is lower drag but that also means more leeway when pointing high upwind. We found a nice low and fast mode on Saturday sailing just over 45 degrees true but moving through the water at 10 or 11 knots, our high mode with the main strapped in harder was only a few degrees higher but speed would drop to mid 8's. VMG wise it was a no brainer and going low is ok if you can get a few shifts and we did along the way.
overall Timberwolf is a better boat and is miles faster in reaching conditions than it was before. It is still a great and fun boat to sail on and a huge pleasure to own.
I wish I had a lighter main hull and a taller rig with some new sails but at the moment it is what it is and it won't be changing for a while.