Nikrum, by what method does one resharpen Occam's Razor [}:)]

kiwi307 said...

landyacht said...

A wire stayed rig has massive loads when fully sheeted. that picture of pigs might fly is a stayed rig , the rear axles flex by 4" each side and the front beam(55mmODx2mm carbon steel ) flexes by over 2". Thats what makes a stayed rig work. if the chassis on a stayed rig is really stiff, it will probably be a dog
, Maybe kiwi 307could comment on that opinion, as he has more experience in these things.

Absolutely agree. I have had a load cell under the foot of a Class 3 rig in wind not quite strong enough to fly a wheel, before I went to the really flexi axles, it was reading in excess of 3 tonnes!
The axle on the yacht in my avatar was solid ash, 10" by 2" in the middle 7 by 2 at the tips, aerofoiled to NACA section largely 2" thick through the major chord. The wheels are 15" with 125 Michelins so OD of 25" approx. Straight unloaded, 3" ground clearance under gust load. This means a bend of 9" under load. A fair bit of that comes from stay tension on the windward side pulling the axle up at the tip. Lots of planing on the beach to get it how I wanted, and it made massive performance differences. Then I was dumb enough to sell the good axle (and the buyer then put CSM on it with polyester!).
We did put a load cell under a class 5 mast, but it only read to 500kg and just went almost straight to the limit of the read out. I still reckon the cantilever loads are greater. Fairly easy to see how big they are. Attach a string at the height of the centre of effort, climb aboard and then get someone else to try to pull you over. They might succeed on a Mini, I have never achieved it with one person pulling a 5. Never tried with a measuring device in the "pull over rope" but it's pretty high, and even this does not take shock loads into account.

After watching my Mast work yesterday in gusts of around 50Km I should think that the 500kg is insignificant against any Torsion Loading. This would have many different loadings according to Sail Area, Spine Diameter, Mast and Yacht Construction etc. However If one can get an exact Sail Area and work out the KW that is generated by a given wind speed and apply that power to a given point at the base of the Mast one will be able to get a rough Idea of what is happening at that point. I've no doubt what so ever that there will have to be an equation used to allow for twist of the spine and amount of material there in. I will leave that up to the Brains Trusts in the forum[}:)]. Better still a Load Cell mounted in a 3" Tube with a Mast Step affixed to it, This then is mounted in a Base which could be mounted to a Ute. One could drive the measuring device to a Venue and test several different Sails whilst Logs are kept of Wind Speed and Torsion Loadings??? I may be wrong but it is just a thought.

Ron

Nikrum said...

Of all people to ask that question! You disappoint me Test Pilot, everyone should know that! By Honing ones Mind, Not trashing it against Rock Piles.
Ron

I always thought thaat by honing ones mind you ended up with a 'sharp' mind.
But as to El Razor dont go getting "strop'py with me.

Whats the point of trying to measure the forces on the mast?.... you can't change it.

If you want to measure things try measuring the rolling resistance of a yacht and is there a link between tyre pressure v surface v wheel size?

Do balanced wheels improve performance?

Just another thing to think about... how much wind drag is against your arm if you place it out the car window at 60km/h? Now how much drag is against your body, legs and arms sailing at 60km/h?

All of these things CAN be changed and would be worth measuring.

aus715 said...

OK, so the load going through the mast step of a Blokart would be what do you think?

With what size sail, is the sail rigged as a full draft or flat, in what wind strength and on what surface?
I'm not trying to be negative but why do you need to know and what will it tell you?

But why?

Nikrum said...

Knowing the facts. Is all.. When you build shiite it is good to know why, for instance, one might use 3" Steel Tube for a Chassis instead of Aluminum. Why Fallshaws are better than cheap Chinese Muck. Why one uses a Safety Belt in a Land Yacht to some it is Bleedin' obvious to others there is no reason for using these things so we don't bother.

While knowledge is wonderful.... do we need to measure things that that don't change or should we just accept that some things work and others don't.
Have you measured the water salinity or have you got the correct voltage into your house before you make the morning coffee? Have you checked gravity this morning, or the frequency and RF signal level of the local radio / TV transmitter or do you just accept it?

We know that that steel tube works for a LLMini and Ali doesn't.... well use steel
We know Fallsaws work and chinese wheels or plastic bike wheels don't..... people still use stuff that is proven not to, don't they?

I also have a desire for knowledge and often lose sleep over one thing that has troubled me for many years "Is there really 43 beans in EVERY cup of Nescafe"

The difference between Knowledge and Wisdom is... Knowledge is the knowing of facts.... Wisdom is the sensible application of good quality knowledge...

kiwi307 said...

.
The maths for power generated is well known, and will surpirise you how little a sail develops. If you do a bit og googling you should find it, or else find a copy of the tome by Marchej and study to your hearts content.

As a guide, windsurfers when powered up generate around 2 horsepower, I would expect a landyacht to develop significantly less, probably around 1 HP.

Doesn't sound like much when you think about engines, but then think about a horse thundering along with an arrangement of pulleys to zip you up to speed... 1 HP is in the right ballpark I'd say.

Hiko said...

nebbian said...

kiwi307 said...

.
The maths for power generated is well known, and will surpirise you how little a sail develops. If you do a bit og googling you should find it, or else find a copy of the tome by Marchej and study to your hearts content.

As a guide, windsurfers when powered up generate around 2 horsepower, I would expect a landyacht to develop significantly less, probably around 1 HP.

Doesn't sound like much when you think about engines, but then think about a horse thundering along with an arrangement of pulleys to zip you up to speed... 1 HP is in the right ballpark I'd say.

Something that has stuck in my mind for years after reading it somewhere
was 100sq feet of sail in 15 knots of wind generates 7 horsepower
interesting if someone can confirm that

Whoa There Neddy!! Do you guys hear what you are saying I perceive that you are saying that a Human is as Strong as a Horse or that 2 horses are not capable of lifting a human (Well maybe not one that is really FAT). No matter how you look at it a Human is a direct part of a Windsurfer system being as they use their Body weight to counter the Wind pressure against sail, Mast and Boom. Again just watching what was happening to My Windsurfer Mast the other day I don't think any Human would be capable of holding any part of it as it bent under load. If you think you can hold it then I will watch you TRY! The Mast held rigid at the Mast Step bent a good Meter outwards from the Axis of Travel I don't think I have ever seen a Windsurfer mast bend that fare and seriously doubt that a horse could hold the Leverage created on the Land Yacht. I will also say that in those conditions I did have cause to let the Sheet out to get a;ll wheels back on the ground. This all gets back to the very questions I have been asking about Torque Pressure at the Mast Step for which I think there are the odd persons about that seriously doubt my Sanity I am not insulted by the doubts as at Time I seriously Doubt whether I have all my wheels on the deck as well.

Mast Test 1; Suspend the Mast at either end by Ropes then apply your body weight approximately 1/3rd the distance up from the Base. How Far does it bend

Test 2: Suspend the Mast by approximately (To be generous) 400mm of the base and apply your body weight to the tip of the mast. How Far does it Bend

I will be London to a Brick on that there is more Leverage on Test 2. Academies once said "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world"
Ron

Just to give a comparison this class 5 was traveling at approx 80 kph when this picture was taken. The landyacht has less surface drag so does not need to generate much power.

Ron, I have sat back for a long time re your claims of how close to the wind you can sail. If what you claim is correct, in relation to TRUE wind, you have the absolutely best LY on the planet. 45 degrees is closer to the truth. Even 10 degrees to apparent is absolutely amazing!
The figure of hp which has been quoted is higher than anything else I have seen, which is why I suggested you do some research on the Marchej books which are deeply esconced in very sound, well researched science, which seems to appeal to you.(Also keeps me off the hook on being rubbished)
You also suggeted a few posts back about measuring sail area, again another well known thing, even appears in the rules on this site I suspect

Hey Nikrum, please don't take anything I say as having a go... I really enjoy these discussions, and would dearly love to be proven wrong

In the end you've got more experience sailing a landyacht than I do, so please set me straight if I've made a mistake

Comparing the above pictures of sailboards v land yacht is comparing apples and oranges...

The sailboards are using a fibreglass or carbon fibre mast and the land yacht would be using Ali. the bend and flex characteristics would be vastly different

Has others considered using masts that have more for/aft flex and less side flex similar to what is used by Finn and OK sailing dinghies?

With sail power measuring... what wind speed? what aspect ratio sail? what draft/ camber in the sail? at what angle to the wind?

What has MORE power.... a tractor or a race car? [power not speed]

And to measure a sail have a look here for a guide.
www.seabreeze.com.au/forums/Land-Yacht-Sailing/Blokarts/Blokart-sail-measurements/

Hiko, you are right that Marchaj (corrected spelling) makes your head hurt. I like your comparison of power, however a though (and from Marchaj), is that the power of a sail is NOT proportional to the area, there is a scaling effect. You can't get double the horsepower from a sail twice the size. I can't remember what the ratio is, but I do remember some the stuff that was done in Bristol at British Aerospace in the late 70s, and a 5 metre sail was sub 1hp. There are all sorts of corrections for altitude, density etc ad nauseum, which is why all the pure science stuff does not use windpeed, but a corrected unit named "slugs".
FWIW when Gossamer Albatross was being designed for the X channel flight I think they rated a human at 1/7hp for extended time frames.

In answer to Giz to Hik ( Damn I Kill me!)

On sails and HP/KW I tend to agree with the 3hp thing but going by what is being said I think the only true way to test the theory is to Set up a Wind Experiment (Mast and Sail Set up in free running bearings and rotatable with Stress Gauges in place and take measurements in all directions. On thinking about what has been happening about me as I sail it would appear that running Down Wind with the Sail Reaching there less speed happening but as you generate speed then that can be increases greatly along with power by swinging away from the wind and hauling the sheet in to further increase in power and speed seems to happen when one swings further into the wind though the machine seems to be a little slower to gain speed tighten the sheet to the max and and bring it right up toward the wind and it seems that one can get fairly close to the wind. This is what I am experiencing up to a point once you start to get very close to the wind you start to drop off speed at and increasing rate until the sail Luffs.
I found out earlier today that running on sand/Beach that it takes a lot more power to move a vehicle and all bets change with the degree of firmness of the surface. Hence the Airport is the very best surface to run Speed Trial on. High tire pressure and Tarmac = very low rolling resistance. It is a pity the swine are filling my Tarmac up with Gravel Heaps. Nobody uses it = nobody uses it. Somebody uses it for fun= Everybody wants to Spoil FUN. Sorry for the Bad Language I am thinking.


Even Tractors and Cars is like Comparing Apples to Oranges and Land Yachts to Windsurfers (This will cause an outcry) as the Land yacht is the Pure Bread of the line, The Windsurfer by the nature of the medium it works in has to be designed more like a Tractor to get itself moving fast enough to break the surface tension where as the Land Yacht has a very low Rolling Resistance/Surface Tension to deal with so is designed to use the wind more efficiently for it's purposes. This is not a sneer at Windsurfers but is a fact of life. The greatest advantage of Land Yachting over Windsurfers is that I have never in my 65 years seen a Crocodile or Shark out on Salt or Clay Pans or dry land chasing anything, let alone Land Yachts[}:)][}:)]
Ron