## Design a wake boat forum,sailboat charter fort myers beach unterkunft,used wakeboard boats dallas texas,houseboat rentals naples florida news - Easy Way

### Published 31.01.2016 | Author : admin | Category : Diy Sailboat Plans

Usually we recive a IGES hull from our customer and we can obtain more information about the ship.

In my first try I used the michlet but when I finished to do my script and executed it with a example, I could see that there not was a bow wake, I am stupid man, I always say to my self firstly I have to read the documents, I am a enthusiastic man and always I do the same job twice. The wake height is to high, I do not know why, could you please help me to obtain a correct wake for my ship? Seaviews View Public Profile View Seaviews's Website View Seaviews's Gallery Find all posts by Seaviews « Printing Freeship .dxf output to lifesize plan?

When making potentially dangerous or financial decisions, always employ and consult appropriate professionals.

Location: Australia Wake size I am trying to increase the size of the wake without weighing down the boat and sinking it.

I have seen some ski boats with plate or foil attachments to the stern (and on in-boards accross the transom) that i believe are used to create more wake.

The tabs control running angle, giving better control through the speed range of the vessel.

It's very important when using such devices to be sure that you are very far from shore before deploying them.

Location: Australia MArshmat I am not talking about the Wedge from malibu (I have seen it) because i have an outboard and something like the wedge will only work with an inboard cause of the position of the Wedge and the prop. I am talking about foils that will extend of the stern on either side of the outboard (and therefore prop) and they will also create a less than 180degs angle with the bottom of the boat meaning the foils will create more drag and therefore i am assuming more displacement. Such a device does nothing at all when it's up, and forces the stern to rise higher when it's down.

Location: VICTORIA Hi just a couple of questions Where abouts are you located in Australia? Look forward to seeing the pictures and if you can provide any other information that you think would be of use please send it through along with you asking price. Location: Hills District, Sydney, NSW, Australia Just wondering if this is still available.

Location: Australia Boat moulds still avialable for purchase Hi, Have been away a while, these moulds are still available for sale if you are interested. Moulds Wanted » Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Search this Thread Advanced Search Similar Threads Thread Thread Starter Forum Replies Last Post Boat moulds for sale! Location: UK Bow Wave and Kelvin Wake I suspect I'm on a 2+2=5 with this, but if wake leaves a boat at angle of around 19 degrees does it help to have a bow angle smaller than this so that the wake doesn't run along the hull? Location: UK That's why I was thinking that if the bow angle was less than 19 degrees the wake might diverge from the hull.

Originally Posted by WilliamP So maybe this is a critical bow angle, below which there is a step change reduction in drag?

Location: Italy (Garda Lake) and Croatia (Istria) My understanding is that Kelvin's theorem considers the ship as a tiny pressure point on the surface. The problem with an ever decreasing angle of entrance is that this results in a greater curvature required to bring the lines, or slope, back to zero at the max beam. Originally Posted by Ad Hoc you need to create shape, otherwise you?ll have a triangular plan form hull. So you say that it is mathematically defined as an angle to the line connecting intersections of divergent waves and their tangents set at an angle of 35°16' to the centreline? Originally Posted by Leo Lazauskas It is not, as depicted incorrectly in Ad Hoc's graphic and many other places, the line through the intersection of the crests of the transverse and diverging wave systems.

Originally Posted by Leo Lazauskas I don't know if there is a precise simple formula as for the Kelvin angle and the wave angle (theta_K) at which it occurs Again, according to these reference books, it can be shown to be 35.267 degrees mathematically by superposition of parallel systems of wave crests. Originally Posted by tspeer There's a simple principle to minimize the drag due to negative lift at the head.

It's true that the wake wash in the Trefftz plane is a quantity that is peculiar to the Trefftz plane, being far enough away from the lifting line that the bound vortex has no effect and yet not having the wake rolled up, either. However, if you look at the criteria qualitatively, it says for minimum drag, the wake should be shed as though it were a rigid sheet of metal, being extruded out the trailing edge at a uniform speed all along the span. This has had me wondering if the same qualitative principle would apply to the near field of a real flow, even though the near-field velocities normal to the plane of the wake will have both bound vortex and shed vortex contributions. So I have a hypothesis that making the velocity normal to the plane of the freestream or lifting surface have a linear spanwise distribution when measured in close proximity to the trailing edge, will result in minimum induced drag for a given spanwise location of the center of effort. The immediate intuitive reaction of people I've approached with this idea is that the hypothesis is not true. If the hypothesis were to prove true, it would have huge implications for aviation as well as sailing. Another attraction is that, if true, one can look at a wash distribution and immediately say whether it is optimal - is it a straight line or not? Originally Posted by tspeer So I have a hypothesis that making the velocity normal to the plane of the freestream or lifting surface have a linear spanwise distribution when measured in close proximity to the trailing edge, will result in minimum induced drag for a given spanwise location of the center of effort This can't be right. The integral is over the entire y-z plane anywhere behind the wing (even close to the TE where there is no rollup yet), provided that the transverse velocities v,w are only those associated with the trailing vorticity. The reason is that the exact integral, including pressure-work terms and the streamwise perturbation velocity u is Di = Int Int 0.5 rho (v^2 + w^2 - u^2) dy dz.

For the bound-vorticity contributions to u,v,w the v^2+w^2 part gets perfectly cancelled by the -u^2 term, so these contributions can be simply omitted. 2) The total normalwash velocities v,w close to the wing at some specified location can be easily changed by merely redistributing the chordwise loading.

Location: Brisbane Interesting theory, if it is true I think it gives a lot of power to 'intuitive' aerodynamic design, which is so much of what design is.

I'm an intuitive thinker, and usually create a design by 'assembling' theoretical components to get the best result. So while I only understand a little bit of lifting line theory I think I follow what you mean. As well as the velocity normal near the trailing edge (say, a small distance dx just after the trailing edge) I'd have thought you would need to add the spanwise velocity as well. Say, the take spanwise velocity just before the trailing edge - as this would contribute to the strength of the vortex.

And that edge would be a critical variable for vorticity and drag creation, which is where I see this hypothesis to be most useful. Another version of your hypothesis would be to take the velocity normal to the edge regardless of whether it's a trailing edge or not. The expression of all the forces (viscous and inviscid) on a body only in terms of the velocities and pressures in its downstream wake.

The assumption that the flow at each spanwise location of a wing is the same as a 2D airfoil flow, but with a modified freestream velocity. The TP expression for the induced drag happens to be identical to the LL expression for the induced drag, but their derivations are very different. Aside from whether or not such a change would be feasible for a membrane sail, do you get less drag at the same lift if you adjust the twist so as to make the crossflow velocity distribution more linear along the span for the Finn sail?

Originally Posted by markdrela This might be a good time to write down some definitions of the various terms being thrown around here.

Yes, you probably could get less drag by adjusting the twist - you would have to go to negative numbers (not feasible for membranes), since in this light wind case the leech is practically straight - but separation would increase, so this is not far from optimal. Attached a wake shot colored with Z-velocities, roughly in a similar scale to the planar sails. Originally Posted by Leo Lazauskas At an AR of 10, there is about a 10% difference between LL and lifting surface theory. I was mainly discussing Di prediction accuracy obtained when the lift distribution from an LS (or panel, or Euler) calculation is plugged into LL's Di formula. Originally Posted by markdrela Yes, but in this plot you're also in effect comparing the lift-distribution prediction accuracy between LL and lifting-surface (LS) theories, because the lift distribution alone is sufficient to determine induced drag (Di).

How Do Dolphins Swim So Fast » Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Search this Thread Advanced Search Similar Threads Thread Thread Starter Forum Replies Last Post Simple wash rule?

I understand there is no replacement for displacement but can a foil oir the like be used to make better use of the existing displacement? You have now pointed out what i wanted to know, that they wont work and that there is obviously no other way to create displacement but weight. Any pressure field that is moving has the same effect and same classic Kelvin wave pattern. What exactly would you be looking for in a CFD analysis, velocities in a plane perpendicular to the trailing edge exit or what? It sort of hints to my perception about Tom's hypothesis being linked to the lifting line theory (?) - after all, lifting line theory ignores the chordwise distribution of lift. Although the geometrical twist is about zero, effective twist from the zero lift angle, allowing for draft variation from foot to head, is clearly negative.

Stay tuned for everything from custom HD wallpapers to spruce up you're device screens and social media icon packages, as well as vertor graphics packages for all you multimedia developers and designers out there. With the popularization of wake sports over the past two decades, companies like Nautique, MasterCraft and Malibu have continued as industry leaders, innovating and redefining what it means to produce quality tow boats. Hence, the resulting wave pattern and the characteristic 19.5° angle are relative to the far-field of the ship's wake. So this intersection is brought fwd to help create the volume; a hollow in the lines if you like. More specifically these companies have each contributed major design features that appear on nearly every iconic wake boat on the market today.

If you make the angle of entrance so fine, where does this line intersect the hull beam, that being the 2.0m, or rather 1.0m either side of the centreline? But, where this line intersects with the max beam has an increase in its slope (the hollow) simply to get back to the max beam further fwd rather than further aft…which means an increase in the pressure disturbance, ergo an increase in drag not lower.

I was simple referring to the shape of the wake, planar for the planar wings and complicated for the real, triangular sail not touching the deck. It’s not exactly human anatomy, but this will school you on some of the features and innovations that make ski and wake boats what they are today.

In my first try I used the michlet but when I finished to do my script and executed it with a example, I could see that there not was a bow wake, I am stupid man, I always say to my self firstly I have to read the documents, I am a enthusiastic man and always I do the same job twice. The wake height is to high, I do not know why, could you please help me to obtain a correct wake for my ship? Seaviews View Public Profile View Seaviews's Website View Seaviews's Gallery Find all posts by Seaviews « Printing Freeship .dxf output to lifesize plan?

When making potentially dangerous or financial decisions, always employ and consult appropriate professionals.

Location: Australia Wake size I am trying to increase the size of the wake without weighing down the boat and sinking it.

I have seen some ski boats with plate or foil attachments to the stern (and on in-boards accross the transom) that i believe are used to create more wake.

The tabs control running angle, giving better control through the speed range of the vessel.

It's very important when using such devices to be sure that you are very far from shore before deploying them.

Location: Australia MArshmat I am not talking about the Wedge from malibu (I have seen it) because i have an outboard and something like the wedge will only work with an inboard cause of the position of the Wedge and the prop. I am talking about foils that will extend of the stern on either side of the outboard (and therefore prop) and they will also create a less than 180degs angle with the bottom of the boat meaning the foils will create more drag and therefore i am assuming more displacement. Such a device does nothing at all when it's up, and forces the stern to rise higher when it's down.

Location: VICTORIA Hi just a couple of questions Where abouts are you located in Australia? Look forward to seeing the pictures and if you can provide any other information that you think would be of use please send it through along with you asking price. Location: Hills District, Sydney, NSW, Australia Just wondering if this is still available.

Location: Australia Boat moulds still avialable for purchase Hi, Have been away a while, these moulds are still available for sale if you are interested. Moulds Wanted » Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Search this Thread Advanced Search Similar Threads Thread Thread Starter Forum Replies Last Post Boat moulds for sale! Location: UK Bow Wave and Kelvin Wake I suspect I'm on a 2+2=5 with this, but if wake leaves a boat at angle of around 19 degrees does it help to have a bow angle smaller than this so that the wake doesn't run along the hull? Location: UK That's why I was thinking that if the bow angle was less than 19 degrees the wake might diverge from the hull.

Originally Posted by WilliamP So maybe this is a critical bow angle, below which there is a step change reduction in drag?

Location: Italy (Garda Lake) and Croatia (Istria) My understanding is that Kelvin's theorem considers the ship as a tiny pressure point on the surface. The problem with an ever decreasing angle of entrance is that this results in a greater curvature required to bring the lines, or slope, back to zero at the max beam. Originally Posted by Ad Hoc you need to create shape, otherwise you?ll have a triangular plan form hull. So you say that it is mathematically defined as an angle to the line connecting intersections of divergent waves and their tangents set at an angle of 35°16' to the centreline? Originally Posted by Leo Lazauskas It is not, as depicted incorrectly in Ad Hoc's graphic and many other places, the line through the intersection of the crests of the transverse and diverging wave systems.

Originally Posted by Leo Lazauskas I don't know if there is a precise simple formula as for the Kelvin angle and the wave angle (theta_K) at which it occurs Again, according to these reference books, it can be shown to be 35.267 degrees mathematically by superposition of parallel systems of wave crests. Originally Posted by tspeer There's a simple principle to minimize the drag due to negative lift at the head.

It's true that the wake wash in the Trefftz plane is a quantity that is peculiar to the Trefftz plane, being far enough away from the lifting line that the bound vortex has no effect and yet not having the wake rolled up, either. However, if you look at the criteria qualitatively, it says for minimum drag, the wake should be shed as though it were a rigid sheet of metal, being extruded out the trailing edge at a uniform speed all along the span. This has had me wondering if the same qualitative principle would apply to the near field of a real flow, even though the near-field velocities normal to the plane of the wake will have both bound vortex and shed vortex contributions. So I have a hypothesis that making the velocity normal to the plane of the freestream or lifting surface have a linear spanwise distribution when measured in close proximity to the trailing edge, will result in minimum induced drag for a given spanwise location of the center of effort. The immediate intuitive reaction of people I've approached with this idea is that the hypothesis is not true. If the hypothesis were to prove true, it would have huge implications for aviation as well as sailing. Another attraction is that, if true, one can look at a wash distribution and immediately say whether it is optimal - is it a straight line or not? Originally Posted by tspeer So I have a hypothesis that making the velocity normal to the plane of the freestream or lifting surface have a linear spanwise distribution when measured in close proximity to the trailing edge, will result in minimum induced drag for a given spanwise location of the center of effort This can't be right. The integral is over the entire y-z plane anywhere behind the wing (even close to the TE where there is no rollup yet), provided that the transverse velocities v,w are only those associated with the trailing vorticity. The reason is that the exact integral, including pressure-work terms and the streamwise perturbation velocity u is Di = Int Int 0.5 rho (v^2 + w^2 - u^2) dy dz.

For the bound-vorticity contributions to u,v,w the v^2+w^2 part gets perfectly cancelled by the -u^2 term, so these contributions can be simply omitted. 2) The total normalwash velocities v,w close to the wing at some specified location can be easily changed by merely redistributing the chordwise loading.

Location: Brisbane Interesting theory, if it is true I think it gives a lot of power to 'intuitive' aerodynamic design, which is so much of what design is.

I'm an intuitive thinker, and usually create a design by 'assembling' theoretical components to get the best result. So while I only understand a little bit of lifting line theory I think I follow what you mean. As well as the velocity normal near the trailing edge (say, a small distance dx just after the trailing edge) I'd have thought you would need to add the spanwise velocity as well. Say, the take spanwise velocity just before the trailing edge - as this would contribute to the strength of the vortex.

And that edge would be a critical variable for vorticity and drag creation, which is where I see this hypothesis to be most useful. Another version of your hypothesis would be to take the velocity normal to the edge regardless of whether it's a trailing edge or not. The expression of all the forces (viscous and inviscid) on a body only in terms of the velocities and pressures in its downstream wake.

The assumption that the flow at each spanwise location of a wing is the same as a 2D airfoil flow, but with a modified freestream velocity. The TP expression for the induced drag happens to be identical to the LL expression for the induced drag, but their derivations are very different. Aside from whether or not such a change would be feasible for a membrane sail, do you get less drag at the same lift if you adjust the twist so as to make the crossflow velocity distribution more linear along the span for the Finn sail?

Originally Posted by markdrela This might be a good time to write down some definitions of the various terms being thrown around here.

Yes, you probably could get less drag by adjusting the twist - you would have to go to negative numbers (not feasible for membranes), since in this light wind case the leech is practically straight - but separation would increase, so this is not far from optimal. Attached a wake shot colored with Z-velocities, roughly in a similar scale to the planar sails. Originally Posted by Leo Lazauskas At an AR of 10, there is about a 10% difference between LL and lifting surface theory. I was mainly discussing Di prediction accuracy obtained when the lift distribution from an LS (or panel, or Euler) calculation is plugged into LL's Di formula. Originally Posted by markdrela Yes, but in this plot you're also in effect comparing the lift-distribution prediction accuracy between LL and lifting-surface (LS) theories, because the lift distribution alone is sufficient to determine induced drag (Di).

How Do Dolphins Swim So Fast » Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Search this Thread Advanced Search Similar Threads Thread Thread Starter Forum Replies Last Post Simple wash rule?

I understand there is no replacement for displacement but can a foil oir the like be used to make better use of the existing displacement? You have now pointed out what i wanted to know, that they wont work and that there is obviously no other way to create displacement but weight. Any pressure field that is moving has the same effect and same classic Kelvin wave pattern. What exactly would you be looking for in a CFD analysis, velocities in a plane perpendicular to the trailing edge exit or what? It sort of hints to my perception about Tom's hypothesis being linked to the lifting line theory (?) - after all, lifting line theory ignores the chordwise distribution of lift. Although the geometrical twist is about zero, effective twist from the zero lift angle, allowing for draft variation from foot to head, is clearly negative.

Stay tuned for everything from custom HD wallpapers to spruce up you're device screens and social media icon packages, as well as vertor graphics packages for all you multimedia developers and designers out there. With the popularization of wake sports over the past two decades, companies like Nautique, MasterCraft and Malibu have continued as industry leaders, innovating and redefining what it means to produce quality tow boats. Hence, the resulting wave pattern and the characteristic 19.5° angle are relative to the far-field of the ship's wake. So this intersection is brought fwd to help create the volume; a hollow in the lines if you like. More specifically these companies have each contributed major design features that appear on nearly every iconic wake boat on the market today.

If you make the angle of entrance so fine, where does this line intersect the hull beam, that being the 2.0m, or rather 1.0m either side of the centreline? But, where this line intersects with the max beam has an increase in its slope (the hollow) simply to get back to the max beam further fwd rather than further aft…which means an increase in the pressure disturbance, ergo an increase in drag not lower.

I was simple referring to the shape of the wake, planar for the planar wings and complicated for the real, triangular sail not touching the deck. It’s not exactly human anatomy, but this will school you on some of the features and innovations that make ski and wake boats what they are today.

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