presto 30 sharpie 3d model to download for free

Hi, this is Presto 30, a beachable cruising cat ketch sharpie by racing boat designer Rodger Martin that later in his life advocated for sharpies, free-standing masts, centreboards and kick-up rudders, etc.

It has the same name as Ralph Munroe's Presto built in 1891, way before Herreshoff fanboy mania enforced by club regattas we still endure today, in an age were train and steam ships weren't widespread and transport workers used those boats for fast deliveries and unloading the cargo on beaches, a thing that has to return sooner than later and most of todays boats can be retrofitted to remove keel ballast and use cargo ballast only and centreboards.

Don't trust this boat old fashioned appearance, this is a performance sailboat with the same specs as Pogo 30 (builder of mini transat boats, similar to imoca fraud, which are mostly catboats and sharpies flat hulls but ruined with too much beam difficult to upright after capsizing and cetacean killing and reef grounding big span keels) and beat almost all boats you encounter on the water. It has partial ballast on hull and centreboards and fishbone rig and kick-up rudders

I designed the boat on sketchup based on pdf files and added a performance wooden construction touch and this can be accomplished with multiple frames with 30/60cm separation to reduce hull shell weight and cold forming and strip planking just like "windward passage" sailboat or current wooden boats as Paolo Bua, La28, comuzzi yachts, etc. Also without fin keel and sloop mast demanding midship structural reinforcement the weight of a boat can be reduced with just internal cargo distributed along the bilge center in watertight compartments




3D Warehouse https://3dwarehouse.sketchup.com/model/0a768b0f-3ce9-4f11-a3b5-a97f3a4e5de2/presto-30-sharpie-cat-ketch-contact-at-ammrzprotonmailcom

 

Those are a lot of claims on performance. As far as "Herreshoff mania" he highly praised Munro's design.

 

Actually I found this boat by tweaking sailboatdata.com advanced search, which is a really underrated tool and it had similar ratios

Yes I'm not that fanboy and probably herreshoff would be dismayed with current big aspect ratio bulb keels, both cetacean and crew killers while he brought the concept of tandem keel which means that for lateral resistance lift it doesn't matter so much span but aspect ratio and total keel area just as "Wild Oats" boat with LDL hull and CBTF (canting ballast twin foil) that beats imocas and pogos in close hauled angles and i will update other boat that i just designed that uses similar approach

 

Real measured data is what really counts though. It has advantages like being able to sail into shallow water, but it won't have the performance of a modern sailboat. I don't refer to cruisers, but real high performance boats.

 

This sharpie probably goes faster than the pogo just because less wetted area, otherwise it seems that it lacks performance upwind but this is rather an issue that can be fixed by adding lateral resistance like leeboards.

You already know the so called "performance" boats are mostly big wetted area boats that go fast downwind by planing but in upwind they keep in displacement mode and are really slow close hauled compared to foiling catamarans or CBTF because they have foils or LDL less wetted area and more lateral resistance respectively

Upwind behaviour is mostly a matter of safety in a lee shore with broken or no engine

 

Heres a video

 

Herreshock - It appears that you designed this boat based on numerical data from sailboatdata.com and presumably photos/videos; and that while it is similar to Roger Martin's Presto 30 design it is not exactly the same. Is that correct.

 

Rodger was generous and published the below pdf with some hull lines and decent resolution in his page now maintained by his family so i just guessed the transition curves from stern to midship and midship to bow.

It's not an exact replica however I suppose it matches the overall boat lines and besides some published old hull lines diagrams have errors probably on purpose and I have tried to design replicas of several sailboats (both canoe shape and flat chined hulls) by using stern and bow pictures in hard stand or from brochure pdfs etc, and usually a similar hull can be obtained

I made it with sketchup mostly by hand without plugins in few afternoons.

 

That is not correct, sharpies have never been as good upwind as other more suitable hull shapes. There is plenty of data to support it. Further, sharpies evolved to get into shallow water and not for speed or pointing high.

That is incorrect too. Monohull foilers will go upwind faster than traditional hulls of any type if the wind is strong enough. It makes little difference if they are monohulls or catamarans when they are foiling and completely out of the water. Boats with canting keels will also go upwind much faster than traditional boats. The boats winning races prove it.

Wrong again. Upwind VMG matters for reaching ports with perishable produce in the world without engines you advocate.

 

You should edit the post quoting me with [ quote ]

A imoca is basically a sharpie chined hull but wider and cat ketches go fine upwind and you can check the famous freedom cat ketch video





As you can see, upwind is not only about lateral resistance but the clean lift created in the bow by a cat mast.

Also besides that a flexible wingsail creates more upwind lift than common sails and thats why AC72 has the fastest upwind wind diagram even if using rigid multi element wing sails and fractional jib



Also forward or frontal rudders improve the upwind capabilities by placing the lateral resistance close to the bow and that's why "wild oats" front rudder gave a similar wind diagram upwind results as AC72 however they removed front rudder because hitting debris and installed daggerboards in the last modification

On top of that upwind performance is improved by reducing weight and wetted area an thats why the glider and foiling AC72 makes a imoca look like a upwind carrack

Weight is one of the major underrated aspects and we still build monohulls with fixed ballast weight to counteract big span masts and even ketch rigs are pretty tall.

If you remove fin keel and single mast you also reduce a lot of structural reinforcement weight and that means less wetted area and more speed so without keel ballast a short mast is enough to heel the boat and reduce wetted area and create that heeled inertia gravitational force that increases speed

Also people dont realise that a a fin keel ballast create a lot of more wetted area than the same ballast proportional across the length of a boat and thats because in a fin keel all the ballast weight and hence pressure/area is applied in a single point and so it sinks increasing wetted area

Sure upwind also matters for cargo routes besides lee shore safety, however the ideal cargo delivery isn't fixed commercial routes but cruising sailing boats doing transportation during their trips, and that means people can wait for days with better conditions so theres less pressure in boats pointing or performance abilities.

However the usual fear of a current sailboat is breaking the engine in a lee shore

 

Here's a comparison of upwind polar diagrams between foiling-gliding boats as ac72, LDL hulls with twin foils, wide hull imoca and centreboard

These diagrams are also flawed because they don't account wave action not to mention types of waves or multiple swell direction...


Ac72

The polar diagram starts at 20°, same as Wild Oats super maxi








Wild oats

Similar TFCB boat with narrow LDL hull






Imoca 60


Big wetted area slug







Centreboard Li yachts




3m/s is 6 knots, centreboard sloops are not that good at upwind and can be improved with a cat mast at the bow, or a rudder in the bow or just adding lateral resistance as a leeboard





Act72
7 knots boat speed at 30° and 3 knots wind speed

Wild oats
4 knots boat speed at 30° and 3 knots wind speed

Imoca 60
4 knots boat speed at >>60°<< and 4 knots wind speed

li yachts
5 knots boat speed at 60° and 6 knots wind speed

 

That is like comparing a F1 to a dump truck. You also call a slug a boat that is showing 19 kt speed. What makes you claim that wave action, types of waves and direction are not taken into account? It is getting tedious your criticizing good technology and successful boats. Also, making unfounded claims to justify your superiority for deriding modern technology. Maybe you should turn off the computer and start writing letters. That is, writing on papirus with a quill.

 

Don't forget that the only superiority or supremacist talk is the supposed "modern technology" that is just old papirus but with light screen format, and to be honest i could do the same cad 3D design just with pieces of paper and cardboard

You should know that polar diagrams are based in flat water, and imoca is a slug at close hauled angles compared to wild oats and ac72 that otherwise have 25knots and 53knots top speed respectively at the same 25knots of wind speed

But anyways speed for what? What it needs a boat is safety and movement comfort and the higher the speed the bigger the collision damage

 

If you are old at heart, that makes sense.

 

Rather makes sense if you have not been scammed by the 1950s speed advertising that is killing and hurting millions of people in roads and also making an average of 50% of vendee, imoca,etc boats to abandon because fast speed collisions with cetaceans and debris and structural failures and also suffering motion stress.

In the 1979 fastnet race catastrophe the major cause of abandoning ship was motion sickness by the most "experienced" sailors and some people died by abandoning ship while all of them missed the sailboat when boarding the liferaft

Motion stress and fatigue also harms the body muscles when cruising and mooring lifeaboard