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(Working Vessel) Dumas Osprey
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About this boat
This was built from a Dumas kit, no longer produced and Imported from America. It represents a New England fishing boat. The kit was planked rather than having sheet material for the hull, which looked quite good. It was fun to build and detail using Macs Mouldings(?) and George Turner figures. It is 1:12 scale. (Motor: Graupner 500 Eco) (ESC: Mtroniks 10) (9/10)
Since 2019 I have used a 1ah 2s lipo and kept the old, defunct NIMH pack as ballast.
Since 2019 I have used a 1ah 2s lipo and kept the old, defunct NIMH pack as ballast.
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It turns out that I had rigged it almost exactly as designed, the only problems were that the boat had been butchered a lot, so I had to make some adjustments based on what bits I had in the parts bin.
I finished the basic setup on Saturday evening, and threw her in the water in all the high winds on Sunday morning!
What a great little performer! No adjustments necessary, and a beautiful hands off boat in gusts!
Originally, I was going to make the boat seaworthy, and find a new owner, but now I am thinking of stripping her down to rebuild with better sails, and add her to the "permanent" fleet!
On another note, a fellow member "DGOSS" has aked me for an electronic copy of the manual, but I was thinking that I might, with your permission, copy the one or two sheets I need, and just send him the whole package........is that ok with you?
Thanks again,
Brian.
I may have to wander down to County Hall one Sunday morning.
Our sailing is always done on Sunday morning, but I may have to play truant to thank you in person.
This photo was taken, I believe, at the Arboretum, June 2014.
Regards,
Brian.
What do I owe you for copying and postage?
the Sirius is almost ready for testing.....I have pulled a set of "B" rig IOM sails from my parts bin, and they should do the trick being exactly the same measurements as the originals.
I sail with Worcester Model Boat Club, out at Cob House Fisheries, near Wichenford, they have a great reastaurant which makes Sunday mornings a treat!!
But I know your venues, I was a member at Droitwich for a year or two back around 2012.
If I remember correctly, all sailing stopped for a while due to blue green algae, is that all sorted now?
The picture shows a couple of my boats.
Regards, Brian.
I won't, unfortunately, be in the area Monday morning.
Would it be too much trouble to post the pages, and I'll send you some cash by return post?
Regards,
Brian.
Brian Hill, 15a Broad St, Pershore, Worcs., WR10 1BB.
The sails I have are original, just the jib has been painted red by a Magic Marker, by the look of it!!
I can measure off them anyway, but thanks for the offer,
Brian.
Just the pages in English, and let me know the cost of printing and postage.
Mine had been butchered for another type drum winch, I think, so I've rebuilt it to fit a winch from my parts bin, shame, but it will sail......and I will probably raid the parts bin for an IOM sail rig to use,....cut down "A" or a "B".
I opened and read the link.
No fear. Everything works.
Ships have sailed upwind since the time of Andrea Doria but without knowing why. They continued to do it for centuries without knowing the reasons but improving the techniques until today (that you sail faster than the wind that generates the motion, incredible).
Exact things were written in the link, the only inaccuracy in my opinion is this:
"In airplane wings, the pressure on the top of the wing is less than the pressure on the bottom of the wing, because the air moves faster on the top, so this difference in pressure creates a force on the wing that lifts the wing up into the air".
In particular this is wrong:
"because the air moves faster on the top".
On the web it's all copy and paste and the easiest theories go a long way in blogs and among YouTubers (even physics professors).
Lift is not an easy concept and if it is oversimplified, mistakes will be made. There are debates and different ideas even among physicists.
Check out these links from the NASA website.
I'm still digesting Bernoulli and Venturi's refutation.
https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/foilw1/
Is this the source where you got the information you posted on the forum?
I wrote to you privately because in my opinion this explanation is wrong:
"Air has to travel further around the back of the front this means it travels faster. Faster means low pressure on the back and high pressure on the front."
It is true that in hauled closed gait, the sail behaves like the wing of an airplane.
It is true that in wing lift Bernoulli's laws are used (demonstrated by the Venturi experiment), therefore in a particular system, to conserve energy, where there is greater speed there is less pressure.
What is wrong, even if many YouTube videos and various brochures disagree with this explanation, is the double path theory.
Even NASA refuted these "rumors". It is not at all true that on the hump of the wing the air is faster because the path is longer and on the belly it is slower because the path is longer.
There would be a lot to write about this but I'll try to summarize as best as possible.
Bernoulli does not apply it like this (back-belly difference) because the difference in speed and pressure must be found entirely on the back (and, in concave-convex profiles, entirely on the belly independently).
Considering only the convex part (the "hump"), on the leading and trailing edges of the wing the pressure is greater than in the center (let's say on the hump to simplify). In the center the air flows faster.
Considering only the belly (in a concave-convex profile) the opposite occurs.
In fact, even if a fluid flows only on the back and nothing on the belly, the suction phenomenon (depression) still occurs.
I won't go into further detail but you can experience for yourself that lift is created even if the fluid passes only over the back.
Place a spoon under the water jet on the convex side. You will see that it will be sucked in even though not even a drop of water passes through the concave part.
Another test is to place two empty aluminum cans standing very close to each other; blows hard in the space that separates them. you will see that they will touch each other.
The air only passed over the back.
In both cases there is no double path.
For wing lift, not only Bernoulli affects but also the law of action and reaction combined with the Coanda effect and many other interesting things, but remember that the double path has no scientific presupposition in Bernoulli's explanation.