MartinRF

When I studied electrical engineering some 40 years ago some mechanical engineer students built a ram-jet driven bicycle. Think Nazi buzz-bomb engine mated to bicycle frame. I never saw it in action but I heard it. It was VERY noisy. /Martin

Navigatrix may interest you guys: https://navigatrix.net/nx/ /Martin

Completely off topic but why is it named Administration Bay? There must be a story... /Martin

Swedish air-force pilots did a lot of showing off when we were out on the Baltic. "Look, the navy, let's have some fun!" type of... Sub? No way. A sub being that easy to detect would be very undesirable. /Martin

I did my military service in the Swedish navy. Among other things I was involved in 'de-gaussing' ships. What you do is kind of similar to erasing a tape (remember those?) but on a much larger scale: You move the ship through a strong magnetic field that is switched back and forth. The magnetic compass went berserk. It not only rotated like wild, it also stood on its end and flipped from side to side. /Martin

Off-loading the board is what I do: a quick bear-away synchronized with pulling the board up. Slowing down is safer though. /Martin

I use nothing. The trick is to realize there is no need for a very tight fit and apart from the exit hole in the bottom of the hull the fit can be quite sloppy. For support higher up in the dagger board case you can use synthetic carpet material or astroturf to take up the slop and avoid noise. I use this both top and bottom in my rudder sleeves. Adding a wear protecting 'rail' (my English failed me) to the rear of the dagger board case is nice as that edge of the board can be a bit 'aggressive'. Rudder sleeve seen here: http://hem.bredband.net/b262106/pages/index.html /Mar

On smaller cats with accommodation in the hulls the presence of a dagger board case is a serious obstacle. Hence it is angle one way or the other to get it out of the way. This means there is a vertical force component when sailing. The other day I amused myself by making an approximate drawing of my boat and calculating the forces: The green arrangement is what I have on my boat. Ease of handling is an obvious advantage. The numbers show a non-trivial increase in righting moment for the red arrangement and it is for free (I think) -- a compelling argument for the red version.

This guys is testing and repairing battery chargers and some other stuff. He also tests the recon function. Might be of interest: https://www.youtube.com/channel/UCxQND04oRmv_KgEpWjW0-mg /Martin

"waypoint" may be too much for the uninitiated reader. I have no better suggestion. It is your language, not mine, after all. /Martin

This is science click-bait. Nature (the publication) does this all the time but this time it is Science. Looking up the paper in Science I find the H2O2-treated balsa is not as strong as glass. Far from it actually. The numbers reported are lower than those of the pure epoxy resin! Glass fibres reinforce resin. In this case it is the other way around. The epoxy is AeroMarine 300/21. https://advances.sciencemag.org/content/7/5/eabd7342 https://www.aeromarineproducts.com/product/300-21-laminate-epoxy-resin-1-5-gal-kit/ /Martin

1990s Strockholm: https://youtu.be/QQvYogFP9mw 1989-90 Gothenburg: http://hem.bredband.net/mschoon/af_Chapman_II/ and MIT did something like the manta even earlier, I think. The Trampofoil guys got some free TV time at the time. They tried to go commercial but this simply too niche. In later years one of them has been involved in a foiling motorboat project with better economical backing. That project may take off (pun intended). https://candelaspeedboat.com/ /Martin

Reminds me of "Never Again II". I don't know if this name exists outside internet fora /Martin

Over on this side of the planet there once (1980s) was a sailboat called "Ormgas". With its original name it was banned from entering any of the regattas arranged by the Royal Yacht Club. It is not too hard to figure out the original name by rearranging the letters in "Ormgas"... In the late 1990s I came across a catamaran mentioned in a multihull rag from Australia. Its name was "LBTPASB" or "light blue touch paper and stand back". Not being a native speaker of English this was mysterious to me. What is light-blue touch paper? Eventually someone explained My own boat is named after

Here is an example of a winch-less system on a boat that is slightly smaller than an Open 8.5. /Martin

I have 35-ish years of experience of a fully battened mainsail (square top at that for the last 22 years) of about 30 sqm and I don't think the weight of the battens is what bothers you if you have problems hoisting your sail. I would take a look a at what I could do about friction. In my case it helps a lot to clean the luff grove of the mast. Batten pocket hardware and how the sailmaker positioned it relative to the bolt rope also plays a sigificant role. All this assumes bolt rope in luff groove. Dirt and friction are factors regardless. /Martin

OK, I know this thread has been hibernating for two weeks now but I just came to think of this old dinghy description by Richard and Lilian Woods. See attached document.Crayfish__Woods_1982.pdf /Martin

👍 /Martin

I asked for the source of the efficiency figures appearing in your first post. That was all. /Martin

So the data is your own? /Martin

This made me remember an anecdote told to me by a fellow at usenet news rec.boats when that forum was still active. My source had worked either for the U.S. Navy or the Coast Guard in southern California back in the day when hippies were a thing. One day they came across this sail boat heading straight out into the Pacific Ocean and since they were already some distance from the coast they decided to check things out. The boat was crewed by a bunch of young, bearded men claiming they were heading for Hawaii. Sure enough they had food and water to last the trip but very little navigational

Where did you get those efficiency numbers from? The reason for asking is I looked into this (for non-vehicle reasons) a few years ago and what I found then was not that high. /Martin

Mousing line in place! 4 x 3 m lengths of 16 mm plastic piping made it possible as it was quite easy to push the plastic tube all the way from the bottom of the spar to the top. Cutting the end of the leading tube to a sharp point helped avoiding catching on rivets and bolts. A 4 mm hole drilled near the tip was used to attach the mousing line and the sheave at the mast top was removed to make access easier there. The rest should be routine work (famous last words?). /Martin

Good idea, only snag is that there is no way to get to the top of the mast to feed bicycle chain into mast. I have even saved some worn out bicycle chain in case I may need it for this purpose. Main idea right now (before going to bed) is to get some cheap plastic piping (16 mm outer diam, 3 m lengths) and push this in from the bottom end of the spar. I hope I can figure out a way to attach mousing line. /Martin

Tried the shop vac idea tonight -- didn't work. At best I got about 2 m in. The tube is fairly clean inside but there are some obstructions including the jib halyard and the spi halyard. I could remove them but progress stopped before I got to where they could obstruct. Also, there are a number of leak points. I tried to deal them with tape but it was not good enough to make a difference. I could push rods or tubes in from the bottom of the spar but how do I get to the mousing line at the top? Fish tape or fiberglass snake might work but I can see how they may act up on the way. Ther