So here's my second attempt at a gantry.
Its got a different control mechanism too. I told myself when I launched the boat that I wouldn't change anything till I figured out how to sail it, but breaking my first gantry accelerated my development program a bit. The new one has held together through two days of sailing in 0-5 kts so still haven't been able to really put it to the test. The adjustment mechanism seems to work. The biggest problem is now that I can adjust rudder angle easily, it's easy to put it in the wrong place.There's a million things I would do differently for the next one, and might get the chance to do soon, as Karl's new rudder is coming along and he's thinking about a new gantry to go with it.
It weighs about 725g with the adjustment mechanism which is about 200g heavier than the last one. I think I could get about 150g out of it easily for the next one. What's a good weight for a gantry?
Interesting design for the slider. Also interesting that you decided to make the lower part take all the vertical load. What was the thinking behind that?
ReplyDeleteKirk
The lower rudder gudgeon already takes all the vertical load so a vertical tube on the gantry is redundant.
ReplyDeletemechanism looks very much as the kind the 14 footers are using to control the AOT of rudderfoil
ReplyDeleteOle Frey Denmark
I've seen it and its very neat piece of construction.... All we need now is foiing conditions, which typically happen on Monday not Sat or Sun
ReplyDeleteRichard
We'll see how it works out. The mechanism is definitely inspired by some 14 rudder mechanisms.
ReplyDeleteOn the upper tubes taking vertical load, my thinking went something like this: The elements of a truss structure by denefition take only compression/tension loads. Since the upper tubes of a gantry are essentially horizontal, they cannot take a vertical component of load. Even if they did, the stiffness of a 25mm tube in bending is much lower than the rest of the structure of the gantry under a vertical load. So I don't think that the upper tubes of most gantries take vertical load.
They definitely do take side load and for/aft load.