Nice Pics. Looks like a hell of a ride.
Dick & Marcus
You’ve both made some important references to weight. Weight aloft on these models becomes extremely critical, especially when hit by a puff while beating to weather. The tendency to pinch up to maintain control will also exert centrifugal force on the rig, which is the last thing you need to keep the boat upright. Dick’s shrink wrap coating will pay a price if it’s much heavier than monocote, so I would be inclined to choose the latter. Lightness is prefered over durability. Kris Seluga’s LS-4 Landsailer wing
(http://www.rclandsailing.com/photos/photo_63.jpg ) is reported to be very light, using monocote. Marcus, you mentioned your foam cores weigh 90g, so I weighed one of my NACA 0020 cores & it came it at 51g. The entire mast comes in at 150g with 6 oz cloth & epoxy, although at 173 cm it’s a bit shorter than yours.
Regards,
Bill
Bill
Just reading thru some oder post and can across this one. I am building a Ghost Train, and was thinking of trying wing masts. Just a couple of questions.
I have been to the CNC Foam Factory website, and it says that their foam cutter can handle up to 48", do you get your foam blanks in two pieces and join them?
Are you still using wing masts, and have you come up with any new ways of building them?
Do you think that using carbon instead of glass would be a big advantage( I have access to cheap carbon)?
How do you send your designs thru to the foam factory to get cut, or are you using a design of theirs?
Thanks
Martyn
Martyn,
Yes, I simply glue the sections together end to end. Sometimes it takes a bit of trimming to get them to fit together squarely, but the connection isn’t at all critical to the eventual stength.
I’m still using the wingmasts & haven’t tried a new way to build them, but have a couple ideas in the back of my head that I might try at some point.
One thing you might consider is a CF tube with a deep sleeve luff tube that will start to approximate a wing shape
Carbon could be lighter, which of course is always desirable. However, I’m playing around with lateral mast bend as a means of gust absorbsion, so the stiffness potential of carbon isn’t necessarily needed. The DN iceboat guys are building extremely bendy masts & have found that fiberglass will tolerate severe deflection better than CF which can explode as it reaches it’s elastic limit.
The Foam Factory only needs an airfoil profile (eg NACA 0020), overall length, & chord dimensions top & bottom
Glad to hear you’re thinking about wingmasts, as I think they have good potential on multihulls.
Regards,
Bill
One more question.
What method are you using to control the max rotation of the rig compared to the sail?
Some of the cats I have sailed on have a lever system on the base of the mast with a retaining line running to the boom to control rotation. This is probabaly the simplest method that I know of, but are there any others.
Martyn
Martyn,
Since simplicity is desirable with models, I have tried to make mast rotation be contolled automatically with the design of the rig itself. I suppose it could also be controlled manually with more servos & channels, but that’s alot to think about at speed.
Here’s some images to help show what I use, from my friend Tom’s rig:
http://img138.imageshack.us/my.php?image=tomsrig6hr.jpg
The hound connection acts as an adjustable lever arm to force the mast to “over-rotate” due to the tension from the side stays that are attached towards the outer end of the hound :
http://img138.imageshack.us/my.php?image=tomshound6yf.jpg
Then the attachment points at the boom & sail clew will limit the amount of rotation & control the amount of sail camber (draft):
http://img138.imageshack.us/my.php?image=tomsboomlet6cj.jpg
An additional control is now under development which will de-rotate the mast when it is fully sheeted in & approaching max speed. This one will
reduce sail camber & produce a more efficient (less drag) airfoil shape.
Regards,
Bill
Bill
I got some prices back from CNC Foam factory, and they seem very good.
Just trying to come up with some ways of fitting the boom. I like the idea of the boom being under the mast, but how do you set up a vang this way?
Any ideas would be much appreciated.
Martyn
Martyn,
If you look closely at this image http://img393.imageshack.us/img393/6797/k1ss0bn.jpg
you will see that the boom is cantilevered about 4" in front of the mast, with a tensioned line running up to the hound. This will vang down the boom creating leach tension without inhibiting mast rotation. The vang line & forestay are located adjacent to the leading edge of the foil, so as to be close to the axis of rotation. The side stays are attached further out on the hound, which will ensure that the mast rotates quickly to change sail camber on the new tack.
Hope this helps,
Bill
Has anyone got a new web address for the CNC foam factory. Their old site does not seem to work anymore.
Martyn,
The Foam Factory went out of business. I found this fellow who turns out a similar product & price: http://www.flyingfoam.com/launch.html
How is your project going?
Bill K