flexi-tip rigs

Rcsailing.net Technology Discussions
1

this is a new concept i’m playing with on my vic and am going to translate over to my one meter if it works.

i basically started with a shaft of tapered graphite and a aluminum tube (half the rig is aluminum top half is graphite) using two spreaders and 3 shrouds per side i set it up to maximum height alowed by class rules. this renders the top 3-4 inches or so useless in the rig. with the top 6 or so inches very flexible. also mind you, the rig is stiff as hell side to side when the uppers are tensioned. in light air with forestay tension and loose back stay the rig stands straight, it responds quickly to very little backstay also, i find this to loosen the leech but not put excessive tension on the forestay. now spilling air through the backstay is all well and good. when its really blowing though all i have to do is apply a small amount of back stay and loosen the uppers, this bends out the mast tip under load spilling air more efficiently i find, while still keeping a realitivly good sail shape (no excessive leech curve).

i was just wondering what other people thought of this idea it has yet to be water tested but will be in the next week or so. i really think this is going to make for a very fast, very competitive victoria, it will just require extreme attention to detail in the mast tuning.

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

2

Okay, you seem like an ambitious guy. Here is something to chew on. Probably choke on is more like it. Too much data.

Upper mast bend automatically relieving the pressure on the mainsail in high wind/puffs is a nifty problem. It seems like there should be a solution and it also seems like the optimum solution will take tremendous effort.

There is not a lot of available universal across-model-boat-classes data. I suppose there is not a lot of available data period with respect to any classes of model boats.

It seems to me that the optimum is that the boat be fully powered up until the wind is high enough to make the boat heal beyond say 30 degrees. At that point the sails should automatically start to depower. One of the automatic adjustments would be mast bend especially upper mast bend. There is a lot of info available on the internet by doing a google search under such things as ?upper mast bend?. You can look at the WB Sails website where there is good info. Bethwaite in his High Performance book talks about an ancient Finn mast where the top of the mast flopped to the side at a certain point/wind strength. This is possible for a cat/no jib rig. There are lot of books that mention mast bend and depowering the sails of course. One interesting item that I found was from Paul Elvstrom in his Keelboat and Dinghy book. He said that he was sailing a Dragon in a 30 knot wind with the mast bending so much that he was afraid the jumpers would break. A very hard puff hit and the jumpers folded righ tback and th eboat became tremendously fast. When the jumpers folded the top of the mast went to leeward and the mid-mast wnet a little forward and also to windward due to the tension of middle lower stay. So in, he said, in the hardest puff the mast adjusted its sideways bend automatically. On page 173 of the hardcover book.

That is one well known automatic depowering tool that you are not using ? having the uppers be looser than the lowers thereby allowing the mid-mast to bend to windward relative to the upper mast in puffs. Lester Gilbert talks about that on his website ? see short spreaders. You do not need a mast made of two different materials to do this.

I think the original TS2 sailors conducted extensive 2 boat testing to optimize the rig and cause the rig to depower dynamically in puffs. Some of the things they came up with were location of the stay attachment on the mast and (short) spreader length, I believe.

The problem becomes how to apply what you read to your particular boat. And you can probably envision that it will be difficult to determine what works and what doesn?t without extensive 2 boat testing.

It is apparent that your idea of two different materials does has not caught anyone?s interest on this board.

Some interesting sites
Depowering the Star by Mark Reynolds
http://www.quantumsails.com/products/onedesign/cni.asp?NID=229&CID=5

Dynamic Response ? Frank Bethwaite ? Reach for the sky
http://www.boats.com/content/default_detail.jsp?contentid=7516

Composite tip ? Frank Bethwaite ? Rig elasticity ? Woollahra Tasar
http://www.members.shaw.ca/raspencer/racing/franknotes1.html

Ups?And downs of side bend ? WB Sails
http://www.wb-sails.fi/news/98_2_SideBend/SideBend.htm

Some thoughts on sailing light ? Steve Ulian
http://www.usaj22.com/sailing_light.html

Interesting pdf site
http://www.proctormasts.co.uk/fittings/Proctor_catalogue.pdf

http://www.c-tech.co.nz/article_ausailingmay01.htm

http://www.snipe.org/articles/sw5-93.html

There is a wealth of info available. Big problem trying to determine what is applicable and how to apply it.

Scott

3

yeah i was just throwing out an idea to see if anyones tried it and had it work, i have my stays set up so that when the uppers are lossened only the top quarter of the mast bends, which basically means that only the head and a small amount of the main would spill (the jib is a frac) the two different materials i found to be a better idea because the loads on a victoria are not alot and carbon and aluminum just wouldn’t bend enough (at least i don’t think) the whole concept is probably a lot more complex than think it is though, but if my shot in the dark worked than i’ll post more on it. also my upper spreader is reasonably short. hopefully some of the more experienced modelers will post in reply to my topic, any input positive or negative is at least some what constructive.

`alex

i wish i had a digi cam to post some pictures

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

4

I think you probably are on to something and I think you should continue to explore it with two boat testing if at all possible.
I don’t sail boats with pointy(“normal”) rigs since my boats use modern versions of a gaff or rotating “bent back” tips to allow the use of sails similar to square tops without needing full battens. Early on I did two boat testing with a new rig and old type rig and learned a lot that way.The rigs I use aren’t legal in most classes so the experiments you are doing could be valuable if you can make a flex tip work really well within the class rules. Good Luck!

Doug Lord
–High Technology Sailing/Racing

5

Hobie Cat tried their “CompTip”<font color=“red”><font size=“1”>tm</font id=“size1”></font id=“red”> concept in the mid 1980’s. They came out with an aluminum mast section but the top 4-6 feet was made up of a composite plastic material. I don’t think it was carbon, as it was very flexible. In fact, most of the serious racers in Michigan bought a lot of the older masts and stashed them away.

Since shrouds on a cat end up somewhere between 1/2 and 5/8 of the way up the mast (to allow mast rotation) and no spreaders on the 14, 16 or 17, the upper part of the mast was uncontrollable, and added way too much twist to the sail. Vang tension was limited as a one-design (2:1 I think), and the newer masts just wouldn’t go to weather as good as the older, all aluminum.

Hobie introduced the idea as a safety option - I guess a few “shocking” incidents at launch ramps when sailors forgot about their mast and managed to snag power lines in the ramp launch area. First couple of years is was optional, and they would sell retro-fits for do-it-yourself modifications. Then they required the “CompTip”<font color=“red”><font size=“1”>tm</font id=“size1”></font id=“red”> for any Hobie sanctioned or sponsored regatta as a mandatory requirement.

Now - with so many manufacturers offering full carbon masts, I guess they aren’t too concerned about a few “Krispy Kritters” at the ramp!

Express - just watch yourself when launching - be aware of overhead power lines ! [:D]

6

i got off work early!!! the mast fittings are being finished today and the boat is going to hit the water tomorow hopefully with some good wind and if all goes well next week it gets a nice red paint job to match the trim on my new black magic sails. i’ll let ya all know how the rig works in the gusts hopefully it spills the air and accelerates the boat like it should, if not its just going to make it slow no happy median[:-boggled] well off for a shower and quality model boat-me time.

bye bye

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

7

i took out the boat today nice and windy and the mast racked like hell forward need to make a better mast step. and the flexi tip needs jumper and than it will be perfect. just thought i would update, o and my girlfreind had a blast sailing it too, it was her first time. well i’m off to figure out how to make jumpers, and seal the deck too.

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

8

i had a similar idea, loosely based on the 49er rig (hey, they sail from my club its hard not to get some influence)

attached is a rough ms paint drawn picture, also showing batten configurations

9

Neat drawing! Have you tried the rig on a model yet?

Doug Lord
–High Technology Sailing/Racing

10

Nah, havent got the money

once i finsh school ill build it.

The drawing is only very rough