Given that you want to use a CF spar and CF spars are not avail as groovey, then the cotterpin/jackwire system probably offers the next best control over sail shape. This system is used frequently in IOMs sucessfully. You need only to secure the jackwire at the top and bottom (maybe with a tension adjuster at the bottom) and at two or three points down the spar.
John
Hi John, CF groovey not available in the US of A ? they are here in Europe (see attach pic)
Claudio, I have spare 14 kg drum winches in the workshop, are they sufficient for AC 120 78 & 74 dm2 sail area or would you recommend something more powerful ?
Cheers K1
Claudio,
About to start making the Fin Bloc & thinking through what needs to be done. When comes to mount the assembly into the hull I see that there is hull base plate (grey area in your Fin Bloc drawing)
I can push the hull around the keel area with my finger (without too much pressure) and quite easliy indent the hull, so this base plate needs to be very strong to distribute the load that is going to be transmitted to this area via mast support & keel box which has narrow foot print. What materail should used here ?
Cheers K1
HI K1,
No problems, but what type of servo is ?
Thanks.
Cheers
Claudio
This grey should represents a layers or two of 160g/m² CF cloth that generally is used to reinforce the fin box area a the mast support area.
Similarly the rudder stok area is reiforced to.
In the AC33 discussion is shown the subject : http://www.rcsailing.net/forum1/showthread.php?t=4991&page=9
Ciao
Claudio
Hey K1…
I know those days mate!
Thanks for the luff to mast diagram, interesting. What does everyone else who sails a 120 use?
Matthias suggested I use a 12mm OD round carbon tube for the mast and I will have to figure out a connection method.
Claudio - do you make your own adhesive paper backing for fibreglass strips by using spray on glue?
In your AC33 build, the reinforcement strips look like fibreglass instead of carbon fibre, is that correct?
Cheers
Goose
Hi Goose,
the adhesive paper used for the FBG panels borders is simply normal paper scotch cut to 2/3mm wide once fixed on FBG.
Right, was FbG and not CF but 2 layers instead of 1 therefore increasing weight. At that time I din’t got 160g/m² CF.
Cheers
Claudio
I was afraid it would be CF, but makes sense …now need to find it during the holiday season here :scared:
The drum winchs are ACERC WQ 2811 from Thunder Tiger Europe. Today will try out composite fin box construction, 1 mm aircraft wood sheet and 2 layers of 150 gsm cloth.
Eh …got the bathroom sequence right this morning a good start to the day 
Cheers K1
Regarding the previous references to groovy carbon fibre masts; these are available worldwide via Graham Bantock’s agent network - that includes Italy, Germany, Canada, New Zealand and the USA. Here’s a link:
http://www.sailsetc.com/buying.htm#Agents
I suspect that perusal of his catalogue will reveal some useful offerings for other fitting-out needs. No, I don’t have any alliance with him, I’m just a happy customer.
by way of assurance Bantock’s reputation and quality are second to none and he must be one of the very top radio boat skippers in the world, having won world and national championships.
Ray
Hi Ray,
Thanks great help, happy customers are always the best reference.
Goose I finally managed to find that article on sails attached, happy reading (pages 19-21)
:zbeer: K1
K1W1 & V8Goose :propeller:propeller:propeller
I couldn’t take any more! Reading your thread has sent me running to the stores. Bought all the stuff this a.m. to start on a new plug :D. Spent afternoon redrawing shadows - removing 3mm to build plug for USOM Mistrals. I have been asked to build two. Make a profit to pay for my IACC12 build :).
I plan to treat your thread like a bible and copy every step.
Thanks for making all of your information and photos available. Especially the mistakes! Hopefully this means others can build better from your excellent example. Oh and cheers to Claudio for his input :lol:. Might get T-shirts made up saying “Claudio is my hero”. I’ve been using Claudio’s gizmo to make sails for ages. Now his boat building techniques.
:jump2: :jump2: :jump2: :jump2:
Time for me to hop-to-it!
Larry L.
Hi John,
availables also with Walicki in Germany : http://shop.walickiboats.de/ and in France (forgot adress)
You can also make it yourself, and will be certainly much cheaper .
This is the sample I made :
Cheers
Claudio
Hi Larry …great stuff looking forward to seeing your progress, wondered if the mistakes would be interesting or not, glad to hear they are … oh I"ll take one of your Claudio T-Shirts 
Claudio just checked out that German link and at 300 Euro plus for CF mast & needing to buy two they just got struck off my shopping list ! … your home made one is brillant, I’m thinking about maybe giving it a try :rolleyes: how do you go about cutting the groove in the 6 mm CF tube for luff slide ?
Thought would submit “Weight Budget Update” just so everyone knows where I at :blkeye:
Cheers K1 :zbeer:
Hey guys…
Claudio - Thanks for that. I’m going to assume the tape is masking tape? Wow that mast looks sweet! Going to investigate that more.
K1W1 - Good to hear you’re back on track mate. I had Sailetc bookmarked… looks good.
All - What are you using for 120 masts?
Cheers
Goose
Hi
just to avoid mis understanding Goose, this the paper tape :
this instead may help to understand how to make the mast. The grow is cut with a Dremmel diamond blade.
The Tool :
the blades :
Cheers
Claudio
One thing to bear in mind with aero section masts such as that described by claudio is that you need to have the rotating in order to create an effective leading edge to the soft sail - if used fixed fore and aft they’ll actually detract from the performance of the rig by creating too much turbulence.
Also, for a truly effective wing mast you need to consider the mast and soft sail as an aerofoil with a smooth transition from mast to sail (on both tacks).
Ray
Here’s an interesting paper on the subject of wingmasts…
http://www.tspeer.com/Wingmasts/teardropPaper.pdf
Ray
Nautiboy, at the risk of hijacking this thread (sorry Alan, Goose and Claudio), The article on foil sections was a interesting read, however it did not really give a pro/con conclusion relative to standard round section spars…I would be very interested in this…surely a round section will have significant airflow distortion issues as well…question is…which section provides best overall results…this is probably a post which deserves a thread all of its own.
Cheers…Gary
Gary -
I think I have a good illustrative comparison between the various mast shapes, and then if the mast is allowed to rotate. Unfortunately, I am home and it’s 10 PM here - and I recall the image being on my work computer. Will post tomorrow if it is. Was part of a series on wing shaped masts and their improvement in airflow for big multihulls.
I do know/recall several articles on sail to mast attachments, and it was a given that a sail attached with sail rings, and allowed to rotate around the mast to leeward side had much better flow attachment than a sail fixed to the center-line on trailing edge of a round mast. As I recall it also discussed the use of a double-luff type of mainsail (much like a sailboard sail).
I will see what I can find.
ADDED: A rotating wing shaped mast that allows the leeward side of the sail to be an extension of the leeward side of the mast is much more efficient than a fixed wing (or tear-drop) shape that doesn’t rotate. One reason even small beach catamarans all come with rotating, foil shaped masts. It has also been proven that full size trimarans can easily sail with only a wing mast and no soft sail in strong winds. Remember - I’m talking wing “MASTS” - not solid wing “SAILS” !
Hi Gary,
I agree it should be a separated tread, nevertheless to stick to the actual fixed and not rotating mast profile, the oval section is just a little bit better then a round one . I picked up an interesting figure from a book :
The wing mast is another story and deserve a separated tread, it happen that I’m working on a possible application, but only few classes will permit their uses, the AC120 may be one of.
Cheers
Claudio