Sunday, March 28, 2010

first sail

fist go in a moth for quite a while! needless to say i was a pro and not rusty at all... anyway there wasn't too much skill required, it was just a quick check of the boat to make sure everything was going together well. It was 8-10 knots so perfect for a first go.

almost everything worked and didn't break. even though i hardly sanded the foil and there were pin-holes all through it, the boat lifted off pretty early. you could feel the skin friction so with a bit of bog and paint i reckon it will go well. much, much better already than the last foil. about half the weight too. the second attempt at the horizontal came out lighter again. the sikaflex hinge let go though. i hit the bottom once, and i think the tip got ripped off a bit and after that it started to separate. does anyone know exactly which Sikaflex you're supposed to use? i just used whatever one i had that was open. i might try a hidden hinge system of some sort, even if it means i have to make a new flap.

the 'dial' thing works well. i was a bit skeptical but the lever and rope that i have going is really effective in controlling the ride height. basically the wand pivot fitting is upside down so everything is in tension, and then the lever just slightly adjusts the length of the rope between the wand and bell crank. i have a slight problem with rope stretch/spring, but i think that will improve with use and you can compensate for it with the system.

the wand pivot is strong and declared good. basically its a Harken ball-bearing sheave stolen from an old block glassed into the hull. i modified it a bit so by tensioning the bolt you control the friction/slop on the sheave and hopefully find the happy medium. very direct, straight and very low friction under load.

the AOA adjuster on the centreboard works well except as it it you cant adjust it when the board's in the boat, because of the centreboard case prongs. bit of crap management but ill sort that out. eventually i think it will have a dial too or some other way of moving it on the water.

the weird kingpost i made seems fine but not yet tested in breeze. the cleat attachments are interesting and they seem to work. i did that because i couldn't fit them on otherwise, without buying new cleats. and the small stainless ones were like $80 each. the vang retainer is good as well - i got the angles right so the vang doesn't tighten up as you ease sheet, like it used to. wave peircing bow also a tick - i have the same freeboard as the assassin but heaps more volume because the old girl is a lot fatter, so the boat sits higher in the water and sails quite well lowriding. the water sheds well off the peaked foredeck. i reckon a proper wave piercer with no compression strut is definitely on the cards at some stage. i think it has legs. i dont actually mind the fatter hull when i think about it, because it will keep the freeboard down and thats less windage. i think i could cut another 50mm off the freeboard and 50mm off the rocker of this boat.

the gantry is shit but hasnt broken yet. the product of a vacuum bag that got a hole in it. i chucked it on anyway, but i think ill do something different. i really like the assassin gantry, might do something like that.

the flat wingbars also work. in fact the boat is noticeably easier to sail as a lowrider, really nice to sail as a foiler and much cooler looking. the little wings are good - i cant imagine they need to be bigger, actually could be smaller again.

the rudder is the final thing. i designed one already for Sam Schneider's SR71 foiler. it looks about right, at some point ill scale it back down and pull some moulds off it. i'll make the rudder foil available for download from the blog too at some point.

so im going overseas now, so the boat will be mothballed for a while. but its all set up for some serious tuning when i get back! really pleased i got it sailing before i left.

this is a good way to do the moulds if you're going to cnc it. helps to keep everything straight because the MDF is so crap with heat. that said, id minimise the use of MDF because it shrunk fairly considerably in the oven. no big deal as long as you let the foil cure before you heat it, as i did because i accidentally didn't turn the oven on! the first time round i used chip board glued to MDF, so the mould surface was still in the MDF but the whole thing had a 18mm chip board backing, and that didn't shrink as much.

below is a comparison of my foil and the assassin foil. area is pretty similar.


Rob said...

Hi Nick,

Up in Dubai I have used FixTech MSP190 for around 5 flaps, no problems so far that I have heard about. It is an Australian made structural adhesive.

We were using either 3M 5200, or SikaFlex (not sure which, probably 252 or 296) but in the Dubai heat we had a few flap failures.

After the worlds I noticed a tube of Sika 291 in my gun, I think that as what the Sweedish guys were using, but from the chart I have, I think that is more sealant, than adhesive. I cant read the tube, its all in Scandanavian languages!

Try the MSP190, seems to work ok, dosnt need a primer (that might be your problem with as Sika some need primer) and dosnt go off once you open the tube.

nick flutter said...

hey rob, thanks for the info. i think the one i used was more of a sealer than an adhesive and i didnt know about the primer. ill check out MSP190.

actually ill be in Dubai from tomorrow for a few days, im pretty keen to come down to the club and have a look - what day does the moth fleet normally sail?

MalteM said...

BR front foil replacement instructions are here:
They use Sikaflex 291 with activator and 206 primer.

Cookie said...

I like your db head adjustment - I had something similar a couple of years ago but you've done it far neater!

I use sikaflex 291 for flaps.