i550class.org

We are building away... Well to be honest, I got someone better and more experienced than me to do the actual building . Location - Belgrade (and Kovin), Serbia.

A few photos below:








All feedback and comments will be appreciated (positive or negative).

Not aiming for the ultimate racing machine really - just a nice boat to enjoy.

Few key decisions made along the way:
1) Wide cockpit large cabin version. Well sort of 1/2 way between the wide cockpit and narrow cockpit plans similar to TTB.
2) Keel will be at max weight 80kg but aiming for 1.1-1.2m total draft.... To suit local conditions - river.
3) Spinnaker pole will be deck mounted - sort of Seascape 18 style and added at a later date. I want to get sailing as soon as I can, and will add spinnaker pole and spinaker when I can afford one - hopefully in not too distant future.
4) Wedge type keel box to hopefully avoid problems other people have been having... and probably encounter a whole new set of problems...
5) The mast will be a copy of TTB mast based on the class dimension limits and the photos kindly posted on his build blog. Main mast extrusion - aluminium window framing (round corner section 85mm diameter 1.5mm wall thickness compressed into eliptical probably 65x100ish mm).
6) Top of the transom and the back of the seat will be sort of open... I've seen that on some boats recently and kind of like it... not sure how it will turn out on this boat. This should explain the extra stiffeners at the back.
7) Rudder and keel are getting CNC cut in foam + fiber
8) All ocoume ply was CNC cut on a waterjet then dried (:

Love the idea of the wedge-shaped box! I'm busy tearing out my square shaped one. Well, just the sleeve, really. The boat is fighting back, of course....

Great looking build, Marko!

Nice looking work! Velocity Boat Works is using a wedge-located keel for their GRP version ...

Oh no, pipedream's buildblog is down. Google won't even let me download the cached version for some reason! I am assuming the wbsite got hacked.

I hope it's been archived. Would really love to get the rudder tutorial resurected at least as it was beyond excellent!

Hi Mark,
I have a handful of posts beginning in August 2010 from my build blog. I think Kevin's (Pipedream) 2nd rudder build was patterned after mine.
I think you can start here: http://i550knotracing.blogspot.com/2010 ... stuff.html
...and then scroll through the newer posts to eventually see the rudder completed.

Not much happening in the forums so thought I might post a little update. Things are moving forward down below... Open transom slowly beginning to take shape! We'll soon see whether it was a good idea or not!

All the photos seem rotated in portrait orientation so appear oddly cropped above - sorry!

Chad wrote:Hi Mark,
I have a handful of posts beginning in August 2010 from my build blog. I think Kevin's (Pipedream) 2nd rudder build was patterned after mine.
I think you can start here: http://i550knotracing.blogspot.com/2010 ... stuff.html
...and then scroll through the newer posts to eventually see the rudder completed.

Just realised I should have replied to this! Indeed your posts have been translated and printed! Just the 'spine bit' that was added later to reduce the compression of the core was very neatly detailed in pipe dream's blog. But it looks like I will be attempting the lamination process of the rudder myself so should be able to work from memory! Because it is something that is a bit difficult to explain in words and instructions yet is very easy to see from the photos!

One thing I am not 100% sure you and other people who compiled neat build blogs realise - just how many times people like me have gone over your posts and photos!!!

One question - the aft frames were cut to design and the rudder mount is not very tall (or whatever it's called). Having gone over the photos of other builds on the forum I noticed everyone's gone for a biefier design.

Now I could easily mount a triangle to the back of it which will increase the thickness of the mount and wrap it all in cf to ensure that it does not break. However, it does limit the spacing of the pintles and thus the forces in the fixings. It will also make the cassette shorter and thus the forces within it will be greater.

So, my question is - can I keep the height of the mount as is or do I need to increase its height? Is there a consensus amongst the builders that the original design is inadequate?

edit: just realised Chad's is somewhat on the small side as well.

mmarko, if you want, take a look at my build log on http://nbayracing.com/i550Build.htm

scroll way down to

5.31.11 "Long Month"
10.16.11 "Snake it"
10.30.11 "Boatbuilding's a Beach"

and you'll see how I altered the rudder tower. I based mine on the Viper 640 (link is provided, hope it still works) and am glad I did (I also use the hollow tower as a hook-up/battery connection spot for my electric motor, too)

Mine might be overkill, but based on the number of reported rudder failures early on, I think it's a good idea to separate the pintles a bit more than what is originally spec'ed.

Marko, I am concerned about the strength of your unsupported side deck. I think the transom frame would fail at the connection between the side and the deck and the deck would collapse. A simple solution that would preserve the open look that you want would be to put two struts down to the connection between the cockpit sole and the side shell. My Soling had something very similar for its side decks. You could use wood struts, or like my Soling, 25 to 40mm diameter stainless tube. On the Soling the stainless steel tube was simply glassed to the hull and deck where it contacted them. You could even use aluminum tube from a broken Laser top section.

Warren Nethercote wrote:Marko, I am concerned about the strength of your unsupported side deck.

Don't worry Warren - it is not going to be nearly as open as it is now. The plan is to just notch the bottom aft corner of the side panel: something like this


Additional struts have been inserted underneath between the cockpit floor and the hull where the nothing begins.

Of course, once it is all glassed up, and we still have too much flex, we can always add an extra couple of struts in the corners as suggested

admin wrote:mmarko, if you want, take a look at my build log on http://nbayracing.com/i550Build.htm

ruddtower.png

Thanks Admin - I think will definitely go for something like that - perhaps a tad smaller.

Marko, you are correct, with the side panel running nearly full length like you show, the deck should be well supported. It sounds like you are adding some internal structure (hanging knees?) in there as well which will offset the loss of torsional stiffness with the open after end. Torsional stiffness of the open-ended after side-deck structure is important because repeated sideways distortion of the deck structure could lead to cracking of the side shell in way of the cockpit sole/hull side intersection.

Warren, I think you are right! Will probably look to add some form of stiffening 200-300mm in.

I think you all know where this is going:


Note the little stiffener inserted in the middle. By cutting it short we stopped the core from disintegrating... The lamination process per Chad's blog & the link provided therein.



Now we wait...

Also finally realised why nobody has photos of the actual lamination process: it is impossible to take photos whilst you are elbows deep in epoxy! Which is a shame. Perhaps we'll have better luck with the keel and less leaky gloves!

Also, my phone no longer recognises my fingerprints!

One question: when making the rudder cassette, what is stopping the rudder from floating up? Just the friction? If so, this means that there can't be much spacing between the rudder and the cassette?

I was using friction from fuzzy weather stripping (for a sliding door), but the rudder still floated a bit, especially after some of the weather stripping came off. I just modified my rudder cassette by adding some small tabs on the back edge where I'll have a bolt and wing-nut to provide clamping pressure on the rudder. I'm going to try it out in a couple of weeks.

Phil

Thanks Phil, that's very useful.

I am thinking about putting in a pin somewhere towards the top of the casette, but I am still worried about creating a weak point within the structure of the rudder. Definitely something to think about over the next few weeks.

The rudder turned out... okish. Few notes for all future builders:

1) If you can't make the core in one piece, make sure you glue the pieces together beforehand and fill and fair all the joints. The same goes for the blanks that go on the outside to compress the layup. Otherwise all seams will get scribed in the finished product.

2) Do make sure your absorber cloth is in one piece. My idea to lap two pieces of cloth was dumb dumb dumb. Of course, the overlap got scribed onto the rudder! Don't know what I was thinking - that the cloth will compress before the core?!


Anyway, a fair bit of filling and fairing is now in order, but structurally it seems to be ok.





I hope the keel will turn out better!

Progress (:

Chainplates are in @ 22.5 degrees.


Extra stiffeners as advised:


and the open transom will look a bit like this:

How to make a bulb in 4 easy steps:

Attempt to print the plug using a 3d printer.

Printer breaks down. Order Parts. Wait for them to arrive from China. Replace parts, print another section. Printer breaks down again... order more parts. Remain patient

Put the pieces together. Fill in gaps.


Make a mould out of gypsum.


Throw the mould away as it's no good. Make another one. Throw that one away again. Contemplate pouring lead yourself. Get someone else to do it. Et voila, finished bulb:


It is a simple symetric plug - dimensions as per build instructions. Chad did kindly send me the low cog model, but i wanted to do it in two pieces with the steel strut in the middle. Was very worried that the two halves would not end up being the same size because I can't be sure how much the plug will shrink after printing. The final bulb is around 80kg, and I will be going for a slightly shorter keel to reduce draft to around 1.1m as the rivers here are quite shallow. Basically, keeping to the tried and tested draft that works for the sailboats that sail around here but going for max weight bulb.

I can see monster and warren are soldiering on. Well done to you guys.

Thought I'd post a bit of an update:




The prod receiver tube is in (is there a better name for it?), as are the chainplates. The interior is all done up and ready for paint.



And the seats are smooth as silk. Looks like the additional stiffening (which is just not seen in the photo) did the job and the seat feels sufficiently stiff with the open transom.

But most importantly space is clear for the boat to be moved underneath the roof mounted crane so that it can now be easily flipped as needed!

Just a quick update - the bottom is now faired and ready for the paint



The cockpit is also faired and ready, only the cabin is yet left to be assembled.

hoping to find the water line

Getting there! Next summer sailing does look to be within reach now!

Your boat is looking great. Congrats and keep it up !

It is definitely started to look like a sailboat

thank you for the kind words jerome!

Nice work! Fun to see somebody else's results.