Werzko 4.5 - 15' ply stitch-n-glue sail dinghy

Adding floatability?

Hi all,
I spent time googling and oggling the designs NED mentioned, and saw something in the NS14 that was an answer to a thought I had earlier, namely teh addition of two flotation tanks under the side sitting decks (or watchamacallit in seaspeak).
The image below shows what I mean.
Do you think it would be overkill to add these to the Werzko 4.5 dinghy? I plan to waterproof the inside of all flotation tanks before closing them (installing leak-proof inspection hatches, of course).

But I guess I better tie them somewhere, right? Otherwise they will not be much help when the boat capsizes (and capsize she will)

 

That's not a bad arrangement, particularly if you have scuppers in the transom. I used to sail a Finn that was set up like that, and I could stick the masthead in the water, swing my feet onto the centreboard, haul the thing up again and sail off with a dry boat before it even stopped.

Only catch is that if the boat goes completely upside down it can be hard to get right side up again, due to the great inverted stability that such side tanks give. A sealed mast will stop that though (wont go further than on its ear).

 

I've sailed racing dinghies that regularly get water inside them, sometimes capsize completely, and never have milk bottles or anything else inside the bouyancy tanks. It works. Seriously.

And................

...if you put drain holes and plastic bottles in them they will take up quite a bit of water when you capsize the boat, or even if you just take a wave over the top.

 

floatchambers waterproofing and higher final weight

I have "borrowed" the picture below from this interesting thread:
http://www.boatdesign.net/forums/wo...n/mirror-16-foot-sailing-dinghy-12064-12.html
My question is twofold:
1) The flotation chamber seems to be partitioned, which seems logical - and smart - to me (titanic anyone?). Would you guys recommend this small upgrade in my project?
2) The poster restoring that Mirror 16 hailed the good shape of the chamber as a result of "good waterproofing": which materials/ techniques would you recommend for the job?
3) (guess I lied about the "twofold") The more I add up to the original project (like the two lateral float tanks, this partition, etc.), the heavier the Werzko 4.5 becomes. Am I supposed to expect any problems in the boat handling, responsiveness as a consequence of a higher-than-projected final weight? Which ones, please?

 

The partition is actually a web frame to stiffen the front end of the boat under loads from the forestay/jib. It has nothing to do with the Titanic. If Werzko's design is strong enough without it then I wouldn't add one in.

Epoxy is presumably what you'll be using to stick everything together. It works.

My 2c is that you want a distribution of bouyancy tanks that allows the boat to float level, with some stability, floating high enough to be able to bail it out, but not so high that you can't get back onboard when you're soaking wet. There are several ways you could get this result. I haven't taken a close look at Werzko's plans, so I'm not currently sure what he has allowed for in the way of built-in bouyancy. Might be worth dropping the guy an email and seeing what he thinks. I wouldn't go too bonkers with adding stuff, simply because it'll cost you more money and make the boat harder to handle on the beach.

 

Guessing how much epoxy for the project

The Werzko 4.5 has a flat bottom and two chines. Taking this in consideration, would anyone be able to give me an estimate of how much resin I will need (in Kg)?
I have also learned that resin=base+hardener. Please tell me what is the base/hardener ratio (consider that Israel has a rather hot climate - daily temperatures here are around 25-25C this time of the year. It goes higher when it is full summer).
Thanks!

 

Well, a novice gotta do what a novice gotta do - which is to research and not expect everything to fall on one's lap.
After trying to find some sort of "Tutorial on Epoxy" (apparently non-existenton BDnet), I have found elsewhere (google is your friend...) this interesting, very didatic link on how to work with epoxy:
http://www.torreypinesgulls.org/epoxy.htm
I guess Vuykin will like to add it to his all-inclusive links thread!
There might be others, just as there is a lot of information on (for instance) "epoxy resin, working with epoxy" here on BDnet - the problem is to find it, and make sense of it. So here is a suggestion: how about a Tutorial on the subject? Of course the knowledge needed by a stitcher-and-gluer like me are very different from those of people like this guy http://www.boatdesign.net/forums/fi...ilding/resin-infusion-light-weight-38070.html
or this guy http://www.boatdesign.net/forums/boat-building/health-effects-epoxy-37659.html
or this guy http://www.boatdesign.net/forums/fi...ing/stringer-replacement-materials-37987.html
The knowledge is already there - perhaps I was unable to find it, or it needs to be organized as subtopics of one big item: epoxy (and other resins).

 

Well there are several the most helpful i found was Western system guides, PDF downloadable and great for beginners, here is the link:
http://www.westsystem.com/ss/use-guides/

Also system 3 have a good guide:
http://www.systemthree.com/reslibrary/m_published-literature.asp

I remember i posted these some where in the thread ? Will need to double check.
Hope these help

P.S one more epoxy FAQ guide
http://www.uscomposites.com/faq_epoxy.html#11

 

Yah they are there phew ... You got me worried there for sec !

 

See? See?
Your post is already so long (I mean "rich") that we might soon need to "organize" it a bit! Or show the newbies how to "search within a thread".
Really Vulkyn, the generosity and patience of the people here is noteworthy.
Thank you!
Aharon

 

My pleasure Aharon and yah i should get it in wiki format for easier viewing / searching (will do some time soon)

One more guide from Raka http://www.raka.com/manual.html

 

Just been to the plywood distributor. The 12mm marine-grade 4' x 8' ply is US91 each, while the 6mm external-grade ply is US40 each. I find the US524 bearable, not like "an arm and a leg".
Now to find the epoxy resin. An uruguayan friend who built the same boat told me he used 3Kg resin total (base+hardener).
Seems I will not have to mortage my house to fulfill my dream after all!
Vulkyn, thanks for the nice PM. If I need I will SCREAM!

 

The qty of resin will differ depending on my factors, from your experience with handling it too type, how many layers you put on and glass type.
Check this post with some details on Epoxy calculation qty:
http://www.boatdesign.net/forums/bo...er-wood-fishing-boat-33193-19.html#post397011

Also be sure to check marine plywood grade, they differ a LOT here is a helpful explanation
http://www.boatdesign.net/forums/materials/marine-plywood-jargon-34729.html#post400541

 

home-made wooden mast

Thank you for the hint, Vuykin my dear neighbor! I enjoyed reading the thread. However, I will use resin only to glue the chine joints, not to cover the boat's whole wood panels, so the quantity needed will probably be much less than that project!

on masts: I have read the thread
http://www.boatdesign.net/forums/fi...e-made-small-fiberglass-mast-spars-37684.html , and would like any input from you guys:
In diy audio, you make it yourself not to save money, but to produce something which will be better than the "run of the mill" product, which is plagued by the compromises that mass production demands. So you use better capacitors, a beefed up trafo, etc.
After reading this thread, I saw that that is not the case in boat building.
My boat plans require a 6.3m aluminum mast ("aluminum alloy spar, section approx. 57 x 73 mm, required transverse momentof inertia 14cm4, lenght 6300mm"). Please do not ask why "57 x 73 mm" because it looks round to me in the drawing...
Would you good sirs give me an idea of the dimensions for a mechanically equivalent birdsmouth mast? Should it be tapered?
Thanks!

 

Is this the "sailfeed"?

Browsing Dwyers Masts website, I came across a question when simulating a purchase, to figure the cost of a mast: "sailfeed location - opcional".
The plans I got show a cross section similar to the picture attached, with two kind of "claws" on the drawing (seen from the top).
Is this a kind of tunnel where the sail edge goes?
Does it run the whole mast lenght?
Do I need it at all? (is it some kind of alternative to tying the sail to the mast, thus facilitating putting it up or down?)