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The weight of the hull is just under 28 kg. The added weight comes from the mast sleeve which is probable too large, but at the same time it can take quite of bit of abuse. It is made of plywood 10x10x8 inches, layers of plywood separated by foam layers. Added wooden elements, dagger board box...

Hi there, thank you for the message. I sailed the boat this summer quite a bit. Never used the floats. I have made a few changes, like redone the rudder brackets and built a kick up rudder. The tarp sail I made worked exceptionally well. There were a few challenges while jibing, but after a few...

A while later, the boat is finished: Rigging is from windsurf board. I have carbon fiber two piece mast and two sails. The boat will go into the water this weekend. Will paddle first to see how stable it is ( have a short version of centerboard - 6" depth). Once the stability is deemed...

What you say is very true. Obviously one needs to add a structural reinforcement to the foam elements. I am in the late phase of building a 12 ft flat bottomed foam sailboat (34" beam). Between the bottom tow layers of foam I have placed two 8 foot long 3/8" plastic coated rebar coupled with 7"...

My objective was to build a very light craft, which I have largely achieved by using foam as building material. From the weight perspective it would be nice to keep both the rudder and daggerboard at the low end, weight wise. What would be the minimal thickness of these elements? I was thinking...

I finally got to the rocker build. There will a lot of rasping. Since the rocker came up as topic after I had started rounding the chines the additional layer of foam will have a slightly smaller footprint than the original surface of the hull bottom. Do I need a halyard if I can reach...

Thank you Paul. Can I use resin over canvas? I would prefer not to work with fiberglass cloth. As for the attachment bands - I was thinking of inlaying the straps in the hull surface, glue, fasten them in with screws (4" spacing") and then apply the next layer. Only the loop or possibly o ring...

Thank you again. I understand the concept of displacement. As the buoyancy is the upward force exerted on the submerged (partially of fully) object. From the material properties, the foam in this case, a cubic foot of foam will hold 55 lbs of weight before it is fully submerged in fresh water...

Thank you for the explanation. I was not quite sure whether I was on the right track so I used the buoyancy spec for the foam which was lower and in my mind safer (not untrue).

62.4 - 64 lbs of water per cubic foot of air. The buoyancy specification for rigid insulation foam I have used for hull states 52 - 55 lbs per cubic foot. Considering that immersed portion of my hull is made out of solid foam I have used the foam spec as the calculation parameter.

The dagger board trunk is an interesting problem considering that the hull is made of foam. Here is the design: a plywood box of required dimensions (sides and spacers in between). Attach 1x1" reinforcement 'square ring' around the bottom, flush with the opening of the case. In order to fit...

I was concerned about the amount of foam I need to scrape therefore I focused on the 'empty' volume calculation. By reversing the numbers in depth column (4 - current value) I arrive to an immersed hull volume - 6.61 cubic feet. 4 inch draft -> 6.61 cubic feet * 52 lbs = 343 lbs. 3 inch draft ->...

I have taken your advice and did a calculation. I planned 2 inches rocker depts on bow, 4 inches rocker depth on the stern. I looks like that mid section is almost flat. Attached is the spreadsheet screenshot of the calculation. I will do another calculation based on your latest suggestion. I...

Regarding the rocker design calculations - you have provided a great guide. By taking away material from the bottom to create the curvature there would be some impact on the draft. In order to maintain the above the water heigth a new layer needs to be added at the bottom before the rocker can...

The sail center of effort will be at 69 inches from the bow. Pretty much at the middle of the boat. Wouldn't that be too far if the rudder assumes the function of the keel?

So how much of rocker do you have in mind? If 2" is enough, another layer of foam on the bottom will give enough material to scrape out a nicely curved bottom. I have already applied some bottom curvature - about a foot length at transom as well as about a foot at the bow. The mast is an...

The boat is currently in sanding / shaping phase: 1. Need to set the mast sleeve - 3" ABS pipe (the mast is 10' spruce linearly tapered from 3" @ 8" to 2" @ 10' 2. Once the mast sleeve is in the mast bow pieces can be secured, including the top 3. Straps installed on (around) the hull: at least...

No floats or float hardware included in the calculation below: The flat bottom surface is 26 sqft Total hull volume is 22 cubic feet (including the cockpit) Total bouyancy based on the foam properties 22x52= 1150 lbs of bouyancy Main hull should weigh roughly 30 lbs, with the rest of the rig...

Hi, Thank you for the thorough explanation. I was hoping to avoid making floats and akas, but it seems like that a multi hull would be the best course of action given the issues with the boat's shape and size. I am going for 8' foam floats, with a 3' plywood fin in the middle. Since my hull is...

Thank you. Regarding the daggerboard area: I used 4% formula of sail area as the guideline. That calculation points to 253 sq inches or lateral resistance. Over 10' length that would amount to just over 2.5" keel, Considering that full keel would interfere with steering, what would you say...