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Scott Dunsworth

28 foot Crusier

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Got both shelves glued up and we are making the rest of strips. Hopefully we will be ready for epoxying the joints by weeks end. I'll post a picture of the shelves this evening.

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All the strips are on and will be starting the epoxy gap filling very soon. Plan to tack her together between the frames and fairing strips one day. On the second day remove all the screws and finish filling the gaps. Then its on to the sanding and fairing marathon.

Our goal is still to have the hull finished and turned sometime in July.

As soon as shes glassed we'll start laying up the keel and skeg for the rudder.

Graham I am hoping we can build the shaft tube in while laying up the keel and skeg.

Scott

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Tomorrow morning we will start filling the gaps. I tried a small area tonight with good results, the thickened epoxy went between the planks fairly easily. Some of the gaps are as small as 1/16" and those take a little more effort to get it through completely. The 1/8 to 3/16 gaps it filled with one swipe of the squeegee. Only trouble I had was I mixed to much and it started to kick off before I could use it all. So we are going to make smaller batchs and spread them out so it doesnt kick to quick.

Should have it completed by Sunday evening.

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Here's a few pictures of the epoxy gap filling. One shows the gaps filled between the frames and the fairing strips. Also after all the screws were removed and the whole hull filled. One picture shows the goal of having the epoxy squeezing through.

She sure is ugly now before sanding. The mixture is about half microballoons and silica by volume. So I am hoping it doesn't sand to hard.

Also I am sure missing my Belhaven.

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Looking good. One big point- sand quickly. epoxy /silica gets harder and harder the longer you wait. Get the rough sanding at least done soonest.

I speak from sad experience. Filled cracks, staple holes, etc on an outer hull of a 35 foot tri. Let it sit while I finished building the other outer hull- when I got around to sanding, might as well have been sanding concrete :o

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I like the scraper when epoxy is still somewhat green - faster and sandpaper clogs like a bugger with not fully cured epoxy. Not to mention green epoxy dust/particles are dangerous to your health record. Scrape scrape scrape and then let her cure for a few days and hit it with a sander.

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Nice progress Scott.

Tech question; does the filler serve a structural purpose that will be compromised by the micro balloons or is it primarily a filler/fairing and all (majority) of the strength come form the glass sheathing?

Thanks,

Jim

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I don't think either is truly the case. Like all composite stucture the strength comes from the interaction of all of the component layers. So even though microballons reduce the adhesive characteristics of the epoxy it still does serve to join the planks. But then not until the glass layers are added does the hull start to really achieve it's total integrity.

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The way I understand it from Graham before I started this build is, the wood gives the strength from bow to stern. The bi axle cloth gives it strength in the other directions. They all work together along with interior bulkheads and structures. While the epoxy between the strips is important it doesnt give the hull structural integrity like the rest of the components. Theres another way to look at it also there has been much bigger boats than this built with nothing but foam inbetween the layers. I'm sure the wood glued like in this build would be as strong as foam.

Of course there is the possability I dont have a clue about any of this.

Got her sanded down today, going to need some fairing but not as much as I had feared.

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Carbon / foam /carbon sandwich boats simply use the foam to separate the layers of carbon (epoxy saturated carbon cloth) and bond them together. So as such the foam adds virtually nothing individually to the structure, but the fact that it bonds the carbon layers to each other spaced is very important. So I guess you can say it contributes nothing, but it sure is important in the grand scheme, and it contributes with very little weight.

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This boat will also have small frames every foot or two. Not for structural reasons but to allow me to insulate the hull with 1/2 inch foam. They will be around 1/2 x 1 1/2 run vertical across the strips. The foam will be inserted then a very thin layer of marine ply for the interior finish. She is being build to have a dry bilge and I also want to keep condensation to a minimum. So these small frames will also add to the structural integrity of the hull also, but that is not their purpose. The foam will add to the flotation numbers also, but its primary purpose is insulation.

A lot of people tell me ventilation is the key to keeping a boat dry. Ventilation is part of the remedy, but only part of it, insulation is the biggest part for a dry comfortable craft.

Scott

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A lot of people tell me ventilation is the key to keeping a boat dry. Ventilation is part of the remedy, but only part of it, insulation is the biggest part for a dry comfortable craft.

I don't know who this lot of people are, but I agree with them. I am not saying don't insulate, but if you ignore good ventilation it (insulation) not only won't keep your boat dry but it will invite mildew by trapping moisture. I would also suggest the use of ceiling (horizontal strips of wood across the frames spaced apart) instead of plywood for the interior finish. This will further facilitate ventilation.

edit: Insulation will reduce and possibly eliminate condensation, which is very desirable, but it will not eliminate or even reduce moisture getting into the boat or being trapped in tight spaces.

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Like I said ventilation is a part of the remedy. My Belhaven would sweat inside on the cool Florida mornings with three of us sleeping inside. So we tried it with every port opened and the screened hatch with the same results. My carport roof sweats sometimes and you can't get any more ventilation that it has, but my insulated pole building don't. I guess what I'm trying to say is ventilation is important, but not the whole ball of wax. When I was at Grahams he put a temperature gun on the out side of one of the big cats hulls that was outside in the sun and it read 165 degrees. While the inside read 75 degrees. Its foam cored hull makes that much difference. As we all know when warmer water vapor comes in contact with a cooler surface it will turn to condensation. Here's where the insulation comes to play.

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As we all know when warmer water vapor comes in contact with a cooler surface it will turn to condensation. Here's where the insulation comes to play.

Correct, but the insulation does nothing to reduce the humidity in the air in the boat. The moisture is still there. It merely keeps it from condensing. And when you have people on board exhaling moisture in their breath it is in the boat, and the insulation does nothing to remove it, just keep it from condensing. While sleeping ventilation is even more important than when you are in the cockpit as you are adding moisture constantly and only ventilation will remove it, well, unless you have a dehumidifier or air conditioner. Maybe this discussion is a matter of semantics, as moisture and condensation are related as different states of the same water. The insulation does not remove any, just keeps it from changing state.

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"The insulation does not remove any, just keeps it from changing state."

:D Exactly, and this is the goal :D

Back to the fairing and sanding today, I'll post some pictures tonight. Before that first sanding she sure looked like a train wreck.

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Something I have often wondered is how much insulation value do you gain from the thicker wood or plywood on these larger boats? Enough to matter? I've seen the same thing with buildings. My folks have a steel frame machine shed and on some days, it rains inside the shed as suddenly warm moist air condenses on the cold steel beams. I have not seen that happen on sheds with wooden trusses.

Scott.......what insulation material will you be using?

BTW, I also agree with the need for ventilation. The average adult gives off something like 1 to 2 pints of liquid water as vapor a night......both through breathing, but also through the skin itself. It has to go somewhere. Some folks find the moisture as water under their bunk cushion in the morning and wonder where the leak came from. It came from them!

In addition to the ventilation and insulation, a little bit of dry heat will do wonders too, but that is a different can of worms.

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Howard I don't have a clue about the insulation value of the 11/16ths cypress, but I bet its available online some where.

I plan to use blue 1/2" board on the hull sides, but haven't talked to Graham about what to use on the foam cored decks and cabin.

My wife is still pushing me for marine air and heat, so far I have resisted. I keep telling her it's just a 28 foot boat not a 40. We just cant have everything on it.

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