Aluminum de25

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TomW1
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Re: Aluminum de25

Post by TomW1 »

OneWayTraffic just for the heck of it I went back and checked the 3 boats I mentioned all are welded. These guys all have to take the weather of the Great Lakes and the wave length can be short and high if they are fishing in a Tournament, more like a 4' chop. Those are not cheap boats the Tracker was $60k and the Crestliner over $65k. They make up for the thinner hull with a stronger frame work.

Cracked Ribs this comes into your comment on these being light duty boats. Both the hull weight of the Silver Streak' 21 and Crestliner 2050(22') are within a 100lbs of each other, 2150 - 2175. These are both listed as there hull weights, much like Jacques lists his hull weights, it is a pretty standardized number with nothing in the finished hull.

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cracked_ribs
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Re: Aluminum de25

Post by cracked_ribs »

I can't comment on the weights listed because I don't know what they include and in my experience numbers like that from manufacturers aren't necessarily comparing the same information, but I'm familiar with trackers and crestliners.

They're not in the same league as plate boats. They're barely even playing the same sport. It's not that you can't, in theory, have super closely spaced stringers and get away with thinner skins...but those boats are what we call "tinners" and aren't comparable to any real welded aluminum boat. You will never see one doing ocean work here, ever. They won't withstand it.

At any rate I don't think anyone is going to build a crestliner, and it makes a lot more sense to pattern a one-off build after small manufacturers than Walmart boats.
I designed my own boat. This is the build thread:

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Rziel
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Re: Aluminum de25

Post by Rziel »

Going back to the idea of fiberglass. Does anyone use polyester resin for these boat builds. I have found Polly to be easier to work with except the smell and so much cheaper. I have a full faced forced air supply which works great once you get used to the air hose. I know epoxy can be stronger in certain cases but I have found Polly can be adjusted for working time and seams to smooth out the glass much easier

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Re: Aluminum de25

Post by jacquesmm »

Rziel wrote: Fri Jun 11, 2021 2:19 pm Does anyone use polyester resin for these boat builds.
NO, don't use polyester, the boat will fall apart. I design those boats for a specific type of resin and fiberglass (directional).
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OneWayTraffic
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Re: Aluminum de25

Post by OneWayTraffic »

Remember these boats are a thin but strong skin of glass over a full core of wood. The bond of the glass to the core is critical, as is the elasticity and peel strength of the resin that binds it. Possibly the most important thing is the water resistance of the resin. Polyester does not have any of this. Water will get in, just a small amount and the wood will swell. Then the glass will work away from the wood. Wood in production boats is often used as a pure former, covered by a much thicker coat of glass. Still rot gets in. I have a perfectly good glass boat that I will rubbish because I can't take the time to replace the transom on it.

Epoxy is much easier for a homebuild. And works out cheaper in my view. Just build it as designed, and it will work.

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Re: Aluminum de25

Post by jacquesmm »

Thank you OneWayTraffic, good brief explanation.
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Evan_Gatehouse
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Re: Aluminum de25

Post by Evan_Gatehouse »

I've designed a number of boats on this site and commercially I design in aluminum all the time. (I am a N.A./mech. engineer)

5052 is not as strong when welded as 5083 so if prices are not much different then 5083 is a much better choice.

You can't just say 3/16", 4 or 5mm or 1/4" plating without considering the stiffener size and spacing. Thicker plate = less stiffeners, wider spacing.
For little boats like this I'd always use T extrusions. They bend easier than angle (no tripping), have way more section modulus (stiffness) than simple flat bar and are very weight efficient.

Rule of thumb like in Gerr's book are a good starting point, but you really want to design the structure in a proper way.

I have torn polyester/glass off wood structures by hand lots of time. It just doesn't stick well to wood; it sticks to itself in a fully molded hull just fine. Polyester resin is not a good idea with a wood cored hull.
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Evan_Gatehouse
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Re: Aluminum de25

Post by Evan_Gatehouse »

Fuzz wrote: Mon Jun 07, 2021 12:53 am Over the years I have fished several wood boats, glass boats and aluminium ones. Each material has its strong and week points. One that does not get talked about with aluminium is cracking in the weld zones. Fished a high end boat built in Seattle that we spent half the season sowing it back together after each opening. Had two friends whose set net skiff had the transom come out of it and killed both of them. Like all materials it can be good but it not perfect.
Weld cracking is either bad design or bad workmanship and I would suspect the latter. Welding aluminum properly is HARD. It demands really careful attention to cleanliness and has to be done inside (or your shielding gas blows away from the weld and the weld gets contaminated)

Nothing inherent in aluminum done properly should show weld cracks.
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Re: Aluminum de25

Post by fallguy1000 »

Evan_Gatehouse wrote: Fri Jun 11, 2021 6:22 pm I've designed a number of boats on this site and commercially I design in aluminum all the time. (I am a N.A./mech. engineer)

5052 is not as strong when welded as 5083 so if prices are not much different then 5083 is a much better choice.

You can't just say 3/16", 4 or 5mm or 1/4" plating without considering the stiffener size and spacing. Thicker plate = less stiffeners, wider spacing.
For little boats like this I'd always use T extrusions. They bend easier than angle (no tripping), have way more section modulus (stiffness) than simple flat bar and are very weight efficient.

Rule of thumb like in Gerr's book are a good starting point, but you really want to design the structure in a proper way.

I have torn polyester/glass off wood structures by hand lots of time. It just doesn't stick well to wood; it sticks to itself in a fully molded hull just fine. Polyester resin is not a good idea with a wood cored hull.
Agreed. Just grabbing a spec from thin air is a bad plan. Reading Gerr and resulting in a too heavy boat also a bad plan. Listening to a guy say 1/4" seems heavy (me) without considering framing is more bs. I said it more as food for thought. 6mm seems heavy is all

A boat in aluminum needs to be drawn by a naval engineer/architect, and welded by a competant boat welder. We saw a boat getting welded on another forum and not even a mousehole. Getting a designer to spec every panel is perhaps another challenge. Many designers draw at a high level and you won't get each item specified....like a countertop..
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