45' solar catamaran

Both flat part of the roof are now done. One at the top of the garage and the other one still cure.
I learned a lot and I'm happy of the result.

Next step is to build the two symmetrical half front part with windows (green on 3D).

 

Preliminary support design is done for the array (16x 650W = 1200 lbs of panels).
Build from 1-1/2'' and 2'' square aluminum tubes.
It will not win any beauty contest, but it should do a great job and still be below 350 lbs.
I will be able to climb on the Cat roof to clean the panels.
On top view, one panel is pink to show orientation.

 

As you can see post above, over the 11 supports between array and boat, some will be fix with screws on our new 30PSI foam roof.
So, I plan to add 4 sleeves/support inside the foam core to allow weight (140-150 lbs) of each support to be transmit across the foam.
I thought about aluminum sleeves epoxy glued on the foam and fiberglass, but is it better to find fiberglass sleeve or some other material?
Is there some downside to do this? Is there some pitfall to avoid to do this? Is there better way to do this?
Thanks

 

Typically the way to reinforce foam core construction is to rout out an annulus in the foam using a bent nail or something similar. I've gone to using allen wrenches with the short leg cut shorter and the tip ground to a chisel shaped edge. Then the void is backfilled with thickened epoxy and then the final bolt hole drilled through the epoxy. Gougeon Brothers On Boat Construction, still available free online I think, covers the process quite well. A major caveat for your application is the exotherm from the epoxy has a tendency to melt the polystyrene foam. You will need to use some extremely slow setting epoxy and test carefully.

 

Excellent! I downloaded it.
I've even forget the possibility to simply add thickened epoxy.
This book also remind me that aluminum sleeve can suffer from some corrosion. So I think I'm better to find some plastic tube or rod to glue in place.
The load is not that much and aluminum sleeve is overkill.

I like the method seen in Duracell project video: Cut hole with hole saw - remove first fiberglass layer and some foam - remove the foam with a ''end mill' the same diameter than the hole saw.

 

I need to build a new I-Beam (red arrow) to support the new front panels of our Cat.
What wood would I use?

I plan to build those I-Beam from 3/4'' plywood bonded with epoxy.
From my search, spruce plywood is not great and cherry can be a good option.
Other good choices easily available or advices to build a good I-Beam?

 

Plywood is a poor choice for the flanges of an I beam, only half the grain is resisting bending forces. Stuff cut from an LVL beam is far better.
It's probably better to just use the LVL as a rectangular beam, there's a lot of fabrication to make I beam for little gain in less weight (if any).
LVL (laminated veneer lumber) is basically linear plywood. The trick is to find the better quality stuff, depends partially where you are.

 

Nonsense.

On the "poor, fair, good, excellent" scale it would rate "good".
That's a long way from poor.

 

Let us agree to disagree ;-)
From a strictly theoretical structural standpoint one flange of an I beam is in compression, the other in tension. Assuming 5 equal plies and oriented correctly, a plywood flange is resisting those forces with 60% of its cross section, the other 40% is dead weight.
From a practical standpoint I'd lean towards doing something like this with a box beam. Flanges of good lumber, hard to find or buy, or pieces cut from an LVL available in almost unlimited lengths. Webs would be`plywood grain vertical ( 45% is theoretically better but the difference is nominal ;-)).
I was going to say making I beams is harder to make but probably not if you fasten a piece on each side of a plywood web but the box beam is still far better at handling torsional forces.

 

I don’t know how anyone can argue about whether plywood is or is not suitable without knowing spans and loads. No typical off the shelf i beam uses ply for flanges, on the other hand. For me, this is nothing more than argument seeking.

I mentioned somewhere here before that the rooftop needs to be crowned as well. That will make building an i beam from wood; especially timber rather difficult, but I am a bit confused about if your roof it flat now.

Rather than an i beam; you ought to considering building your own lvl, or similar. I would not recommend using plywood. But base your build on the load demand and span.

For most loads; you would probably be able to build a glued up beam that is very strong with, for example, 4 pieces of 3/4” pine; the width would determine the capability. If you want to minimize the likelihood to twist; that can be done by bonding it to supports under.

You can build i beams using marine foam and glass as well.

You can also purchase timberstrand lvls and/or find their deflection data online.

Part of the reason for crown in a roof is deflection is certain and crown gets you above negative in plane deflection, if you will.

To test your beam or lvl; you can screw the wood together well and stand on it. The deflection will be calculable and if you don’t want to pen the issue; you can start by standing on two pieces of say 2x6 or 1x6 and measure their deflection and add more pieces and calculate the amount, or 1x8’s, etc. Once you determine a suitable beam, precoat all ides and use 1/16” vee trowel or 1mm vee trowel and 30 minutes after precoating, apply thickened epoxy to all sides and bond the components; you can rescrew them or clamp them. I recommend some pins as things get greasy and move once you apply resin. The ideal bondline is 1mm finished, so avoid overclamping. Always precoat; it is amazing to see what happens to bonding with cabosil filled resin when the wood steals the resin from the filler.

The only reason for an i styled beam is if you are worried about (in this case) twist. But a conventional lvl does not twist much because the wood is denatured a bit when made of thin plies.

Anyhow, this is a late nite post, so perhaps a bit rambling, but would be my approach, although I would calculate the beam’s specs..

ps~use about 2:1 cabosil to epoxy by volume for the putty; add enough filler so the mixture does not collapse which means the vee trowel work will stand while coating all the sides

 

Thanks for your inputs guys.
I was tempted to learn by building a I-Beam myself, but I admit that simply use a LVL beam cut to my needs is quite an easy solution.
I have to twist my mind about all this, because, of course, my first idea was to use an aluminum tube

Yes. Each half of the roof is a flat part of 80'' wide. Those will be installed at 2° to allow water to flow.

 

Here is the battery I plan to build.
51 kWh and two in parallel will give us 102 kWh.
The 12 battery modules are coming from a Caddy Lyriq 2024 who sadly had hit something strong.

Battery measure 60''x15'', roughly 640lbs (each module is 84 lbs).
I will have to assemble it inside the boat
Everything is aluminum. The battery box, the supports, the busbars.

 

Hi Yabert,

I have NOT read thru your long subject thread yet, but it looks like it might be interesting,...but why chose a catamaran hull form ?? (and this is coming from a long time multihull advocate)
Let me throw a curved ball to you.
In the first place why chose a catamaran hull form to place your TWO electric motors into to cruise at 6-7 knots??

What if you were only powering up a great little liveaboard canal cruising boat with a single electric drive system (in place of the single diesel engine),...and you were sourcing a lot of you power with a big array of solar panels up on the top deck of this smart little trawler. You might end up with a delightful little cruising boat that would have market appeal?

Redesigning the Pilgrim 40 Trawler / Canal Boat / Coastal Cruiser https://www.boatdesign.net/threads/redesigning-the-pilgrim-40-trawler-canal-boat-coastal-cruiser.57140/

 

I saw some of this silly talk about pushing power of electric motors verse ICE engines early in this subject thread.
I am amazed at the number of folks that don't understand the great efficience of pushing an automobile with an electric motor vereses a gas one. The torque differences ar so in favor of the electric drive !!

I once imported a 37; French cat to the USA, and I powered with a 9.9 HP engine that had gear reduction in the drive train. It turned a larger diameter prop, and I could get 7 knots out of the boat after cupping the props.
Louisiane 37' first one into the US
RunningTideYachts.com

 

Propeller design is its own art form, but in general the larger prop you can turn is an advantage. But if you turn that larger prop too fast you loose efficiency at the tips. There are some advantages to dual props.

And if you are not in direct line, I prefer 'silent-chains' to belt drives.