FDM 32 V-Hull Build - Need Build Advice

[Tamelesstgr]

Gents,

Starting a new log on what I hope to be a really fun and educational build. I feel really lucky to have purchased this Fine Design 32 hull. It really fits the overall size I was looking for, and somewhat different from the norm in today's modern FE boat designs. I've only seen 1 movie on YouTube and a handful of boat pictures on this hull, if you have any info about this boat I'd really like to know more about it. Power will be provided by ProBoat 1500KV and a ProBoat 60amp ESC on 4s for now. This set up includes Octura running hardware and a piano wire drive.

Initially I would like some advice on fabricating some replacement rails, servo platform, and motor mount. I've considered moving the motor closer to the transom and secure the batteries forward of the motor. Initially the Aluminum motor mount is too large for the bolt spacing on this brushless motor. What are my options for fabricating the rails and motor plate? I'd basically just like a cleaner look for the interior, and the support of the stuffing tube needs to be addressed.

This isn't going to be a speed rig (needs to be "competitive" with an SV27 running 12 cells nimh and BJ29 V3 running 4s) but it would be nice to plan for a future motor/esc upgrade. Budget is $200 and I still need Tx/Rx and misc parts to finish the boat.

As she sits today:

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[Tamelesstgr]

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[lt130th]

http://www.KintecRacing.com also has a rail for $23 that could make things a little easier. Gives you the option to upgrade to 40mm motor in the future & addresses your stuffing tube support.

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It comes in pieces, so if the servo tray prevents you from moving the motor closer to the transom, as you describe, you can always cut the rails & find another mounting solution for the servo.

[properchopper]

I got your PM. Seems like it130th has a really good suggestion - I'd go with it. As far as strengthening the ABS hull, an inlay might be a reasonable consideration. I've never inlaid an ABS hull, maybe Randy at BBY can help with tips.

[Tamelesstgr]

Came to the realization that I need to run an offset rudder if I want to run larger props on this set up. This one snowballed on my quickly lol.

[Tamelesstgr]

After much careful removal and sanding I have a clean sheet to start with. Materials coming today so I can start laying out the rails and motor mount. I'd like to be able to move the motor closer to the transom and run a single 4s pack in the middle of the hull to keep all the weight near the bottom of the boat. If not I will have to stick to 2 - 2s packs mounted on each side. Also decided to give the wire drive a try and get this thing on the water. If it doesn't prove to be what I want then I can start planning for more power and hardware changes over the off season.

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[Tamelesstgr]

Started mocking up placement of the motor and ESC, I plan on trimming the stuffing tube a little bit, but ultimately I can not place the motor as far back as I would like. The alignment is too low, so I need to keep the motor in roughly the same location and run 2 lipo packs along side. I will have enough room to slide them forward or aft to adjust COG though, so I am happy about that. I am thinking about building a shelf above the motor to affix the ESC to yet remove it if needed.

Also need to figure out how I want to run the cooling lines inside the hull and still have a clean look.

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[Tamelesstgr]

Ok guys, in getting my strut / rudder assembly set up I noticed a few things. With the stock drilled holes I was only able to fit about a 41mm prop before the blades would be hitting the aluminum strut. I can move the strut up on the hull and have ample room to run larger props. The next issue I need to solve is the strut angle. It tends to want to settle at a negative angle (and would be pushing the bow down) I can get the angle to neutral (which I would prefer) but then when I install the wire drive, I can feel a noticeable difference in the smoothness when rotating the wire drive assembly. Obviously I want a smooth operating shaft, so do I give up the strut adjustability and run it at the negative angle? Could I compensate with battery location based on the hull behavior once I get it on the water?

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[Tamelesstgr]

Slowly getting things worked out. Made decisions on my water pickups, re-drilled the strut bracket, drilled locations for mock exhaust tips. Love the OSE dual discharge, pricey, but very nice!

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[Tamelesstgr]

Also made some changes where the servo arms pass through the transom. I didn't like how they were very small and binding when actuating the servo lock to lock. I took some Aluminim tubing and cut an end of a battery terminal cover to make a flexible pushrod seal. Works pretty smooth with some marine grease on the pushrod. A lot more room for the pushrod to actuate as well.

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[Tamelesstgr]

Motor placement, I trimmed about an inch off the wire drive because it had a flat spot on it. Trimmed the stuffing tube as well, it will be supported by a fiberglass crossbrace once I fabricate my rails.

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[Tamelesstgr]

Little progress on the motor rails this week, need to make a servo tray and esc tray and I think I can get to epoxy

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[lt130th]

Hey, looks like good progress. One thing you may want to consider is rotating the water jacket so the rear outlet is on the very top. This is to allow air bubbles to escape, rather than building up inside the jacket and creating an air cavity where no water can circulate around the top of the can & transfer the heat away.

[Tamelesstgr]

Hmm, that's interesting, so potentially the water enters the bottom of the jacket currently and could potentially just be rushing past the bottom of the motor and exiting? I see how placing the rear exit would force the water to fill the jacket.

[lt130th]

The cavity within the water jacket is under pressure. Draw a 2D cavity of any arbitrary shape on a piece of paper, and draw a vector in the plane of the paper to represent gravity. Within that chamber you have two fluids - one much less dense than the other. The less-dense fluid in the chamber will always seek to rest in the opposite direction of the gravity vector you drew. Now add a single inlet and a single outlet and consider the walls of the 2D cavity the boundary of your control volume...no matter what the mass flow-rate of fluid is into and out of that chamber through those two ports, the less-dense fluid will remain at the top unless you put the outlet near the top for it to escape. And if you continue adding the less-dense fluid with the mass flowing into the chamber, it will displace the "heavier" mass/fluid to the level where you placed the outlet. So if you want your motor can completely surrounded by water (which you do to transfer the heat energy out of the system) you have to place the water outlet at the highest point. Otherwise, any air in the lines between the water jacket and rudder will all go into your water jacket when the boat begins to accelerate. And any air that enters your rudder pickup during your run will collect within your water jacket until it reaches the level/height of the outlet...if you're viewing the water jacket from a 2D side-profile. Now if your water jacket outlet is on the port side of the motor, and you do a lot of right-hand turning, that might help let the air out, haha.

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