Electric Re-Power Progress Update 3
07 11 2011 Posted by Daniel
Its time for another installment of the ongoing electric motor installation saga! Here we go…
We left off with the fuel tank removed and the battery mounts glued to the hull. After laying a few layers of heavy cloth over them to more firmly tab them to the hull, it was time to fashion the actual battery “tray”: a heavy plywood base containing stiffeners and spacers to ensure the batteries would be held solidly in place yet still have positive air circulation for cooling and venting. I’m using AGM batteries, so off-gassing of hydrogen is minimal to non-existent in routine circumstances, but it always pays to be careful and ensure the batteries stay as cool and well vented as possible. So let’s take a look at the tray construction.
I started by careful measurements and shaping a piece of plywood to roughly the right dimensions. I noticed that despite my efforts, I had apparently laid a couple blocks a few inches off of the targeted spacing, so that had to be accounted for. The tray has cutouts for webbing straps to hold the batteries down. The cutouts double as drains to prevent any errant water from pooling up underneath the batteries.
After a few thick coats of epoxy, the tray looks great and is well sealed. From this point forward, any holes drilled in the tray or the mounting blocks were sealed with epoxy before bolting. Note the addition of battery spacers, stiffeners, and glass-reinforced endcaps in the finished tray, shown here during a test fit of the batteries:
And batteries finally installed and strapped in place:
Great! The batteries are solidly in place, now its time to replace the cut cabin sole stringers. I obtained some very nice white oak boards and the shop was able to plane them to the precise dimensions, saving me a lot of trouble. Some quick work with my excellent Bosch palm router (many thanks to Bob @ Boat Bits for this and several other extremely worthwhile tool recommendations) put a nice bullnose edge on them, and I trimmed them just a wee bit oversize to allow for the slight compression that the original stringers were under. I had noticed while cutting them initially that the compression force was just enough to make the gap approximately two millimeters shorter than it had originally been, and by making the ends ever so slightly wedge-shaped I was able to effectively jam them that distance back apart. In order to ensure the joint’s integrity under tension forces I went one step further and “keyed” the ends of the oak pieces. By drilling a heavy stainless lag screw into the original stringers, I was able to drive the oak onto and over the bolt heads. The wood joints were glued with epoxy, and I filled the “keyholes” with thickened epoxy. The new stringers are now both adhesively joined as well as mechanically pinned into place with the bolts. Given that the stringers do not appear to be attached to the cabin sole particularly well, I think even this may have been overkill for something that is not integral to the hull structure, but better safe than sorry. Another engineer on the dock took a look at it and generally agrees that it is “adequately supported”!
In any rate, since I was all sticky with the epoxy I wasn’t really able to get any pictures of the process here, but the end result was pretty nice:
At this point, the new batteries are properly installed and cabled, the stringers are replaced, and with the exception of a little bit of additional maintenance I want to do to the boat’s plumbing and electrical, I am ready to reinstall the cabin sole. Next up: Just before the motor installation, we’ll be getting to some of the electrical bits while we have easy access. Stay tuned!
_________ /) __________
Categories : Ship EquipmentWe left off with the fuel tank removed and the battery mounts glued to the hull. After laying a few layers of heavy cloth over them to more firmly tab them to the hull, it was time to fashion the actual battery “tray”: a heavy plywood base containing stiffeners and spacers to ensure the batteries would be held solidly in place yet still have positive air circulation for cooling and venting. I’m using AGM batteries, so off-gassing of hydrogen is minimal to non-existent in routine circumstances, but it always pays to be careful and ensure the batteries stay as cool and well vented as possible. So let’s take a look at the tray construction.
I started by careful measurements and shaping a piece of plywood to roughly the right dimensions. I noticed that despite my efforts, I had apparently laid a couple blocks a few inches off of the targeted spacing, so that had to be accounted for. The tray has cutouts for webbing straps to hold the batteries down. The cutouts double as drains to prevent any errant water from pooling up underneath the batteries.
After a few thick coats of epoxy, the tray looks great and is well sealed. From this point forward, any holes drilled in the tray or the mounting blocks were sealed with epoxy before bolting. Note the addition of battery spacers, stiffeners, and glass-reinforced endcaps in the finished tray, shown here during a test fit of the batteries:
And batteries finally installed and strapped in place:
Great! The batteries are solidly in place, now its time to replace the cut cabin sole stringers. I obtained some very nice white oak boards and the shop was able to plane them to the precise dimensions, saving me a lot of trouble. Some quick work with my excellent Bosch palm router (many thanks to Bob @ Boat Bits for this and several other extremely worthwhile tool recommendations) put a nice bullnose edge on them, and I trimmed them just a wee bit oversize to allow for the slight compression that the original stringers were under. I had noticed while cutting them initially that the compression force was just enough to make the gap approximately two millimeters shorter than it had originally been, and by making the ends ever so slightly wedge-shaped I was able to effectively jam them that distance back apart. In order to ensure the joint’s integrity under tension forces I went one step further and “keyed” the ends of the oak pieces. By drilling a heavy stainless lag screw into the original stringers, I was able to drive the oak onto and over the bolt heads. The wood joints were glued with epoxy, and I filled the “keyholes” with thickened epoxy. The new stringers are now both adhesively joined as well as mechanically pinned into place with the bolts. Given that the stringers do not appear to be attached to the cabin sole particularly well, I think even this may have been overkill for something that is not integral to the hull structure, but better safe than sorry. Another engineer on the dock took a look at it and generally agrees that it is “adequately supported”!
In any rate, since I was all sticky with the epoxy I wasn’t really able to get any pictures of the process here, but the end result was pretty nice:
At this point, the new batteries are properly installed and cabled, the stringers are replaced, and with the exception of a little bit of additional maintenance I want to do to the boat’s plumbing and electrical, I am ready to reinstall the cabin sole. Next up: Just before the motor installation, we’ll be getting to some of the electrical bits while we have easy access. Stay tuned!
_________ /) __________
