On this week's episode of "Is this a shore dive?" - Burlington Horse Ferry

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macado

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On this week's episode of "Is this a shore dive?" our target was the wreck of the Burlington Bay Horse Ferry in Lake Champlain.

Although it's usually reserved as a boat dive the Horse Ferry is probably the easiest and most beginner friendly wreck that is commonly dove in Lake Champlain. The wreck sits in approximately 45-50ft of water off North Beach in Burlington, VT and is north of the Burlington breakwater.

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"The fragile horse-powered ferry in Burlington Bay is the only archaeologically studied example of a turntable “team-boat,” a once common North American vessel type. Animal powered vessels were introduced into North America in 1814. They became a popular form of transportation for short-distance river and lake crossings, until the middle of the 19th century, when they were surpassed by the increasing use of steam power.

Lake Champlain’s long, narrow shape created the need for many ferry crossings between Vermont and New York, crossings that were ideally suited to horse ferries. The use of horse ferries on the Lake appears to have peaked in the 1830s and 1840s"
(Source: LCMM) https://www.lcmm.org/.../vermont-underwater.../horse-ferry/

Based on sidescan data we knew the horse ferry passed very close to the northern water intake pipe that runs approximately 1.5 miles from shore. The intake pipe served as sort of "primary guideline" to help us location the wreck.

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Our total distance navigated underwater was 2.8 nm (3.2 miles roundtrip). We also visited the end of the intake pipe approximately 1500ft past the Horse Ferry wreck.

I was also testing a custom 20Ah battery for the Blacktip. I ended with approximately 51% battery capacity. I was using drysuit + doubles + AL80 stage and towing a dive flag. My buddies both had 12Ah batteries for reference. This is the longest scooter dive that I've attempted with the Blacktips. This is pretty much the limit of what I am personally comfortable doing with this scooter in open water with 12Ah batteries.

This now makes 3 wrecks (General Butler, OJ Walker and Horse Ferry) that are easily DPV-accessible from downtown Burlington.

I say “easily” with some caveats and warnings. These dives although shallow are very much a virtual overhead environment in the summer due to high boat traffic. I would only recommend doing these in the early spring or fall/winter when boat traffic is minimal. Our average depth for these dives for planning is around 40ft. You should plan to have enough gas reserves to swim back in the event of a scooter failure (a long very long swim) and/or a scooter with enough burn time to tow a buddy or a tow backup scooter.

I’m sure people reading this thread know that most “expedition grade” technical scooters like Seacraft, Suex, Bonex, etc have no issues doing dives in these ranges but you really need to plan these dives carefully on the Blacktip since the battery reserves are much smaller. I would not venture much further than this on Blacktip honestly.

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Do you have any semi accurate way to estimate wh used for your ~3 mile trip? I’m guessing your getting really close to max range on those blacktips
 
Do you have any semi accurate way to estimate wh used for your ~3 mile trip? I’m guessing your getting really close to max range on those blacktips
Yes. I'll have to check what I wrote down in my notes. I believe I can actually get the Ah used on my 20Ah battery BMS. I can probably also check the resting voltage of the DeWalt batteries but I don't think that will be super accurate.

I was actually hesitant to post this online because I realize this is getting dangerously close to the range of the Blacktips and I wouldn't really encourage people do this dive without a backup tow scooter, sufficient gas reserves to swim home or divers that have scooters with much larger batteries. I just wanted to show people some "real world" data from the Blacktips vs. the range on paper. I say this because I realize scooters can cause people get into real trouble if they are not properly prepared.

The divers with 12Ah batteries ended up with 1 bar left but it's not a very accurate gauge of battery life. Nobody had to be towed or swam back and none of us actually hit turn pressure in our doubles and we still had gas in our stage bottles. I would not advocate this type of planning in an overhead environment.

The 3.5 mile range of the Blacktip is based on the drag of the single tank diver + drysuit. Obviously drysuit + doubles + stage adds significantly to the drag.

We gave ourselves a little bit of leeway because it's shallow open water depths with no current and no decompression. We've also done many ~2-2.5 mile dives before with the Blacktips and we had sufficient gas at our disposable to swim back if we really wanted to.
 
First and foremost I'm not gonna give you any grief, I'd do it too. I wouldn't commit to that in a cave or in the ocean, but surfacing would be an acceptable plan C for me no problem.

I didn't know you had a 20ah in there, that helps a lot too.

I'm asking to see help get an idea of energy usage in these things. I use a Watts Up when I recharge my piranha but my blacktip and PTB sierras are a WAG. I have almost zero confidence in what the battery charge lights are telling me. I am ASSuming they are just a voltage guage and that is basically useless.

Definitely want to hear what you estimate power usage was.
 
First and foremost I'm not gonna give you any grief, I'd do it too. I wouldn't commit to that in a cave or in the ocean, but surfacing would be an acceptable plan C for me no problem.

I didn't know you had a 20ah in there, that helps a lot too.

I'm asking to see help get an idea of energy usage in these things. I use a Watts Up when I recharge my piranha but my blacktip and PTB sierras are a WAG. I have almost zero confidence in what the battery charge lights are telling me. I am ASSuming they are just a voltage guage and that is basically useless.

Definitely want to hear what you estimate power usage was.
No worries at all. I know people like to argue on the internet about what is safe and not safe so I am ultimately preparing myself for that "battle" that will inevitably follow :) I've got a little more risk tolerance doing this in a lake at 40-50ft with no boat traffic this time of the year. Plan C or D is very much surface. There is also a beach that is much closer than the route we took to get to this wreck that we could swim if sh*t hits the fan but this time of year the parking is closed so didn't launch from there.

I actually would like to put a WhatsApp meter on the Blacktip. I think it would really useful. I'm sure someone has probably do it already but I haven't seen the data yet.

I also don't have a lot of confidence in the "bars" on the DeWalt batteries. I did check the resting voltage of the two sets of batteries after that dive. They're both sitting around 17.25v (one set) and the other set is sitting at 17.34v. It's 5S pack in the DeWalts so each cell is sitting at around ~3.45-3.47v
 
Maybe I missed it, but what gear were you cruising at?
 
Maybe I missed it, but what gear were you cruising at?
The guys on the 12Ahs never went above speeds 3-4 to conserve battery life. They scootered there on speed 4 and spend 3 on the way home. I realize speed 3 with doubles + stage is really slow.

I was jumping around a bit because I was testing my 20Ah battery. I estimate I spent 80% of the dive in speed 4 with some playing speeds 5-6. I ended with 51% capacity on my 20Ah battery.
 
FWIW, my blacktip and my sierra are both on the 12aH dewalt batteries. I loaned them to buddies this weekend and I estimate they did about 1.5-1.75 hours on them. I wasn't diving with them the entire time so I don't know what speeds they were in or how much each actually got used. That said, I just measured the voltages on the batteries. The two batteries from the Sierra are at 16.1v and the dewalt battery gauge shows 1 bar. The 2 from the blacktip are at 18.49V and the dewalt guage shows 2 bars.

Not sure what to make of that as to whether or not the sierra got used more or if it's just that inefficient. I will have to get more data points to develop a better feel but figured that might be useful info for others reading this.
 
https://www.shearwater.com/products/swift/

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