Electric motor options for inflatable dinghy

[sparrowhawk1]

Originally Posted by Adelie

No but I'll try to remedy that.

Yes, in a perfect world it would sail 45* off the wind and it would be 1.4x the distance. In 15kt I can't imagine it being worse than 1.6 or 1.7; 15kt with a bad chop maybe 2x (60* off the wind)

5x is clipper ship performance in a gale and they didn't have daggerboards or centerboards.

Don't mean to be rude. But what you imagine is far from reality. If sailed dinghies where anywhere close to the efficiency you suggest don't you think we would see more sailing dinghies?
PS. Please tell us your experience with sailing dinghies

[Adelie]

No, I don’t think they’d be used more if they were that efficient, and I do think most can make 50*-55* off the wind or better depending on wind strength, sea state and centerboard arrangements.

I think sailing dinghies are not attractive to cruisers for a number of reasons.

A lot of cruisers really are just decent sailors and can’t get the best out of their dinghies.

Sailing involves ceding a certain amount of control to wind and sea conditions. People want to point the dinghy at their destination and go. Sailing involves tacking up wind. Look at the ratio of power boats to sail bots for local and moderate distance use.

Sailing a dinghy limits the load carrying. Heeling while sailing means that you can’t load the dinghy as much as when motoring or rowing.

Finally, most of the time a sailing dinghy takes a LOT longer going the same distance. There’s setting and dousing sails at each end of a trip. Shipping and unshipping the mast each morning and evening.
The added distance upwind while moderate is significant. The big thing though is sailing a dinghy is just going to be slower than motoring. The WB10 has a hullspeed of about 4kt. With a big enough motor you might push that up to 4.5-5.5kt, especially if you ignore the 3hp rating and put a 5-6hp on it. Sailing in perfect conditions you might hit 4kt but 2.5-3.0 is a lot more likely especially with the stock rigs sized as they are. Loaded the dinghy is going to be even slower.

Let’s do the math. Assume a really good sailor is handling the boat in perfect conditions. The destination is 1nm to windaward.
He/she has 1.5x the distance to sail upwind and same distance the other way. So, round trip, the sailing dinghy has to sail 2.5nm vs 2.0nm for the motorized version.
The sailing dinghy makes 4kt vs 5kt for the motor version.
That’s 24min round trip for the motor dinghy and 38min for the sail.

Let’s say starting/stowing the motor and untying the dinghy takes 2 min at each end for a total of 8 min.

Let’s say raising/lowering sails and getting underway take 5min at each end for a total of 20min.

Adding those to travel time it’s now 32min motoring vs 58min sailing. That’s almost a 2:1 difference for a very good sailor in ideal conditions.

Less than ideal conditions will decrease both boats speed, the sailing boat probably more so. And even if there was an equal drop in speed the percentage drop in speed will be greater for the sailing version.

Lackluster sailing will decrease speed further.

The moderate increase in distance covered magnifies these effects even more for the sailing dinghy.

Pretty soon you are looking at taking 3-5 times as long sailing and this doesn’t even take into account needing to make an extra trip because of loading limitations and the time involved shipping and unshipping the mast daily.

You don’t need to grossly exaggerate the effect of the extra distance sailed to figure this out.

I started sailing dinghies in 1986 and teaching in 1988. I’ve sailed on:
Laser
Laser II
420
470
505
I-14 (both 1970s and 1995 vintage boats)
Flying Dutchman
Lido 14
Finn
Lightning
Flying Scot
C-Scow
E-Scow (2nd biggest dinghy currently after the A-scow)
Tempest (though this is really a dinghy/keelboat hybrid. )
Victory 21 (very small keelboat, large dinghy)
Hobie Bravo
Hobie 16
Hobie 18
Hobie 18SX
Hobie 21
Supercat
Manta
Plus several others I only sailed a couple of times and don’t remember.

I raced Stars for 2 seasons though that could be considered a keelboat.
And I was race committee for the Seattle Laser fleet for about a year for their Sunday practice racing in the late 1980s.
And I raced a Boston Whaler 16 once in a beer can race using a Flying Scot rudder, the rig from a 470 I think and 470 centerboards C-clamped to the side as lee boards.

Probably the Lido 14 was closest to the WB10 in size and hull shape but even that had comparatively reasonable sail area.

For comparison the Laser which is 156lb vs 126lb for the WB10 has 76sf sail area vs. 50sf.

The WB10 really is under canvassed with stock sails which makes for mediocre sailing but a good business decision. The good business decision is that they are just cheap enough to lure in more customers but small enough that they are are less likely to overstress the boat and rig and incur liability.

For the last 10y I’ve been sailing keelboats almost exclusively.

PS: What’s your experience sailing dinghies?

[sparrowhawk1]

Okay let's get back on track please. I currently own a walker Bay 8 that I sold the sailing rig to because in real life it took five times as long to get up wind than to motor. And one of the biggest problems was I couldn't leave the mast up because it would flip over unattended. The biggest problem was the wind was either too strong or non-existent

[jibstay]

Originally Posted by rsn48

I'm looking at a Torqueedo both because of its electrical use - rechargeable - and weight. I don't want gas engines due to fuel problems if old fuel left in, etc. Also they weigh more than I want to contend with at age 70. I also looked at propane engines ridding the old fuel problem but still has the weight problem.

If I'm going to lug heavy batteries into a dingy bouncing up and down, I might as well get a propane engine. But for weight versus hp, I'm pretty sold on the Torqueedo or the ePropulsion, currently leaning towards the ePropulsion - price.

I’ve been very happy with my ePropulsion. Plus, the battery floats, if you drop it in the water.

[Adelie]

Originally Posted by sparrowhawk1

Okay let's get back on track please. I currently own a walker Bay 8 that I sold the sailing rig to because in real life it took five times as long to get up wind than to motor. And one of the biggest problems was I couldn't leave the mast up because it would flip over unattended. The biggest problem was the wind was either too strong or non-existent

Ah, ducking my question.

[bluenomads]

Originally Posted by sparrowhawk1

Okay let's get back on track please. I currently own a walker Bay 8 that I sold the sailing rig to because in real life it took five times as long to get up wind than to motor. And one of the biggest problems was I couldn't leave the mast up because it would flip over unattended. The biggest problem was the wind was either too strong or non-existent

The missing sentence was something like "I'm sorry, I was being a twit and have vastly less experience than you do."

[sparrowhawk1]

Originally Posted by bluenomads

The missing sentence was something like "I'm sorry, I was being a twit and have vastly less experience than you do."

I've read a bunch of your comments and I think you're a troll and I don't like feeding trolls. But for the benefit of the doubt: I've been sailing since I was 8 and I'm 55 now and I've been living on the hook for over 20 years and believe me I've tried to use sailing dinghies I currently own two. I love the idea but it just doesn't work in real life if you have a job and try and go to shore on a regular basis.

[sparrowhawk1]

I have been thinking of the "hundreds" of boats I've owned over the years but I don't want to keep drifting on this thread. ,, let me know if you guys want to hear about my Styrofoam boat ,my sailing canoe.etc and I'll start another thread

[rsn48]

Lets drop the whole sailing dinghy thing, its not on topic. Also just not practical sometimes with goods to move and dog to transport. The topic is electric motor options for an inflatable dingy.

[sparrowhawk1]

Okay back on track. Just to refresh I have a walker Bay with a solar panel and a brand new battery( this is critical because over the years I've tried using older batteries and it just doesn't work in my humble opinion) a 30 lb thrust trolling motor. I believe the trolling motors are designed to push bigger boats like maybe a 12 or 14 foot fishing boat and an inflatable can get about the same performance as my WB for a half-hour up to an hour after that the thrust drops dramatically. Edit: 90 AMP hour group 27 battery

[liquidice]

Originally Posted by sparrowhawk1

Okay back on track. Just to refresh I have a walker Bay with a solar panel and a brand new battery( this is critical because over the years I've tried using older batteries and it just doesn't work in my humble opinion) a 30 lb thrust trolling motor. I believe the trolling motors are designed to push bigger boats like maybe a 12 or 14 foot fishing boat and an inflatable can get about the same performance as my WB for a half-hour up to an hour after that the thrust drops dramatically. Edit: 90 AMP hour group 27 battery

Sounds like the battery is being discharged normally and then you get the low thrust. In my experience with budget solar solutions, the panels charge slower and slower as you get towards full, and many panels lack the voltage to charge to full. There are many and more theoretical physicists and electrical engineers on the forum, and I wouldn’t presume to challenge their authority. It sounds like you’re good with the new battery which comes +\- 80% charged. As you use the charge to spin the prop, it goes down, and then you recharge with the solar. Most panels I see in use charge 12v deep cycle marine batteries up to 50% and it takes at least a day or more depending on the latitude/panel(s)/cloud cover/angle/discharge prevention in the solar setup. Most solar setups I see are used to maintain the charge in the house battery bank for lighting, radio, and other low-draw applications.
I use a MinnKota 30 lbs motor on a 8’ rollup floor zodiac. I use a 12v deep cycle battery to power it. The working life on a “full “ charge depends on load but generally it runs fine for at least an hour. I charge the battery on shore power using a battery tender brand battery charger/maintainer and it takes 8 hours to get back from below 50% to 50%, and a full day to go from 50 to 80, and another day from 80 to 100.
I suggest 2 batteries, one charging on the big boat while the other is in use. Have you checked your charge levels? Maybe you’re not getting charged back up just from solar by the time you’re looking to use the battery again.

[sparrowhawk1]

Originally Posted by liquidice

Sounds like the battery is being discharged normally and then you get the low thrust. In my experience with budget solar solutions, the panels charge slower and slower as you get towards full, and many panels lack the voltage to charge to full. There are many and more theoretical physicists and electrical engineers on the forum, and I wouldn’t presume to challenge their authority. It sounds like you’re good with the new battery which comes +\- 80% charged. As you use the charge to spin the prop, it goes down, and then you recharge with the solar. Most panels I see in use charge 12v deep cycle marine batteries up to 50% and it takes at least a day or more depending on the latitude/panel(s)/cloud cover/angle/discharge prevention in the solar setup. Most solar setups I see are used to maintain the charge in the house battery bank for lighting, radio, and other low-draw applications.
I use a MinnKota 30 lbs motor on a 8’ rollup floor zodiac. I use a 12v deep cycle battery to power it. The working life on a “full “ charge depends on load but generally it runs fine for at least an hour. I charge the battery on shore power using a battery tender brand battery charger/maintainer and it takes 8 hours to get back from below 50% to 50%, and a full day to go from 50 to 80, and another day from 80 to 100.
I suggest 2 batteries, one charging on the big boat while the other is in use. Have you checked your charge levels? Maybe you’re not getting charged back up just from solar by the time you’re looking to use the battery again.

Yes I think this is normal. As far as my solar panel, it puts out 20 volts open circuit full sun and 4.4 amps into my battery at 12.4v measured before charging testing through my multimeter. If you look back I discussed other charging options. I agree having another battery on standby would be a good idea

[liquidice]

Cool I’m just offering some ideas; I use my electric motor on the dinghy to the point that I took off the oars. I get questions about it all the time since it is so hassle free. I have used two such motors simultaneously, each with their own battery, on a board attached to the motor mount to push my Catalina capri 25 on calm days. 1-2 kph, but in the right direction. Maybe a twin motor setup would work better for you on your dinghy?

[Peregrine1983]

I saw that this thread was revived recently... and I felt compelled to chime in and let the group know how my dinghy-power-option search ended up.

The die hard electric fans are not going to like this one... as I ended up selling my soul. After trying for months last year and a few months this year to make the solar/electric dinghy setup work for serious cruising, I threw in the towel.

For going back and forth to my boat on a mooring the electric trolling motor was (usually) OK, but for long hauls with lots of stuff in varied weather conditions, I realized it was just not feasible.

I originally bought a Newport Vessels 55lb motor, a 50w solar panel, a 100AH agm battery, and a cheap amazon charge controller. The Newport Vessels 55lb is an excellent trolling motor. What I could never get to work properly was solar charging (the lithium people will chime in now... as they maybe should ) with the 100AH AGM battery I had.

I ended up installing up to 100w of solar on the dinghy and I just could never get the battery charged up. I was always running low.

We've been doing more serious cruising and my dinghy rides are getting longer and in more varied conditions. So the electric set up just wasn't cutting it. I bought a well-used 2002 4hp Mercury 4 stroke that's been serving me very faithfully all season. It's efficient, pretty light, has an internal tank, and has the perfect amount of power for my needs. I am very strict about feeding it only non ethanol gas and I am positive that's contributed to its reliability.

Looking back, after many long trips with the Mercury, I can't imagine powering into moderate chop and wind with just the trolling motor and a draining battery with my wife and dogs on board.

Long story short, IMHO the trolling motor dinghy setup is only for those who will A: not be going far and B: not be going at all in bad conditions.

[sparrowhawk1]

I think everyone would like to know what speeds you get with your inflatable dinghy and 30 pound thrust