Building a Ross Lillistone First Mate

[ulav8r]

The speed coils dump energy to heat, lowering the efficiency. Pwm controls should give more range for the power consumed. I have purchased a couple of pwm controllers but am too busy trying to get a house finished enough to move, may be a year or two before I can start working with the controllers.

[The Jeff]

I've been doing some experiments with a fairing around the motor shaft lately. I settled on a NACA 0025 foil after a fair bit of research, downloaded a 200 point drawing from Airfoil Tools which I imported into Rhino, then I modeled my trolling motor and designed a fairing around it which I 3d printed. Tests show no improvement in speed, but a 2.6% to 7.7% decrease in wattage. Unfortunately the test conditions were far from ideal and about all I can confidently say is a fairing looks like a worthwhile pursuit.



The fairing is 8" tall, 6.5" long and 1.6" wide. I printed it upside down so there are no overhanging structures that need support. To print I export my model from Rhino as an .obj file, import into Cura at 2540% to convert to millimeters, then slice it for PLA filament and 15% infill. It took about 15 hours to finish on low quality settings and came out quite rigid and sturdy feeling.



After cutting the part in two I taped it onto the motor with some packing tape. I assumed the tape would be fine, but halfway through the test I noticed one strip had come loose and was flapping along beside the motor leaving the saw cut exposed. Surely not good for performance!



I took my canoe out at high tide so there shouldn't be much current to deal with, but unfortunately there was a bit of inconsistent breeze on the creek. I did two runs at each speed to try and minimize the variables. I'm happy that the bare shaft run was within 1% of the previous trial, that gives me some confidence that what I'm doing is repeatable.

The fairing did a really nice job of decreasing the turbulence and noise from the bare shaft, although it is a bit short. At higher speeds water started spilling over the top so I tried a full speed run with the motor positioned just below where it started to suck air. No significant change although there was possibly a very slight increase in speed.

I'm assuming the voltage is up because it was quite a bit hotter than my first test. And don't put much stock in the range or hours column... that's just a guide for what results with a 614Wh battery. I'm thinking I'd like to end up with a 10 mile range at top speed once this is all said and done. Anyway, I'm currently printing fairing v2 from what I learned with this one, and I plan to test a 10x6 model airplane pusher propeller and prop spinner as well. Eventually I'll get it onto Moga to test and get back to something at least tangentially related to a wooden boat!

[cracked lid]

You could probably get similar results by simply bending a flat sheet around the shaft and connecting it at the back end and making it about 1/2 as long. The additional thickness as compared to the shaft and the resulting increased chord length of your print are adding both additional form drag and skin drag.

[The Jeff]

Haven't had a lot of time lately, but I did manage to do a few tests with the trolling motor on my First Mate instead of the canoe. I've changed the 5 speed switch to a 60A PWM controller and added a model airplane 10x6 pusher propeller. I'm pretty confident with the red, yellow, and green lines since I did runs in opposite directions in calm conditions at slack tide and averaged them together. The latest setup with the PWM and pusher prop is less rigorous, I just measured different speeds as I took the boat back to the ramp and it was breezy at times. I'm pretty sure that 85% power run was heading into a bit of a gust and I know I was against the tide the whole time. I'll get the boat back around when the weather looks a bit nicer and try for some better data. It'd also be interesting to see how much of an affect the PWM has vs the stock controller with the stock propeller.



It's so surprising to me that such a spindly propeller has such a big effect on performance. Top speed increased 47% from 3.4 to 5 MPH and the power dropped 23% from 190.4 watts to 146.4 watts at the same 3.3 MPH speed. I haven't had any trouble with weeds building up on it, but I'm sure that will be an issue to be aware of.



Not a bad place to do some boat testing!

[The Jeff]

We've had a few nice days lately so I launched my boat for some more trolling motor tests. I finally bought a LiFePO4 battery to replace the ~6 year old starting battery I've been using and what a difference! More power and no lugging the lead acid battery up the hill to charge after every outing.



I feel pretty confident with the data since the conditions were very calm, it was right at the top of high tide, and I averaged a run in opposite directions. It looks like there will be some nice days next week so I plan to repeat the test a few more times just to be sure. Maybe I'll put the stock propeller back on and see how it does with the PWM controller.

The battery is sold as a 50Ah/640Wh battery but claims it has 768Wh of usable energy. Multiple people in the reviews tested it and found a capacity from 58 to 63Ah, so I assume it's a 60Ah battery. If I limit it to 80% discharge then I have 614Wh of energy available. At 100% speed I get a range of 8.1 miles at 4.8 MPH, and at my average sailing speed of 4 MPH I have a range of nearly 15 miles. The longest I've had to row when the wind died was 4 miles, so I think I've got plenty of range!

[pez_leon]

I just love these data. It looks to me like you have very clearly illustrated the problem with the stock controller When it's set to anything less than full speed, it wastes power. As I understand it, this is because the stock controller increases the resistance of the circuit, and in so doing converts electrical energy to heat.
From that perspective I'm surprised that the stock controller is not more wasteful. If I'm reading your data right, at the lowest possible setting (around 70 watts), you get a 25% speed boost when you swap the stock controller for the PWM. At higher settings the marginal benefit of the PWM is smaller. Is that correct?

Thanks for gathering and publishing these! It's much appreciated.

James

[The Jeff]

You're right, at higher speeds the PWM controller saves you less and less over the resistive controller. You wouldn't expect it to save anything at full speed and I was relieved to see that the speed 5 data point lined up perfectly along the PWM curve. Makes me feel like I'm doing reproducible science or something haha. I think the reason the speed is lower is because the lead acid battery was so old and worn out it couldn't supply the amperage. I've read there's some benefit to buying an overpowered motor and running it at lower speed with a PWM, but I haven't really looked into it much since this is the motor I've got.

I plan to test a shaft fairing and spinner as well, eventually. I think the pusher prop is right on the verge of ventilating and Whiskyfox found a simple fairing fixed the problem and slightly decreased the power consumption: http://forum.woodenboat.com/showthre...lectric-dinghy Mcdenny thinks the fairing is a bit more efficient and has a super slick motor well setup that I fully intend to steal for Long Steps: http://forum.woodenboat.com/showthre...Electric-Power

To be honest, I'm probably never going to need every last bit of efficiency wrung out of this setup, but it has been a ton of fun to tinker around with and quite a bit cheaper than the commercial offerings.

[The Jeff]

I changed out the analog ammeter and volt meter for a magic box that shows me volts, amps, watts, and total energy consumed all at once. It's just temporarily wired up at the moment and I'll make an enclosure for it soon. The PWM controller does get a little warm so some of the kayak fishermen I've been stealing this idea from add a small CPU fan to move the air around.



It's been a tad too windy for motor testing, so I took my wife and son out for an hour long cruise. I didn't try to keep any accurate data, but the few times I looked at the box the wattage and speed seemed to align pretty closely to my previous graph. We ended up using 176 Wh to go 3.3 miles. That's 53.3 Wh per mile so I figure with the 614 Wh I have available we could have gone about 11.5 miles. I can see us going on a lot of short little trips this summer to explore nearby creeks.



Henry had a great time walking around up there. Spinning the jib cleat, eating the belaying pins on the mast partner, unhooking the centerboard... He also learned about echos! He'd belt out an ear splitting scream, listen to his echo, and then give us a toothy grin. It won't be too much longer before he'll be able to climb over the side.

[dbp1]

Wonderful!

[pez_leon]

I remember that age! Pretty soon, they start moving about as fast as an echo themselves - but only when your back is turned. What a happy, lucky kid!

- James

[The Jeff]

I managed to stuff all the electronics back into my walnut box and make a new lid for the PWM controls. Despite the inside being an absolute rat's nest and all the components have to be installed in a specific order, it's working pretty well! I may need to add a small CPU fan though, I ran it at 200 watts for an hour and things were getting a little warm. I couldn't smell anything burning but I do wonder if it could overheat during the summer temperatures. Also strain relief on the cables has been a bit of an afterthought... maybe I can find a gland nut that will thread into the holes in the box or make some sort of wedge shaped clampy thing that screws together.



I brought my boat around again and got one calm morning to do some tests. I repeated the PWM and pusher prop combination with very similar results so I'm going to call the blue curve good. Then I swapped out propellers to the stock one and found it matched the end of the yellow curve very nicely. I assume the increase in max speed is completely down to the new battery I have since both controllers should be putting 100% power into the prop.



I also got around to making a spinner for the propeller to see how that affects the efficiency. For some reason Wikipedia's page on rocket nose cone shapes gave me little to no idea which is best when mounted backwards on a trolling motor, so I just drew a tangent ogive that looked about the right length.



It is absolutely wild to me that I can design a part laying in bed at 10pm, fire up the 3d printer in the morning and have it done by supper. The main part of the spinner fits around the propeller and in effect is just a washer. It has a hole through the center big enough for a socket to get the nut on. Then some 1"-8 threads at the end for the tip of the spinner to thread into. This is the first time I've printed threaded parts and I've heard it can be hit or miss. I made the male threads 10% smaller than the size of the female threads and it screwed together quite easily after trimming the first half a thread that was a bit warped. Next time I might try 5% and add a fillet for a bit more strength.



Sunday night looks like it might be calm around high tide, so I hope to test it then.

[Breakaway]

Very cool!

Thanks so much for sharing the tech details and performance curves.

Kevin


Sent from my iPhone using Tapatalk Pro

[The Jeff]

Very cool!


Thanks so much for sharing the tech details and performance curves.


Kevin

Thanks! It's been a lot of fun learning about this stuff and testing it out for myself. I'm relieved that my data is matching up to boats of similar size pretty closely.


Sunday night high tide was at 9:30, so there I was out doing laps on the creek in the dark. I've never taken the boat out at night and it was pretty cool to see the moon and stars reflecting off the water with lines of dark trees on either side. Venus was setting in the west and so bright I thought it was an airplane's landing lights at first.



Unfortunately, it's hard to say that the spinner does much. Possibly ~3% less drag at higher speeds but that's totally within the margin of error. For whatever reason the tide on the creek wasn't as high as it should have been and a light breeze came up halfway through. So I think I'll repeat the test when conditions are a bit better.



That reminds me of another project I've been thinking about... a tide gauge for my dock. The more I've been messing around with this trolling motor project the more I've realized that tide predictions are just predictions. It'd be cool to have a device that constantly measures the water depth and sends it up to the house to a graph so I can see exactly what the creek is doing. I've thought of a few ideas on how to build one but whatever I end up doing will be something fun to tinker with.

Anyway, next up I'm going to make a fairing for the motor shaft. Other people have reported it'll reduce drag ~20% and a previous experiment showed it did help prevent ventilation of the prop which I'm now almost positive is happening. I'm still thinking of a way to make it easily removable because it will interfere with the bracket when raised for sailing. Right now a two piece job with high strength magnets is in the lead.

[The Jeff]

Lately I've been working on a boom tent for a possible overnight trip later this summer. It's pretty cheap and not made with the best practices, but since I'm planning to start a Welsford Long Steps build in the next year or so I'm not too inclined to make this tent amazing. If it'll hold up for a dozen outings in nice weather I'll be satisfied. Anyway, it started off as a 10' x 10' nylon rain fly from Amazon. There was just enough material left from cutting along the curve of the sheer to make some triangular doors for the end and I made some simple ties from folded nylon strips to hold them closed. They could probably use some reinforcement patches.



I think loops of line under the hull is the least invasive way to fasten the tent to the hull. I imagine hooks fastened to the hull would be quicker to set up, but I'm not sure I want to get into making the modifications to the boat. So I designed and 3d printed some hooks to attach a bungy cord around the hull from one deck carlin to the other. Once the bungy loops are fastened under the hull, secondary hooks come up to the tent's webbing loops. It's a bit fiddly getting the tension right on everything, but I think it'll be more difficult to get the loops under the boat and attach them to the tent at the same time. The knot on the tail end tells me this is the first loop to put on which goes up towards the bow.



Plus, with the secondary hooks I can undo a few and keep half the tarp up without the whole thing falling apart. I'm hoping by having the tent higher at the stern it'll want to weathercock into the wind. On my lone camping adventure to Tangier Island I used a blue tarp that was basically opposite and it was a miserable night with the tent inflating and deflating every time the boat swung through the wind.



The first hook got a bit messed up until I changed the bed adhesion settings so I tested the hook strength. It was more than strong enough for this application. If I were going to use the tent long term I'd probably make some copies out of plywood and line them with leather or something. Now that I think of it I could have rounded all the edges so they weren't so sharp before printing.

[The Jeff]

With the tent ready, it was time for a test! I had my wife drop me off at the local boat ramp after supper and I motored over to a small cove and dropped anchor. Everything went surprisingly well and I had the tent up in less than 20 minutes. The bungee cord loops weren't too hard to get under the hull and I found it easiest to hook one side on the carlin and inchworm my way along. The sprit down the centerline was a bit in the way and required some acrobatics to get the tent hooked onto the bungee cords up at the forward end.



I had a nice secluded cove to myself and I watched the sunset through the trees. Later I watched the 5% crescent moon and Venus follow the sun down and even later I saw a meteor sputtering across the sky before it broke up. Honking geese and ospreys eventually gave way to the constant hum of crickets, katydids, and the occasional fish splash.



It was a flat calm the entire night and the next morning I woke up to a low mist and pretty sunrise. The tent did well, it was wet from the dew but everything inside was dry. It definitely won't work in rain though since water will funnel in by the mast and I doubt the end doors will do much.



A nearby island came into view as I swung around.



After opening the doors a bunch of noseeums came in so I figured it was time to get going and I motored back to my dock in time for breakfast. So far I'm pleased with the tent, although I wish there was a bit of a breeze to see how it did. I may also try to add some way to attach mesh netting to keep the bugs out. Not totally sure how that would work though. Also I need a wider sleeping platform and my sleeping pad I last used in 2006 no longer self inflates.

[dalekidd]

Good first night out. I'm sure you'll work out the "bugs". I chose the CIY for several reasons, one being the sleeping platform. I've yet to use it and don't have any pics of it since the boat has been finished. But here are a few taken during construction.

Taken from the stern. You can see the lip around the cockpit that the platform will rest on.

IMG_8314.jpg

Taken from the bow with the platform raised.

IMG_8309.jpg

Here's one with a 2-man tent erected. It's a free-standing tent with the door in the end. It also has a rainfly. One thing that I'll have to allow for is the boom, yard and sail setting on the seats. The tent will have to be set up over those with them set off the one side. There's enough extra material in the tent that I think it will work. I may end up sewing some darts in the tent to tighten it up, especially in the back where the platform is a little narrower than the tent.

IMG_8371.jpg

I'm eager to try it out.

BTW: I'm from VA. and lived in MD from '81-98. Wasn't sailing in those days, but have since made one trip to the Bay in 2000. Launched from Deale. Only anchored out one night in Fox Creek off the Rhode River. I had planned the trip for the time of the tall ship parade celebrating the new millenium but the trip got delayed and we missed it.

Here's a pic of a pic that I took the morning in the anchorage. There is a deer in the pic. Kinda hard to pic out but was a memorable moment.

I've enjoyed your thread. The Phoenix/First Mate was on my short list of possible builds.

Good luck with your mods!

[pez_leon]

Great report and quite inspiring. I imagine it must feel great to be able to get some beautiful country all to yourself for a very short overnight.
You are about the only person I know who makes a 3d printer seem useful!

- James

[The Jeff]

Dale, that platform looks really nice! I slide my side benches to the middle to make a sleeping platform, but they're just 1x12's so it's pretty narrow. I think having some open space along the sides is helpful though so I can shove unused stuff underneath. I grew up canoeing and sailing a Sunfish around the mouth of the Rappahannock and these days I'm still pretty close by. I found Fox Creek on Google maps and it looks like a pretty snug spot!

James, it really is great living in a rural area with some nice undeveloped spots here and there. I'm pretty sure my wife thinks this boat camping thing is crazy, but watching the wildlife settle down for the night and wake up again the next morning is something not everyone gets to experience. I've found a surprising number of useful things to make with the 3d printer, especially since I can 3d model and design things to meet my exact needs. Part of me gets annoyed that the parts are plastic, but the other part of me realizes I have limited time and it's the easiest way to keep projects moving forward.

One last look at the cove. I'm hoping to try again in a few days when I take the boat back around to pull out. There should be a breeze so we'll see how that works.

[gray duck]

I bet it's hard to completely bug proof a boat tent. You can get a solo mesh tent (which is really just big enough for you and a sleeping bag) just for bugs and sleep in that under your main tent. Oh and if you haven't heard of it - Avon Skin So Soft is the ticket for Gnats.

[The Jeff]

Gray duck, thanks, I'll have to give the bug guard a try. I have some bug netting I was thinking of attaching to the ends of the tent and letting it drape down, but maybe some sort of bug bivy sack would be better.

The other evening I took the boat back around to the ramp and tried the boom tent again. I made a quick and dirty sleeping platform plank from a scrap of 3/4" ply and 2x stiffener glued and screwed to the underside. This really increased the comfort as I gained an extra 16". It's not terribly practical to carry and I really should get around to making my side benches two layers that hinge open. I also borrowed a buddy's Thermarest camping pad which was amazingly comfortable compared to my old Coleman. So big improvements on that front.



This time I tucked up in the lee of the island and found another guy had the same idea. Hopefully I didn't annoy him too much with all the banging getting the tent set up.



There was a bit of a breeze during the night which raised some new issues to solve. The bungee cords are doing a good job of holding the tent to the boat, but the seam across the middle of the tarp rubs on the sprit just enough to make an annoying squeak as the boat swings through the wind. I wedged a sock in between which fixed the problem, but I'm not sure if that should be standard protocol or if I should take the time to make something more purpose made. Either way, I eventually got to sleep. If I hadn't woken up with the sun and singing songbirds, I would have from the wake of a deadrise blasting along to check a line of crab pots.



With that it was time to take the tent down and head over to the ramp. I'm hoping to continue my trip down New Jersey's barrier islands this summer and a two day trip will make organizing transportation easier. So hopefully these two tests have been enough to work out the big issues.

[dalekidd]

I believe the Alaska has folding bench seats. I was always enamored with the concept.

[pez_leon]

Jeff, I thought you might enjoy this video of a Long Steps under construction:

https://www.youtube.com/watch?v=39swvFtTasQ

James

[The Jeff]

Thanks! I saw the teaser video a few weeks ago on the Welsford boats Facebook group but didn't catch this one. There's a ton of good information on the group, but I find it hard to keep up with what's going on and much prefer forum threads. I'm really excited to build Long Steps, but so far it seems like the honey do list just keeps getting longer.

[dbp1]

There's a ton of good information on the group, but I find it hard to keep up with what's going on and much prefer forum threads.

At the risk of thread drift, YES! I find the facebook groups fine as entertainment, but really frustrating in that stuff just gets buried. The search works okay, so if you are looking for old stuff, you can sometimes find it, but there is no good way to have long-running threads (as adding new comments won't reliably bump them to the top).