Date   

Re: Table Saw Blues --- Burnt out motor !!

 

I had no idea useful battery table saws existed:

https://preview.tinyurl.com/y3ntfrkr

But I'm lucky enough to have a place to plug in a saw.

I sure do love cordless drills and impact drivers, though. :o) Chuck the Duck told me that there was no reason to get anything bigger than the 12 volt (nominal) ones, and he was right. Plenty of power and handier than the bigger ones. I think the big ones are marketed towards the same sort of men who drive huge pickups and put great big motors on their boats. <g> Chuck was also right that once I tried on of the impact drivers I'd fall in love with it. ;o) I went with a Makita set, and haven't been sorry. The same batteries power my mini-vac and a little bitty circular saw.

On 9/2/2020 7:43 PM, Case wrote:
When we sold our last house that had a shop I sold all my big floor saws.
I now have all Deealt battery operated gear. Chop saw, table saw, drills, etc.
Really like all of them.
--
John <@Jkohnen>
I'll believe anything, no matter how wild and ridiculous, if there is evidence for it. The wilder and more ridiculous something is, however, the firmer and more solid the evidence will have to be. (Isaac Asimov)
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Re: Table saw notes.

Jove Lachman-Curl
 

I've not used Carson saw yet,
The mexican food cart there is indeed good, I've eaten there several times.
-Jove


On Wed, Sep 2, 2020 at 11:04 PM John Kohnen <jkohnen@...> wrote:
If a carbide blade is from a good manufacturer it might be worth having
its bad teeth replaced. I go to Carson's saw shop, on Blair between 6th
and 7th in Eugene, for my sharpening needs. They go all ga-ga over my
old Freud blade when I bring it in, but they reluctantly replaced some
teeth on a Grizzly blade after I did the math and concluded that it was
enough cheaper to fix the cheapo blade instead of buying another.

https://www.carsonsawshop.com/

They say that the Mexican food stand parked out front is real good too,
but I haven't tried them yet...

On 9/2/2020 9:24 AM, Electri-Cal wrote:
> ...
> I scrapped 3 older saw blades, chipped teeth, gone carbide ,
> hitting ss screws, a great help, maybe other coots might take a
> dedicated look at one of our most used tools, while its warm enough to
> enjoy the task.  At least a new red Diablo combo saw might help the
> cutting process??
> ...

--
John <jkohnen@...>
Any fool can make a rule, and any fool will mind it. (Henry David Thoreau)


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Re: Thanks Coots, getting started on "stuff"

Myles Twete
 

It would be an interesting experiment to compare running one vs two motors driving the boat at a given speed. It's likely a wash in terms of loss in the controller and given near identical prop characteristics between the two, you're talking about doubling the prop loading in the 1-motor scenario compared to 2. At low loads (and speeds), that might not amount to much of an efficiency reduction to drive with just 1 prop, and might even result in the prop operating closer to its higher efficiency zone (Gerr's prop manual might inform here). But as the boat drag goes up with the square of the speed, at the higher speeds, having the dual props and dual motors sharing the load likely wins out big time assuming we're talking about speeds where the loading nears the high end of the motor's rating. And motor torque via motor current delivers that force.

Motor heat loss (2mtrs) ~ 2 * k2 * Rmtr * (Fdrag/2)^2
= k2 * (Rmtr * Fdrag ^ 2) / 2

Motor heat loss (1mtr) ~ k1* Rmtr * Fdrag ^ 2

Assuming k1 ~ k2 (conversion losses in controller, prop loading, etc. are near same), we should expect the single-motor configuration to have about 2-times the heat loss as for the 2-motor case.

So even if prop efficiency for the 1- or 2-motor scenario were identical (unlikely) at the high speeds, we should expect twice the heat loss.

Now, how much of the total power to the controller(s) is lost to motor heat due to motor current? It's a lot, but the efficiency of the propeller, combined with the drivetrain is the shortest stick---this could be as high as 70% at speed or as low as 50-55%. This, compared to a difference between 90% vs 80% efficiency for a lightly, vs highly loaded motor. Controller efficiency is likely in the 95% zone. Cable and battery losses also factor in.

Add to this, dragging an undriven prop thru the water---best to drive that prop with just the right amount of power that its current draw just starts to increase. At that point, it is presenting minimal drag.

Bottom line: Prop efficiency is paramount. Loading the prop to the point that its operating point moves out of the higher efficiency zones quickly defeats other gains you might attain elsewhere (e.g. by driving with just 1 motor). Add to this, I^2R losses in the motor and battery/cabling quickly conspire against you. But it all depends on the loading. At low speeds and loads, the single prop drive likely wins out. As speed and load increases, single prop loses.

Still, let the data speak :-) .

-MylesT

-----Original Message-----
From: oregoncoots@groups.io [mailto:oregoncoots@groups.io] On Behalf Of John Kohnen
Sent: Wednesday, September 2, 2020 10:55 PM
To: oregoncoots@groups.io
Subject: Re: [oregoncoots] Thanks Coots, getting started on "stuff"

I visited Cal today. His ammeter was hooked up somehow so it measured the current going to the motors, at least, but he was using a 200 amp shunt for a 100 amp gauge. which I now know isn't kosher. We moved the shunt to the common ground and replaced the shunt with a 100 amp one Cal had lying around. Maybe even the one that originally came with the gauge. <g> He should be getting more accurate and complete current readings now -- if the shunt's mV rating matches the gauge -- but we can't tell until we get the boat in the water, and Cal bunged up his knee so that'll be later, after he gets it rested up.

The dial ammeter Cal's been using isn't very precise. It has a range up to 100 amps, and the swing of the needle is only about 90 degrees. We really should keep trying to talk him into getting a digital gauge so he can keep better track of the current draw under different conditions.
Like trying different propellers.

Cal's idea about switching off one motor to save juice is an interesting one to ponder while sitting in our armchairs. Since he started dreaming up Surprise I thought Cal only needed one of the 80 lb. motors for her.
But now he's got two bolted to her bottom. Let's say he's cruising along with both motors at 3 mph. the switches one off and "throttles" up the other until he's going 3 mph again. Will he use less juice? The motors have a fairly efficient pulse width modulated speed control, so not much juice is wasted when running both motors at a reduced speed. If he switches off one motor it's still there under the boat with its propeller free wheeling causing drag. Two motors running slow, or one motor running harder and dragging a dead motor. Which will give longer range? If we can rig up a more precise ammeter in Surprise we can have fun doing some experimenting. :o)

I looked at the documentation that came with Cal's motors. Their instructions for installing them are probably OK, but I was looking for specifications. In vain. <sigh> But I did find something interesting.
They said that the rule of thumb for current draw for their 12 volt motors is 1 amp per pound of thrust, but the rule of thumb for 24 volt motors is 3/4 amp per pound of thrust! I wonder whty it isn't just half the draw of the 12 volt jobs, as you'd expect... So Tuffy;s 50ish amp draw at full chat isn't above her rating. Cal's motors could draw 120 amps at full power,


On 9/2/2020 7:56 AM, Electri-Cal wrote:
...
When Myles Swift and I at the very first trial used my 40 lb clamp on
Minn Kota at Dexter, we had a great time. Same at first Fern Ridge
trip, clamp on 40 lb. -- big ol' stick handle up in the air, no other
power needed. So, back to the beginning, using one 80 lb., like the
one on John Kohnens sail boat, coupled to 4 series 27's and the "close
"enough for now" gauges ought to run for quite a while.
...
--
John <@Jkohnen>
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It is a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. (Jimmy
Carter)


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Re: Table saw notes.

 

If a carbide blade is from a good manufacturer it might be worth having its bad teeth replaced. I go to Carson's saw shop, on Blair between 6th and 7th in Eugene, for my sharpening needs. They go all ga-ga over my old Freud blade when I bring it in, but they reluctantly replaced some teeth on a Grizzly blade after I did the math and concluded that it was enough cheaper to fix the cheapo blade instead of buying another.

https://www.carsonsawshop.com/

They say that the Mexican food stand parked out front is real good too, but I haven't tried them yet...

On 9/2/2020 9:24 AM, Electri-Cal wrote:
...
I scrapped 3 older saw blades, chipped teeth, gone carbide , hitting ss screws, a great help, maybe other coots might take a dedicated look at one of our most used tools, while its warm enough to enjoy the task.  At least a new red Diablo combo saw might help the cutting process??
...
--
John <@Jkohnen>
Any fool can make a rule, and any fool will mind it. (Henry David Thoreau)
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Re: Thanks Coots, getting started on "stuff"

 

I visited Cal today. His ammeter was hooked up somehow so it measured the current going to the motors, at least, but he was using a 200 amp shunt for a 100 amp gauge. which I now know isn't kosher. We moved the shunt to the common ground and replaced the shunt with a 100 amp one Cal had lying around. Maybe even the one that originally came with the gauge. <g> He should be getting more accurate and complete current readings now -- if the shunt's mV rating matches the gauge -- but we can't tell until we get the boat in the water, and Cal bunged up his knee so that'll be later, after he gets it rested up.

The dial ammeter Cal's been using isn't very precise. It has a range up to 100 amps, and the swing of the needle is only about 90 degrees. We really should keep trying to talk him into getting a digital gauge so he can keep better track of the current draw under different conditions. Like trying different propellers.

Cal's idea about switching off one motor to save juice is an interesting one to ponder while sitting in our armchairs. Since he started dreaming up Surprise I thought Cal only needed one of the 80 lb. motors for her. But now he's got two bolted to her bottom. Let's say he's cruising along with both motors at 3 mph. the switches one off and "throttles" up the other until he's going 3 mph again. Will he use less juice? The motors have a fairly efficient pulse width modulated speed control, so not much juice is wasted when running both motors at a reduced speed. If he switches off one motor it's still there under the boat with its propeller free wheeling causing drag. Two motors running slow, or one motor running harder and dragging a dead motor. Which will give longer range? If we can rig up a more precise ammeter in Surprise we can have fun doing some experimenting. :o)

I looked at the documentation that came with Cal's motors. Their instructions for installing them are probably OK, but I was looking for specifications. In vain. <sigh> But I did find something interesting. They said that the rule of thumb for current draw for their 12 volt motors is 1 amp per pound of thrust, but the rule of thumb for 24 volt motors is 3/4 amp per pound of thrust! I wonder whty it isn't just half the draw of the 12 volt jobs, as you'd expect... So Tuffy;s 50ish amp draw at full chat isn't above her rating. Cal's motors could draw 120 amps at full power,

On 9/2/2020 7:56 AM, Electri-Cal wrote:
...
When Myles Swift and I at the very first trial used my 40 lb clamp on Minn Kota at Dexter, we had a great time.  Same at first Fern Ridge trip, clamp on 40 lb. --  big ol' stick handle up in the air, no other power needed. So, back to the beginning, using one 80 lb., like the one on John Kohnens sail boat, coupled to 4 series 27's and the "close "enough for now" gauges ought to run for quite a while. ...
--
John <@Jkohnen>
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It is a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. (Jimmy Carter)
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Re: Mini 12 meter Boomer parts for 4 boats

 

Jove still has a job. Cuts into his boat time terribly, but they keep throwing money at him, so what can he do? <g>

I thought Toledo Joe would have piped up by now. The Retired Old Geezers at the Toledo Boathouses sail Dragon Force 65s. I don't know how much of that is going on now, what with the Dread Virus. <sigh> It seems like RC sailing ought to be something folks could do with safe social distancing.

https://dragonforce65.us/

On 9/1/2020 4:58 PM, Electri-Cal wrote:
Come on by, Jove !!
...
--
John <@Jkohnen>
Just think what a dull world it would be if everyone was sensible. (Lucy Maud Montgomery)
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Re: Table Saw Blues --- Burnt out motor !!

Case Turner
 

When we sold our last house that had a shop I sold all my big floor saws. 

I now have all Deealt battery operated gear. Chop saw, table saw, drills, etc. 

Really like all of them. 

Case

Sent from not here

On Sep 2, 2020, at 6:54 PM, Jhcalbany@... via groups.io <Jhcalbany@...> wrote:

Don't be like me, Cal. I had a cheepie Craftsman table saw that I got on sale for $ 99.00 & in 3 or 4 years burnt the motor out. I got all the numbers & gave them to my wife & had her order a motor from Craftsman. When it got here the bill was $ 102.00. Jim

--
Dirt


Re: Table Saw Blues --- Burnt out motor !!

Jhcalbany@aol.com
 

Don't be like me, Cal. I had a cheepie Craftsman table saw that I got on sale for $ 99.00 & in 3 or 4 years burnt the motor out. I got all the numbers & gave them to my wife & had her order a motor from Craftsman. When it got here the bill was $ 102.00. Jim


Re: Table saw notes.

Pete Leenhouts
 

very helpful, Cal, thank you.

Pete
Port Ludlow
Having table saw troubles 


-----Original Message-----
From: Electri-Cal <calboats@...>
To: oregoncoots@groups.io
Sent: Wed, Sep 2, 2020 9:24 am
Subject: [oregoncoots] Table saw notes.

Finished the belt replacement, new brushes as long as the motor was out.  I added a 3 wire plug, then wrapped that in dust proof cover.  If another service is needed, it will just unplug in a jiffy.  It was good to have the motor to get the right belt etc,. without the hassle of unwiring the switch way up inside.  Harbor Freight makes a dust catcher for most table saws for $7.00  that hooks under the stand up frame, think i'll add one of those.  Gets tired of the cats in the sawdust.   Maybe a paneling in of the floor stand would catch more too.  All this, and I scrapped 3 older saw blades, chipped teeth, gone carbide , hitting ss screws, a great help, maybe other coots might take a dedicated look at one of our most used tools, while its warm enough to enjoy the task.  At least a new red Diablo combo saw might help the cutting process??

Just in case !!!  Do we have a good source for a driveway blading and re gravelling ??  Our access is needing a new smooth and topcoat this year sometime.

Have a great day, ----  Cal


Table saw notes.

Electri-Cal
 

Finished the belt replacement, new brushes as long as the motor was out.  I added a 3 wire plug, then wrapped that in dust proof cover.  If another service is needed, it will just unplug in a jiffy.  It was good to have the motor to get the right belt etc,. without the hassle of unwiring the switch way up inside.  Harbor Freight makes a dust catcher for most table saws for $7.00  that hooks under the stand up frame, think i'll add one of those.  Gets tired of the cats in the sawdust.   Maybe a paneling in of the floor stand would catch more too.  All this, and I scrapped 3 older saw blades, chipped teeth, gone carbide , hitting ss screws, a great help, maybe other coots might take a dedicated look at one of our most used tools, while its warm enough to enjoy the task.  At least a new red Diablo combo saw might help the cutting process??

Just in case !!!  Do we have a good source for a driveway blading and re gravelling ??  Our access is needing a new smooth and topcoat this year sometime.

Have a great day, ----  Cal


Thanks Coots, getting started on "stuff"

Electri-Cal
 

I see Jove got me to relook at the gauge, I installed it yesterday.  I used a bridge that was there all ready, so just double the voltage figures, easy to do.  Same for the larger amp draw gauge, ordered a convenient rated unit, so both can be looked at and read as a 12 volt setup,  As i mentioned, when under clear water easy cruise. solo minimum weight to push it also works, I think.  Plan is to periodically change from one 80 lb. thrust single to the other to minimize wear factors, cruise then should be pretty good with all 4 batts,. on one motor at a time.

When Myles Swift and I at the very first trial used my 40 lb clamp on Minn Kota at Dexter, we had a great time.  Same at first Fern Ridge trip, clamp on 40 lb. --  big ol' stick handle up in the air, no other power needed. So, back to the beginning, using one 80 lb., like the one on John Kohnens sail boat, coupled to 4 series 27's and the "close "enough for now" gauges ought to run for quite a while.  I might even try the original 2 blade props, since one 3 blade prop shut down, has more drag.  For testing, I plan on the same 2 - 24 volt packs and see if the in water range gets extended by much, using each alone -- so the reserve power is still there, for now.

Still planning on that genset, or back up pack, since I own two extra batts. for later options.   That should give me (estimate here)  from notes in summary -- 15 amp. is 2.8 mph --  then jumps to 20 amps at  3.1 mph.  -- 30 amps at 3.6 so that is not so hot.  That's with both motors, cut that close to half draw, don't add more speed to compensate over 3 mph.   Does 10/12 amps at about 3.0 mph one motor running make sense, in the right weather and load??   I'm an optimist of course, so a repeated testing at Dexter looks to be a good step, soon as the easier reading wider scale amp meter comes in next week. 

PS, older Honda (small) 400 gensets do NOT use standard fuses, odd special sizes from 1978 types.  I ordered mini blade type fuse holders to take modern fuses, some stuff can not be predicted !!

Later, Coots time for home chores, lunch with John K. here, yay !! ---  Cal



Anyhoo!!  That is the plan, as always observations are welcome 




Re: This Saturday: Sauvie's Island Circumnavigation Planning Meeting

Richard Green
 

I seldom go anywhere but I’d be there except just got tested the second time in five days for the covid so having to lay low.  I’ve circumnavigated Sauvie island a few times in different boats including one trip at close to 40 mph in a old friend’s boat, still have nightmares.  Willow Bar, a pooka on the Columbia side used to be ‘just a moorage’ until the PYC bought it for a destination for their members.  I moored my Columbia 21 there for eleven dollars a month.  Ten minutes from parking and you were “out to sea” in the Columbia, mid island.  Spent a couple summers there, the best small boat sailing on the entire lower river.  Winds all summer blowing upstream so tack down to St Helens, run back to Kelly point.  Anchor and swim in to the Marshall Beach Tavern a bit upstream from Willow Bar, clam strips and shoot pool…until it burned to the ground a couple years later.  

Rich



On Sep 2, 2020, at 1:37 AM, John Kohnen <jkohnen@...> wrote:

This Saturday, the 5th, starting at 1:00, we're gonna have a socially distanced, outdoor lunch and planning session at Earl's, north of Corvallis, for the Columbia River and Multnomah Channel cruise later this month. Cherrill will make us lunch. Please let us know if you're gonna come, so she can make enough food.

Coots who aren't planning on doing the circumnavgation can come too, just to get some boat BSing in.

If you don't know how to get to Earl's, let me know and I'll send you directions
--
John <jkohnen@...>
A facility for quotation covers the absence of original thought. (Lord Peter Wimsey)
Sent from some sort of mobile device.





This Saturday: Sauvie's Island Circumnavigation Planning Meeting

 

This Saturday, the 5th, starting at 1:00, we're gonna have a socially distanced, outdoor lunch and planning session at Earl's, north of Corvallis, for the Columbia River and Multnomah Channel cruise later this month. Cherrill will make us lunch. Please let us know if you're gonna come, so she can make enough food.

Coots who aren't planning on doing the circumnavgation can come too, just to get some boat BSing in.

If you don't know how to get to Earl's, let me know and I'll send you directions
--
John <@Jkohnen>
A facility for quotation covers the absence of original thought. (Lord Peter Wimsey)
Sent from some sort of mobile device.


Re: Mini 12 meter Boomer parts for 4 boats

Electri-Cal
 

Come on by, Jove !!  I have one of the 12 's the electric runabout of course, and you would be welcome to set awhile, bag a beer, or whatever.  I have week days off till 4 pm, when my wife gets home.  Unfortunately that also has my weekends pretty full.  Seems like John Kohnen, and Charlie Vader are the other locals who can make it this a way, so the more the merrier.  The  is well along, but I'm ambiguous about it at this point.  Everything is good even a new radio, etc. at least worth a viewing so you can see what it looks like.

ZZZZipp !!  Later, ----  Cal



Re: Mini 12 meter Boomer parts for 4 boats

Randy Torgerson
 

If you watch Acorn To Arabella, the boys there bought Victoria for parts and I believe she was an Atkins Eric.  There are several videos on Victoria and the one where they dismantle her is very informative of that happens to a wooden boat when you don't maintain her properly.  The keel was rotted away and filled with junk.

Randy


Re: Gauge Number from eBay ---- Wiring question, about 24 volt and "bridges" -- update for today

johnacord
 

Jove,

That's an interesting graph of state of charge, SOC, vs discharge rate, and appears to be at a constant load (with various load rates graphed).  How does that relate to varying loads?

SOC of a lead acid by voltage reading is normally determined at rest, and for an accurate SOC at rest for 12-24 hours.  When the load goes to zero, or some small %, then the battery will rise to a voltage less than true reading of SOC.  This can be a good representation of SOC with a somewhat small bias short of real SOC as long as you take the reading in the same way consistently.

Before I had an Amp-Hour meter I just had two readouts, voltage and current.  By reading the voltage a time after the current dropped to the minimum value (assuming there were always some small loads) I would get a good idea of the SOC.  It seemed to be within a few percent, but the main thing was to see that I did not discharge too deeply.

John A


Re: Gauge Number from eBay ---- Wiring question, about 24 volt and "bridges" -- update for today

 

That's good to know. Thanks, John. That means for about 16 bucks Cal could get a battery monitor that seems to work alright, from the reviews, and wouldn't have to buy anything extra:

https://smile.amazon.com/exec/obidos/ASIN/B01JOUZELG/themotherofal-20

I keep learning... I thought that the voltage drop rating -- mV -- was for a set current determined by some standard. Say 100 amps, so a 75 mV shunt would have a voltage drop of 75 mV at 100 amp current, whether the shunt was rated to handle 100 amps or 500 amps. No. That'd make life too easy. <g> If your gauge says to use a 75 mV, 100 amp shunt, then you'd better use a shunt just like that:

"Shunts are rated by the maximum current and voltage drop at that current. For example, a 500 A, 75 mV shunt would have a resistance of 150 microohm, a maximum allowable current of 500 amps and at that current the voltage drop would be 75 millivolts. By convention, most shunts are designed to drop 50 mV, 75 mV or 100 mV when operating at their full rated current and most ammeters consist of a shunt and a voltmeter with full-scale deflections of 50, 75, or 100 mV. All shunts have a derating factor for continuous (more than 2 minutes) use, 66% being the most common, so the example shunt should not be operated above 330 A (and 50 mV drop) longer than that."

https://en.wikipedia.org/wiki/Shunt_(electrical)

I'm gonna visit Cal Wednesday to see what's going on with Surprise's wiring.

On 8/31/2020 6:02 PM, john acord wrote:
If you are running 80A, a 100A shunt is fine.  If you run a bit more than 100A it will just heat a little and that's OK for short periods.
I like to keep a shunt and meter around for testing and setting things up.  A meter made for panel mount is generally not so practical, generally needs voltage too, so I just use a shunt and my digital voltmeter.  The photo attached is a 50A 50mv shunt:  each mv read across the shunt is an amp.  I just wire it into whatever circuit I want to measure.
I don't know why 75mv shunts seem prevalent.  ?? Makes the reading an odd factor of amps, ie 75mv = 100A.  So how many amps is 32mv.........??
Remember, a shunt is just a precision resistor.  If you want to measure small currents just go buy a 1% resistor of the appropriate value from the electronic supply house and use the same way as in the photo.
--
John <@Jkohnen>
Words ought to be a little wild, for they are the assaults of thoughts on the unthinking. (John Maynard Keynes)
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Re: Mini 12 meter Boomer parts for 4 boats

 

I believe only David Birch has completed his Boomer. It shouldn't take much to get mine sailing, but it's been sitting on the back burner.... Cal's is coming along too. I don't remember who has the fourth Boomer...

The Triton and Eugene Yacht Clubs have tried to get RC sailing in the winter going. I don't know if they're still at it. I've heard that they got too serious and competitive and scared the fun people away. <sigh>

You should ask over on the Fernsail group:

https://groups.io/g/Fernsail/

What! You're not a member? Shame on you. ;o) I'll send you an invite.

On 8/31/2020 3:51 PM, Jove wrote:
John,
As the fern ridge sailing season tapers off, I'm finding myself more and more interested in RC boats again.
Where can I catch people sailing RC boats around here?
How did the Boomer project go for everyone last year?
Are there any boomer hulls or other RC sailing equipment available?
Here is a nice picture of an RC model of Suhaili, Robin Knox-johston's 32'er. made by some French RC group.
At this point, I'd really like to try sailing and RC boat to just see if I like it before invest much more time or effort into the idea, So if anyone has a boat, knows a group, or etc. Let me know.
image.png
best,
--
John <@Jkohnen>
As I slowly grow wise I briskly grow cautious. (Mark Twain)
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Re: Mini 12 meter Boomer parts for 4 boats

 

Suhaili is an Atkin Eric. Robin Knox-Johnson bought some cheap plans in India, where he built Suhaili, and years later discovered that they were the Atkin drawings copied with the designer's info blocked out!

http://www.atkinboatplans.com/Articles/MacNaughton/Eric.html

Bill Crealock took the Eric (actually Thistle -- same hull, raised deck) design and modified it for fiberglass construction as the Westsail 32. After the first few boats were built Westsails had a trunk cabin, like Eric. The first manufacturer of Westsails paid a royalty to the Atkins. The original Erics and Thistles sail better than Wetsnails. <shrug>

http://www.atkinboatplans.com/Sail/Thistle.html

http://www.atkinboatplans.com/Sail/Eric.html

On 8/31/2020 4:06 PM, Rich G wrote:
I sailed a FC version of Suhaili named Suhail, cutter rigged,  from Honolulu to Astoria in1980.  Fun trip, a bit bouncy.
--
John <@Jkohnen>
He who establishes his argument by noise and command, shows that his reason is weak. (Michel De Montaigne)
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Re: Gauge Number from eBay ---- Wiring question, about 24 volt and "bridges" -- update for today

Jove Lachman-Curl
 

Good info guys,
here is a good diagram from another ebay meter I came across. (nice URL link feature John will like that)
I think Cal should be able to use voltage as a good proxy for how much capacity he has left. He may want to throttle off, and measure pack voltage, that is one area where the steady voltage decline of lead acids is realy helpful vs lithium ion which don't seem to have much voltage sag over the central 90 of their capacity so voltage doesn't tell you much unless you're FUL or very empty. This should negate the need for a "reserve tank"... second image. C rate on the right side of the curve is full battery discharge per hour. so C=1 is discharged in one hour. C/3 =3hours. The article is an interesting read.
image.png
image.png

On Mon, Aug 31, 2020 at 6:02 PM johnacord <jcacord@...> wrote:
If you are running 80A, a 100A shunt is fine.  If you run a bit more than 100A it will just heat a little and that's OK for short periods.

I like to keep a shunt and meter around for testing and setting things up.  A meter made for panel mount is generally not so practical, generally needs voltage too, so I just use a shunt and my digital voltmeter.  The photo attached is a 50A 50mv shunt:  each mv read across the shunt is an amp.  I just wire it into whatever circuit I want to measure.

I don't know why 75mv shunts seem prevalent.  ?? Makes the reading an odd factor of amps, ie 75mv = 100A.  So how many amps is 32mv.........??

Remember, a shunt is just a precision resistor.  If you want to measure small currents just go buy a 1% resistor of the appropriate value from the electronic supply house and use the same way as in the photo.

John A