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Blast from the past..Dumas Miller American convert to brushless

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Blast from the past..Dumas Miller American convert to brushless

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Old 09-09-2019, 08:37 AM
  #26  
Hydro Junkie
 
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Okay, have a question and some thoughts for you:
1) What is that black thing in the end of the header? Is that a plug to keep crap out of the engine, as it appears to me?
2) Your vertical fins need to be more upright and the wing between them shorter. If you can find pictures of the full sized boats, you will see that the vertical fins are roughly at 90 degrees to the deck but not totally vertical. Here's a link to a shot that shows the angle of the fins:

3) Before you paint the boat, you need to fill in the excess slotting for the strut. I would tape over it for testing, just in case you need to either adjust the height or location of the strut. The holes on the left side of the transom need to be filled as well. I'd epoxy in dowels of the appropriate size.
4) You need to move the drive dog back from the strut to approximately one flex cable thickness. The cable will shorten under load and the result, with the present spacing, will be a broken cable and lost prop/stubshaft
5) If you're going to leave the CMB in the boat, you may need to add another tank, probably under the deck. I run 50% nitro fuel and use between 18 and 20 ounces of fuel during a roughly 5 minute run in competition.

Last edited by Hydro Junkie; 09-09-2019 at 08:53 AM.
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Old 09-09-2019, 09:02 AM
  #27  
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THX Hydro,

1. Yes just a plug to keep krap out. When I got the engine, I sealed everything up.
2. Yes, I noticed that also, but as built to the plans. The fins will come in a wee bit when the top wing is actually installed, just sitting inbetween for photo op.
3. Yes, I know I have to pack out the strut mounting and make it "tighter", but still being able to make angle/depth adjustments. The "holes" are actually "ballast tubes" I put in there if I needed nose or inside right weight. I made sealing plugs for those if/when needed.
4. I left a bit of length for a thrust bearing on the drive dog, and I make a slip yoke for cable to engine connection will allow almost 1/2 " inch of cable wrapping due to torque.

But I know I can nestle in a 6s 5K MAH battery into the nose, but may have to go to 8s or 4s2p? and relocate battery location. Looking for info on the suggested components to go electric, Motor, (with applicable watercooling jacket or mount, waterproof ESC etc.
I don't know, that's why I am here asking you guys. And I have no issue with redoing the bottom pan if need be. Just need help in choosing the more correct motor/mount and ESC, then I can start to see what I have to do to go electric.

Last edited by flycaster2; 09-09-2019 at 09:23 AM.
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Old 09-09-2019, 09:34 AM
  #28  
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Here are a couple of images on the slip yoke" I made, the cable is not cut to final length yet, and I did take into account torque wrap:

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Old 09-09-2019, 10:23 AM
  #29  
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What the guys that race electric scale boats run are one of the following motors:
  • NEU 1527 1.5Y 850KV
  • HET Typhoon 700-98 840KV
  • Turnigy SK3-3994 850KV
  • TP 4040 10Y 830KV
You will need an ESC that can handle the load. Again, those that race run an ESC rated to a minimum 130 Amps and rated to handle a minimum of 8s battery configuration.
As far as batteries, those that race are restricted to a maximum capacity of 8S Lithium Polymer (LiPo) batteries. The maximum total
mAH capacity of the battery pack(s) will not exceed 6000 mAH. Only LiPo batteries with a cell
rating of 4.20 or less volts per cell are approved.
Almost forgot, 30C is the minimum discharge rate allowed.
One other thing that's limited is the prop. Props are limited to 57mm to keep the speeds down to nitro boat levels. If this is going to be just a fun runner, you don't need to follow all of the above rules.
Now, with all of that said, if you don't want to run that much power, I'd check with Offshore Electrics https://www.offshoreelectrics.com to see if they have something that would work with less power than what's listed above

Last edited by Hydro Junkie; 09-09-2019 at 10:49 AM.
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Old 09-10-2019, 09:08 AM
  #30  
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All those limits are depending on who you race with. Namba's limits are quite different. 10s for me, using the motor's kv's on the voltage its meant for.
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Old 09-10-2019, 05:07 PM
  #31  
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All those limits are depending on who you race with. Namba's limits are quite different. 10s for me, using the motor's kv's on the voltage its meant for.
Good for you. The OP doesn’t plan on racing, and 8S is the voltage those Kv values are “meant for” considering the many folks who do race those motors on 8S. Why not run on 12S? It’s bound to be faster and some Europeans think that is the voltage those motors are designed for.



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Old 09-10-2019, 06:36 PM
  #32  
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Okay guys, let's keep it civil. I gave the information above for three reasons:
1) If he decides to race the boat later since he lives in NAMBA D-9/19, his boat will be legal according to the NAMBA rules
2) The parts I listed are readily available
3) I KNOW THE SETUP WORKS!!!!!!!!!!!!!!!!!!!
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Old 09-11-2019, 04:03 AM
  #33  
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Question for flycaster: What is the size of the cable that is in the boat? If it is 3/16" I have been told
that most of the modern day electric motors on 8-12 cells will break it very easily, as the torque is
instantaneous with brushless electric power versus the "wind-up" with nitro power. I have been told on
any 1/8th scale FE boat to go with 1/4" drive cable with the shaft stepped down to 3/16. Just an
FYI before you go much farther into the conversion.

Bill D
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Old 09-11-2019, 06:12 AM
  #34  
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Originally Posted by Bill Diedrich View Post
Question for flycaster: What is the size of the cable that is in the boat? If it is 3/16" I have been told
that most of the modern day electric motors on 8-12 cells will break it very easily, as the torque is
instantaneous with brushless electric power versus the "wind-up" with nitro power. I have been told on
any 1/8th scale FE boat to go with 1/4" drive cable with the shaft stepped down to 3/16. Just an
FYI before you go much farther into the conversion.

Bill D
Morning, it's a 1/4" cable. I actually don't remember if it's stepped down, but looking at the image, looks like it may be a full 1/4" all the way. Will have to look at it when I get home.
And yes, a very good point on the torque wrap, being almost instantaneous on FE vs. gradual on the nitro.
So starting the interweb search on motors,100mm? running around 850kv and a "waterproofed"/water cooled 130/150 amp esc, nominal 8s (or4s2p) with "headroom" for 10s.Now I realize I will need a water cooling jacket for the motor, but most of the motors I see are "open frame?", vs. a few that look like they are more "enclosed" i.e. Leopards? Any benefit over one or the other?

Thx
I can see cooling benefits for the open frame type, but any advantages of the more fully enclosed motors, i.e. water "resistance"?

Last edited by flycaster2; 09-11-2019 at 06:27 AM.
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Old 09-11-2019, 02:34 PM
  #35  
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Correction, 8S is not the same as 4S2P. The former is 29.6 volts, the latter is just 14.8 volts. They require completely different motors. You want 8S for your boat, 8S1P for less weight, 8S2P for longer run times (and twice the cost).

You want an inrunner motor, the “open frame” motors are outrunners. The former are much easier to cool, in years past a few 1/8 scale racers used outrunners, but today I’d use inrunners. A 40mm x 100 mm motor will work well with the ~850 Kv. I use OSE a lot, the owner supports hobbyists and racers.

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Old 09-11-2019, 07:06 PM
  #36  
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As stated above check Offshore Electrics out they have an awesome site, geared just to FE, ordered
a Leopard 4092 30 KV 3Y motor from them today for my Dumas Atlas Van Lines. They have everything
you could possibly want or need for electric set ups.
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Old 09-13-2019, 07:29 AM
  #37  
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RPM:
Yeah, I mis-typed it, meant to be 4S2S xxxmaH will give me the 8s, just depends on capacity. But that may change, depending on mods needed for the conversion.

Bill,
Yeah, I;ve been cruising there in and out for the past couple of days. Thanks for the clarifications on the in runner vs. the out runner motors
Are you converting a sport or a scale AVL? I did a sport AVL for my first boat, came out ok. But went with the bigger boats after that..
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Old 09-14-2019, 02:58 AM
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The Atlas Van Lines kit I have is for the 1/8th scale boat, built one several years ago for a friend
was a very heavy boat, but the Picco 67 seemed to push it pretty good, but not up to competition
standards, fellow eventually put an 80 in it to go have fun and play with, the kit I have was a "Thank
You Gift" for building the boat, it has been up on a shelf in the top of my shop for several years. I will
be putting this one a diet to shed some of the weight that the first one had, but at the same time I will
be adding blue foam for floatation.

If you are really serious about getting into 1/8th scale boating here are a few good web sites to explore>
For laser cut wood kits: https://mlboatworksrc.com
For fiberglass scale boat hulls, cowling and accessories: RCBoatCompany 1/8th Scale RC Boat Hull Kits Thunderboats Gas Scale
For 1/8th scale hydro plans: http://www.newtonmarine.com/index.php
For
1/8th scale decals and vinyl lettering: Thunderboatgraphics.com
For scale engines and exhaust moldings: https://www.scale-3d.com/products

Check them out you might find something interesting for a winter project, I am going to be building
the U-62 Thriftway Too kit from ML Boatworks.
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