Prather lap cat, converting to electric

[BeachCustoms]

Let me start by saying I am new to this so be gentle.

I purchased this hull from a scream and fly member for my 8 year old son. It will soon be burnt orange (his favorite color) and black, that part is easy. As you can tell from the picture I have removed all the guts to be able to start fresh (this was a nitro boat). I purchased a F1 outboard (http://www.hobbyking.com/hobbyking/store/__66148__CNC_Aluminum_Outboard_Style_Boat_Drive_w_ o_Motor.html), servo (http://www.hobbyking.com/hobbyking/store/__64705__BMS_616DMGplusHS_Digital_Buggy_Servo_MG_1 0_2kg_12sec_46_5g_AR_Warehouse_.html), speed controller (http://www.hobbyking.com/hobbyking/store/__67040__HobbyKing_50A_Boat_ESC_4A_UBEC.html) and battery to start with(http://www.hobbyking.com/hobbyking/store/__21361__ZIPPY_Compact_4000mAh_4S_25C_Lipo_Pack.ht ml), these were all recommendations from hobby King. I am having trouble finding how I need to set everything up. From what I have found the servo should be towards the back, then the transmitter with the battery in front of that. If anyone has some pictures of there set up or just some ideas that would be great.

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[Commotion]

That's a neat looking O/B. I have not seen that one before.

[tlandauer]

Hi Welcome!
While I am by no means an expert on tunnels, I did a conversion awhile back. here is the link: http://forums.offshoreelectrics.com/showthread.php?41910-My-take-on-the-Top-Speed-3-Conversion-Build&highlight=
There are several thoughts on the set up.
a) The servo should be at the fore front, clearing out the rest of the box so the battery can be used as a means to adjust the COG. Keep in mind that your ESC would take the real estate in the back. Another advantage is that if steel cables/wires are used as pull-pull to control the out board, the distance from the tiller arms to the entry point of the wires into the box will allow vertical adjustments of the out board. ( the wires run outside the box until close to the servo at the front)

A different variation is to place the servo in the front but use push rods (http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD871&P=SM) for a pull-push set up. Typically the rods enter thru the back of the box and run alongside on each side of the box, the battery will be in between the rods, it offers a more direct feel but you can't adjust vertically at will, need to bend or increase the distance between the tiller arm and the connector for the rod. It is worth noting that on a well set up wire system, steering slack is not a problem, so the "more direct" of a push rod feel is a mere subjective opinion in the minds of people who prefer the wire set up.

b) As you have mentioned, the servo in the back, and typically actuating push rods.
One thing to consider is that we all want the ESC to motor cables to run as short as possible. If the servo is in the back, then comes the ESC, those wires will have to be pretty long since the motor is outside in the back. Unless your box is tall and the ESC can be placed under or above the servo in the back......

I did not adhere to the cardinal rule that the cables /wires should enter near the servo in the front, in retrospect, I should have adhered to that but I was quite sure where to drill the holes to mount the out board and I did allow some room to move up or down.
Other than that I am not familiar with this hull nor the particular out board unit you got, i am sure more knowledgeable people would chime in and be able to help you.
Cheers!

[BeachCustoms]

Thanks for the input, I am still looking for a 2845 motor, Hobbyking suggested that I use a 3700 kv motor. Do you agree with that? Do you know where I can get one? Hobbyking has one that will work but shipping is more than the motor.

[RandyatBBY]

I did a conversion several years ago. little hotter build. if I remember right the lapcat was 36 inches long.
http://forums.offshoreelectrics.com/showthread.php?19553-Nitro-Lapcat-conversion

[BeachCustoms]

I did read your build last night, it was very informative. I think I have a Lapcat II, I say this because it is not 36" long, more like 28" long.


I did a conversion several years ago. little hotter build. if I remember right the lapcat was 36 inches long.
http://forums.offshoreelectrics.com/showthread.php?19553-Nitro-Lapcat-conversion

[BeachCustoms]

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I finally got around to painting the boat, so far it is coming along. I am still waiting for parts to come in so I can start assembly so this is a good time to get the painting finished. I still need to add the decals and clear it but that's next weekends project.

[BeachCustoms]

Well I finally finished the boat this past week and tested it today, with that being said I am having some trouble. A few things have changed since I started the project, I got sick of waiting for the outboard that I originally ordered to come in so I ordered this one, http://www.hobbyking.com/hobbyking/store/__22953__Sprint_F3_Tunnel_Hull_Outboard_Motor_Set. html . I also got this battery and esc to match the motor (recommended by HobbyKing), http://www.hobbyking.com/hobbyking/store/__28223__HobbyKing_90A_Boat_ESC_4A_SBEC.html , https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9613 .The boat started off fine seemed to go pretty good (speed wise) then it just cut out. From that point forward it would only go about half as fast. I checked the battery and it was right at 11.1V, I have read that the motor on these outboards suck. Could this be the issue? or is it more likely the ESC? Any help would be great, my son was disappointed to say the least.

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[785boats]

If your pack is reading 11.1V at rest then it is flat, & the ESC is reading low voltage & going into protection mode. The ESC is doing its job & protecting your battery. A fully charged 3s pack should read 12.6v. That's 4.2 V/cell. At 11.1V the cells are at 3.7v/cell. which, allowing for the 20% you should leave remaining in your packs is depleted.
Why such a small pack with only 2550mah in a 28" boat? Surely you can fit a 5000mah pack in there for a bit more run time.
Here's a handy guide for voltage/capacity.

[BeachCustoms]

Ha, well I guess I need to charge the battery. I was told not to go over 3000 mah by HB, they also told me that the boat will not run on 4S. I found that weird because I have seen videos of guys running this motor on 6S. I have a 4S 4000 mah pack as well, would it be ok to use a 4S pack on that motor? Thanks for the info, I will charge it and try it again in the morning.

[785boats]

I wouldn't run that motor on 4s. That's over 44,000 revs. That outboard won't last long in my opinion.
On 6s it would be spinning at over 66,000 revs. Total disaster.
Post a link to that video of that 3000kv motor running on 6s on an outboard please. I'd like to hear what it sounds like.

[BeachCustoms]

I looked and couldn't find the video, the only one I found was heavily modified. I will purchase a couple of 5000 mah packs, I assume this will give us twice the running time we currently getting. What pitch prop would you guys suggest? I assume the pitch numbers work like a regular prop, the higher the number the greater the speed and slower the hole shot.

[ls1fst98]

Yes given same diameter, but also increase in amp draw.

[BeachCustoms]

Well I learned a few things today, the pond that we used the boat in drops off faster then you would think, mud really holds them flip flops and my phone is water proof.

My son was driving the boat no problem, then got the dreaded puff of smoke from the motor. Not to sure what happened but the wires are melted together where they come through the cowl. The only thing I can think of is the wires rubbed on the cowl exposing them and that was that. I read those motors sucked anyway, time to research a replacement. Anyone have any ideas?