Largest Motor/ESC Combo In JAE Mini Sprint

[SweetAccord]

Manual attached:

[SweetAccord]

Manual

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I have also put this info in my album: http://forums.offshoreelectrics.com/...p?albumid=1389

[SweetAccord]

Kits like these are hard to beat for the price: https://www.amazon.com/Shrimp-Wooden...ds=rc+boat+esc

[NativePaul]

Hi Rob, I hope you don't mind me posting the reply to your questions here (as there is nothing personal), I tried to PM you with it but went way over the 5000 character limit and got denied.

IMO a 2845 is bigger than needed, someone asked what was the biggest that will fit and I said 2845, people seem to have taken that as a recommendation, but my own had a 28x36 Mega 16/15/x and I feel that is plenty.

The 4420 would be silly fast for you on 3s and a good speed on 2s, I raced with a similar KV on 2s spinning an X427which gave me 5 minutes runtime using 2200mAh at about 30mph at that speed throttle control is only needed in rough conditions so it is a good platform for newbies. Swapping to 3s on the same setup results in a much higher speed, and if you don't care about runtime you can prop up a little to get better acceleration too, best acceleration came from a detongued X435, best speed from a P735, my favourite prop was an detongued X632 for a good blend of both speed and acceleration. The small hull cant cope with the higher speeds unless it is calm so reading the water and throttle control will be important for it to finish the right way up, it is very fun to run on the ragged edge of the hull's limits, and much cheaper to do that with a mini than a bigger boat, but make sure you have a means of rescue with you if pushing a non selfrighting mini above 30mph.

The motor mount I used is a stock zippkits one, I think it is great and wish the other JAEs came with one similar instead of the overweight PITA the .21 comes with.

I don't like the Leopard water jackets and hate the HRC ones, I recommend the Chinese Lehner-esque ones like this which cool just as well but are smaller in diameter so will fit in tighter spaces, half the weight of the Leopard jacket, and are cheaper.

I don't have a seaking60 or the boat to test fit, but I cant imagine a 60A ESC not fitting, there is quite a bit of space inside, i did measure up the internal dimentions and put them in the what's the biggest motor the minisprint will take thread if you want to check fitment before purchase.

Recommended props are above, same props will work on both KVs apart from the X427 which will only work on 3s with the lower KV, replace that with an x430 for 2s 3650KV. The only 3 bladers I tried were Octura V9 series V930, V932, V935 trying to get more speed, but they didn't work well, there are no 3 bladers really suitable at the moment and the hull doesn't need 3 blades, but I have seen an ABC prop list with small 1/8" 3 bladers on it that I want to try, but I have not seen them for sale yet and are not on the ABC website yet.

The strut/stinger/stuffing tube combo is pretty craptastic and if I was building one again I would use an actual strut, but I was intrigued as to how well it would work and how long it would last (better than I thought and longer than I thought, but not as long as a proper bushing and not as easily replaceable as a bushing or bearing). The rudder it comes with is too long and draggy, I cut mine down to just below the water pick up with no ill effects. I would swap to 4mm ID boom tubes to take metric booms that are available here rather than having to sleeve down the 3/16" ones to 4mm.

I didn't have an issue with my turn fin mount, and didn't have an issue with my rudder mount until about my 15th buoy strike, so I am not sure how much of an issue there is there, though maybe it helps that I am a racer and always either going round buoys or an imaginary aproximation of buoys with a set turn radius, rather than just banging the rudder full over at top speed to try a 180 on the spot.

The OSE cable is probably a good idea, I know several of is from the first Zippkits batch lost props due to separation of the stubshaft from the flex, I heard they are better now and suspect it was just an old pot of glue they were using, but I hear never hear bad things about OSE shafts.

No bushings will fit in the stock drive arangement, the stubshaft runs directly in the stuffing tube, which has a small sheath on the end to stiffen it where it exits the hull. as the brass tubes are all sliding fits on each other, it would be possible to fit one tube over another and solder together until you built up enough ID to fit proper leadteflon bushings or ball bearings inside.

Depends what I was building it for, if I was building another to race the 6 minute Naviga Mini Hydro class, I would build from the plan not the kit, make slightly shorter sponsons, use much thinner wood, I would downsize the motor to a28x29 Mega 16/7/x, use a smaller 30A ESC, fit metric boom tubes, put a little less bend in the turn fin, use a 1.2mm wire drive, fit a ball raced strut, mod and fit this rudder, ditch the servo mount, and use 3.5mm connectors.
If I was building another for the silly fast MPBA Mini Hydro Sprint Class, I would cut off the tips of the sponsons, fit metric boom tubes, get a trusted flexshaft, ditch the servo mount, cut the rudder down, add a diagonal support to the rudder mount, and fit a strut.
Paul.

[Dashunde]

Thanks Paul, thats a lot to absorb and the wife has plans for me today, in the meantime one thing did catch my immediate attn...
What strut would fit on this tiny thing? Still use the ski? I have two of the soldierd cables already, so I'd want to use them w/ the strut.

[NativePaul]

I use full 1/8" shafts now rather than the stock 4mm stub stepped down to 1/8" so I can wrap a ballrace around it without increasing the outside diameter of the strut. I modded one of these for my minisprint's Mini Hydro replacement, it is the wrong way round in their picture. I cut the nose off mine and drilled each end to take the smallest 1/8" ballraces I could get, it is only 7mm outside diameter so it leaves paper thin alloy around the bearings but with retainer they have held up fine and it runs like a dream, though I will probably mod a 4mm strut for my Mini Hydro Sprint to leave a little more meat around the ballraces (as it is not as weight critical and spins a bigger prop).

Etti do a fairly small and light 4mm ballrace strut, and TFL do a leadteflon 4mm strut that I haven't used but might have a smaller diameter. Are the OSE shafts cut to exact length? If so you may have to run the stock setup to get the length right, and just replace the stuffing tube when it wears out and gets sloppy.

I would still use the ski.

[SweetAccord]

Look at my album and you can see how I did bearings in the strut. It's pretty easy. Cut off the stock stuffing tube, add a larger diameter that the drive shaft fits though and the brass stuffing tube hold diameter wise, and pack it all in there. I don't recall all the sizes and all but that what I did in a nutshell.

http://forums.offshoreelectrics.com/...hmentid=136676

http://forums.offshoreelectrics.com/...hmentid=136685

You can even see the bearing on the end of the stuffing tube.

[bob horowitz]

Hey Guys,
I finally got to test the changes I made on my Mini. Like I said in previous posts, I'm running a Leopard 2845 3650 kv motor with cooling, a 60amp HK Blue ESC with a cooling plate and a variety of 2200 mah 3S batteries. The thing that made the biggest difference in how this boat runs, is the prop I'm now running. It's a 3 blade 1214-15/60 prepped by Brian Buass. The prop is the bomb. The boat is faster and handles better with this prop than anything else I've tried. My boat is pretty heavy, so it's probably not as fast as some, but it still gets up to about 52 mph on my Gps. I want to cut down my rudder a little, and adjust the turn fin attitude and maybe I can squeeze it a little more. Maybe I'll add a wire drive. They kind of intrigue me. Never tried one.
Regards,
Bob

[ray schrauwen]

I use full 1/8" shafts now rather than the stock 4mm stub stepped down to 1/8" so I can wrap a ballrace around it without increasing the outside diameter of the strut. I modded one of these for my minisprint's Mini Hydro replacement, it is the wrong way round in their picture. I cut the nose off mine and drilled each end to take the smallest 1/8" ballraces I could get, it is only 7mm outside diameter so it leaves paper thin alloy around the bearings but with retainer they have held up fine and it runs like a dream, though I will probably mod a 4mm strut for my Mini Hydro Sprint to leave a little more meat around the ballraces (as it is not as weight critical and spins a bigger prop).

Etti do a fairly small and light 4mm ballrace strut, and TFL do a leadteflon 4mm strut that I haven't used but might have a smaller diameter. Are the OSE shafts cut to exact length? If so you may have to run the stock setup to get the length right, and just replace the stuffing tube when it wears out and gets sloppy.

I would still use the ski.

Hobbyking sells a nice ball raced strut for 4mm as well.

[SweetAccord]

Hey Guys,
I finally got to test the changes I made on my Mini. Like I said in previous posts, I'm running a Leopard 2845 3650 kv motor with cooling, a 60amp HK Blue ESC with a cooling plate and a variety of 2200 mah 3S batteries. The thing that made the biggest difference in how this boat runs, is the prop I'm now running. It's a 3 blade 1214-15/60 prepped by Brian Buass. The prop is the bomb. The boat is faster and handles better with this prop than anything else I've tried. My boat is pretty heavy, so it's probably not as fast as some, but it still gets up to about 52 mph on my Gps. I want to cut down my rudder a little, and adjust the turn fin attitude and maybe I can squeeze it a little more. Maybe I'll add a wire drive. They kind of intrigue me. Never tried one.
Regards,
Bob

Wire drive is what works really well in this hull since the drive line is a long smooth curve. You will gain more speed with one. Keep the liner in it and get the following:

- Octura Coupler Flex Hex 1/8" to .062 piano wire
- 1.6 mm wire drive

A back cut prop will yield more rpm's also. So if the one you have is not you may want to look into that also or have some tongue removed depending on the type.

Good info on prop mods in my album: http://forums.offshoreelectrics.com/...hmentid=147331

[bob horowitz]

Hi Sweet Accord,
My boat has the standard brass stuffing tube in it. Do you just put the wire drive in instead of the flex and stub shaft? No mods to the stuffing tube? I don't have to cut the tube and use a strut with bearings?
Bob

[SweetAccord]

Hi Sweet Accord,
My boat has the standard brass stuffing tube in it. Do you just put the wire drive in instead of the flex and stub shaft? No mods to the stuffing tube? I don't have to cut the tube and use a strut with bearings?
Bob

Correct. Use the stock brass tube. Find bearing that fit the drive shaft, and use about 3 of them. RC car bearing work well, use Corrosion X to keep them from getting corroded as they are not sealed. Ceramic type are even better as they don't corrode. You can add a brass or aluminum spacer or insert like in the pics to give some support. I just did all bearings I think with a tiny spacer to fill in the gap.

Cut off the send and measure the depth of the 3 bearing and fit them into a brass tube that is longer and epoxy it over the existing brass tube. I don't know all the sizes but if you look in my album you can see it finished. It's not hard to do and free's up the drive line a lot. Yes to just adding the wire drive, but you have to use a different drive shaft. I think I got them from Jeff Wholt, maybe it was OSE. I don't recall as I did this a while back. The wire you can get at local hardware shops, online, even ACE Hardware has them. Very cheap.

There is no strut to use, again look at my album pics, you keep and use the stock stuffing tube. If you want to use a strut for support you can but that will be more work and have to drill into the back of the tansom. It's not really needed as the rear of the JAE has plenty of support as it's a short exit and a strut is not needed. That was part of the design. Plus less weight. Less weight = more speed.

Hope that helps.

[SweetAccord]

Here are pics to give you a visual to see what it looks like:

[bob horowitz]

Pretty cool. I'll have to look in my bearing catalogs to see what size bearings are available with a 1/8 ID. I might even have something here in the shop. I could probably even use a couple of needle bearings. Help keep the OD small.

[SweetAccord]

Pretty cool. I'll have to look in my bearing catalogs to see what size bearings are available with a 1/8 ID. I might even have something here in the shop. I could probably even use a couple of needle bearings. Help keep the OD small.

Sure, you can't do it wrong really. There are few ways it can be done. The only scary part is to NOT cut too far off the existing stuffing tube that exists out the back or you are screwed. In the example above they already did a larger stuffing tube so they did not build up the stuffing tube. In your case since it's already built, you have cut and add a sleeve to it and go bigger to get the bearing to fit.