My KBB45 build, suggestions welcome.

[kevinpratt823]

I have been busy in other areas of life lately, so I haven't been on in a while. I hope everybody had a great holiday season.

Finally got around to drilling some holes yesterday, so here it is.......
This is my first build of this nature, so a lot of new ground for me. I don't have anybody out my way running anything like this, so most of what I have come up with for guidance has come from research, and a lot of guidance from a Keith, ChrisG, Mike(Iridebikes), and a couple others on the forums. I hope that this thread may serve to help somebody else in my shoes jump into a build like this without being too intimidated, so I will try to emphasize all the little questions I had to answer for myself as a newer builder. Here is the thread I used for input on choosing my components and such, as well as get my head in the right ballparkhttp://www.kbbforums.com/kbb45-build...nts-t1488.html
Above all, I'm just aiming for a successful running boat, it will most definitely be much faster than anything I've done thus far(74mph in a Whiplash), and I am treating it as a learning experience for future build more than anything, I've really got nobody to impress so my attention to detail may not be on the level of some others, just aiming get this thing on the water.

In a nutshell, this is what I've got:
KBB45 hull, green gelcoat
Lehner 2250's
KBB SF300's
KBB drives
KBB Lipo sleds
KBB motor mounts for this hull
115mm type A rudder
Type A steering linkage

[kevinpratt823]

For starters, I added a little glass in transome of the sponsons to build them up a bit(it wasn't as dry as it looks, the flash made it look awfully white, though it did turn a bit whiter/dryer than I would have liked). Then went back and forth on wether or not to do an inlay. I had some blue/black carbon kevlar laying around, so I just went with what I had. This was my first time using the West Systems epoxy, and I love it! the pumps take the guesswork out of it, and it doesn't stink like poly resin. Now I can actually work with this stuff at my house, where before I had to go to my father's with the smelly poly resin as my girlfriend couldn't handle it.

Then came the inlay. I know I could have done better, but it serves it's purpose.

Applied some painters tape to rudder bracket for a template, then also to a piece of CF plate in case I want to back it from the inside, and drilled both.
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[kevinpratt823]

The inside of the rudder pocket is really tight. The holes come through at a very irregular area due to the angle and the thickness of the glass/CF. My CF plate doesn't really fit in there too well, even when ground right down to the edges of the holes. I have since filled the area in with epoxy and bits of CF, and have ordered longer screws, we'll see how that goes.

I ground down the brass nuts for the drives as it has been suggested, in order to get them mounted as low and as far inside as possible. I then got in there with the 90 deg dremel attachment and tried to get the area in the corners cleaned up and more square and tight, the added glass and inlay really bulked that spot up. Then I layed the nut in one side, and ran a drill bit out from the inside at approximately the center of the nut. I drilled in with a step bit from the outside, then opened it up with the dremel until I got he fit I wanted. The first hole did end up a little oblong as I was able to bring it down a bit further than I expected once I ground the inside a bit more. I used painters tape to make a template of the rear of the sponson just like I did the rudder, then flipped it over and held it in place to mark the other side. I touched up the ground spots inside with a thin coat of epoxy, and Because I was planning on flowing a little epoxy around the nuts after to keep them in place ad seal it up, I greased the threads of the drives up good so they wouldn't sieze in any overflowed epoxy in case I ever want to remove them, seems to have worked out OK. The second hole was nice and tight and in a good location, while the first one had a bit of give to it, so I did my best to match them(mostly by eye) when I tightened them down.
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[kevinpratt823]

I found that a 7/32" brass tube slides into the drive, although a bit loosely. Something with a tighter fit would have been better, but I wanted to move forward and that is what I had on hand to line up the drives. The drive support/strut pushes through the back of the mounting plate, so I got the rough location and drilled the center relief for that first. Then I used a straight edged along the inner edge of the sponson to try to get the drives as close to parallell as I could. Again mostly by eye and a little double checking with calipers. Marked and drilled the holes, double checked the alignment with all 4 screws in, then put a thin coat of silicone on the plates and bolted them up.
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[kevinpratt823]

Now, I could use a little insight on determining motor placement.

First of all, can somebody give me a target CoG for this hull so I can mock up my components? It would seem to me that I want to put these motors about as far back as I could, just leaving enough room for the bend in the tube and the collet, as the 2250 with the LK cooling fan is rather long, and 7s/5000mah is starting to seem like an awfully tight fit, I may be leaning more towards 6s/5000, or 7s/4000mah. Shelving these motors for a bigger build and going for a set of 2240's or something else smaller isn't entirely out of the question either. I really wish these controllers had a little more length on the wires, it seems innevitable that I will be extending them. Any suggestions from experienced builders would be appreciated.
Thanks for looking!
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[Pheyd]

Looks like a great build. Can I ask what windings you got on the 2250s? I'm contemplating an MHZ 45" cat build and still undecided on the 2240 vs 2250 debate as well as windings.

[kevinpratt823]

I have 2250/4's, and will be running them in Y configuration for a little over 1700KV. Going by input from others, the 2250 is on the large side for this build but still do-able. I know plenty of people have built some really fast cats with the 2240's, so mine may be overkill, but my next build will surely be a bigger boat so I wanted to have the option of using these.

[Pheyd]

Interesting choice. I'm currently debating either a pair of 2240/7 (2100KV) vs 2250/6 (2000KV) in Delta/Triangle configuration. The current plan is to run each motor on 6S.

[nata2run]

Interesting choice. I'm currently debating either a pair of 2240/7 (2100KV) vs 2250/6 (2000KV) in Delta/Triangle configuration. The current plan is to run each motor on 6S.

Both should get you going fast! Remember LMT are rated under load. Depending how fast you want to go the 2250/5 "2360kv" (delta) will fly dangerously on 6s, but no room for mistakes. On the other hand, in Wye mode you will have a nice sport setup running around 80mph. Add 7-8s and it will be even faster and less amp hungry. Both the 2240/7 and the 2250/6 on 6s will be quite capable of some serious speed. If you want a safe 90's mph boat I would go the 2240/7 with worked 47 props and play it safe. You can then add a cell down the track and play with some more aggressive props for more speed.

[kevinpratt823]

My build, with the 2250/4's, is aimed at 7S/5000mah per side, with the potential of 8S/4000mah if I get comfortable pushing it.

[TheShaddix]

Looking nice so far! Do the hulls come green like that? Your hardware mounts look clean, I like the masking tape trick, never thought of that. Also, just my suggestion, but for the inlay use a foam roller next time, it'll get rid of all the puddling. I go through a few of them at once to get a more dry look. You can find cheap black foam rollers on ebay which do not leave any visible residue when the resin gets a bit more tacky (as opposed to the white ones from lowes, etc). Always great to see some updates on this forum, keep posting!

[kevinpratt823]

I'll have to take a look for e foam rollers, thanks. The hulls are made to order, and they have a few colors of gelcoat available if requested.

Sent from my SCH-I535 using Tapatalk 2

[kevinpratt823]

Trimmed the sleds on the tablesaw no prob, then beveled the edges with a belt sander, but I think I going back to take a bit more off to allow a little more room for esc's. Also epoxied in a small CF plate in the filled rudder pocket to give the screws a more true surface, sanded the mounting surface a bit flatter, mounted up the rudder, then squared it up by eye with a T-square before tightening fully. I also spent some time scratching my head trying to figure out exactly how it's all going to fit together and I think I have a good idea of what I need to do.SAM_0584.jpgSAM_0583.jpgSAM_0586.jpg

[kevinpratt823]

Mounted motors. From what I can tell with mocking up for CoG and fitment of components, I need them back as far as possible. I bent a stuffing tube and cut it down to leave at least about 3/8" of straight un-bent tube before the collet, fitted things up, measured from every angle I could to make them even, tacked them in with CA, then epoxied.SAM_0604.jpg

I will likely be looking at drilling for pickups about 1" behind the mounts all the way inside, which ends up about 3-1/4" forward from the rear edge of sponson, maybe farther back if I have the space. From what I am told as long as I am inside of the driveline they don't have to be all the way back.

Here are just a couple pics of the ways I attempted to measure the mounts to get them even, along with the current location of motors/driveline. I will likely order a fresh set of tubes to rebend, as I feel I can do a bit better on the transition, but this keeps me moving. Both shafts spin pretty free/smooth when locked in the collets, even at this point. One is just a bit tighter, but it is the shaft, not the line, as I swapped them and still felt it more where that shaft went.SAM_0605.jpgSAM_0606.jpgSAM_0607.jpg

And here are the motors locked in with shafts bent and lined up.SAM_0608.jpg

[kevinpratt823]

So, it appears to me(AFTER I cut the motor leads lol), that the Lehner motor leads off the back of the can have some insulating lamination applied for the first few mm outside the can AFTER they are tinned......I trimmed back the leads, then noticed this, so I had to spend some time with the dremel getting them all clean at the spot closest to the can. I probably would have done this anyway even if I realized it beforehand, as I'm trying to give myself as much room as possible in there. I then found a brass tube that accepts the 6.5mm bullets perfectly, wrapped them in foil, put it in the vice, and went at it with solder. Filled the bullet, brought the motor lead onto the tip while it was still on the bullet and let it melt just a bit, then plunged it in. I held the iron on the side of the bullet to keep it from flashing right to a cold solder joint, but it is tricky with all the heat wanting to draw right into the motor. They cooled real quick but I think I got 'em pretty good.
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