Sprint Cat 40/80 build

[kevinpratt823]

I have accumulated some stuff, and will be working on this here and there over the winter, so the thread may move slowly.........
Here is the thread with some questions I had while accumulating partshttp://forums.offshoreelectrics.com/...ild-components
Started today by cutting and fitting a piece of CF to close off the turbine. Tacked it in with JB weld, thinking about glassing it from the inside after........
Power will be 6s2p, in the sponsons with a Neu 1527/1Y and SF240 HV Pro+ ESC, just ordering a more appropriate strut to mount up before I figure the rudder bracket location.....

[NativePaul]

That is a very good looking way to do it, but if you are going to use tape to seal the hull you may find it very hard getting the tape to remain watertight when it transitions from going across the back to up the pipe.

I cut my pipe off about half an inch in front of the back of the hatch, put a piece of waxed card on top going between the ends at the back and laid up some glass under it, forming a flat lip at the back when it was dry and the plastic was peeled off, I do prefer the stock looks of the pipe overhanging the back, but it doesn't look too bad and you cant beat an easy and secure tape job IMO.

[properchopper]

Kevin,

I agree with Paul. As long as you've got some time on your hands, consider doing it something like this :

(On my old Gen 2 MV) ;

Before

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After trimming (shortening) the turbine, I built up the deck where the piece of cowl was cut off

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I plugged the turbine hole much the same as you did and used filler to make a smooth add-on deck piece:


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taping seam is now easy

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[kevinpratt823]

Thanks guys, this is why I started the thread, for good feedback. I was thinking the same thing, trying to come up with something in between, as I really like the look of the overhanging turbine, but at the end of the day easy-on easy off is still better. I've had great success with some of my boats with hatch locks with O-rings under the spring, and foam rubber gasket, (regaurdless of what some insist, my sniper45, cyberstorm33, and explorer36 were never taped, and only took on minimal water when upside down for 10+min) but this hatch is a lot longer, and there's really no place to put a third set of locks. I may end up just putting them on all 4 corners and taping the sides and front only. In my limited experience, the hull that relied solely on tape would break the seal and lift the tape on a heavy impact, where the locks/gasket allow the pressure to relieve without breaking the seal for good, there's no racing here, so it's been good for my application thus far, but it doesn't hurt to plan for both..........Thank you both for the feedback, and please, keep it coming.
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[Heaving Earth]

ill jump in here and ask, is there any way to do a sub hatch?
I've had great luck doing it that way….

[kevinpratt823]

ill jump in here and ask, is there any way to do a sub hatch?
I've had great luck doing it that way….

I'm sure it would be possible, but the deck rails are rather low to the tunnel, would certainly have to do some shaping to fit over the components. For me personally, the less taping the better though, as I am usually only at the pond for a short time and run at least 2-3 different boats, so I will avoid having to tape/untape/re-tape at all costs, even if it means dumping out a shotglass of water now and then, which tends to happen sometimes even with my taped hulls, but I certainly will consider it.

[Heaving Earth]

yeah i agree taping is a pita.
besides now that you've got the kayak, they never sit out there for long anymore

[kevinpratt823]

I spent an hour or so on the boat this morning.......I had already glassed in the CF to the turbine, I still have to finish it off and match it up at some point, but I'm gonna give it a go this way and if I don't like it I can cut it off and revert back to something like you guys showed above. Drilled and bolted some hardware, but I'm thinking of pulling it to put some glass in the transom, at least some strips around the edges. I will likely experiment with a shorte rudder bracket, the 4" puts it rather far out. One thing I noticed that seemed a bit dissapointing on the hull was how uneven it ended up when they joined the 2 halves. One side has almost no overhang on the side(towards the transom), while the other has about 1/4".........

[kevinpratt823]

Pics of the uneven overhangs of top half of each side.......I kind of expected better than this for the price of the hull, would you guys agree?

[grsboats]

Agreed Kevin ...that's what I really dislike with most Aeromarine hulls BUt I must confess that its one of the best heat Racing cats on the Market till now.I use to aplly two laywers of c.f fiber ribon(2"widht) in this área for better reinforcement.Gill

[NativePaul]

Unfortunately not, I have come to expect terrible mouldings from Aeromarine, my two are by far the worst I have seen for many years, but they have thrown enough material at mine that they are plenty strong enough, and the designs are excellent for running ovals or general sport running.

I have that same rudder and standoff on my .40/.80 with the bracket flipped over so the blade sits about .5" to the right and .5" lower than yours with the servo in the sponson, it handles great and I'm sure yours will too.

[kevinpratt823]

Ran a strip of glass across both seams inside, and the lower transom to tunnel seam. Notched out a couple 300mm CF batt trays to fit around the steps on outside edge, then installed with MAS epoxy and some filler. The inner edges sit nicely on the step on the inside of the sponsons. I was going to glass in the trays, but man this MAS epoxy is strong stuff, I don't think I'll even need to. I like that the trays will be up off the floor of the sponsons to keep them out of any water that may get in, and it is just that much easier to get them in/out, I'm rather pleased that this worked out, MadMikepags had mentioned having Aeromarine doing something like this when they build it and I can see why, it is very tricky to get into the area and it would have been a cleaner job if I had ordered the hull unassembled, but I build less for looks and more for function and fun anyway.

[kevinpratt823]

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I found some foam from something packaged at work, soaked some overnight to make sure it wouldn't retain water and it didn't. Trimmed some pieces that fit the contours of the outside wall and up over the top deck perfectly, then the packs fit right in, with a bit of velcro on them to keep from shifting, and another flat foam squeezes in over them and holds them in nice. Bolted in the motor mount from the bottom, and used some rubber washers inside primarily because the tunnel has a slight "V" to it, but also to absorb some vibration, I will likely trim them at some point just for aesthetics. Trimmed a CF batt tray down to size, then shimmed it level(again because of the V of the tunnel floor), and epoxied it in place for the ESC(SF240HV pro+). Cooling inlets in the rear, outlets on the sides, just trimmed the contoured foam at those spots.....

[kevinpratt823]

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Big ETTI cap bank in the sponson for good measure. Very slight "S" in the stuffing tube lets the motor lay a bit flatter, thrust bearing in place, a little 2-part expanding foam in the very front to fill it in, then stuffed with some other chunks of foam. I put a strip of adhesive foam rubber across the back edge of the hatch to seal it off for now, and when I drop it in rear first, it's a snug squeeze to get the front edge in as the foam rubber compresses, then taped the front edge and sides. I ran a set of packs the other day with a modded X450 just to shake it down a bit and she came back bone dry inside, not sure how this method will work in more extreme blow overs, but there is still a lot of tape surface holding it down. I will say, though it was choppy, I was super impressed with not only the speed I got with just the X450, but the handling was awesome! Initial impression was that I will be moving the RX pack up front for starters, then play around, as it seemed to want a bit more wieght up front. It seems to bank the turns a bit like a mono would. And the sound of the Neu 1527, running in a comparatively low RPM range(25,000) is mean, data logging showed a max of 167 amps and 66 deg C. Can't wait to get some props, and a fresh set of Dinogy's!

I will neaten things up like wiring and cooling lines once I run it a bit and get an idea of what works, and maybe even a little windshield and accent paint. Right now my initial windshield is trimmed electrical tape :)