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-   -   Finally almost ready 12.5" bbyracing micro jet boat (https://www.rcuniverse.com/forum/speed-electric-109/6544301-finally-almost-ready-12-5%22-bbyracing-micro-jet-boat.html)

headhunter23 10-26-2007 10:59 PM

Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
Well here's one of my builds, almost complete. I love the whole making process but absolutely hate the "I don't have any _________, damnit now I have to go get some." The thing is a bbyracing 12.5" abs boat. The boat came overly well packaged for the size, hell the shipping cost as much as the boat (20 bucks). I'm going to dump a bunch of photos on this thread because seeing is better than reading... well most of the time.

The jet drive is a graupner micro jet. The motor and Esc are from UH. The motor is a 1600rpm/kv outrunner, runs on 10 amps burst for 30 seconds at 15 amps. Esc supports 10 amps with burst to 12 amps.

The lipo's are 11.1v from RVM shop on ebay... love these guys good prices. It can unload at 12 amps and burst to 20 amps (hope I have that right... lists 12c and burst of 20c).




headhunter23 10-26-2007 11:07 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
K I have a couple issues. First is the servo, seems its stuck in gear used the back up. Any ideas to fix this?

Real issues is setting esc in the boat. I'm having trouble picking a spot. I designed a spot right in front of the motor so when I add a small prop to it for cooling it would cool the ESC too. But wire wise it's an issue because I don't want the prop hitting the wires, on top of that the wires to the lipo's aren't great either. So thinking of redoing it, just need to figure it out. Might not even need cooling at 10-12 amps, so could hide it somewhere.

Another thing that kinda's a pisser is the lipo's, the way they are in the image is the best balance. Was hoping to put them all the way to the back of the boat, so instead maybe it's a good place to stick the esc and receiver?

Oh note for people using the micro deans. They work nice but I find there are 2 issues, 1. make sure both wires are set properly for both charger and batterys, and that would solve the issue of pluging them incorrectly as they aren't like normal deans where it only plugs one way. Also when your solidering make sure you don't let the pos touch the negative otherwise you will blow your lipo!!! (one down, still one good one).

headhunter23 10-26-2007 11:11 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Wow youtube cleared the video's quick...

Here's testing the motor http://www.youtube.com/watch?v=tX0wSK3bne8

Here's testing the boat in the tub (seeing that it's raining and I couldn't see crap anyways at this time)

http://www.youtube.com/watch?v=aMQSY6fsx90

hemiblas 10-27-2007 08:45 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
I might be a little worried about the esc. You usually want one that can handle way more amps than you are pulling. Looks like a cool build though.

headhunter23 10-27-2007 11:11 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
What would be the issue with matching the amps to the motor? If anything it would mean the motor would run possibily less than the specified maximum. Which I'm not sure would be a bad thing as it would increase the run time. And based on the thrust in the tub she should match the hammer atleast, would be happy to hit 15+mph would really be happy at 20 mph but not sure how much energy would be required for that with the inefficiencies of a jet drive setup.

Ivan.

CadillacDTS2001 10-27-2007 11:32 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
that esc will work Don't worry

ryan_t888 10-27-2007 12:37 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 


ORIGINAL: headhunter23
If anything it would mean the motor would run possibily less than the specified maximum.
If your motor happens to demand 12A, it will take those 12A regardless of whether your battery or ESC can supply it. If not the weakest link will burn up to due to excessive heat caused by over loading a component.

Ryan

headhunter23 10-27-2007 10:38 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
To be honest I would be surprised if 10 amps even made it through the wire... it's a very high gauge whatever it is.

Ivan.

ryan_t888 10-27-2007 10:49 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Ivan,

Like I said before, if 12A is demanded by the motor it will take it regardless of anything else. If your wires are the weakest link they will glow and burn up. That's how electrics work. The weakest link gets the hottest. All Electronics fail due to excessive heat.

You'd be surprised as to how many amps the smaller gauges can handle.

Ryan

headhunter23 10-28-2007 01:06 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
I guess... the original wires looked to be higher than 18g my guess would be 20g, it's 18 now, which can allow for 16 amp draw.


Anyways need some help on the inrunner motor. As bellow you can see the motor. Apparently the "hat"(term hobby shop guy used, not familiar with term) needs to be removed for me to stick on a prop (am using the prop as a fan to keep motor cool), but it does not appear to be removable. 2 questions, a. is it really removable? or is it part of the whole can (magnetic part). b. Cutting the cap off is possible with the motor running and the dremel, the question is is it wise, the two screws that were in the "hat" is that for keeping the magnet side of the can on the shaft or is the shaft just pressed in. Help would be appreaciated.

Other than this, retesting motor, heating heat shrink, possibly making little battery holders and gluing the top on, she appears to be done.


headhunter23 10-28-2007 10:05 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Ok well took her out, noticed a couple things, I would say the boat hits 20km more than likely max speed, was hoping for 25 min. Another thing is the boat seems to need more weight and obviously I need to reposition the batterys to stop the porpoising.

Take a look let me know what you think.

The other thing, because I'm disappointed with the speed I decided to slap in my old 3200/rpm v 25 amp brushless. I know this will more than likely burn out the lipo as its rate for 20 amps max. Will only half throttle it just to see.

http://www.youtube.com/watch?v=hh7-85hHbi4

headhunter23 10-28-2007 12:22 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Well the 3200rpm/v 25 amp motor really spruces it up... found a new problem though, Jet drive seems to leak. Going to goop it up and I think I'm going to leave in the 3200 inrunner... will require cooling plus new lipo's at 7.4v, plus a little more work on the mounting plate. Unfortunately the remote batterys were almost dead so it was way too short a run, maybe rerun it tomorrow.

HOW TO STOP THE PORPOISING?

Ivan.

headhunter23 10-28-2007 05:31 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
Yep it's confirmed, 11.1v on 3200rpm/v it's quick but overpowers the hull big time. Could only get 2/3s throttle before she starts jumping and porpoising everywhere and that is with all the weight moved to the front. So much so that the jet actually comes out of the water with the nose almost completely in the water, so I would have to push the back down just to get the water pumping through it, then let it go. Ordered some lipos 7.4 at 2000mah, it's 20 grams heavier per Lipo so it will add 40 grams total to the weight of the boat when running 2 in parallel. With any luck this will be enough weight as it seems to be just too light, you would think being lighter would be better.

Also ordered a new esc for the inrunner, apparently they have 30 and 50 amp Esc's that run both forward and reverse! The reverse on the jet will be nothing to write home about but it can actually move in reverse providing the jet is fully in the water.

Well after talking to Quicksilver, I've decided to flaten the hull, the front of the deep vee might be the issue... will find out later this week. Going to leave the drive as is for now.

Here are some more pics.

alloutcustom 10-30-2007 03:09 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
my suggestion would be to even out the hull as quiksilver suggested. also the weight should be more in the back than the front i beleive on jet drives(to keep the drive in the water) however im not an expert on jet drives so you may want another opinion. pretty sure tho. btw, nice build, looks fun!!!!
mike

skidooguymxz550 10-30-2007 04:45 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
it looked pretty peppy to me. i think more speed could be had in calm water. i know i real life my jetski goes the fastest on dead calm were or boat goes it's fastest in 2-3 foot chop.

the key to jet drives is keeping them in contact with the water. when your running waves the intake takes in the air

headhunter23 10-30-2007 05:03 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
Yea actually haven't updated the thread... well here goes, I essentially ripped everything out, fibreglass gone, and cut the hull. Currently this is the flatest I can make it though the hull seems to still bow a little half way through the cut. Going to try dragonfires idea of molding the abs with some heat to see if I can get it a little nicer. Got some aluminum off a buddy, cheaper than buying but its either 1/4 or 1/8 of an inch. Whatever it is it's thicker than I wanted. Unfortunately buddy is borrowing scroll saw for tonight so I can't cut the luminum plate. But atleast I can design it on photoshop so should be a breeze to cut tomorrow or friday (got yet another exam... geez). Here's a bunch of photos.

oh yea note. bought a couple 7.4v lipos (2000mah) and 1 more 11.1v (1200) will be here in a couple weeks, on top of that rvm shop on ebay has forward and reverse escs(30 and 50amp models) available for sale now! Picked up one for this boat, hopefully I won't have to put the ugly bucket on to get reverse.

Oh yea some of these images are posted on the "unofficial jet drive" thread so some might have writing on them.

Ivan.




alloutcustom 10-30-2007 07:08 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
i think sooting higher would increase speed because i think it would be the equivilent of angleing the stinger up on a surface drive. it should run looser, and therefore, faster.

headhunter23 11-01-2007 06:56 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Yea been kinda thinking that too, specially since everyone seems to be saying the front of the boat should be high so it sucks through the jet better. Will have it all modded with aluminum plate tonight, will be ready tomorrow to test in the morning once everything is mostly dry. If I still have the porpoising, then I will shift the jet up.

Ivan.

headhunter23 11-01-2007 11:30 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
1 Attachment(s)
Well got aluminum skid plate done, it's glued into the hull using shoe goop. This stuff is strong, would think a day is enough, 4 and the plate would be hell to come out. Was thinking of fibre glassing it in but I think I might want to redo the plate in a thicker aluminum, plus have the aluminum go all the way to the top(along the hull right to front, sharpened and shaped) so it will offer more protection when hitting rocks and certainly ice this winter. Will test tomorrow after school on 11.1.

Here's some pics!:D


headhunter23 11-02-2007 01:51 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 

No luck on the mini boat with aluminum plate. It is in fact more uncontrollable and jumps out of the water even more now.

Which only leaves the repositioning of the jet as the real issue to stop the porpoising.

Will have video up later... gotta think about this and possibly have a few drinks.

Ivan.[:@]

headhunter23 11-03-2007 09:55 AM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
[:@][:@][:@][:@][:@][:@][:@]

I cut everything out and reglued the jet to shoot out higher bringing the hull up. There is no change in the porpoising. I even put the outrunner 1600 rpm/v back and and it skips worse than before.

Seems putting the plate in was a bad idea.

Starting to think this is the time for a new hull.

Ivan.

headhunter23 11-03-2007 03:22 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
:D[8D]

Finally getting somewhere!

Made a trim tab straight out the back, tested on the smaller motor 1600 rpm outrunner and adjusted. It worked!! Just stuffed in the larger motor. And ran her full throttle, she works!!! Needs a little bit of trim adjustment, but I'm not going to do too much because unfortunately I think I am going to rip it all apart so I can get grills even with aluminum skid plate. Man I really really really wished I did this before putting the alumium plate in.

Oh well... will have pics up later. I think for now, tear apart, rebuild and have the hull perfect so all i need to do is solider the new ESC to the motor when it comes in.

So should be a week or two before I update this thread.

Ivan.

headhunter23 11-04-2007 06:50 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
Anyways here's updated videos

before trim tab, adjusted jet to shoot higher and bring bow up... didn't work[:'(]
http://www.youtube.com/watch?v=QgQjh321txM

and with trim tab installed just bellow jet, needs adjustment still but I'm ripping it apart again so not going to bother fine tuning...
and voila the video http://www.youtube.com/watch?v=D8y5F2JB8aw
:D

DRAGONFIRE81M 11-04-2007 07:00 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
the first run is bad but still cool your still running faster then me while hopeing the sec fun your just flatout hulling *****

DRAGONFIRE81M 11-04-2007 07:01 PM

RE: Finally almost ready 12.5" bbyracing micro jet boat
 
oh ya how hot is it after a good run


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