Thanks for the tips

I have a flat pad for my single jet and the pump is fully immersed at rest, no problems with drive at low speed in that it primes fine. I have a scratch built mono form V hull 20" long, with a 25° V handles great at speed and in rough water.

One thing I added 2 turning fins which can be seen on you tube in the surf video

FPV Sumner Surf all the Claires hot footage and a bit with a dog (6 min 38 sec)

Not only did they help with handling but the reduced the cavitation problem. I like doing FPV in some of the local wetlands at slow speed and the fins fix the low speed handling issues well.

Some one else told me that a bigger jet would perform much better, as I'm cash poor most of the time I would have to build one but I need some basic ratios, like nozzel to impeller which is very important I'm told.

well I've had my NQD for about a year now waiting for it's mods. I finally dove into it. It's all apart now. Going to put a brass bushing in, and 1/8" shaft.

I am experimenting with cutting down props to fit. I started one tonight. Once I get the boat built, we'll see how she performs. I am trimming the prop on a lathe. If it works out, I would love to sell these. Really looking for input here.

Nice impeller looks like a nice fit, the stock impellers I have got seem to have lots of mould flashings that need trimming

I have seen modified units with flex shafts on Ebay

This is a fully modified Jet Unit ot suit the NQD Tear Into Jetboat and SicRC Jet Sprint 410 Jetboat. The unit comes with your choice of motor couplers to suit 2.3mm, 3mm or 3.17mm motor shafts, simply specify the coupler size you require when you order. Tunnel Diameter is 20mm. Mods include: Brass shaft sleeve. Flex shaft. Stainless intake grille. Water pickup.



http://www.ebay.com/itm/Modified-Jet...item27cca8aaf1

Yes I saw that in this thread. That is awesome. But he is Australia, and the shipping cost for us here in the states is pretty high. I am not trying to compete with him, just maybe offer props turned down properly for those that want to do it themselves. I may also offer a service to correctly bore out the housing for a bearing or bushing using my mill.

Ant, dont forget the balance issue..

I was planning on balancing the whole assembly, if that's what you mean. I could just balance the props as well. I can't imagine they would be too far out as they say these props don't need balancing, and I am taking off an extremely even amount by doing it in a lathe.

What do you think about using a flex shaft?

Originally Posted by chidago

its a $40 pool toy, we are lucky we got what we got, as they say..

I have nothing against people trying to modify these boats. After all, that's the purpose of the thread and I've done my share. That said, once you have done the normal mods, anything else is just dickering at the margins. Much over 25,000 at the impeller and anything more is just wasted effort. I've got Graupner impellers in two of mine and a SicRC flex-shaft in the third. It cuts vibration but the limiting factor is still the size of the drive.

I don't know anything like as much about water-borne craft as chidago because my engineering was in both full-size and model aviation. A 60" model of a WW1 fighter will operate at around 20ozs/sq.ft. wing loading whereas the full-size ones were around 125ozs/sq.ft. - primarily because air can't be scaled down.

Neither can water. And it doesn't compress. Look at chidago's post with GPS readings a few pages back. You will see that with careful tuning like his (when I say 'at the margins' I don't mean that unkindly) you can get this 1/12 scale boat to run at 1/3 of full -size speed. In other words 4 times scale speed. Whatever you do you'll never do much better with an NQD.

The clearances on even the most carefully engineered model are enormous compared with a full-size jet boat. As chi said, they have wear rings round the impellers, tiny clearances, and yet he still reduced nozzles in only .030" steps when tuning (on something like an 8" drive in a full-size boat).

None of this matters for creek runners. On most creeks you can only use WOT for a few seconds before it goes out of sight round a bend or you hit a rock. Most running is at 1/2 throttle or even less. For lake-boat use where you can spend more time at WOT the only way to go much faster is a longer hull and a bigger jet. As chidago said, a 22" hull with a 28mm or 40mm KMB or Graupner.

Originally Posted by Firehawk989

You could try adding a rudder to the bottom of the steering nozzle to keep it planted in the turns.

Seems like a plan, Fire. Might try that although I'll need to shorten my ride-plate first to allow the rudder to fit. Also, while OK on a lake-boat one would need to be careful on a rock-climber that it didn't foul on rocks and come off - taking the nozzle with it!

Originally Posted by madbugger

Seems like a plan, Fire. Might try that although I'll need to shorten my ride-plate first to allow the rudder to fit. Also, while OK on a lake-boat one would need to be careful on a rock-climber that it didn't foul on rocks and come off - taking the nozzle with it!

Yes, certainly not a mod you would make for creek running. I broke my steering nozzle once already without the added risk of a rudder! I have thought about making a ride plate, but my "beefed up" steering nozzle has held up very well since then. (Ran a case screw from a standard size servo all the way through the nozzle to hold everything together.)

Originally Posted by Firehawk989

(Ran a case screw from a standard size servo all the way through the nozzle to hold everything together.)

Man after my own heart. Anything can be fixed if you've got a big enough hammer I put a ride plate on mine before it first saw water, having learnt about them elsewhere. Have never regretted it, particularly given where these boats get used.

Well, I'm gonna try making a little rudder on a spring, sorta like a outboard motor can kick up when it hits a log..could all be too small to work with, dunno.

When I can, I am going to try and find some brass tubing stock to see if any stock sizes work for a wear ring, but, if one can be found, its gonna load the motor more, but, will no question, help thrust.

What are you guys finding when you do a ride plate??

just jet protection? is it affecting handling? trim?

Mine needs to do double duty well, rock climbing, and lake.

Originally Posted by chidago

What are you guys finding when you do a ride plate??

I am not really in a position to comment on the pros and cons, since I fitted one from scratch.

My main objective was jet, and therefore servo, protection in creek running but from various videos of boats with and without I get the impression it helps with stability. In the sense that the boat is less likely to get the bow coming so high out of the water when hitting waves or submerging as much if you spin out. In other words, it reduces porpoising. This in turn may be helping with keeping the drive 'lit' although in extremes it still cavitates with high-G turns as everyone else has found.

Reason it works, IMO, is that it effectively lengthens the hull on the centreline, where it matters most for fore-and-aft trim. For that reason you may need to experiment with the longitudinal angle of the ride plate, in the region from a couple of degrees below level with the hull bottom to a couple of degrees up from level to get the maximum benefit. Mine is level with the flat area at the back of the hull (from front to back) with a couple of mm at each side (looking across the boat) bent up to follow the upwards slant of the V bottom.

That said I have never experimented with changing the thrust angle of the jet or adding trim tabs each side, both of which you've done. Perhaps these mods have the same effect, although my ride plate goes back further than your trim tabs.

What is needed is comment from people who have run the boat with and without a rideplate.

I fitted 2 fixed fins fully aft each side of the jet intake on a single 20 mm jet 20" deep V hull, helps with fast turns and when its running slow in the wetland creeks I FPV in, doesn't noticeably effect performance. Back in the day we had a 20 ft stern drive boat on the the river in the UK which handled like a pig at low speed after fitting home brew trim tabs which had max 30° of down angle, straightened her up 4 knots with the tabs fully down and she was a breeze no constant steering corrections like before.

FPV Sumner Surf all the Claires hot footage and a bit with a dog (6 min 38 sec)

I sacrificed 2 nozzles on the rudder idea, too complicated in too small a area..wound 4 springs, aluminim rudder, but, will not work, and kick up correctly..

But, dont know ya cant do it till you it up a few times..