Electric straightlines in California this weekend

[crowebar]

Sorry if this electric report is a little intrusion on this board but I just heard an interesting report. Joerg Mrkwitschka from Germany set a 32 cell record of an average 113 MPH on his first run of the day. He had a fast pass of 115. I've been told this was a conservative setup pass.

There is a specail award for the first guy to eclipse the nitro record? Maybe this is the year?

Dick

 

[Ian Inverarity]

Dick,

Wow, that is pretty quick!

I would guess that in this sort of SAW configuration, the electrics are probably more powerful than the nitro motors?

Ian.

 

[crowebar]

Not sure Ian, I really don't know the HP specs. I do know I run hotter setup for SAW's then I do for Ovals. That may all change with the advances in Lipoly cells.

Every year the available power increases for electrics. Most of which has been happening in the battery department. The next step will be a huge one. We will go from 3300 MAH cells to 8000+ mah Lipoly cells at a fraction of the weight. It makes it hard to keep up with. A nice problem to have!

Dick

 

[Ian Inverarity]

Dick,

Surely you would have some idea of the output power from the input power? Do you know how many cells are being used and what the average current draw is, or could you guess at that?

I postulate that electrics have the ability to extract alot of the energy stored in the batteries in a short period of time, ie if the cells are mostly used up in two short passes then the power available is very high. With the nitro setups, there is only so fast you can efficiently burn the fuel, so in that respect the power is limited. When you get 8000+ cells you will be able to more than double the current, and thus power, available for the two passes. With nitro, that cant be done! ;D

I would guess that electric will soon permanently eclipse nitro for SAW speeds at least! 8)

Unless there are some pretty radical changes in the nitro engines....

Nitrocrazed racing: Can you say TURBO.

 

[Slideblues]

Got a little news that someone is running this weekend ;D

 

[Ian Inverarity]

Gene,

I am still betting on electrics for SAW purposes. Unless someone starts building motors as 1 run specials and starts running propylene oxide or some such!!

Andy might get the record back in the short term, but if they are soon going to double the battery capacity then the electric guys can double their power....

Nitrocrazed racing: I love the sound of 50000 rpm...

 

[Slideblues]

I think its just WAY KEWL that both sides are going so dang fast!!!!

Gene ;D

Phase III Racing: Its a great time to be in R/C boating 8)

 

[Ian Inverarity]

Gene,

So long as some of the technology filters down to us heat racers...

Nitrocarzed racing: I've never even driven my car that fast....

 

[nitro junky]

whatever

 

[TimD]

There is no question that the electric boats have more potential for SAW racing. It would not surprise me at all to see 150mph in the next few years with the advancing technology with cells and brushless motors. However they have a way to go in terms of oval racing before they are close to the nitro riggers.

Personally the main attraction to r/c boats for me is nitro engines. I'm not likely to start playing with electric boats but the 120mph pass certainly got my attention!

 

[crowebar]

There is no doubt there are pros and cons to each side. One of the biggest troubles for electrics has been runtime. When I got serious about electrics years ago 1200 mah packs were the ticket. Today we have 3300 mah packs that make the 1200's look silly.

To give you an idea of the leaps and gains in the batteries alone, I ran a 8XL Hacker Master 99 controller V940 prop and 24 Sanyo 2400's. My average was 90+ with a 1 way pass of 94+.

This year a friend of mine from Alaska (Tim Higdon) ran the same exact setup in a similar boat and averaged 99 with a 100+ pass. One of the biggest differences was Batteries. He used the GP 3300's. I've been using these batteries in oval racing and they are way stronger then the 2400's.

My point is this has been happening every year for the past 5 years. The next step is LiPoly. This is still years off for us. Curreny Airplane guys have been pulling 100+ amps with 8000 mah cells at 1/3 less weight and have over 200 charges on a pack! What will it be like in 5 more years? All the speed and the runtime we've been lacking.

Will Electric ever replace nitro, no way and it never should. They are 2 different power sources and shouldn't be treated any differently.

Will the nitro boats get the SAW record back? I'm counting on it. Will they keep it? That's the fun part!

Dick

 

[Ian Inverarity]

Dick,

I saw mention of 90 amps for the 3300 cells, for 32 cells assuming that the JAG boat was running 38.4V and 90A, input power would be about 3.5kW or 4.6hp. That isn't as high as I thought it would be, good 15cc's put out up to 7hp. Any idea of the weight of a 32 cell boat?

If that electric power doubles with the new cells it would be very impressive! 8)

As a hardcore nitro guy I like to see the competing forms of power (gas and electric) advancing, it should spur us nitro guys on to do better! ;D

Ian.

 

[TimD]

Couldn't agree with you more, Dick.

I would not be surprised at all if Andy owns the SAW record again very shortly - I think recent events have probably given him more motivation The question will be how much can he raise the record by, and how long will it be before the record can be broken again (isn't technology great )

While the pressure is on for the Nitro crowd to win the record back - is there any pressure on the other electric guys to try and match Jeorg?

P.S I remember Sanyo 1200SCR's being "the hot ticket" - that was a long time ago!

 

[crowebar]

Couldn't agree with you more, Dick.

I would not be surprised at all if Andy owns the SAW record again very shortly - I think recent events have probably given him more motivation The question will be how much can he raise the record by, and how long will it be before the record can be broken again (isn't technology great )

While the pressure is on for the Nitro crowd to win the record back - is there any pressure on the other electric guys to try and match Jeorg?

P.S I remember Sanyo 1200SCR's being "the hot ticket" - that was a long time ago!

The pressure is always on! I'd love to break Joergs record. The problem is Joerg is a tough act to follow just as the big nitro names are. Still, anytime the bar is raised no matter who does it....it's a good thing. I'll be pushing on it next year.

 

[crowebar]

Dick,

I saw mention of 90 amps for the 3300 cells, for 32 cells assuming that the JAG boat was running 38.4V and 90A, input power would be about 3.5kW or 4.6hp. That isn't as high as I thought it would be, good 15cc's put out up to 7hp. Any idea of the weight of a 32 cell boat?

If that electric power doubles with the new cells it would be very impressive! 8)

As a hardcore nitro guy I like to see the competing forms of power (gas and electric) advancing, it should spur us nitro guys on to do better! ;D

Ian.

The trouble is that we really don't know what kind of amps are being pulled. It's a guess. Without that knowlege it's hard to determine what they are doing. I do know we've burned up a lot of 100 amp controllers but the 170 amp controllers seemed to work fine.

Dick

 

[Ian Inverarity]

Well, assuming the current draw was more like 150A then the input power would be about 7.7hp, in which case for a boat that is presumably a good bit smaller and lighter than a 90 size SAW boat them it has a better power to weight ratio.

I read elsewhere that the prop was a 1945. At 48000rpm the tip velocity of the prop is 407.1kph or 252.9 mph, which is considerable higher than I have calculated for nitro setups. So presumably the very high potential for speeds is from good power to weight and very high prop velocities.

I am curious about the JAG boat design, it is quite different from what I am used to seeing. Why the very rearward CG? Doesn't this put a lot of load load on the prop? The tub has an airfoil section and is wider and flatter in proportions to most of the current nitro designs. I am guessing that the tub runs with ground effect type aerodynamics, which is only really going to work on flat water.

A very interesting boat design! 8)

Ian.

 

[Ian Inverarity]

If indeed prop tip velocity is indeed the key, for a 90 engine at 22000 rpm the prop diameter woudl need to be 98mm. Or for a 90 running a 67mm prop the engine would need to rev to about 32240 rpm!

Hmm! nitro is in trouble....!

Ian.

 

[forresterace]

Ian

Clearly the tub is an airfoil-shaped lifting body but also the tail is a lifting stab (stabilizer) which in standard aircraft practice, requires an aft CG for pitch stability.

It very definitely is an example of a WIG or WIGE (winged in ground effect) vehicle, which I think that any boat that hopes to go much above 100 mph must be.

 

[rcrdps]

When you calcualte tip velocity, are you meaning he speed of the tip, or the speed of the water over the tip? Seems like you just need to find a way to make a high pitch prop launchable. If you aren't near cavitating(loosley termed), go down in diameter and up in pitch. Considering the current props, it's going to take a custom prop to get that.

From all the SAW video's I've seen, only a few of them seemed to have problems getting on plane. Can they go down in diameter?

Gene

 

[rcrdps]

Doug,

Interesting point. Lifting with the tail will tend to keep you from blowing off since more lift will just cause it to nose down and lower the lift. The sponsons just become sensors rather than the lift points. Seems to be the object of a canard type boat, except this actually works. Good job on their design team..........though they did blow off on their last run. Hmmmm..... Maybe a larger tail to make it more sensitive to pitch movements?

Gene