Building a 12 +cell tunnelhull

[riggerman]

Hi im considering building a 12 cell tunnelhull i have plans and templates for the Dunlap D-27 its 27'' in length and has a 11'' beam i have had great results running it as a nitro version with a os .21 outboard .Would this hull with a 700bb on 12cells or maybe a Astro 25 work? Has anyone built a D-27 for a electric outboard ? 14 years ago i built a Stark tunnel plans sold in RCBM 22'' in length 1/8'' balsa and 1/64 wingskin construction powered by an Astro o5 6 turn through a beltdrive unit on 12 cells. Dos anyone still run these Stark tunnels ?

 

[raptor347]

I'm not positive, but that may be the hull that holds the NAMBA P OPC record. Any good tunnel designed for stock nitro outboards should work well with the limited power of the 700 motors on 12 cells.

I don't know about the Stark boats.

 

[Kris Flynn]

Larry Larsons scratch built starks held the record in P OPC for a few years...but Pat M knocked it off last year with a WOF JD 29.

The starks boat are good for low power motors like the 700's but not so for brushless today...we need 30" boats or so. The Dunlap 27 would be good though.

I also have the plans in the free plans section from the front page of this site...they seem to work real good for me.

 

[David Kingston]

Kris is correct, a 27inch hull starts to get kinda small when you want to power it with the motors of today.

A run a 28inch grim racer villain, on 12 - 16cells.

10Xl hacker on 16cells and a nue on 12cells.

Its scary fast with the nue.

If you consider upgrading motors to a mild to hot tunnel setup, then 28inch would be the smallest i would go on 12cells. 30inch WOD dunlap would be a nice oval 12cell OBT boat.

The trick with the e-tunnels is to make a water tight hatch. Sooner or later they will blow off the water and with all the expensive electronics in side its nice to know that they will not get drenched.

David

 

[topfuel443]

Hi David, which Neu are you running?

when you say scary fast, what does that mean exactly?...lol

Got any MPH readings?

Just curious, as the Neu (on a villain) is also my motor of choice, but I have yet to run it.

~James

 

[David Kingston]

Hi David, which Neu are you running?
when you say scary fast, what does that mean exactly?...lol

Got any MPH readings?

Just curious, as the Neu (on a villain) is also my motor of choice, but I have yet to run it.

~James

James,

I have run a 1515/2.5D (1700kva) on 16cells (3700's), 440 prop. And i need a bigger prop and it worked fine, and was a cool setup.

I also have run a 1515/1.5D (2700kva) on 12 cells (4200's). This was the insain setup. It wanted to fly. I only took it out for a little squirt as i didnt want to flip the boat and get the motor wet if i flipped the hull.

The 1700kva nue is the same as a 10XL with RPM, but the 10XL can only push the 440 prop. 442 might be ok, but have not tried it. However the nue had the cells come in cool. Needed more prop or tweak up the pitch.

A better nue motor on the OBT would be 1515/1Y (2200kva) with a 442 prop to start with and 12cells.

When i raced 3.5 OBT's back in november i ran the following setup.

10XL

120mgm ESC (no cooling)

438 prop

16 3700's cells. (18months old)

I did a 1.50 time on the mile oval after 5 laps and i did a full corse mill. I went past the 3.5 tunnels. My goal is to get a 1.30 race time with my e-tunnel as this was the fastest 3.5tunnel record set in AUs to date. The 1515/1Y would be the motor to do this. The 2700kva nue is far to hot and would not make the race distance on the nitro oval. If i had brand new 4200's instead of the 3700's i might have got a 1.40 race time.

So if you can do a bit of math

1500m total race distance, 1minute.50seconds to do it in.

David

 

[topfuel443]

Hey David, very good info thanks!!

I am running the 1512/2D Ive been told this is also too hot of a set-up... what are your thoughts?

I have no idea how many/what kind of cells I was going to run, especially now after your report. I was thinking about running 16 cells...??

I have no clue? Any suggestions?

~James

 

[David Kingston]

A 1512/2D, Thats nuts.

Would be fast, but my guess is that you will pull over 100amps in a 12cell setup.

As we race on the mile oval here in Aus our setups are slightly different. That 1512 motor might work on the small electric oval. Id say it would be to hot, but i would still give it a go. If your hull is light and strong then run it. Props might be the only problem. Start with a x438, if you can get one smaller with a 3/16th bore then run that. The 1512 motor is smaller than the 1515 series and wont be able to take the heat like its bigger brother can. Run the boat loose to start and you should be ok.

16cells - just depends. Sub C - to heavy - no way.

16 2/3rds CP cells might be worth it if its just a sport boat.

12cells sub c will be very fast, and you wont kill the motor/cells/ESC

Make sure you have a good quality ESC and plugs. 5.5mm on everything would be worth it.

What hull have you got???

 

[andrewhendler]

Would the TS2 be a good electric tunnel boat

 

[David Kingston]

Would the TS2 be a good electric tunnel boat

Yes

It would need a few mods to make some extra water tight compartments.

I have only ever been around a TS2 for a weekend, nitro setup, and they seam to bounce a bit in the turns. Electric weight (cells) might help stop the bounce. But for sure the boat would be a fantastic hull for 12 cell/4s lipo electric OBT. Could even take more power

david

 

[topfuel443]

David, the hull is my villain.

I was thinking about the Barracuda 125...

I know im gonna have to swing a small blade, but even with that it should be quick.

So 12 cells definately?

~James

 

[David Kingston]

David, the hull is my villain.
I was thinking about the Barracuda 125...

I know im gonna have to swing a small blade, but even with that it should be quick.

So 12 cells definately?

~James

Yeah the villain is a great hull.

125 should be fine with the new programming.

12 cells and a small prop to start. Id check temps every minute. I dont know if the barra's have thermal shutdown.

It will scream.

I use to run a 8XL with a hacker 99. 12cells. Water cooled also. 440 prop was no problem.

Start with the 438, or if you have a old crappy 438 prop, cut it down to a 436. I think you should be ok, but you wont get much run time.

Have fun

 

[topfuel443]

Thanks for the info David, it really helped!

James "FE Newbie" Clegg

 

[Tim_Duggan]

James,

I was there when David ran his Villain against our nitro tunnels and it was very impressive (for the record, I DNF'ed in that heat).

The time he mentioned (1min 50) is what I ran at the same pond / course with a stock OS / Lynx / 1440 a month earlier - if that helps to give you an idea of the speed he was running at.

David,

Last time I checked a mile was 1609 metres. We DON'T run a mile course in AMPBA. Our course at Penrith is 1500 metres for 5 laps with 100metre straights. :lol:

Tim.

 

[David Kingston]

Tim,

A DNF, sitll the e-tunnel had a massive acceleration boost of the line. It was kinda funny as it was at full song before the nitro boats were at 3/4 throttle. How can i twist your arm into putting an electric OBT together.

I'd like to see some e-OBT racing in the future. Would be a top class. Id be happy to bolt on the electrics to that LYNX and give it a test.

Im bringing the Tunnel to BOTB next month.

It will have a run in the open electric class. Not really keen on racing it against boats that are not tunnels as if it gets hit by a 1/8th its going to be distroyed. Ive got another boat in the works for the open class. Just have to complete it.

David

 

[Tim_Duggan]

Tim,
A DNF, sitll the e-tunnel had a massive acceleration boost of the line. It was kinda funny as it was at full song before the nitro boats were at 3/4 throttle. How can i twist your arm into putting an electric OBT together.

I'd like to see some e-OBT racing in the future. Would be a top class. Id be happy to bolt on the electrics to that LYNX and give it a test.

Im bringing the Tunnel to BOTB next month.

It will have a run in the open electric class. Not really keen on racing it against boats that are not tunnels as if it gets hit by a 1/8th its going to be distroyed. Ive got another boat in the works for the open class. Just have to complete it.

David

Yes, your E-Villain sure was impressive for accelleration. I can understand the not wanting to get nailed by some bigger boats, but until the numbers are there it's just not feasible to have another separate class. From what I've seen you would be very competitive speed wise in Open now as long as you can keep it prop side down!

I'd like to see more e-OBT happenning also! I had a look at Kris' plans and thought I'd like to do that but then I got out to my workshop and realised I have too many projects to complete before starting another.....

Twisting my arm? What did you have in mind? I could be bribed into doing an e-OBT before I do the LSH I had planned on building one day :lol: :lol:

 

[Kris Flynn]

Hey Tim, I could be persuaded to Part with this tunnel for the right price LOL

I thought I would get this boat built up so i could TEST my equipment before it goes in the new boat (and the fct that the new boat is only a pair of sponsons at the moment).

INFO

16 Cell GP 3700's (Currently) soon to be IB 4200's

Barra 125 (hope it survives LOL)

Hacker 9XL (or 10XL if AMPS are too high with the 21 tunnel props i want to use)

Lawless outdrive counterbored so the motor mounts directly o the mounting plate the nitro's use

Hull is a Graupner Formel 1

https://www.intlwaters.com/gallery/albums/userp...mb_IMGP0220.JPG

https://www.intlwaters.com/gallery/albums/userp...mb_IMGP0221.JPG

https://www.intlwaters.com/gallery/albums/userp...mb_IMGP0222.JPG

 

[theringwah2002]

Hey David,

you are correct (or very close) re heat times of A/OB's in OZ. One thing you need to keep in mind is that that heat time was all that was required to win. There may be a few MPH in reserve on that Lynx and Shaman for that matter.

MJ

It may be fun in open water at BOB to line our boats up together.

 

[David Kingston]

MJ,

Your lynx is way faster than my electric tunnel.

Then again, my motor is $100 bucks. LOL.

Im not game to put a $400 electric motor on the back for racing, even if it is "HEAPS" faster. I would if i had some engine cowl which was water tight.

I'd still like to see how they compare to one another in open water. Im keen for that. (Kris, i may need to borrow some 4200 packs, dont think that 2 year old 3700's will be a good enough). It much prefer to run the boat with other OBT than in the open class with riggers and 1/8th's.

While i am thinking of it, has any one considered a GYRO with a servo to the OB leg for instant trim when it starts to blow off?

 

[theringwah2002]

David,

what do you think about my recent suggestion on the OZ thread re an "Open Outboard" class?

MJ