New Project: Electric Airboat

[Kmot]

Next project is an airboat. I bought this thing a few years ago. Tried a 540 car motor with an airplane prop and a battery. Melted the motor. Didn't know what the heck was wrong or what I was doing so I put it aside.

Now I want to get it going. I tried a Traxxas Titan 12-turn motor and it made some strong airflow on that same prop and it didn't melt the motor. So that is what I am going with for now. I will also be using an Mtroniks Tempo esc I have.

The thing is very flimsy around the propeller ring and rudder. One rollover and it would all be busted. So I have added some carbon fiber strips to the rudder and firmed it up. I have epoxied two layers of fiberglass inside the prop ring. I think I will have to do a couple more layers to get it as rigid as I want.

The airboat came with a solid metal rod that has a z-bend but I am going to scrap that and use a Nyrod instead.

I know just a teeny weeny tiny little bit about electric motors and airplane props so I am open to suggestions about a propeller for the Titan motor.

[MILLERTIME]

Nice looking airboat Tom can't wait to see it on the water.
One of these days I’ m going to build a electric airboat.

[ggcrandall1]

If this was an airplane I would first determine the max voltage and current for the motor. I searched all over the Internet and could not find those numbers for this motor.

What voltage are you going to be using?

What is the current rating of the ESC?

What is the diameter of the prop that will fit in the shroud?

Do you have the means to measure current? You should have a watt meter to measure current and voltage.

Glen

[retoabcr]

Get hold of Harold Mcnett of Cajun Airboats . Go google for rc airboats! He's a real gem of a person!

[Kmot]

Glen, I can measure current and I will do so. I intended to run a 6-cell NiMh pack at 7.2V (8V fresh off charge) but I have a 2S lipo I could run as well. Max prop diameter looks to be 10", and currently there is an APC 9x4 turned around as a pusher. It is not a lekky prop so I intend to buy a proper electric propeller. The esc is rated 80A continuous, 210A peak.

On a regular boat, I have measured the current of the Titan 12 out of the water. Inrush current was 9A and continuous WOT was 6A.

[Shaun Hendricks]

9x4 is too large for a short can 500 motor to direct drive unless it has over 27 turns. Most 540's are under 20 turns some down as low as 6 turns which would melt trying to put the RPM's they want on a load like that.

The Titan, IIRC, is a long can 600 series motor. It will probably have a chance at spinning that prop decently but it will still be a stress even on that motor so you'll be pulling some significant amps there if that "12" means 12 turn, probably around 20-30. If you can give me the exact motor specs, I can plug them into my MotoCalc and let you know what the performance parameters will be.

To really turn that prop I'd suggest a brushless outrunner. It would weigh a fraction of the Titan's mass, be more energy efficient and move that airboat like a skipping stone. Of course, the tradeoff is you PAY for it. While they are relatively inexpensive compared to an inrunner brushless, they cost three times what that Titan does and the ESC... well, you're over 100 clams.

So, here's the question, what performance level are you attempting to achieve?

New world airboat record or cool putter around the pond? :D

[ggcrandall1]

Glen, I can measure current and I will do so. I intended to run a 6-cell NiMh pack at 7.2V (8V fresh off charge) but I have a 2S lipo I could run as well. Max prop diameter looks to be 10", and currently there is an APC 9x4 turned around as a pusher. It is not a lekky prop so I intend to buy a proper electric propeller. The esc is rated 80A continuous, 210A peak.

On a regular boat, I have measured the current of the Titan 12 out of the water. Inrush current was 9A and continuous WOT was 6A.

6 amp out of the water doesn't mean much. I expect you would be pulling 20 amp or so with a 9x4 prop in the air. I think that might be a bit much for that motor. Hard to tell without knowing the exact specs for the motor. Try a smaller prop, maybe an 8x4 and check the motor current and temperature.

Glen

[Kmot]

The motor pulls 28A with a 6-cell 4200 NiMh and the APC 9x4 prop.

[Kmot]

So, here's the question, what performance level are you attempting to achieve?

New world airboat record or cool putter around the pond? :D
Cool putter around the pond with a little bit of get up and go. ;)

[avidjeepr]

Cool putter around the pond with a little bit of get up and go. ;)


When will it be ready to go?

[Kmot]

Before your Alligator Air Tours shows up! :p

[avidjeepr]

Before your Alligator Air Tours shows up! :p


July 31st. And waiting.. ;)

[Shaun Hendricks]

Okay Kmot, here's an ultimate recommendation:

Motor: Hyperion 1919-06 (http://www.allerc.com/product_info.php?cPath=7_76_77&products_id=2913)
Performance data on similar prop-
Propeller Size___Lipo Cell___Voltage___Current___Watts___RPM
APC 9×4.5 E........2S...........7.08.........15.7.........11 1......8220

If you want to go 3S (11.1v) you need to up it a notch size wise-

Motor: Hyperion 2209-32 (http://www.allerc.com/product_info.php?cPath=7_76_77&products_id=1588)
Performance data on similar prop-
Prop_____Volts___Amps___RPM___Watts In
9x4.7 SF...7.7........6.2......6060......48
9x4.7 SF...11........10.1.....7860......111

You'll notice that the second motor on 3s doesn't get the same performance as the first on 2S even though the watts are the same. That shows that the motor is being underpropped.

So the first is really the best motor for the application and you can get away with standard 6 cell battery packs to drive it. It will run far cooler than your Titan and the pack will last much longer since it draws under 2/3rds the amps of the Titan.

I think you'll find speed performance is about the same as the Titan on the water.

I switched my Easystar running a 6x4 3 blade prop from a Cobalt 400 to a small outrunner like this and my speed was the same, my flight time went from 10 minutes to over 30 mintues at WOT. It was quieter and the motor never got hot while the cobalt was almost too hot.

I think that Titan is probably being pushed a bit too hard by that prop since it's chewing up 28amps.

[Shaun Hendricks]

If you switched up to this propeller MAS 9x7 3 blade (http://masterairscrew.com/9x73-bladeseriespropellerpusher.aspx) I would suggest the second motor I listed. It would be a speed boost due to the change from 4 pitch to 7 pitch and your RPM's would likely not drop much. The third blade would increase static thrust for maneuvering and "out of the hole" performance while dipping top speed an almost unnoticeable amount for an airboat.

I'd have to motocalc it but it might work better to increase pitch. The Titan would probably fry trying to spin that prop though. I'll crunch the numbers and let you know.

[Kmot]

Thanks a lot Shaun for doing all that calculating work. However, I do not plan to spend any money and I will use what I have on hand. :)

[Kmot]

So I have now added the third layer of fiberglass cloth and resin into the prop ring. It was stiffer than I thought it would be with only the first two layers so this third layer should do it.

I applied some primer to the rudder.

[Shaun Hendricks]

I totally understand. I'm just a little concerned about burning up a nice 12 turn 550 motor.

If you down propped to an 8x4 it would take some stress off the motor without much performance loss since the motor is being pressed pretty hard anyway. In fact you might pick up some speed. An inexpensive GWS 8x4 is around $2 and change.

[Kmot]

I have ordered a couple electric props in the 8x4 size, and also a couple prop adapters in 4mm and 5mm shaft sizes. I have several brushed motors I can try, and some of them required the larger adapter. I will find something that works, and won't burn things up. Hopefully. :p

[retoabcr]

How about a magnetic mayhem from OSE on 7.4 lipo. I tried it in a UFO with a 632 -lipo-7.4-3850 and it was a eye opener. Now it was no speed demon but it really moved. BTW, lenght of your airboat.

[Kmot]

Okay, I am a complete retard. :rolleyes:

The prop is not a 9x4. I tried reading the number on it when it was attached to the prop driver and what I did was read it upside down. It is actually a 7x6. :o

I found out because I removed it to try some other props. Long story, not worth elaborating.

So I have another motor, and it is new and never used. It is a Great Planes "Great Fire" and it comes with a prop driver and must have been sold as an electric airplane motor. I tried the same APC prop (now known it is 7x6) and the amps dropped to 17A. But not as much thrust I don't think. I have tried to Google for info on this motor and can find nothing.

[Kmot]

Alright, I found some info. The motor is called Goldfire (what is wrong with me lately?) and it has been renamed to the Electrifly S-600. I found a chart on the Goldfire:

http://homepages.paradise.net.nz/bhabbott/Goldfire.html

[Kmot]

retoabcr: 24.5" long, 8" beam at the front, 10" beam at the rear.

[retoabcr]

Kmot. thank you for the reply! Good luck on the GP-600!

[Kmot]

The prop ring is finished with the reinforcing. It is a lot more rigid than it started out. I am confident it will be plenty strong enough.

The inside where I fiberglassed is not pretty. I need to learn a lot about fiberglassing. But no matter, it will do the job.

Now I can move forward and assemble the airboat again, set up the steering servo and control linkage, and position the ESC and RX where I want it.

After that I will disassemble the model again for a paint job.

[Kmot]

Wow! I am pretty happy with it so far!

I just put it together real quick, and without a steering servo. I just turned the rudder a bit so it would go in a circle and put it into the pool. It gets up and goes quite nicely! :)

I first tried it on my dry crappy grass and it would not budge and I was like "uh oh..." But in the water it was a whole different story. I think it's going to work out just fine. :D

[MILLERTIME]

[QUOTE=Kmot]Okay, I am a complete retard. :rolleyes: QUOTE]

We knew that!!
Join the club.
We ride the little bus.

[Reckless]

really really interested in this ... I've been thinking that I need to get my air boat back out on the water/grass/pavement

looking at what Kmot has had to do though I'm really thinking I'm gonna need a bigger motor!

http://i56.photobucket.com/albums/g179/Rallytercel/my%20toys/HQ3.jpg

built this thing 14 years ago... other then the lettering and the speed motor decals.. the rest is all airbrushed... its a Puddle Jumper... sterling kit if I remeber correctly... it saw water ONCE... and I found out the wheel wells leaked.. ofcourse way under the deck behind bulkheads that were sealed... at the time I had no way/knowledge of how to seal it up without wrecking the model so it was shelved.

thinkin I might take Kmots build as some inspiration and refit this wonderful lil boat

[retoabcr]

That's a beautiful airboat, looks like it just came off the production line!

[Kmot]

Reckless: That is fantastic! Gorgeous! Do it, get it going again! :)

Since my grass was wet from the sprinklers this morning I tried again. It wanted to budge, but couldn't. I gave it a little nudge with the prop running full power and it took off across the backyard! :D

[retoabcr]

Gentlemen; a website to look at. alex-tretter.magix.net Airboats made of foam with a 3 step bottom and beveled alittle. He's a guru in Europe!

[Reckless]

thanks guys :D

unfortunately there is a little damage to the cabin.. if you close at the picture you can see the rather un even HOLE . but after that happened I kinda looked at it and decided that would be a good spot for the cooling fins of the speed control :D

heres a question for you guys though.... think that speed 400 (atleast I think it's a 400) is gonna nuke a 30 amp Futaba speed controller trying to get the boat moving?

cause I've got all the elec parts already to get it operational... but the old plastic hinges for the rudder have dried up and snapped :( and how to get the wheel well sealed up properly without destroying the boat :( .. ofcourse I have considered just removing the wheels and sealing up the wells and just using some extra stick on skids from pieces I've kept from Storm launchers ;)

[Reckless]

yeah it's a early 90's Graupner "Speed 400 Race" looks like it's top rating is 8.4V . prop is 6x4 labeled Thimble Drome ... I don't remeber much about it except it was like $45 and it's some compsite something or other and the other 2 flimsy props I had for testing and breaking in the .049 IC that was originally on it were like $6 each

as for weight... the 7.2 3300 batt pack weighs more then the boat does with only the motor on it ... it's about 7.5 inchs wide.. and about 14 inchs long

runs aircraft wheels on the bottom in a taildragger setup.. the rear wheel is connected to the air rudder. thinking I might make a bit of a fairing for the rear wheel to make it a little less drag in the water more like a pontoon/water rudder too

got 2 wire skids on the back bottom corners I'm sorta considering extending a little with some balsa almost like a pair of mini keels to help with water stability at speed

I think I'll keep the wheels.. I've got a couple small syringes for my 5 min epoxy (west sys G5) I'll just cut out the inner bulkheads with the dremel and fill in around the wells/axles :D

I'm still a hair worried about the speed 400 pulling too much amperage but I remeber talking with the guy at the LHS moons and moons ago and he said it was more powerfull then the .049 and should do alright ... blah I guess only one way to find out :D

[Kmot]

I would remove the wheels and plug the holes and seal them. Then just use it as an airboat on water and wet grass.

I don't think a Speed 400 can even pull 30 amps?

As for that nylon prop, boil it in water to prevent it from shattering. They are notorious for that and need to be boiled on a regular basis, not just once.

[Kmot]

Nice website retoabcr, thanks for posting the link.

[Kmot]

Okay, the airboat is complete, and tested in the pool. Woot! :D

It runs really well and actually pretty fast if I hold the throttle open. But it skids in a turn so it is kind of risky in my cement walled pool.

I did do some crazy donuts and apparently that got water up the transom and rear deck, and from there it got into the radio box. So the Rx got wet and shorted out. I will have to think of something to fix that.

But, I am very pleased with the results. Now it's time to take it apart again for a paint job! :cool:

[Reckless]

I would remove the wheels and plug the holes and seal them. Then just use it as an airboat on water and wet grass.

I don't think a Speed 400 can even pull 30 amps?

As for that nylon prop, boil it in water to prevent it from shattering. They are notorious for that and need to be boiled on a regular basis, not just once.


yeah .. I've been thinking about it myself... I would break down crying if it tipped and scratched running it on pavement (purpose of the wheels) and loosing the wheels would give it way less drag inthe water.

now heres a couple questions... should I keep the wire bit the rear wheel is on and make it a rudder? or just take the whole deal out and rely on the 'stock' air rudder

how long and how often should I make my Wifey scream and boil that Nylon prop?

and yeah I agree that 400 might not beable to pull 30 amps... but I don't wanna see it TRY either :(

dangit.. as if I didn't have enough projects already! heh...

can't wait to see yours painted and "done" Kmot :D

[Kmot]

how long and how often should I make my Wifey scream and boil that Nylon prop?



Have a look Here (http://www.rcuniverse.com/forum/m_7270339/tm.htm)

[Kmot]

I have the first color laid down. :D

[charlie eaton]

Tom,do you think that's red enough?? You should have good luck with the S-600 motor. I've had very good luck with the Electrifly HT-600 and they're inexpensive.

[Kmot]

Thanks Charlie, that is good to know.

[Reckless]

ooiiyy!

guess I'm looking for a different prop... as much as I want to keep the "vintage" of my airboat... I really don't like the idea of the prop exploding and hurting it :( I'm not exactly sure mines Nylon it might be one of the Fiberglass composites ... but I really don't wanna take the chance.. so I'll keep it for display and nastalgia and just order another prop


Kmot... thats... RED .. like I think I can cook a steak over that RED ... nice :D... paint more! now! post! go go go !

:D

[Kmot]

LOL... it has to dry overnight then I pull the masking tape off. I will be painting the other parts a contrasting color and then pin striping it.

[Kmot]

To paraphrase toesup:

Kmot Boat Werkes - Airboat Division

LOL... :p

Okay, got some more painting and pin striping done today. The hull has been striped along the demarcation line between the deck and the hull. The radio hatch has been striped around the perimeter. And the rudder has been striped along the carbon fiber reinforcement strips. I also have reinstalled the motor mount. The prop ring is drying after its second coat of paint. The Nyrod tube popped loose from the epoxy glue due to my not removing the masking tape properly. :rolleyes:

[Kmot]

I may have found another motor to use. It is an Astroflight 05 Cobalt, 7T. On the same prop and battery, it pulled 17 amps. However, this was on lousy wiring and if rewired with larger gauge will probably make slightly more power. Since I was in my shop, I grabbed my tach and it read 10020 rpm.

What do you think?

[Kmot]

The paint scheme is more or less finished. Unless I think of something else. Sadly, I thought the black paint on the prop ring was fully cured when I started to apply the pinstripe. Oh well, you can only see the fingerprints when you are close.... :rolleyes:

[Mule One]

WoW! That is cool! Also a very quick job. :cool: :D

Richard

[dostacos]

are you bringing it out Thursday?????

[Kmot]

Yes I am Dan.

[Reckless]

woot! can't wait for the action shots that looks really spiffy!

wheels are removed and wells filled on the puddle jumper. should have the rudder fixed this week and the cabin attachment figured out . and going to a modeler friends place to get a bunch of connections soldered up (my Iron blows! need a new one :( )

I just might have my airboat on the water next weekend too!

thanks for the reinspiration Kmot ;)

[Kmot]

Very cool! It will be fun to see action shots of yours too! :)

[Shaun Hendricks]

It looks really smart Tom. Great job!

[Kmot]

Thanks Shaun! What do you think about that Astro motor?

[pkboo]

Mot, does the transorb make a noticable difference? Doesn't it "disturb" the ESC? Thanx, Boo

[Kmot]

transorb

I do not know this word?

[pkboo]

The diode, at least that's how David Harrison calls them! I've always had some kind of fright to install them cause they cross poles. Boo

[green-boat]

Transorb..... that's a new one on me.

Using a diode across the motor terminals will reduce the amount of RFI generated by the motor in a FORWARD ONLY application. In otherwords, don't use a diode if you are using a reversable ESC.

[Kmot]

Yes, a Schottky Diode is used with a Forward Only esc to prevent back emf from going through the esc and damaging it when the motor is spinning on it's own (after releasing the throttle).

Capacitors are installed on the motor to reduce the RFI.

[Kmot]

I just did a comparison test between the Astroflight 05 Cobalt 7T motor and the Goldfire 550 motor.

Used two freshly charged 4200 NiMh battery packs, hot off the charger. One for each motor. However, one battery had slightly more charge to it.

The Astro turned more RPM and used more amps. But it produced less watts. I don't know what that means. But I do know more RPM equals more thrust and speed.

This was with the same APC 7x6 pusher prop I have used all along.

Astroflight 05 Cobalt 7T:

RPM: 11790

Battery Surface Voltage: 8.37V

Minimum Voltage Under Load: 6.93V

Amps Under Load: 23A

Watts Peak: 173W

Goldfire 550:

RPM: 11130

Battery Surface Voltage: 8.65V

Minimum Voltage Under Load: 7.12V

Amps Under Load: 21A

Watts Peak: 228W

Since the Astro turns more rpm on the same battery and around the same amps I am going to use it instead of the Goldfire (for now).

[Shaun Hendricks]

The voltage drop you are seeing is in direct relation to the amps. You're pulling more current so it soak the voltage down more.

Basically, the motors are comperable. The Goldfire is probably working a bit harder (cobalts have always been more amp hungry than non-cobalts but return more work for the amps- which is what you are seeing) than the Astro. I'm also assuming these are 'static' load tests, meaning the boat isn't moving when doing them.

When the motors unwind due to moving, the Goldfire will probably get even more amps back for you so you'll have a longer run time, but the Astro would probably be better at running a course than the Goldfire would be since it would bring the prop back up to speed faster in cornering and such.

If I were racing and had these two motors to choose from, I'd pick the Astro. For kicking around, the Goldfire works well.

Neither motor should be propped much higher than the 7x6 you are using. Both are pretty well loaded at 20amps+. You might get better performance out of an 8x5 though. You'd have to test it out. At some point, the boat just can't do what the prop pitch is asking for and you're essentially running in an inefficient 'stalled' state. The air equivalent of cavitation.

PS: An illustration of this using your numbers. According to the RPM vs Pitch, your airboat should be doing about 66mph if the boat were frictionless. It's not so real world, you probably won't see much difference in top speed but you likely will in maneuvering 'quickness' but even then, it probably won't be significant.

[Kmot]

Thanks Shaun!

I finished installing the components back into the boat. The Rx is now in a balloon. I had to drill a couple of air holes in the motor mount for the Astro.

Lastly, I decided to wax the boat for some portrait photos. I was shocked when the Super Glaze brand wax actually dulled the paint! :censored: Sometimes you just can't win........ :rolleyes:

Anyway, sea trials on Thursday.

[gpzy]

That airboat looks sweet!!! Hopefully I will be there with camera in hand. Plus I have never seen a model airboat in person, and if it is anything like a real one we better have video cameras ready also!!

Manny

[Shaun Hendricks]

That is an awesome looking airboat. A nice aluminum spinner would look great on the hub of that prop!

Fantastic job Tom.

[Kmot]

Thanks guys! :)

I took some video of a short test in my backyard:

http://www.rcgroups.com/forums/showthread.php?t=897358#post10191732

[green-boat]

Tom,

You should put down a piece of cardboard from the pool to the grass, cover the concrete. Then you could run from the grass right into the pool and back. :D

[Reckless]

nah.. needs a set of wheels... I just happen to recently come across a set of 3 if you want em Kmot... heh

as for action shots Kmot... I'll see if I can get someone to hold my camera when I get it out of the lake... we had some interesting chop on the lake on the weekend was thinking how interesting it would have been for the airboat (maybe some jump photos?)

[MILLERTIME]

Very good close up pictures Tom.

[Mule One]

I just did a comparison test between the Astroflight 05 Cobalt 7T motor and the Goldfire 550 motor....

Kmot~
How did you get all of that test data?

Is there a thread I should look at?

Cool boat!

Thanks, Richard

[Kmot]

I use a Watts Up meter:

http://www.powerwerx.com/product.asp?ProdID=3809

[pkboo]

Transorb..... that's a new one on me.

Using a diode across the motor terminals will reduce the amount of RFI generated by the motor in a FORWARD ONLY application. In otherwords, don't use a diode if you are using a reversable ESC.
Thank you GB, that´s what I was afraid off, I don´t remember seeing that warning in the article!

[Mule One]

Thank you. Looks like a required tool for the bench.

[Kmot]

Mule One: It is small enough and light enough that you can connect it to your boat system and then run the boat and see what is happening while under load on the water. That is what I use it for all the time.

[Mule One]

Oh, wow! That's even better. I think I understand now.
Those numbers were actual during an on the water run. :eek:

They weren't just a stationary bench test.
Sounds like I need to get a Watt's Up meter to understand how every thing is working together.

BTW, I'm really impressed with the quickness and quality of the builds that you do. :D :cool:
Thanks again, Richard

[Kmot]

No, the numbers I posted were indeed on the bench. A static test, if you will. But yes, I use my Watts Up meter onboard running boats so that I can learn how many amps the motor is drawing while running on the water.

[Kmot]

The airboat has been tested in open waters at the lake. It ran very well and had a good long run time on the 4200 NiMh battery.

In the future I will be experimenting with a coule of different motors I have, once I get the prop hub adapters from Atlanta Hobby.

http://wavelit.com/media/927/Electric_Airboat/

[Hoghappy]

Ya done good! :cool:

She looks pretty fast in the video too. Now you need a driver and some grassy swampy place to really test her! :p

Capt. Crash

[Kmot]

Thanks Robert! I would love to run this in a swampy area. But in So Cal that is a hard place to find! :p

[Shaun Hendricks]

There are plenty of swampy areas, however the 'environmentalists' have all had them declared National/State wetlands, estuary's and sancutary's for the hobble nosed snail and such.

Your only swamp is going to be soaking your grass to saturation and running it around on that! LOL!

(If you think I jest, they succeeded in having a man made drainage ditch declared a 'wetland' here to prevent someone from building a store next to it.)

[charlie eaton]

OK,OK,He says as he bows his heard down and stares at the floor, Ya done good Tom ,He says at last :p :D :D :D

[Kmot]

Thank you Charlie :)

[retoabcr]

Kmot, you did an excellent job with the airboat, looks great.!

[Reckless]

woot! very nice Kmot... I got almost all my electrical connections done on the 'jumper .. gonna try and get the last bit of placement building and such, MIGHT make a maiden on Sunday *crosses fingers*

[Tony Oliver]

Was it only last September we were talking about airboats? Your input was invaluable then, thanks. Mine's been a success so far, but only in near calm water for the reasons we spoke of then.

It normally takes me a year or so to get startedon a new project, but you've done it in a lot less. Nice looking boat, and a lot more refined than mine (not surprising).

I am about to modify mine yet again with a much smaller(and lighter) brushless with equivalent power, to get the centre of gravity right down to deck level or lower. It should end up with the same weight or lighter overall. Maybe ditch the cage too for the same reason.

I'll post a pic or so when done-and-run. (or maybe a sketch?)

[Kmot]

Thanks fella's! :)

Tony, nice to see you drop in again!

[Reckless]

It... is.... ALIVE! ...... :D :D


Kmot just checked out the vid, looks fantastic!...might be a little slow to what your used too ;) I hope mine runs at speeds like that though.... hopefully I find out tommorow :D

[Kmot]

Thanks Reckless! As for speed, not really. I putt around my Bristol Bay at around 2 knots all day long and enjoy it thoroughly. Different equipment for different purposes. ;)

[MILLERTIME]

Ya done good! :cool:

She looks pretty fast in the video too. Now you need a driver and some grassy swampy place to really test her! :p

Capt. Crash

Dostacos told me to get a GI JOE because Barbie dosn't come with Ken.

[Kmot]

http://static.rcgroups.com/forums/images/smilies/biggrin.gif

[Kmot]

I received some prop adapters I had ordered and a couple new props. I wanted to test two motors I have for potential use in my airboat. I am currently using a 7x6 APC pusher and thought I would try an 8x4, only they are not pushers. So I adjusted the timing on the motors to run at peak rpm in reverse and I put the props on backwards to make them act like pushers.

Man, what a difference an inch makes on an electric motor. I tested an 05 Cobalt 5 turn and it pulled 60 amps and only 8200 rpm! And literally 'smoking hot'. This was fully advanced in 'reverse'. When I readjusted the motor to neutral timing and put the prop on forwards, it dropped down to a more reasonable 27 amps and about the same rpm.

The next motor was a VM 24/16 also fully advanced in reverse. It pulled 10100 rpm and 38 amps. Much more reasonable. So, being what I am, I next tried it on 12 cells. :D Uh, that was a mistake! Smoking hot is an understatement! I think it was around 78 amps but the wires were so darn hot while I was trying to pull off the battery I did not pay much attention to my Watts Up meter. Again after everything cooled off I reset the timing to neutral, put the prop on forward and it pulled a nice 9600 rpm at 28 amps.

The Astroflight 05 Cobalt 7 turn is still king. Although I cannot make a direct comparison because the prop on it is a 7x6, I figured an 8x4 and a 7x6 must be reasonably close in load. And the Astro turns 11160 rpm and 27 amps. I can't compare props because I had to ream them to different shaft diameters on the different motors.

[Reckless]

the puddle jumper was finally maidened.... and the report is as follows...

the engine is too weak (gets going a decent clip but won't 'plane' )

the rudder is WAY too small and doesn't have enough throw .. I can't trim out the torque of the motor and still have enough to turn so driving is really weird

the cockpit/elec cover has a small issue of keeping water on the outside.. especially with said water comming over the bow and such.

so ... I think I have 2 things which I shall work on ...

1 get the battery farther towards the stern which should atleast help with the above issues .. and

2 work on completely new rudder system.. probably a twin setup that pivot in their middle ... which I should be able to do without hurting the paint or original model (The original painter was my father and we lost him a few years ago.. I can't match/fix any paint damage :( )

anyways ... pictures as I 'promised' :D unfortunately once I finally had someone to take some action shot for me... the battery went on it's fast downward spiral to empty land.

http://i56.photobucket.com/albums/g179/Rallytercel/HQ1-3.jpg

http://i56.photobucket.com/albums/g179/Rallytercel/HQ2-3.jpg

http://i56.photobucket.com/albums/g179/Rallytercel/HQ0-3.jpg

[Kmot]

Well, congratulations on your maiden voyage! :)

If I may make a suggestion? It appears from the photo that your prop is angled upward slightly. This will cause the bow to plow into the water more. I would try to get the propshaft parallel with the hull. Or even slightly pointing down which would bring the nose of the bow up.

[Reckless]

the prop guard is angled back.. the motor not so much.. but it is a little angled up... I'll see if I can move it a little.. theres not a whole lot of clearance in the prop guard

on the good good side... several of the club members said I (we) need to make a few more simple airboats and have races ... try and attract some younger blood ...

[Shaun Hendricks]

Yup, noticed the thrust angle as well. The boat is trying to pull its nose into the water.

It's a good looking airboat! Sorry to hear about your father, it's a neat paint job. He was talented!

Most airboats also have very little gap between the rudders and the prop. This might be affecting your steering. If you move those duals you're planning on up behing the prop you'll probably get better steering.

Other than those two things I think you have a winner there!

[Reckless]

so heres the question... tweak the motor angle only first? and try it? or should I move the battery back too? on the 4200 packs I get 15 mins if I can get the bow outta the water I should get lots longer cause the motor won't be constantly working as it plows. while not super agile right now .. if I can get it to plane on the rearward part of the hull the rudder should work better till I can get the new twins made

[Kmot]

One step at a time is the best way to make changes. Try the thrust adjustment firts. ;)

[boatman]

A few of my eletric airboat projects :D

[gpzy]

A few of my eletric airboat projects :D
Did you build the Cajun electric from plans or kit.
Saw a nice yellow airboat on the cajun website. But no kit in production.

Manny

[boatman]

Mr Cajungator and i actually design and built the first eletric from scratch
I believe the yellow boat was a scaled down version of his Cajundragon series
to run as a eletric

Sorry i know mine is a one off protype and i'm not sure if he built anymore
of the his eletric versions but i have seen it run and was a decent runner

[Kmot]

Cool! :)

[GlynnG]

Heres a couple of photos of my airboat. Nothing more than a balsa box about 15 inches long, 6 1/2 inches wide. Designed to look a little like the full sized boats with a driver carved from foam.
A single SPEED 400 motor powered by 6-7 rechargable AA cells gives the model a respectable, sometimes frightening, speed. But, with so little of the hull in contact with the water, turns are more like slides but still safe. Even when the corner of the hull "digs in" it never has rolled over, just quickly stops!
It cannot be steered astern, no surprise there, but reverse is handy for getting out of trouble.
A successful crossover between my hobbies of RC electric flight and model boating, i.e. maximum fun/cost ratio.
Published in UK "Model Boats" magazine Sept 2007
Glynn

[retoabcr]

That should be put up on the mantel. That is a piece of workmanship. My hats off to you!!----------- Model boat 2007--airboat --is that MMI mag. I have 3 more issues left and that's it , all advertising. The yellow airboat is no slouch either. I have 3 airboat but built like 19" by 10 1/2" and 05/540 motors on 6 cells and a pusher 7 x 6.