Airboat for small electrics

[Tony Oliver]

Two week ago I bought the September edition of Model Boats magazine. In it is a free plan of Skimmer - an airboat designed by Glynn Guest who is a prolific designer of model boats. The design is for simple radio and a 400 size motor.

I used a HiTec 5ch micro rx, 20amp aircraft controller and a 7cell 1500mah NiMh battery. Prop is a Gunther - what else? All run perfectly well under water (see later).

I liked the idea of this particular model as I used to operate free-running airscrew driven hydroplanes as a schoolboy in the 1950s. These were usually 1cc ED Bee diesel powered and were very skittish to trim but extremely stable.

After 2 days of cutting, glueing, bending, soldering and painting it was done. As usual I didn't stick exactly to the original, but made it slightly smaller than the 15" x 6.5". The model turned out at 12.5" x 5.75"

First runs were an hour ago! It 'goes' like the proverbial off a shovel! It's got too much rudder movement and the CG was too far back. After a short while at tickover up to 1/3 throttle and steering around to get the feel of it, I tried a half throttle run and tried reasonably successfully to trim it and keep it in a straight line. Any slight turn on the rudder yawed it but the direction stayed the same. Hmmmmm! It was up and planing with no apparent effort and scattered the ducks who are not used to anything very quick.

As it was porpoising at speed (slight ripple on the water) I moved the battery forward a half inch and tried again. This time the slapping was reduced but the tendency was for the bow to duck under - a bit sensitive to CG this model. Maybe I should have built it a bit larger? I halved the battery movement and tried again. This time it was OK but a turn at low throttle caused it to dig-in and it turned over about 30 ft out on the water. Although not waterproof in that position, I found the prop very efficient at low revs in the water and the rudder still operated so brought it back in (rudder reversed of course). As this was a quick trial, the tx battery was low and the voltage warning started so I came home to think about it.

It leans out of the turn even at high speed which means it needs very careful wide turns at speed if I am to avoid turning it over.(The designer warned of this)

It looks like being a fun model but very easy and quick to build. I now need to finish the details on it and waterproof the hatch.

I also think some reduction of rudder throw will be needed - again, I exceeded the designed amount so it was my own fault.

Anyone got any suggestions on improvements? The early free runners all had a shallow Vee hull and never had the rollover problem so I think a more elaborate design may be more able to cope with my ham-fisted style.

I still like the looks of this model though. Two pre-run pics to give an idea of it. None when running yet, as I was the only one there at the time.

Final thought for the moment - RTFI and stick to them!

[Kmot]

Aarrgghh!!

[Tony Oliver]

I understand! :o

[retoabcr]

Good looking airboat. The cg should be close to 30% with the components spred out across the inside interior for balance. I made one about same size and rolled over in 1" waves. The motor should be aimed to the right about 5/16" and down about 1/4". The prop , get a 7 x 6 pusher prop and make sure you aren't top heavy. I saw an airboat with trim tabs on outer edge of transom and flush with bottom of boat. There is a airboat site on Offshores site and get their comments. To me it looks great, my compliments! Rereading that you have a micro servo, ditch it cause they strip gears and went to a 3001 fub. but i run a 9 volt battery with no bec usage. Now if you add weight, do it but on a trial and error basis. Now for straight line stuff takes trial and error too but they are alot of fun at any age. Rereading again, you may have to cut some lenght off the rudder, how much do a trial and error by 1/4" starting with the part of rudder that is closest to prop. Taper this end of rudder to a point for even flow of air so you can get it to run straight. Now if you use small 2aa batteries in a group of 4 gives you 6 volts which is plenty big for a micro servo and a 9 volt will destroy a micro servo if you go that route. Been there, done that. My last airboat is 19" x 11" with a 550 johnson motor on 6 cells! Hope this helps you. Good luck! Forgot, cg , have transom down 3/8" in water with bow flush. www.cajungatorairboats.com

[boatman]

Looks good but with a hull that small & all the stuff above deck
it will be top heavy & very touchy to balance it all out

heres a few pics of the eletrics i have built or worked on

[Tony Oliver]

Thanks for the advice. I seem to be heading that way. I've removed the 'driver' from his seat and am making a foam replacement. That should lower the CG a little. The servo will not be a problem as it's metal geared. It's the receiver that 's the micro so no problem there. I use the BEC as it's good for 2amps and I'll get nowhere near that on a 7cell and only one servo. Flat out, the motor isn't reaching 10amps yet, but the straight line performance is beyond what I expected. It's also quite easy to keep in a straight line too. Turning? That's something I've got to get used to, but it ain't easy to avoid all the birdlife!

Today's runs show it steers OK at speed but when not planing it seems to feel happier inverted. So I halved the rudder movement and used rates to cut that to 50% and it still seems a bit too touchy at low speed so the advice to reduce rudder area is spot on! If I try to push the model over, it needs to be about 45 degrees of list when at rest, so it's the thrust that does the damage.

I hadn't thought of spreading the servo/rx/battery around to help with stability, but that's how I ended up with it before trying the model out the first time anyway. Nice to know for future models though. It's still slapping the waves so there's scope for moving the cg a bit further forward, but I'll keep that for some calm day.

A larger prop will not fit but I will be trying a 3-blader which will do two things - the diameter will be smaller so I can lower the motor to aid stability; and the thrustline will be lower, although a temporary packing to try out the differences has to be tried first with the current prop to check the effect. It might also lower the current draw for a more extended run. Not that I've flattened the battery yet.

All great suggestions and very helpful. Thanks.

I forgot to say that the whole thing, ready to go, weighs 20oz with the heaviest battery.

More after the next runs. - and some pics of it running I hope.

[SFGuy]

I agree with the other guy, to much stuff above the deck will cause you problems. I kept my boat simple and just have the motor above the deck and it works real well.

[retoabcr]

The owner of a airboat site called( self inflicted ) did like you said by making bottom of airboat beveled up about an inch whic for me gives me a headache at my age on how to do it. Cajun has free plans on his site and also builds electric airboats and his quality is beyound reproach. From all my reading , a 20" by 11" is a very good size for electric with a 550 motor. The first one i made was 17" x 10" with a 05-540 motor on 6 cells and it ran great but getting it to run straight, no. I didn't spent enough time with it cause i have several 22" monos in the works at the time. I still have the airboat, going nowhere. How about having your driver lay flat near the bow tied down like spiderman or some other character. When you spread your equipment around, mine would flip and i tried. I used 1/8" light ply with white styrene and was only 2" high. If i knew how to post pictures , i would post mine. TTYL . You could put a wing on each side about half way and just above waterline at wideopen throttle.

[Tony Oliver]

I'm sure you are all right, but the object of the thing was a scale look for a general runabout. As usual it's going to end up a compromise between what works best and what I expected from it. I didn't want a larger or high speed boat so I used the 400. It does, as you suggest, restrict things - it's relatively small, needs fairly calm water and will need some careful work to make it safe enough to operate on our small lake. Luckily, recovery isn't too much of a problem so there's scope for playing around to get it right.

All these suggestions will be taken on-board (sorry about the pun). I realise there's a whole lot of info coming which will be a lot of use to me and others who are starting out with airboats. It will be invaluable having your experiences to draw on.

Great stuff. Thanks!

I really like the idea of the side wings and coincidentally with these replies I got an email suggesting exactly that, so for the future I will probably go that way.

retoabcr - Posting pictures is easy - click on Go Advanced (below the quick reply box) > Additional Options > Manage attachments - take it from there. It's more flexible now in the size and format you can use. I make my pics around 900 pixels wide and the file size up to 100kb which makes it quick to send. If you want to try it out first, there's a Trial forum down near the bottom of the list. We all started there and made mistakes till we got it near enough right.

[retoabcr]

Retired, for me 8 1/2 years. Yes ,calm waters is the key and next is the FUN. I'll work on the picture, mine is nice size airboat. I just got thru with 3 1/2 weeks ago with roto-cuff surgery, completely torn off and down 6" was torn and doing great but will work on picture this pm. Have a good day! Found go advanced and found out what pixels were and will go from there.

[retoabcr]

:) Pumpkin colored airboat, easy to see on the water. I've cut the cage down by 1 1/2" on the motor end.

[Tony Oliver]

Congratulations on the pics! Nice, potent looking boat. Maybe when mine ripens it will be the same colour.

In fact all the pics so far are food for thought.

I like the varied approaches to the airboat saga. They are so different from my usual boats - more like aircraft in the way they react. They're even three dimensional the way they react to water and air forces.

I've now chopped down the pylon by about 10% which seems to have lowered the cg by quite a margin. It's now much more difficult to tip it over sideways - something like 60º now. The three blade prop runs at 12,400rpm instead of the 12,500 of the Gunther so little difference there. I tried it on the wet grass in my garden today, after the rain stopped. Still plenty of poke there and it was steerable. Maybe some castoring wheels at each corner?.....

I'll maybe get a chance to run it on Sunday,

[green-boat]

You could put a wing on each side about half way and just above waterline at wideopen throttle.
That would be called a ground effects boat. Just enough push to get it airborne just over the water surface.

[retoabcr]

We found some camcorder stuff where i'm trying to flip it but no luck. The side edges below water lines were rounded alittle and the 05-540 motors did their job. Now on the cajun site the free plans have the sides at a outward angle which help in keeping the air upright. They are easy to build but make sure the bottom is FLAT. The black switch is a Du-pro on and off for safety. There is a guy on another airboat site who put trim tabs. You know in away you have an advantage in England where models are the norm. I get MMI mag every month and workmanship is outstanding. Boats with belt drives and different ratios and the knowledge is something else. What kind of other boats do you have? TTUL>

[retoabcr]

Green boat, talked to Harold ( Cajun ) lately. Your an ol'e master at these boats and seen your work and you have more knowledge than i. Have a good day!

[Tony Oliver]

Success!

The pylon lowering works well. The CG was moved back halfway between the original 'too rearward' setting and the second 'too far foward' one. Despite being breezy and some choppy waves, once up and planing I had a 70-80ft turning circle at full throttle a,d a little less diameter at about 2/3. In the breeze it weathercocks so downwind steering needed some speed.

All in all, a very satisfactory model and fun to operate. Without the help of you all it would have been very difficult to decide what needed changing first and by how much so thanks to all! Still no pics, but they will come sooner or later.

[Tony Oliver]

What looks to be the final layout.

Cage height and pylon reduced to bare minimum to lower CG significantly.

In the process, rudder also reduced which reduces roll in sharp turns off the plane.

Alteration to hatch to make it more secure and watertight.

Some tarting up with car trim tape.

Local suggestions to fit a water rudder etc were ignored. I may as well make a normall boat if I did that.

Two more pics with the update:-

[Kmot]

Looks great Tony. Here is one last item to tart it up, if you were so inclined. A motor heat sink:

[retoabcr]

Don't forget to put a diode from pos. to neg. post to eliminate purges of current and save motor and esc. Also check for airflow at motor where brushes are located. Now with a pusher blade on motor, the airflow will exit at the prop but not very much at it is mainly sealed, so heat sink will help cause motor has a torque ring on it which will keep heat enclosed. 2 of 1 and 4 of another. Tony, reading what you said and it was SPIKES which can occurr which are almost eliminated by s. diodes. Now are you planning on a little bigger airboat or have fun with this one. I'm retiring from thread as it looks like people stop typing when i show up, so i wish all the best. Time to work on my boats!

[Tony Oliver]

Not necessary thanks.

I've had 15years of flying electrics. This motor is a 'cooking' (nominally 6v running on 8.4v) 400 style cheapo brushed motor.I've got a few from the earlier flying wings I used with brushed motors. It has internal capacitors so surges won't do much if any harm. As for cooling? It seems to get a dunking and plenty of spray. The brushees are exposed to the airflow and that continues right through to the prop end where there are cooling holes. It really doesn't get hot enough to worry about. My submarine will run the same motors 'wet' - ie submerged permanently. I ran one for a couple of hours or so over a week, drying in between to check there's no problem. So far there is nothing going wrong. This one was run-in (break-in in the US?) under water for 30 minutes too. Ain't WD40 useful? The fish oil works a treat in dispelling water with a drop of oil to lubricate when dry.

It's not clear in the pics, but the flux-ring is, in fact, a bit of lithoplate as a strap to hold the motor in place. I ditched the original flux ring to keep the weight and CG down. The motor pulls a little over 7amps so I get around 11 minutes of full speed from the 1500mah NiMh pack. I've just been replacing the original speed controller with a more modern one as it has a better throttle performance. No reverse of course as it's a flight controller. It's not waterproof so that's why I needed to improve the waterproofing of the r/c compartment. Even so, the original proved it still works under water - ie soaking wet!

Most of the stuff is out of recent retirement - getting tired - so isn't a great loss if anything does fail.

Thanks for the concern though. I hope everyone starting out gets to read this thread as the info is invaluable and answers all the unasked questions.

[Kmot]

The heat sink idea was for bling, not efficiency. ;)

[Tony Oliver]

That looks more expensive than the whole model. Maybe I could make one out of balsa.....

Now I've just got about 15 other models on the 'wish-list' then I have this thought of a brushless version, with the power of a .40, and lots of old batteries which I could use up....

Incidentally, I understand that the magnets in brushless motors (out- and in-runners) are very susceptible to corrosion from water. Anyone got any experience of this?

[Kmot]

Ask the Fast Electric racers. They have been using brushless for around 4 years now.

[Shaun Hendricks]

That looks more expensive than the whole model. Maybe I could make one out of balsa.....

Now I've just got about 15 other models on the 'wish-list' then I have this thought of a brushless version, with the power of a .40, and lots of old batteries which I could use up....

Incidentally, I understand that the magnets in brushless motors (out- and in-runners) are very susceptible to corrosion from water. Anyone got any experience of this?

No magnet difference between brushed and brushless unless you are using low-grade brushed which has ceramic magnets (low power, no oxidization). Brushless almost universally uses Neo magnets and most are sealed with a coating of some kind to prevent oxidization. So it should not be a problem. Your WD40 should be good for anti-ox treatments but don't use that as a lubricant, use it after lube is applied. WD40 goes sticky over time. There are better anti-corrosion products on the market.

[Tony Oliver]

Will do!

[Tony Oliver]

Finally, two pics. Taken with my camera by someone unused to it.

The first one was too quick for the cameraman. The second was just as it came off the plane.

Hilarity all round as it hit a wave (still too breezy for safe fast running) and turned over. Even more laughter as I drove it back inverted. Too much for the cameraman!

[retoabcr]

You'd have better put this in the memory bank cause you won't forget it.

[Tony Oliver]

It was quick and cheap to make (I like cheap!). All the bits were from stock and equipment I already had.

I'm keeping it for calm water running (no yachts to hit either) but it's a fun thing to operate.

Only the ducks don't like it.

[Up&Away]

Nice one Tony! At least it isn't pink this time...

[Tony Oliver]

Oh, the shame, the shame! :o

For those who don't know, I built a freeflight contest model and the see-through finish (labelled RED and looking red) ended up looking decidedly pink. Not really my colour (although I do admit to my eyes looking that way after a night out on the booze).

[Kmot]

This thread has been an inspiration to me. Several years ago, pre-brushless, I purchased an ABS airboat designed for electric power. I tried a couple 540 car motors in it, and promptly melted motors and burned up speed controls. Plus the full size radio gear was not a good fit inside the decidedly small electronics compartment. So, it has sat forlorn in the shop waiting for a better day.

Fast forward to today, now there are brushless motors with amazing power direct drive on props, micro Rx's, micro servos, micro brushless esc's. I think this airboat of mine may yet fly across the water someday! :)

[Tony Oliver]

I usually only start threads which I think will not only supply me with useful information on what I need, but also be a lasting resource for others.

This one fully lives up to my hopes. The help and advice of the contributors is invaluable.

I've never been disappointed yet.

[Tony Oliver]

Tom - I for one, would like to see your boat up and running. Although I did mine up as a semi-scale with driver, cage etc, I acknowledge the practicality of that sort of stuff isn't high. The basic hull/power unit/rudder being the only things above the waterline make for a more useful boat.

If you get it finished, any chance of some pics?

[Kmot]

If you get it finished, any chance of some pics?

Me? Pics? Surely you jest!! :p

[Tony Oliver]

Ummm, a sketch?

[retoabcr]

Take care of yourself and good luck boating. No reply needed!

[Kmot]

Ummm, a sketch?
Apparently, you haven't been paying attention to my threads, lol. I take pictures of everything!! ;)

[Tony Oliver]

English sense of humour! Accept understatement and make a suitable understated comment in return. I keep forgetting no other nation does it. When someone does, we miss it. Ho-hum! Sorry about that.

[Tony Oliver]

Things have moved on considerably since the above posts.

I've replaced the cooking brushed 400 and controller with an outrunner weighing 1/3 of the 400's weight. I lowered the new pylon mount. I fitted small fins to the rear on each side which are slowly being whittled away until they give adequate control. They were only to improve directional stability originally but now seem to be of little use. That's because I cut off the flat bottom and replaced it with a shallow vee (see pic). Unfortunately I rounded off the edges a little too much which allowed spray and solid water to curl round onto the deck and through the prop which at the time was a Gunther. This eroded very quickly and the tips looked badly frayed after only one afternoon's running.

To get over that I fitted spray strips as you can see. They have two effects. First is that the water doesn't go anywhere near the prop now, and secondly the displaced water raises the rear slighly to plane flatter at speed.

The new brushless fitted with the Cox 5" three blader is very good and on a 2S LiPo will plane easily but isn't very fast. On a 3S, the thing is transformed and has tremendous acceleration.

The final improvement was to extend the bow by about 1/2" to give a more progressive ramp and allow it to ride over instead of under waves when at low speed.

They all work now and the model is great fun to operate and goes fast enough to make our small pond interesting. The water fowl don't find it at all interesting and clear off out of the way as soon as they hear the motor running. High-pitched whining isn't their thing apparently.

I can't help thinking that Glynn's original larger design would have been better over all, but I do enjoy the messing around to get it all working.

[Up&Away]

Wot, no pilot?

[Tony Oliver]

I think he drowned. The boat went out on the pond, hared around for a while and when I brought it back he was gone. Possible suicide or maybe he just leaned over too far to throw-up and went over the side... :(

I'm training a new one and fitting a stronger seat belt.

[rattyboy]

hi

i just started building one the other day and i thought i wonder if r.c groups has a thread and the first one i saw on the page was an airboat. lol. anyway mines 60cm long 26cm wide and 5 1/2 height. is there an advantage in having the pushing instead of a puller prop.

[Tony Oliver]

I can't say I'm anything of an expert on airboats. The thinking on mine to use a pusher was to get the prop as close to the air-rudder as I could. If you have problems in getting pusher props for an IC engine, then a tractor layout may be best.

As mine is electric, I used a pusher prop and made the motor run in reverse to allow the pusher configuration to work. No one has noticed yet. When I did a similar thing on an aircraft there were a few people scratching their heads trying to work it out.

The secondary issue is that if the prop came loose, it would stay on the shaft whereas a tractor would fly off and be lost.

Why not post some pics and details of your motor/prop setup? I got some invaluable information from people who really know airboats and that saved me from making problems for myself.

[Up&Away]

No one has noticed yet. When I did a similar thing on an aircraft there were a few people scratching their heads trying to work it out.

What are you insinuating here?

[rattyboy]

hi

first time posting pics(so i hope it works)

ok here the haul
http://i242.photobucket.com/albums/ff148/rattyslot/IMG_4855.jpg it is 60cm long 26cm wide and 5 1/2 height.

the nose of it
http://i242.photobucket.com/albums/ff148/rattyslot/IMG_4856.jpg

the tail end of the boat. i think that the slant edge stop the build up of water pushing as it would on a square edge. the body boards have the slant edge.
http://i242.photobucket.com/albums/ff148/rattyslot/IMG_4857.jpg

the brushless im gonna use
http://i242.photobucket.com/albums/ff148/rattyslot/IMG_4859.jpg

and i going to mount it with this great planes motor mount.
http://i242.photobucket.com/albums/ff148/rattyslot/IMG_4860.jpg

anyway i will try to keep the pics comming

thanks

[Tony Oliver]

"What are you insinuating here?"

Rene, you tell me! It was just a little mental gymnastics problem to while away the time. I could explain it but thought I would waste everyone else's time instead of my own. ;)

Rattyboy, it's looking good. make sure you have sufficient height at the bow to ride over any waves it hits rather then duck under them.

I've not seen that motor before, what sort of wattage is it for? (or voltage x amps).

[graphixman]

These boats look like tons of fun! :D

[Eternalflight]

The electric air boats are fun.
I took a Dumas "Windy" and converted it to electric. Battery and speed control is up top in the compartment. Wires ran down through the rudder. It's sleek, fun and fast.
EF

[sergio_Italy]

Hi Tony, last year I built the same airboat according Model Boat free plans. Well, more or less i experienced the same problems you had and may some more too: it is a nice model but extremely unreliable so, after several attempts to made it right, discouraged, I put it apart. Now I understand how many details need a change and may be in the next months I'll do something to improve this little rascal.
I add some pics of it, the pilot was hand carved from balsa, hope you like.
ciao
Sergio

[Tony Oliver]

Sergio, your model is better built than mine! :o

Nice pictures and a beautiful lake too.

I think the design is excellent for getting into airboats as it is quick to build, and has scope for trying ideas on without losing the charm of a smaller model. The designer, Glynn Guest, is very good at providing such things.

Since I lowered the centre of gravity the model is transformed in performance and stability. I have not turned it over since working on that aspect. I can now chase the larger power boats around and jump across the wake, do skid-stop turns and operate in higher waves. The only problem I have now is that somehow I am getting water inside the hull. I will be trying it out again later today with the hatch taped in place to see if the water is getting in from anywhere else.

If there is anything I can give more detail on, please let me know.

There is a video here (http://www.rcgroups.com/forums/showthread.php?t=913272) of it running on the first time I got it all working right.

[sergio_Italy]

Sergio, your model is better built than mine! :o

Nice pictures and a beautiful lake too.

I think the design is excellent for getting into airboats as it is quick to build, and has scope for trying ideas on without losing the charm of a smaller model. The designer, Glynn Guest, is very good at providing such things.

Since I lowered the centre of gravity the model is transformed in performance and stability. I have not turned it over since working on that aspect. I can now chase the larger power boats around and jump across the wake, do skid-stop turns and operate in higher waves. The only problem I have now is that somehow I am getting water inside the hull. I will be trying it out again later today with the hatch taped in place to see if the water is getting in from anywhere else.

If there is anything I can give more detail on, please let me know.

There is a video here (http://www.rcgroups.com/forums/showthread.php?t=913272) of it running on the first time I got it all working right.

thank you for your reply Tony; yes, to tape the hatch (it is suggested by G. Guest too) could be the only solution to keep water off.
I taped mine too to prevent water coming inside and it worked perfectly even when my boat flipped and was in the middle of the lake, bottom up, for a couple of hours before the rescueing.
Ok, right now i am looking to my dusty skimmer with different eyes...may be i'll give it another chance :rolleyes: .
Have a nice day at the lake
Sergio

[Tony Oliver]

I'm back from the latest outing which brought up a problem.
I've had some water getting in. Not much, but this time there was quite a lot of it.
I very carefully taped down the hatch. The boat was out on the water for about an hour and when the tape came off, there was a reasonably large amount of water sloshing around in there.

All possible points were looked at. The hatch was definitely watertight. There are no cracks, holes of any sort in the hull. The wires coming out of the hull to the motor are tight fit in the holes but were also sealed in by using a hot glue gun. The same goes for the aerial tube, and in any case the top and bottom of it are sealed. There is only one other point where water can get in, and that's the pushrod outlet to the air rudder.

Is it really possible that the air inside gets warm and expands, but as it cools it must pull in water and air over time ? There's only water slopping around when at speed so it doesn't seem likely. If that's right, it can be filled up with grease or a bellows type adjuster. The amount of water is quite considerable and wetted the receiver and servo thoroughly, although I have sealed the controller in heatshrink with hot glue at each end.

Any other guesses anyone?

[Rob12]

Hi Tony,

Water ingress will only happen if there is actually a crack or holes somewhere in the hull.
I had an airboat model few years ago, and constantly kept getting water leaks inside after runs, inspecting the hull searching but never finding any obvious holes, I then found a tiny crack on the hull which was only visable when the underside of the hull was flexed with my hand. The gap would have been flexing during runs and letting water in, after i sealed the gap, no more leak. So it might be worth checking the hull over once again.

also maybe you should remove all the Hot glue seals and joins, and use silicone sealant all round instead, it is more elastic and gives a much better seal than hot glue,and it will last longer, also put a bellow on the rudder pushrod

[retoabcr]

Suggestion by Rob12 heeded and success by Rob12 suggestion. Mine is not needed! Apologize for sticking my nose in!

[Tony Oliver]

Rob - I've just had a look at the hull again - twisted it, bent it and generally pushed it around. Definitiely no cracks or holes whatsoever.

So I looked at the wire hot glue seal as you suggested. Got it in one! Although the hot glue attached securely to the hull itself, the wires are now loose in the 'seal' which now doesn't! Silicone sealant today and run it again tomorrow.

One of those daft situations which you don't notice until second look - and of course we don't take a second look as we are certain that it is right first time....

Thanks for the pointer - much appreciated! It had to be something like that but I was quite sure it wasn't any of them.

I'm used to cleaning out boat hulls with a dustpan and brush, not a syringe. It came as something of a shock after all these years. :o

[Rob12]

Reto - I managed to see your post this morning before it was edited, you should have left it on !

It's the perfect example of problems, and how to solve them !

Let's know how it goes Tony !

[retoabcr]

I saw it was the same answer as mine was. --- Ok, i got an email from N.H. Schmidt who make perfect couplers but any who, his airboat won't go straight. I have the same problem. I was told by Harold of Cajun airboats to square the bottom and change the direction of air flow . My original flow was off center 1 degree and down 2 degrees to help raise the transom alittle which will force the air more down to the water. Another item was to use a 8 x 4 pusher prop instead of a 7 x 6 prop ( pusher ) cause it moved more air than the 7 x 6. I believe the size of airboat and size of motor and rpm plus a 7 x 6 prop air cone is smaller. I use 05 old motors and the 7 x 6 prop with 05 motors in a 17" x 10" airboat which is really alittle to big but moves good enought for me.----------Now i believe Glynn's revamped airboat really moves which makes it alot of fun. Thanks for the reply!

[gofish]

My 1st boat! I have a fair amout of experience with electric flight, so I scratch built myself this airboat using electrics.
It is mostly 3 and 6mm depron, so it's quite lite. It moves along pretty quickly, but I never really opened it up due to those water lillies. I found out the hard way they would reach out and grab my boat the way trees suddenly grab my planes. I got lucky and got out of entanglements. I really didn't wish to go wading in there to retrieve it.
It is 14.75" x 9.5" AUW 7.2 oz.
Pretty fun! Now to convince my flying buddy to build one :)

gofish

[Tony Oliver]

The airboat has evolved into a practical and quick fun boat.
Summing up:-
It now has a 1700revs/volt brushless outrunner (HXT2730) which saved serious weight over the 400 brushed motor. It runs on 860mah to 1300mah 3S LiPos. Using a Cox 3 bladed 5x4 prop. The motor draws 5.2amps/56watts on 3S at 14750rpm. It doesn't have a reversing speed controller so I have to be careful not to get it into a position where it needs reversing.

It is now 5.75ins wide by 13ins long. A vee'd hull and less blunt at the bow allowing it to hit waves and skip over instead of through them. The waterproofing is now solved with a bolt-down hatch (seconds to open so not a problem). I fitted spray strips to the top of the deck - styrene sheet stuck on with double-sided tape - to stop water hitting the prop and slowing the boat down. A secondary effect is to lift the tail slightly and that improves stability. It now banks in on the turns. The temporary fins have remained as the screws seem to have rusted in and there's no reason to remove them.

The next thing is to fit twin rudders to give more accurate (I hope) steering at speed.

[Kmot]

Where are the pics Tony? :D