RC Rescue Boat built from Styrofoam

[Bernd]

John,

Your not going to piddle on my parade. If it works fine if it dosen't, oh well. Like Edsion said, he found out 100 different ways how not to make a light bulb.

I see were your going with the catch twenty two. The only reason I'm using air props is the occasional seaweed that gets hung up on the props.

You don't mind if I try to prove you wrong do you? 

HS93,

I've seen all the latest on the lipo batteries and motors.

I'm just having a bit of fun here by trying to use some surplus stuff and throwing it together to see if it'll work. If it dosen't then I guess I'll have to build a steam powered boat for the following year.

Thanks guys. Appreciate your input, but being the block head I am, I'm going to continue. You guys have the reserved right to tell me "I told you so" later.

Bernd

[Bogstandard]

Bernd,

I would love it if you prove me wrong, then you can say 'I told you so'.


John

[HS93]

who said li pol's ?   they work just as well on gell cells.

peter

[Bernd]

Peter,

I've been following an airboat forum and they use the brushless motors and lipo cells. These guys are going for speed. One has reached 98mph. All you see is a streek across the water. To me that's not much fun. I like it slow and easy. Comes with age you know.

I've looked at all that new tech stuff in electronic controls. Really fascinating stuff, a bit expensive too.

I'm going to keep going with this. I just have to prove Bog's wrong or right.   

Bernd

[madjackghengis]

Hi Bernd, I was just going through and looking at old posts, my condolences on your Dad passing, I wasn't able to get to my parents for Christmas, and my Mom is not doing well, so I know it hits hard.
    Regarding technical things, nicrome wire is in fact a stainless steel, just a very special one, designed for heat, so it won't be bettered by ordinary stainless wire.  I hope you get enough power out of your motors, but if not, you can always change over, the brushless ones are substantially more efficient.  Spring is getting closer every day.  All in all, it either works, or you just have to work on it more, until it does, so keep shuffling forward. mad jack

[Bernd]

Thanks Jack,

Mothers first Christmas was a bit tough on her but she survived. Plus she's going to be a great gand ma, so that cheered her up a bit.

As far as the motors go. I think they'll be powerful enough. They just about push the boat across the table now. Next would be to try a bigger prop. It doesn't take much to push a boat through water. We'll see come spring time.

Just need tofigure out a way to mount the air rudduers onto the back. Need to get a radio too. Gives me something to work on between doing the molding in the house.

Bernd

[madjackghengis]

Hi Bernd, it's good to know there is something happening with your mother that is upbeat, attitude will keep a person alive when lack of anything to look forward to leads to depression, it's good to hear she's about to become "great grand-ma", and that she got through Christmas all right.  I just got a call from my mother last night, and she's past the pnumonia and doing better, so I'm much relieved.
    It's also good to see you back on the boat, I suspect you will try many motors before you're done, unless what you've got does just what you had in mind, in which case, why change what works?  with regard to the steering of the air, have you considered a "quarter moon shaped or "C" shaped sheet aluminum piece, around the motors, with the tips of the "C" being the pivots for the rudders, and the body of the "C" being an air guide to reduce the turbulence sure to be generated?  That would put the needed bell crank either above the motors, or beneath them, and out of the airstream, reducing interference and giving a solid mount for the "rudders".  I've seen similar on air boats used in Florida, and out here in the swamps of North Carolina.  I haven't done anything with such things, but a lot of emphasis seems to be put on guiding the airflow into the blades as much as there is in the rudders.  Aerodynamic nacelles for the motors would let the air move more efficiently, and reduce turbulence, which is probably as important for power as the motor design its self.  I don't know much about air boats, but I spent a long time around helicopters, and they tend to give one a good amount of respect for turbulence, given the work done, and the slow speed it gets done at.  I hope this adds a bit to think about at least.  Other than that, you're looking good, and with some time before spring.  mad jack

[Bernd]

Thanks for the kind comments Jack. Things are looking up.

As far as the rudders are concerned. I think aluminum might be a bit to heavy for the back end. I's gotten a piece of 1/32" out in the shape to cover the whle blade length and it would get a bit to heavy with two. Thinking of going with a 1/8" foamboard cover with epoxy to water proof. Will see.

Haven't done much since I last posted the pics. Been a bit on the down side. Recovering though. Lot's of post op deppression to work through. Been there once.

Bernd

[HS93]

A qiuck tip re your motors you need to open up the holes on your motor mount tubes by the brush gear they act as an aid to cooling in your case the air will come in the slots at the front and go out the holes by the brush, if you dont you may find your motors get hot, Just look at comercial motor mounts they always go to the trouble of cutting them out  for the front mounts.

peter

[madjackghengis]

Hi Bernd, just a thought, with weight your concern, some 1/32 balsa covered with plastic sheet or a doped finish is about as light as it gets, and is quite stiff and strong for the weight.  It's kind of funny, with all the advances in science, the same materials that were best for modelling fifty years ago, still are stiff competition with modern materials. Jack

[rleete]

Thin epoxy with acetone (I got a quart at the auto parts store for less than 3 bucks) to make it runny.  About 50/50, the mixture ratio is not critical.  Paint it on any wood, and it soaks in.  Let it cure (a couple of hours for the standard 5 minute stuff), and it's rock solid as well as impervious to mosture.

[Bernd]

HS93,

Nice catch. I pulled the motor out and sure enough there are vent holes by the brushes. Even has blades for a fan effect. Nice project for a rotary table on the mill. Thanks.

Jack,

Good idea about the balsa. Never would "wood" have thought of that.    I'll have to look and see if I got two pieces big enough.

Roger,

I went and spent a large sum this past summer on the "West Epoxy System" stuff. I bought some of that thin stuff that fixes dry rot on boats. I had to do some repair on my mom's house windows. So I have a bit left over might try that with Jacks iddea of balsa wood.

Thanks guys. All great tips and are going to be considered. Will let you know what happens as the spirit moves me. Right now I can't find the dam thing.

Bernd

[madjackghengis]

Well Bernd, it seems like all the advise fell into place together, and that epoxy/acetone idea sounds much stronger than the old material with dope way we did it forty years ago, when we were kids.  When you find it, you will remember why you put it there, but not until then, I bet.    jack

[HS93]

this may help you as well very light and works well.

http://www.rcgroups.com/forums/showthread.php?t=329811

Peter

[Bernd]

A bit more progress on the rescue boat.

First pic is of the boat with both motors and both batteries on board. I weighed the boat with these on and it came in at 7lbs. Not bad.



Now as HS93 mentioned that I would probably need vent holes by the brushes. The next several pics depict how it was done. The motor has 4 vent holes and small straight blades to blow air out of the vent holes.



In order to cut the vent holes in the right spot I made a jig out of a piece of paper. The line on the paper represents the step in the plastic pipe to keep the motor from being pushed out the other side.



The paper is wraped around the out side of the motor with the pencil line just even with the body of the motor.



Then taking the side of the pencil I rubbed the area where the opening should be.



I then used a sharp hobby knive and cut out the opening in the paper.



I cut three of the four openings out. I figured the fourth would be covered by the wood cradle holding the motor anyway.



The paper was then taped to the plastic motor pod.



Now since the od of the motor is smaller than the od of the plastic pipe I was left with a gap. Not to worry.



The middle slot of the three slots was cut first. The other two slots were cut using the "close enough" method since they would not come out at the same place as the ones on the motor.



Another view of the middle slot after cutting with a cob mill.



Here you can see were the "guesstimate" came into the picture. I milled through at about mid point and then made the slot longer toward the needed side.



And there we have it the motor mounted with the slots in the motor pods. I could have added the fourth slot since it woun't be coverd by the wood, but feel the motor has enough air getting at it



HS93, I hope this works. Thanks again for the tip.

Now it's on to the rudders. I found a length of 1/8" thick, by 4" balsa. I cut out two rudders about 8.5" long. Now I have to "engineer" the assembly that will hold the rudder's on. Stay tuned while I order some material in the mean time.

Bernd

[dsquire]

Bernd

Happy New Year.

Looking Good. Looks like you have a good start for the new year. I guess I won't need the prod stick    this year by the looks of it since you are getting such an early start. 

I hope that you realize that you may have as much fun with the rescue boat as you do with the regular boat. Kind of like the kids with a new toy and then end up playing with the box it came in. 

Cheers 

Don

[HS93]

I use a lot of plasticard and drip a small amout of water especialy when drilling small holes  stops it melting good when using a scroll saw as it stops it sealing itself to the blade.this is the sort of thing I do with it


Peter

[Bernd]

Well Don I'm glad you won't be  me. I'd turn all sorts of black and blue from the meds I take. 

Ya, it does look like I've had a good start on it this year. I hope I can keep the "steam" up to get it done. Also know what you mean about a new toy and wanting to play with that.

HS93 I ran the mill at a slow speed. Really didn't have an issue with plastic melting. I think the main problem was a dull cutter.

Sorry can't help ya with the picture problem. Maybe Eric can explain or somebody with more geek knowledge on computers than me.

Bernd

[DavidA]

HS93,

...I tried to upload some picture but I was told it was FULL so no more uploads they where only 131KB...




This is the same problem I'm having.

I don't know if it is relevant but I'm using Firefox as my browser.

Can anyone help ?

Dave.

[DavidA]

Interesting that there have been a lot of pictures posted after I started having the problem.  And most of them seem to be via Photobucket.
I wonder if it is only the direct postings to madmodder.net that are effected.

Dave.

[Brass_Machine]

HS93,

...I tried to upload some picture but I was told it was FULL so no more uploads they where only 131KB...




This is the same problem I'm having.

I don't know if it is relevant but I'm using Firefox as my browser.

Can anyone help ?

Dave.

Fixed. The attachments folder was full. I just made it bigger...

[Brass_Machine]

Interesting that there have been a lot of pictures posted after I started having the problem.  And most of them seem to be via Photobucket.
I wonder if it is only the direct postings to madmodder.net that are effected.

Dave.

Yup... when you attach pictures, you upload them to the server. When you use photobucket, they are only 'linked', so it doesn't use any space on the server.

All fixed now. The attachment folder was full

Eric

[DavidA]

Thanks Eric.

I have moved some of  my pictures to photobucket.

Dave.

[Bernd]

Nice looking boat HS93.

What are the stats, length, widith,etc. ?

Now the big question, what kind of power to make it go through the water?

Bernd

[picclock]

Hi Bernd

Nice looking boat - should be a beauty - looking forward to the finished pictures.

FWIW I'm with the others as far as propulsion goes, but with the correct 'impedance matching' it could be good. The motors you have are powerful but fairly low speed - they are designed that way for kids vehicles. To get a good match with the propellers should probably be large and if possible 4 bladed. Failing that a gearbox to increase the propeller speed may be the answer.  If they are like the ones my kids quad bike had they draw about 12A in use (~ 6 amps per motor). You can check what the original current draw was by knowing the battery Amp Hours (mine were 17) and how long the batteries lasted. From that you can find out if the motors are loaded correctly by measuring the current drawn.

The heat problem with the motor is significant as if its too hot the magnets tend to weaken. At the moment I can't imagine them getting hot at all because of the low load placed on them by the propeller. 

The foam cutting problem is a pain, and although I can get it good enough for my stuff I've never been really successful. I think the problem stems from the fact that differing thermal loads on the wire cause overheating at the edges. In the centre of the foam most heat is conducted away from the wire, this causes the resistance of the wire to fall exacerbating the problem. At the edges the heat is thermally conducted from the unused piece of wire to where the wire is in contact with the surface of the foam thus making that part of the wire hotter. FWIW I found the best results with a guitar string. The frame was H shaped with the cutting wire on top of the H and tension applied with a spring and string on the bottom. The cross bar of the H swivelled.

Just my 2 cents worth - please feel free to ignore.

Best Regards

picclock