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Old Oct 21, 2007, 03:02 AM
Pull out early!
DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
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Catamaran style recovery boat, twin motored (video)

I decided to post these photos of my new boat since I couldn't find many examples on here of retrieval/recovery boats. I have a few dozen flights on a GP Seawind to break me into the water plane game, but while talking to an observer at dusk, I plopped it pretty hard. Needed a boat, didn't have one.

Repaired the damage, was too lazy to remove the cowl and just felt the prop/motor for play, seemed solid. Up until it fell off during the next flying session.

Needed a boat again, didn't have one.

So I built this out of 2" thick bluecore type insulation foam, and used both PU and 5min epoxy to assemble. I hotwired everything, then sanded. Used a wood yardstick embedded into a channel across the bridge to give it strength. Covered the whole thing in packing tape so the white paint wouldn't eat the foam. Two el cheapo cdrom motors from bphobbies, underpropped, no water rudder, just differential thrust in the radio for rudder. Canopy is a section of a gallon Gatorade bottle.

Some stats:

3lbs, 36" wide, 39" long. Pontoon height is 3.5", and draws about 3/4" of water.
3s tp2100 lipo, two 8YSS cdrom motors, 40a ESC 's, APC 7x5E counter rotating.
5amps per motor wide open gives me just enough speed for the job.

I just have to make some sort of fence that I can clip across the front of the bridge to keep a wing from going over or under the bridge while being pushed. I may make shrouds for the motors; not sure if they'd be needed with a proper fence. I am considering turning the "fence" idea into a mesh/grid scoop that extends under the surface and forward, so I could grab all the little pieces that could be floating just under the surface.

Any comments/criticism welcome, I just wanted to throw out an example of a recovery boat that can be made from cheap parts.

Dave

edit: Now with video!
http://video.google.com/videoplay?do...91041862&hl=en
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Old Oct 21, 2007, 06:29 AM
WAA-08 Pilot Eventually
donjiskra's Avatar
Darien,IL,USA
Joined Jul 2000
1,570 Posts
Dave,
Looks like a good one. Nice design!!!
I assume you are using differental power for steering?
How are you going to reverse the motors, if needed?
How about telling us the specs?
Have you "maidened" it yet?
Thanks,
Don
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Old Oct 21, 2007, 01:27 PM
Pull out early!
DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
Don,

Maiden voyage was yesterday on a friend's pond - the differential trust, with no water rudders, did exceptionally well. I mixed the throttle to rudder and then another mix for rudder to throttle, and ended up using 50% rates on rudder and I get a good combination of tight low speed handling and stable high speed turning.

I am considering the idea of "reverse." How important do you think it is for a recovery boat? I figure my lightest option is to go with ESC's meant for RC cars/trucks, and find a pair with reverse (expensive). My other option is to mount another cdrom motor right behind the canopy, and have it for reverse only on a sep channel knob.

I can't think of any other specs besides the electrical - the motors can take 10-12a easily, and usually run a 10x4.7SF at 11a making 600g of thrust. I wanted counter rotating props to eliminate any torque yaw (P effect), and had sets of 8x6E and 7x5E on hand. Haven't even balanced the 8x6's yet as the maiden with 7x5's produced about 10-15mph of speed, more than enough for what I want. I went with 40a ESC's since they wouldn't get much cooling air, and were as cheap as the smaller ESC's at BPhobbies. So far, the only thing that knockoff ESC's are seriously criticised for (no linearity in the throttle curve) has not had any ill effects in this twin setup.

I could have chosen a cdrom motor that spun a larger prop on 3s, which would have been more efficient. I went with a higher KV motor to keep the prop size smaller on purpose - I wanted to make the whole rig low to the water so I could possibly push a really large high wing plane (one day) without worrying about cutting up the wing undersides. As it sits now, the motors are mounted with 3-4" of water clearance, and I may lower it down from here as there is no splash from the pontoons.

Dave
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Old Oct 21, 2007, 08:48 PM
I just love flying
MattZC's Avatar
Traverse City ,MI
Joined Dec 2005
907 Posts
I like this idea and have had similar ideas but never the motive to build or the money for supplys. My idea is also a catameran, with two boat drives,as a real boat, with a lowering square net that would be lowered into the water to get underneath whatever plane or boat or thing and then lower it up out of the water and drive back to shore. I have drawn up little sketches and such or this idean and still dont have the design right. I also have a HUGE amount of of about 1 inch thick bluboard to build it out of just havent gotten to it yet.
My fear with your design would be that the object of retreval would be pushed underwater when the craft started foreward motion. Maby I missed something in your posts.

Good luck with your vessel!

~Matt
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Old Oct 21, 2007, 10:30 PM
Pull out early!
DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
I like the idea of boat drives, since they pose no danger to the plane like air props do. Also, the fact they have reverse is quite nice, too.

I played around with the boat for an hour and a half tonight, used 1500mah out of 2100. Most of the time I was tossing a gallon gatorade jug out as a "downed plane." I was very satisfied with the handling while pushing. I added some water to the jug to lower it and give it more drag, and everything was still fine. As long the plane can't completely fit (while floating) underneath the bridge, I can push it slowly. It took almost full throttle to climb over the jug, and I only did it once since I was risking a prop strike.

The highlight of the voyage was when the pond owner fed the catfish.... imagine the water just coming alive with motion, and I drove through slowly. The boat got hit so hard it came completely out of the water once or twice.

Stress test : Check!

If I add the "fence" (kinda like the square net idea you were talking about) - I will post more photos. Otherwise, it won't have any problems pushing around my seawind as-is.

Dave
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Old Oct 21, 2007, 10:41 PM
Student of Ivan
mountainman2442's Avatar
El Paso, Illinois
Joined Apr 2006
725 Posts
Dave,

I really like your retrieval boat. Good simple designs are often the best.

Quote:
Originally Posted by DiveBombDave
I like the idea of boat drives, since they pose no danger to the plane like air props do.
To minimize the risk of danger to the disabled plane, I wonder how difficult it would be to add guards around the props? Kinda like a Florida swamp air boat...

John
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Old Oct 21, 2007, 10:47 PM
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DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
Thanks!

I am thinking the prop guards are going to be a must, since that would be anyone's fear (if I were going to push someone else's possibly expensive plane). I am trying to think of the lightest material and design that would remain rigid enough that it won't get pushed into the prop. The way it sits in the water now, the battery is basically in the middle from front to back, so different sized packs won't tilt it. However, most of the bridge is behind this point, as well as the motor pylons, motors, long motor wires, etc. So (long story short) it sits with it's butt lower in the water than the front already. So if I add a bunch of weight in prop shrouds/guards, I'm making it worse.

I guess I'm not done with this thing yet!

Dave
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Old Oct 21, 2007, 10:57 PM
I just love flying
MattZC's Avatar
Traverse City ,MI
Joined Dec 2005
907 Posts
Good to hear that it should be sucsessful in retriving your planes and such!!

Heres a little concept model for me if I ever have the time.

The pink rails on the side of the hulls would be the mechanism that would rais and lower the net to pick up whatever there is. Kinda looks like 2 battle ships joined togeather.....


~Matt


EDIT:

I added a picture of a dowels and a hooks in the rails but now I am thinking that each rail will have one dowel or connection that will span the distance between the hulls and and connect two togeather.

From the two joiners, the net can be strung between the two to create the square.......


What'd ya think??
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Last edited by MattZC; Oct 21, 2007 at 11:21 PM.
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Old Oct 21, 2007, 11:48 PM
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DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
I figured using servos to lift (and hold) the weight of a plane was pretty limited.... at least, I thought about using a "seine" net thing that could be lifted out with servos.

Then I remembered seeing a ship on discovery channel that was used to haul yachts across the Atlantic when the owner's didn't want to burn the gas or put the hours on the engines. It was the coolest thing - catamaran style but the pontoons were crazy tall (like 40'). It would flood the chambers and lower the whole bridge underwater, and then all the ships would drive inside. Scuba divers would weld chocks to the bridge to dry dock the ships, and then the captain would pump out the chambers and raise everything out of the water.

I found 12v bilge pumps online for $12, small ones, but would have made my project a lot larger than the 3lb boat I wanted. But still a neat concept.

Dave
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Old Oct 21, 2007, 11:51 PM
I just love flying
MattZC's Avatar
Traverse City ,MI
Joined Dec 2005
907 Posts
My way of raising and lowering would be up to my geinus great uncle and he would find a way to take the load off the servos fairly easaly......


Like a jack screw with a lock function made out of aluminum.....


Here is the latest version.....
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Last edited by MattZC; Oct 22, 2007 at 09:35 AM.
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Old Oct 22, 2007, 08:22 AM
Electric only
rkopka's Avatar
Graz - Austria
Joined Nov 2002
287 Posts
Quote:
Originally Posted by DiveBombDave
I am considering the idea of "reverse." How important do you think it is for a recovery boat? I figure my lightest option is to go with ESC's meant for RC cars/trucks, and find a pair with reverse (expensive). My other option is to mount another cdrom motor right behind the canopy, and have it for reverse only on a sep channel knob.
You could use relais and a switching channel. Just exchange two of the wires to the BL and reverse !

RK
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Old Oct 22, 2007, 12:49 PM
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DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
Quote:
Originally Posted by rkopka
You could use relais and a switching channel. Just exchange two of the wires to the BL and reverse !

RK

What a good idea, never thought of that! Thanks!

Dave
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Old Oct 24, 2007, 06:10 PM
Seaplane Nerd
JimCasey's Avatar
Joined Jan 2005
837 Posts
not to throw out bad karma, but I hope you still have a person-carrying boat available to go get this one when it gets into the god-forsaken snake-infested briar patch......
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Old Oct 27, 2007, 06:46 AM
Registered User
Springfield, VA
Joined Feb 2000
1,192 Posts
I thought about doing something similar to this as well, by the time I figured out the cost of components, time to do, ability to actually capture the plane and then guide back to shore, etc., I settled on a Coleman 2 man inflatable boat with oars from ebay, $40 shipped...
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Old Oct 27, 2007, 12:14 PM
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DiveBombDave's Avatar
Lexington, KY
Joined Jan 2005
1,956 Posts
Jim, you must be from around here.... if you paint a jug of moonshine on the boat, you can get the rednecks to swim.

Pm, yeah, I may still do that anyway, just in case there's a crash were pieces explode. But you'd be surprised how fast the little boat can respond and how easily it "grabs" the plane. I'd like to get some video of it - just been too windy for a week. Blowing up the raft would take some time and energy (or a pump, more money). Tradeoffs....


Dave
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