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1/2A Size Dumas Boat Club

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1/2A Size Dumas Boat Club

Old 12-27-2009, 02:27 PM
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Default RE: 1/2A Size Boat Club

Hi Scott, I was just thinking back on the plans you sent me. It's great to see you around!

That EP1 motor looks decent, a 550 outboard. Even has an aluminum lower unit on it. Electrics are really nice and clean to play around with and can get away with just varnishes or paint to finish them. Much less expensive and less of a hassle than epoxy or urethanes.

I've been wanting to use my old RC10 car stuff I still have with a boat. I still have lots of motors, batteries and a really nice charger just sitting there. Those six or seven cell flat packs I have would fit good in something like the Hedlund. Battery packs have come a long way with this stuff and give great performance.

I haven't been around too many boats that are electric though and not familiar with their power so I would have to guess on a hull length like you're having to do. A Broccoli runabout the size your thinking would be interesting to try out too with that EP1.

Eventually I will have at least one electric to play around with to also use as a means to haul out retrieval line from the fishing pole for when the nitros flip or stall and now you got me thinking about your plans. Keep posted on this because this just might be the ticket for that!

I was going to use the Hedlund idea for a Cox .049 but as an inboard version with a dummy outboard engine, a scratch built Merc Mk20 of course . I've already hollered at Alterscale for not making one. That should have been the first one they came out with. They did recently come out with a Looper though so I'll give them some credit.[8D]
Old 12-27-2009, 03:09 PM
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Default RE: 1/2A Size Boat Club

Hi Dave,<div>  Yeah, I've considered the Broccoli, too.  A counter-weight system on the servo might make it roll up like the real one in the turns.  THAT would be COOL!   The EP1 would be easy enough to fab a Mark 30H cowling for it, too!  </div><div>  Yesterday I took a bunch of pics of the Hedlund and measured it up, too.  It should be slow at work this week, so I'll see what I can do about fleshing out the plans I started years ago...</div><div>- Scott</div>
Old 12-28-2009, 03:05 AM
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Default RE: 1/2A Size Boat Club

Made my own exhaust throttle for the TD 20 simple steelstrapsleeve no play up or down and the dia has it snug on the cylinder. After bolting down I applied the twist in the remaining tab for a push rod. At idle the lil 20 is very quite. Works great and easy way to get throttlefor any size cox engine.
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Old 12-28-2009, 02:38 PM
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Default RE: 1/2A Size Boat Club

very simple, yet effective design I like it. Man those .20's are tiny!
Old 01-06-2010, 02:42 PM
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Default RE: 1/2A Size Boat Club

guys

is there a way to mount a pull start on a cox boat

cus i dont know were to start looking
Old 01-06-2010, 10:38 PM
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Default RE: 1/2A Size Boat Club

Hey Robot,

Cox makes a pull start but I dont believe it can be made to work with a medallion engine. I've seen complete cox .049 baby bee style engines on ebay with a pull start, thoses engines usually came from a Cox tether car, I know Cox also used them in their boats too...heres a pic of a O.K. Cub engine with a pull start. They put out less power than the .049 cox from what I've been told, but still, I think they look cool...
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Old 01-16-2010, 04:25 AM
  #232  
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Default RE: 1/2A Size Boat Club

'56 Chili! 12" Hydro

Check out the sewing thimble fuel tank. Got to work that into the Thimble Drome theme somehow.

It explains how to build the World's Most Labor Intensive Drive Line and Rudder but would be pretty cool when it was done if it came out looking as good as in the pics.

What gives with the springs in the rudder though??? Does it have something to do with it being a tether model? I don't get it. Does it just hold its position but turnable?
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Old 01-16-2010, 12:57 PM
  #233  
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Default RE: 1/2A Size Boat Club

Hi Jet!

Cool looking project, its giving me ideas....I like it alot &amp; think I'll give it a shot. I copied the pics to my PC and they turned out well on my end...
I'm still putting the final touches on my 18" Atlas, finnally gotten around to buying some testors decal paper for the "Atlas" logos....I forgot the decal spray, I need that before my first attempt...

The springs on the rudder is a clever idea...better than a solid rudder attachment. It will help keep the boat stable if it tries to become unstable....
Kinda like a very primitive gyro...

I've also seen springs used as universals or couplers between the engine &amp; driveshaft....Also clever I think, the tighter the shaft turns the more the spring will clamp down...And these tiny lilttle Cox engines &amp; similar ones are not torque monsters...

What do you think would be good age appropiate engines for these boats? I see alot of Cox and some o.k. cub .049's on ebay.
Old 01-16-2010, 01:04 PM
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Default RE: 1/2A Size Boat Club

I can send you better copies I had to reduce these a bit to upload on my dial up but I found the article in Google Books looking through the Popular Mechanics.

I like and have also seen the spring coupler idea and always wondered how well it would work because the soild brass couplers seem kinda overkill and if you're working with an .020 you would almost have to come up with something yourself.
Old 01-16-2010, 01:27 PM
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Default RE: 1/2A Size Boat Club

Jet, by all means please email me some copies.
Old 01-16-2010, 05:12 PM
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Default RE: 1/2A Size Boat Club

hey guys long time no see

nice project you got there
i hope you sucseed

i was digging trough my junk latly and i found an old philips electronics kit
well to keep it short
the clips to pinn the wire down make a great fuelline holder

it doe not come lose anymore.....

and a made a makeshift pullstart (rewinder glued to the flywheel)

and when i can see the water again (there is now 10 a 15 cm ice)
i willcontrol myboat on it's maidenvoyage.


it has also a pet name (noisy red)
Old 01-16-2010, 05:31 PM
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Default RE: 1/2A Size Boat Club

Robot you can always try and use a round shoe lace from a work boot. Don't use your Dads. Maybe even the right string or leather cord.

You have to have someone hold your boat down on its stand and you thread the lace under the flywheel and cross it to pinch it better and see-saw it back and forth.
Old 01-22-2010, 07:18 AM
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Default RE: 1/2A Size Boat Club

Hi,

I have zero experiance with rc boats, but I'm fairly completely addicted to all engines .061 and lower.

I'd love to build a boat for one of the little engines I've got, but I cant work out what you guys use as a drive drive/prop shaft and how you connect it all up.

If I knew how to do that part, I would be sweet and will definitly build a little boat.
Old 01-22-2010, 10:43 AM
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Default RE: 1/2A Size Boat Club

it is just a 1 to 1 link on the prop

so engine-flywheel-driveshaft-prop

i think...
Old 01-22-2010, 02:23 PM
  #240  
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Default RE: 1/2A Size Boat Club

Nope not a good way to do it, you need a universal joint. It gives a place for any wobble to go instead of directly to the bearing surfaces of the engine.

Dumas Products is the only one that makes universal couplers small enough for our boats. They are drilled and tapped for 5-40 threads due to them being made especially for Cox .049's. They use a 5-40 thread into the crankshaft. 5-40 threads because the major diameter of the thread itself is 1/8", a common drill size for airplane props.

The running gear will involve a flywheel, universal coupler, driveshaft, strut, and jam nuts for the prop. A brass tube is glued through the bottom of the boat for a housing for the driveshaft and to keep water from comming into the hull because the top of the tube stays above the waterline.

Dumas Products has a hardware package for their current hulls they offer for 1/2A, but the older kits that are longer like the Atlas Van Lines and the Miss Thriftway use a longer threaded rod for a driveshaft which they don't offer anymore.

The best way to do it is to wait to glue in your engine mounting blocks until you have the stuffing tube installed in the boat, then slide the driveshaft up through it and attach the motor right to it without a universal or flywheel and hang it on the driveshaft and slide your blocks under the motor then glue them in that spot.

It gives the straightest line to the prop and takes work and wear off of the universal joint plus gives you better RPM's.

These boats will definetly give you the thrill of getting them to scream without the nasty thought of it having a dirt diet or worse that only an airplane can bring.
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Old 01-27-2010, 02:42 AM
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Default RE: 1/2A Size Boat Club

I'm looking for a tap &amp; die set. I picked up a bunch of k&amp;s SS 1/8 rod, so I can make my own threaded driveshafts. Any ideas where/who may have a small set? I believe the shafts are cut 5-40 cause I took one of those short driveshafts that came with my H5 hardware kit, which is, for the most part usable except the shaft is way too short, but the shaft screwed right into the u-joint so I'm assuming its threaded 5-40, is that right?
Old 01-27-2010, 02:55 AM
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Default RE: 1/2A Size Boat Club

Correcccccccctooomundo
Old 01-27-2010, 04:14 AM
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Default RE: 1/2A Size Boat Club

look at jetpacks post 232 close and u will see their used a peice of fuel line for a u-joint
Old 02-08-2010, 01:19 AM
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Default RE: 1/2A Size Boat Club

I have tried ball point pen springs and others found in the garage drawers to try and get away from the mechanical loss and the weight of a Dumas coupler but I haven't found one that has held up without breaking. I'll be trying that method again later on because if the right hardness can be found there is a definate rpm advantage.

I think the key would be a supported driveshaft where it goes into the stuffing tube so it doesn't want to whip, which I suspect contributed to it breaking while running.

It was much faster without load using the spring coupler probably because of no balance problems compared to the coupler.
Old 02-08-2010, 01:30 AM
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Default RE: 1/2A Size Boat Club

I kinda like that small Sterling models u-joint over the dumas. Less mass. Thing is you gotta solder it on. That means you wont be able to remove the shaft for cleaning &amp; oiling.
next time i go over to ace hardware over here I'll check to see if they have any small steel springs, those plans for the Chili mention a fuel line,and I think the dumas plans on the thriftway also mention using a spring as a universal however doesnt say what kind or where you'd find one so small...
Old 02-08-2010, 01:40 AM
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Default RE: 1/2A Size Boat Club

...and so cheap.

Another thing I've thought back on was how I pressed out the roll pin out of the universal and went with the next size up in the hardware drawer which fit beautiful, so I drilled out the hole in the coupler and used that.

I noticed it ran much smoother with a lot less noise, and with that being my third coupler used I could easily judge it lasted twice as long without it starting to notch into the brass.

Keeping the driveshaft in-line the best you can with the engine is probably the number one importance with the coupler only being used to take out any small mistake.
Old 02-08-2010, 02:01 AM
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Default RE: 1/2A Size Boat Club

Well my Miss Thriftway boat is finished however I painted it differently. I painted mine to look like the U-30 Muv-Along. I used Testors light blue and vinyl lettering from hobby lobby. Close enough. I'l post pics soon. Im still working on other projects and havent gotten to this one in a while. I'm going with my Golden Bee .049 . I bought some k&amp;s Stainless 1/8 rod and just need to cut it down and thread both ends 5-40. Still need to pick up a die set so i can do that. I'm going with the dumas brass strut under the hull 1 inch forward of the transom, leaving the prop hub just under the transom.
Also I plan on using a mini brass hinge for a rudder mount &amp; just using the dumas brass rudder, its still going to be rc controlable with a Cox micro servo. I can fashion a brass tiller arm and solder it all together for a vintage look....
Old 02-08-2010, 02:09 AM
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Default RE: 1/2A Size Boat Club

If I had to thread I would probably choose steel rod for the driveshaft because knowing dies and hand threading with them, they chip out pretty easy if you dont have a good clamp on the part and a steady hand.

Another thing that helps is if you can spin the diameter down a bit where you'll be threading.

If you can look for one that is adjustable with a set screw. That way you start light with the cuts, adjust the die and make another pass until you're happy with the way the nut fits.
Old 02-08-2010, 06:52 PM
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Default RE: 1/2A Size Dumas Boat Club

Uh, JP, is a 30" Pak hull too big to let me be a member? It's only going to have a little K&B 3.5 inboard for power with a 3280 pipe. compared to the rest of my boats, it's a baby
Old 03-04-2010, 02:15 AM
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Default RE: 1/2A Size Boat Club

Anyone manage to get some vid yet?

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