jetpack

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Dumas Products still carries 1/2A size boats, some are current...some are discontinued, but all have a special quality with them being designed for Cox airplane type motors.

I've decided to start a thread where we all can share our interests in these boats.

With micro radio gear now available, they can be built to still carry speed using a controller, and as far as being glow powered probably the least inexpensive types you can find. They are a good building experience also to get used to using clamps and epoxy before jumping into something larger and more challenging.

Even though Cox is now out of buisness, their engines can still be found by the handfull and quite a few performance parts and options can still be had.

Much of the fast electric hardware that is current can be used also, which helps open the door even more to make life easier and a bit more deluxe than what's supplied in the kit.

Electric drive hardware packages are a lot nicer with these in comparison to the standard Dumas hardware kits they offer, even though there's not really anything wrong with what they do have. Dumas does supply everything to make a running hull minus engine, or radio if you want one.

If you would like to share, post away!!! I hope to see what else is out there besides me, and I'll post as much as I can in the thread as I go along with my builds.[8D]

jetpack

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First thing I would like to start with is to post all the pictures of the boats we're talking about for anyone looking in. They are all approximately 18" in length and come with a mix of aircraft ply, mahogany ply and a small amount of solid wood.

All of these pictures are ones that I have scooped off of the Dumas Products site or past catalogs.

I own most of these kits shown, either in kit form (currently available) or in templates (discontinued) and I am now currently working on building up my motors and hardware collections to help finish them.

I am minus templates for the Short Stuff and Miss Thriftway which are both discontinued, so if anyone watching knows how to obtain them, it would be great to know.

jetpack

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Here are some pictures which I have collected of built examples and kit contents to expand on just the simple Dumas advertisement pictures.

jetpack

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Dumas does offer their own hardware packages for each of their 1/2A size boats, but it is pretty much standard and still in "kit" form, with the rudder plate left up to the builder to solder on the rudder shaft.

One thing about Dumas is they are the only maker that offers a water cooling jacket for the Cox .049, and also appropriate size 1" props both bronze (JG Props) and plastic. Good thing they make 1" flywheels also, something also that's not around anywhere else.

Octura has only one size prop that could work with an .049, and that is slightly over 1" and higher pitched. I have yet to run the Octura prop so I'm not sure how well it will do in stock form. It might have to be trimmed down to get the RPM's up into the powerband of the motor.

I mentioned using electric hardware and have found what looks like would work well with these. Some are on eBay from China, some are available as replacement parts from AquaCraft or ProBoat, some are from the fast electric suppliers here in the US, Offshore Electrics. I've been hunting and looking at items for awhile now to see what can be worked into the projects I have.

Everything shown below is desinged to work with 1/8" diameter bore props, and .098" cable or wire drives.

The cowl picture is a reproduced fiberglass copy of the plastic cowling for the discontinued Atlas Van Lines 18" hydroplane kit offered by someone on eBay. Lots of people have the templates to copy the discontinued hull, but it's hard to come up with a cowl unless you scratch build your own or buy from this guy.

jetpack

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Here's some of what hardware I have collected for my projects.

Sterling Models (out of buisness) used to offer 1/2A powered boats also, and had their own line of hardware to help complete them. Brass flywheels and universal couplers pop up once in awhile too on eBay.

Throttles can be put on Cox engines. Some even come with their own throttle sleeve or throttled exhaust castings. The carb I have pictured is a vintage aftermarket Tarno carb.

Cox did make what they called an .05 RC which was an .051 displacement TeeDee engine and only produced in a small number. It had a similar standard carb such as the Tarno I show plus a very nicely done bullet style muffler, but they are pricey and considered collector items. You just have to comb eBay for most of whats mentioned, unfortunately.

As far as an inexpensive way to set up for Cox power is to find a production reed valve type with the plastic backplate. Those usually go for less than $20 and you can fit any size fuel tank you want up to them, and get an RJL replacement head from MECOA to keep glow head costs down.

Something you might wonder about in the pictures is the turned aluminum cylinders with the small black set screws, which are actually flex couplers to go on after the flywheel to adapt .098" flex cable to replace the brass universal and solid drive shaft items that come with the stock Dumas hardware package.

The couplers were custom made for me by Offshore Electrics. The reason they had to be custom made is Cox engines have a pecular thread size comming off the crankshaft, being a 5-40 type thread. Nothing exists with those threads that would work.

Ron Olson

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JP, if you're also looking for plans for a 1/2-A boat, try www.microhydros.com . They also have parts for really small boats.
When I was working on the Hammerhead .12 project, there was talk at the time of producing a 1/2-A 'rigger just to see if it would work.
There are lots of Cox .049 and .051 parts around yet. One of their large heat sink heads would help for cooling as an alternative to running water lines.
Way back in the late `60's I had a Cox boat that was a free-runner and actually was kind of fast for what it was. It was a dark blue plastic and when I'm on eBay I'm always seeing if I can find one. It would be easy to convert it to R/C.

jetpack

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You know I thought I had a picture of that Cox boat at one time but now it vaporized. I know exactly which one your talking about too. It wasn't the "Water Wizard" that was built like the Prop Rod with a rear mouned airplane motor on it, it was actually an inboard with a submerged prop, and looked like a pleasure boat or ski boat kinda with four seats and an engine box.

They came in only that one color I believe too. Usually Cox had a couple colors of whatever it was to choose from but not this one. Metalflake deck with a white bottom I think? I know they liked using that heavy metalflake plastic on their stuff.

Cox powered boats CAN scoot. The first model boat I built was that Atlas hydro, and I dropped an .049 TD in it, no throttle, no servos, nothing but a fixed rudder and its plastic prop.

I was really careful lining up the angle of the motor so the universal didn't have to really even be there but I still used it, and kept the angle of the prop as shallow as I could with it, and when I hit the needle setting just right on the thing, it would haul the mail so good I could only stay even with it in our light fishing boat with a modern 10hp Merc. I estimate it at a solid 35mph. Not too shabby for an 18" boat.

One time it even climbed the prop and took off like a second stage rocket, but it ran out of rudder area and spun out when it did. I like to think back at it as the "record run" of the thing, even though it was a short ride. These motors can spin a good 25K easy with plenty of power behind it.

Ron, thanks for the link I checked it out, and there's a german guy machining hardware that looks quite tasty. They have a good stack of free plans too that would be perfect for a scratch build. Nice to have marked.

Below I put in an old advertisement for that Water Wizard I talked about. The one you had was different, much more modern and a '70's V-style if I remember right. I'll keep an eye out for one and throw in a pic when I do.

Its good you mentioned that Cox heat sink. They put that on their cars. I also have a "Lite Machines" air cooled head that they put on their 1/2A heli. It takes a Norvel or AP glow plug, but also came standard when they started out with boxing Cox engines in their kits.

I used that original Cox heatsink a few times on the Atlas, swapping out the Dumas cool clamp hoping to save weight and get rid of the drag of the water pick-up tube. The TD would run so hot I was afraid to keep using it.

The Cox racing fuel I was using didn't help that aspect either, and it was my only TD at the time so I didn't want to cook it so I switched it back to the jacket. On a normal port BabeBee engine I'm sure it would work because they don't breath as hard as the TD does. The Lite Machines "buggy style" heli-head I am sure would do the job though.

bokker

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Hey Guys,

That boat by cox was the "Seabee" it came in a metalflake darkblue and a two-tone cream and green, these are the only two color schemes I have seen. They still show up on Ebay on occasion, if they are pristine they will go for $400+ to much for me.

bokker

chief3452

Hi Everyone,

I watched the Ebay model seller referenced earlier for a long time. I was very impressed with his attention to detail and period hardware. Here are some examples of his work, Enjoy.

Scott

chief3452

More tasty bits

jetpack

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Killer builds. Thanks for posting, Scott.

What helps that guy out has to be good reference material which is almost impossible to find, I've looked. I bet he has a great library. Lucky dog.

SeaBee! Bokker wins the prize on that one, it had me stumped! [sm=thumbup.gif]

Yeah, vintage Cox cars, boats and such go for an extreme amount if in cherry condition. Makes me want to rob a bank just to bid on some of that.

Ron Olson

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JP, I just got home from a swap meet. They had one of those Cox prop driven cars there and the price tag was up there. I almost (and should have) grabbed a NIB .074 engine that was carbed and muffled for a give-away price of $30.00!

mr hydro 1

This is my micro Hydro I'm building now,"this is the plug",and should soon have one made of epoxy glass.I still have to make the cowl plug ,hope to have the cowl done in a week or 3. ,,I really like the purple anodized hardware that is picted here.I also like to see this become a race program with different classes(have lots of smaller ponds around here to run on, but no ponds big enough for my larger nitros) . I plan on useing a brushless 380 motor with lithium cells ,If I had to make a name for a class ,I think I would call it ,( "lithium Lites" )sounds like a neet class.the hull is 17-1/2 long and 9-3/4 wide. Here's some pics of my progress.and a pic of what it will look like when done.

jetpack

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Ron, so what do you have there that's in the bag?

Hey them .074's are laid out nice for a boat build, I have a second hand one in my collection...might drop it right into that Ske-Vee 10 and see what happens.

You know what else is nice about those .074's is what you've already noticed, the rear facing carb actually WORKS, and the muffler you seen can be turned around to point backward, and a neoprene hose attached to it to feed the slime out past the transom. I scoped out one of the Dumas cool clamps, and if you had a drill press the hole can be opened up enough without hitting the brass tubing so it can slip over the .074's and the .09's that have the same diameter fins, just the bores are different.

Now here's what is bad about the .074's. They happened to be near the end of the line for Cox production, and they skimped on tapering the bores on them, so they don't have much compression even when new. You have to get them really drunk on nitro to see anything out of them. That's where the .09 steps in, they are made like the good ol' days of Cox. Another thing about the .074's is they are reed valves, not front crank rotary valves like the TeeDee's are and the reed limits its top end somewhat.

All good and bad aspects aside, I'm gonna make a motor plate for mine and see what it actually has in it. I think it would be worth monkeying around with. MECOA has all the head sizes now to convert them over to standard short plugs so that's a relief on keeping them running. Keeping up with the original glow heads for these will put you in the poor house.

That price tag of $30 was a give-away, they usually sit around $60 or slightly even more new on the bay.


Mr. Hydro,
We won't squalk that your a 'lekky, you're a master builder[sm=thumbup.gif] Welcome to the thread. Dang nice hull you have going there! Yes, that anodized hardware is probably right up your alley as far as what you are looking with that transom.

I shot an extra question concerning that particular hardware over on the fast electrics forum here at RCU so maybe brouse on over and mark it for yourself. I'll keep any new news posted here also as it comes up. I'm drooling over it myself and scrambling through my boneyard here to see what I can gather up for eBay to scrounge the funds so I'm ready to git some of dat when I hear the news.

Keep going on your plug build and don't be shy with the pics! A new class is a good chance of opening up for what you have like you're wishing, because with the new batteries and motors really opens the door for it.

When I was surfing eBay last time, I paused on a bare 17 1/2" fiberglass U-1 hull that was approximately the same size your building, and estimating how well a glow motor and rails would fit into it.[8D]

Ron Olson

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This wasn't a Cox .074 but some other brand that I never heard of before but looked rather nice. This looked just like a regular plane engine, nothing like a reed valve Cox.

jetpack

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Ron, I posted a pic. Was it this or no?

mr hydro 1

jetpack ,found this let me know what you think.

http://www.nitrorcx.com/jateinnien2f.html

jetpack

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The link brought me to a nitro buggy, all cool though because I surfed around and I stumbled around and seen that same $75 U-1 glass hull for $35 in plastic, RTR with radio.

I think someone is popping glass copies off of it, and trying to make a buck. Looking at the glass copy though, I wouldn't drop a coin on it, it's so wavey and nothing is sharp cornered on it like it should be. It makes a huge difference in speed, especially on low powered hulls like these where EVERYTHING counts big time if you want more than toy performance.

I also seen the Toki motors. They make a .050 with double ball bearings and it is an ABC type with sleeve that the airplane flyers have been talking about. Better designed than Cox but Cox still wins on power. Definetly a nice looking motor though, and could be hot rodded with a tuned pipe and a machined water jacket head if you have capabilities. Something that really cant be done sucessfully with a Cox engine. They don't take to a tuned pipe because they have sub-port induction which robs the pipe pressure.

Airplane heads just won't be able to carry the heat away like they should, because usually airflow is way down with boats because of the engine bay, plus they dont "fly" as fast as a plane would, so theres just less of air to start with. Plus they are always under more strain than air use. Good thing they offer a Buggy head, that would work too just like my idea with the Micro Lite fins on the Cox.

There's a new quest for 1/2A engines now because of Cox disappearing, and then Norvel diving out also. Really the only two serious makers, now gone.

You can still buy O.K. Cub engines like you see in the vintage round nose models above, still brand new straight from the factory...but unfortunately make more noise and smoke than they ever will on power no matter what you do with them.

Thanks Mr Hydro, you helped bring up more topic with that.

mr hydro 1

see what you can find for .05-.09 pull start micro car or buggy motors.I rember there was a 18th scale car with a ,I think it was a .06 pullstart motor.that be nice. thanks: jetpack

bokker

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Hey Jetpack,

Found some 5-40 nuts at microfasteners, http://www.microfasteners.com/catalo...ucts/NUTHN.cfm

bokker

Ron Olson

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5-40 nuts aren't hard to find as they're a Team Losi part but finding a flex cable collet that's threaded for 5-40 is the trick. You can get .098" flex cable as I might have one laying around somewhere in my disaster area or try a wire drive.

jetpack

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Ron,

Yeah I had Offshore machine me up a few couplers with the 5-40's and .098" hole with set screws. He did a wonderful job on them, better than I could with our junk monster lathe that would work better as a ship anchor. Sure wish I had a little collet lathe at home to play with. Now I'm not even in the shop so everything like that gets put on hold.

I think I talked with you before in chat on the .098 cable and you mentioned it did a pretzel on you. Not sure actually what would work best with the little .049's probably the wire but wire almost needs a straight shot to work right.

These Dumas hulls all except the AVL has the motor set pretty far back and the drive needs to take a serious swoop to make the strut. We'll see. I'm still a newbie with this and not many others have tried, so there's more than likely going to be a learning curve going on with me here.

Bokker,

Micro has them your right I followed the link. Not bad on price either, jeez a $1.75 for a 100 count. I am going to write him and see if they are the small hex pattern like the Dumas ones. I hope so. If you try and use a standard size hex with the props I'll be using, the hex patten falls waaay outside the diameter of the hub of the prop, and just boogers up the whole streamline of things.

Now if I switched to the Octura prop, they don't require it because the hub wall and diameter is larger, 1/4" OD I think, and normal hex stays hid behind the hub.

What I currently am working with brass props are a few vintage O&R examples. Now that Dumas has picked up the 1" JG props again they might be a bit different on hub diameter than these. I haven't been able to pick up any to see yet.

Always a hitch with this stuff! Again, we'll see what happens. Thanks for the dig! I'm gone to check out Ron's info on Losi.

Ron Olson

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The problem that I had with the .098" cable was more of "genius" on my part. It's made more for electric motors and brass, not soft aluminum stuffing box tubing. It should take the power of any 1/2-A with no trouble as long as you use brass tubing.

mr hydro 1

found another engine,

http://www.ofna.com/eng-picco-p0.php

jetpack

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Mr Hydro,

The Picco engine link is awesome. It looks like they have stepped up the quality of the Toki .05.

The Picco advertized as a staggering 36,000 rpm capability, and looks like much higher quality internally than the Toki.

In the 1/2A flyers forum there's quite a thread going there on the Toki, and everyone seems to be quite disappointed with its power and quality. Looks like Picco took care of that problem quite well. Nice motor!

Check out the pics I posted. If you compare the internals to a Toki, the Picco blows it straight into the weeds. Nicely machined con-rod. The Toki has a aluminum/brass old style dogbone and is heavy.

One thing that still handicaps the Picco is the crank end on it, plus the short nose room and clearance for a flywheel. If one wanted to spend time modifying one I'm sure it can all be worked around.

Ron,

Thats a good point you brought up about stuffing tubes, and good to keep in mind. Aluminum sure sounds tempting to use. It bends a lot easier than brass, but if it's going to gall up I guess it's best to stay away from it, unless of course a teflon tube or wire drive is used.

About that China strut and rudder package on eBay, the seller wrote me back and said everything concerning the drive like the propshaft, bushings, threads, ect is all imperial size which is standard. Good news for me, I plan on ordering one then and go with my own soldered flex to stub shaft combo, instead of using the square drive he offers. They rob power, noisey, and vibrate.