Speed - RC Nitro Boats For all your rc nitro fuel burning boating needs.

1/2A Size Dumas Boat Club

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Old 03-17-2017, 02:50 AM
  #501  
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Thank you, yes will be getting some vid for sure. Will build the sponsons this weekend
and be ready to maiden / vid the rigger next weekend weather pending. Will start with a
X427 for a base line 1.14cc comparison to the Picco .8cc riggers first run caught on vid.
Est. potential 46 mph the rigger is much lighter not having a conventional strut / rudder
with less painted wood weight, bit less weight in the battery used and smaller throttle
servo.

https://www.youtube.com/watch?v=Gv7EUv6yfvs Published on Oct 9, 2016

1st Run - Picco P-Zero Outrigger Hydro Profi Tuned Pipe
.85cc / .05 ci / 1/2A car engine converted for boat use.
Very stable, needle valve set a bit rich for the first few
runs, need to lower the strut a bit, tracks very well.
Will do another vid after I tweak the setup.
Stock X427 / 20% castor 30% Nitro. Per Doppler
reading best pass 62.25 Kph or 38.68 mph. / 27,290 rpm

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Old 03-17-2017, 04:23 PM
  #502  
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i am building a jae fast electric rigger at the moment , starting off with a Leopard motor then i may go to a neu motor which specs mention 60k unloaded rpms.
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Old 03-17-2017, 05:44 PM
  #503  
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That is some crazy rpm's times are changing gone are the days with elect nicads from the late 80's I was
thrilled to get 28k on the water then with colbalt brushed Astro .05 motors.

The Picco .85cc gets 50,080 rpm insane for IC engine was fully broken in or I would not tweak the needle
that high.

https://www.youtube.com/watch?v=baxt_4kmO_k

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Old 03-17-2017, 07:57 PM
  #504  
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yes i doubt we would get close to the specified rpms on both electric and i.c. motors. i had an ops 21 speed engine that was claimed to rev to 32k but i think the best it ever did was approx 25k. even the good old Cox .010 was claimed to rev to 30k and that was how many years ago ? 40 ?
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Old 03-18-2017, 11:15 AM
  #505  
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Claim HP on the dyno from the manufacturer can be a bit touted at times, however there is some true gold out there.
It's all in the set up and how you choose to load the engine with craft size / shape and prop selection.

Last summer I did up two small .010 sized planes for all out speed best pass: 130.4 mph / 35.2k rpm / custom cut prop.
Best rpm pass 41,985 stock prop. Doing down wind passes right at the video cam, average speeds are much less into the wind.

No other plane documented on YouTube goes this fast with a TD.010 / stock prop
https://www.youtube.com/watch?v=Lyknz70Eds8 Clip of the fastest TD .010 in the world.

https://www.youtube.com/watch?v=3i4r2kDOBlQ Prop 2.56 x 4N / 30% Nitro:
Static 28,858 rpm / 109.3 mph / .028hp / 21w / 1.5oz thrust
Unloaded best pass per prop calc 133mph audio tach / 130.4 mph per doppler reading
and best pass on this vid 35,184 rpm / 3oz RTF / 2ch RC micro race plane.

The 2nd smaller race plane was set up and tested at the end of last year only 2oz RTF it has hit 118 mph with lower
pitch test prop same prop with the plane shown in the vid does 97 mph. I then shelved it for safe keeping and testing
this yr. should do 145 mph + with it this summer in the thinner air same conditions.

I have been drawn to the smaller displacement engines do to thier ability to run at
higher rpm's without self destructing. The Italian Picco .05 is the most impressive so far
but some of the other small car engines have a shot too so exploring whats possible.

The new rigger design is a step in the right direction for more speed the only way to
truly leap forward in speed is to reduce the tub width even more. Use balsa thin carbon
blended hull, nix the large fancy custom stainless steel fuel tank for a minimalist nylon tank
only good for a 5 min run. Airfoiled carbon booms, carbon rudder, aluminum prop and carbon
drive dog. carbon tube for the stuffing box. Single cell lipo with a step up voltage regulator.
Exhaust throttled header pipe with a tuned pipe and a clean large lipped venturi intake.
I think 55 mph + with the new SH-.07 design and if the above was implemented 85 mph is possible.
Impressive for 1/2A .

0.06957 cu. in. / 1.14cc

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Old 03-18-2017, 12:55 PM
  #506  
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now that 010 model is realy quick , maybe there should be a pylon race class for this size ha ha. i am friends with F3D champ Chris Callow and your 010 craft looks as quick as the large F3D class. as for electric rigger hulls i am building a JAE - Fe 21 size and must say the design looks good the actual weight of the plywood is rather heavy , maybe ok for glow power oval race trim but for faster speeds and electric power i would like to see this hull built with lighter timbers. as you mentioned balsa and carbon would be the go.
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Old 03-18-2017, 01:54 PM
  #507  
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Yes the balsa is to reduce flex being between two carbon sheets, the hand launch guys are using very thin
open weave carbon over balsa and foam. When epoxy bagged it's very strong for the weight. There are different
grades of ply Midwest for me is the best. I am currently framing up my sponsons with 3/32 ply from Finland it seems
softer and heavy. Midwest feels harder, better glue, compressed and cured with care allowing for thinner ply choice.


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Old 03-19-2017, 05:52 AM
  #508  
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Base coat of neon yellow on the right sponson thus far, looks like this will be
my visual aid for the sponsons.


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Old 03-19-2017, 03:10 PM
  #509  
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looks quick. hey have you noticed the Zippkits JAE 21 / FE sponsons ? there is a nice step on the front section of the bottom ride plate that helps disperse water from the front are of sponson so the rear main ride plate is clear of any water. this is supposed to benefit in extra speed. actually the tub botton also has a simular set up [ ski plate and front step ] .
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Old 03-19-2017, 11:02 PM
  #510  
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Yes here is a pic for reference
The idea is if you bang in a hard turn in rough water and bury a sponson it will pop
up on top and recover faster keeping the speed up. The trailing upper portion of the
sponson is great for supporting the weight of the batteries with sitting stagnant. It's
a good design if you have the power to push the extra weight and size.

The entire Picco sponson is free out of the water less about a inch in the trailing edge.
See example still shot of the Picco rigger on the water.

There are some big difference's in these sponson's for the .07
They are not as wide (.656" vs Picco at 1") as the over all rigger weight is much less and
much longer (10" vs Picco rigger at 5.5") to absorb windy day water. The water at the
club can be glass smooth but many days the wind comes in from the other side of the lake
bad enough to only allow gas mono's to enjoy jumping around. The sponsons weigh less because
I did not have the same ply thickness on the outside to support the boom attachment the same way
as the Picco rigger.

The entire build was meant to improve what I learned from the Picco rigger at the existing body of water / conditions
the rigger will have to deal with. The design is like the long lanky Jap boats that run on big water off shore, where
they follow in a chase boat. I hope this rigger will handle rollers not so much as to jump off them rather cut through
a bit of a mix of the two actions.

......

Zip kit 21E in rough water slow motion - watch and see what
would be needed to run in these water conditions:


https://www.youtube.com/watch?v=uymBzwqz0rQ
Smooth water comparison:

https://www.youtube.com/watch?v=L8H6DQ0K88c#t=29.828417
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Old 03-20-2017, 12:18 AM
  #511  
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Done 457g / 16.12oz less fuel:


SH-.07 Rigger 1.14cc

All ply with balsa core sponsons.


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Old 07-23-2018, 10:51 PM
  #512  
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Old 08-06-2018, 01:52 PM
  #513  
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I accidentally posted my Lil Swamp Buggy to the last page of the 1/2A Atlas link rather than this one. Thankfully, Pond Skipper responded. Anyway, I am so happy to find other hobbyists who love 1/2A. I have a Lil Swamp Buggy powered by a .051, outfitted with a Tarno carburetor that I built for my kids in 1980-1981 and they had a blast with it. After a few runs, I realized the engine mount fuel tank didn't have enough capacity for each of them to have a turn and looked for a solution. A 1oz Sullivan fuel tank was the perfect solution. Lots and lots of running time and laughter. The boat was very fast and the kids learned to overcome control reversal which came in handy when they later learned to fly RC. I remember being unsure if mounting the tank so low below the carburetor centerline would work but it was beautiful since, unlike an airplane, it would never be inverted...well, not supposed to be inverted . Anyway, I am so happy to find others who have an interest in 1/2A. Funny, I would fly 1/2A plane, taxi out and land with a carburetor at the flying field and the big displacement guys would often come over and look in awe. We were in Europe where fuel was enormously expensive and I could fly all day and smile. Anyway, glad to see there is a Dumas 1/2A link. I send good will and cheers to all of the members!
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Old 08-09-2018, 09:43 PM
  #514  
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I received a SK Daddle Jr. in the mail today. The plans for the former's are on a typical letter size paper
and numbered to help reference to the written instructions. The second plan sheet was drawn up full size here is a pic to share.


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Old 08-12-2018, 07:21 PM
  #515  
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Here are some of my 1/2A props, I have two others currently being used with my 1/2A outrigger hydro's.

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Old 09-02-2018, 06:31 PM
  #516  
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Found two very rare new old stock Dumas 1/2A metal props on ebay the other week. 1"x1" prop originally meant for submerged drive.
I have one bought back in the day and modified it for surface drive works very well, tweaked the tips with some needle nose pliers.





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