Cox 049 powered race boat

OVERLORD Thu Oct 23, 2014 12:06 pm

This video was posted a few years ago by Brad I think, on RC Universe. It's a Black Widow powered boat that goes quite well. At the end, the boat turns over and the pilot gives a detailed and technical explanation of what happened exactly.

Some more pictures and info can be found here:

http://www.rcuniverse.com/forum/speed-rc-nitro-boats-117/8498373-1-2a-size-dumas-boat-club-13.html#post10369573

Lieven

Davenz13 Thu Oct 23, 2014 4:14 pm

The explanation may not have been in English but it wasn’t hard to translate lol!

My brother was involved in speedway for about forty years, first as a rider, then helping in international meetings. He often recounts how he found it quite funny to hear Russians Poles Czechs Danes etc gesturing and talking in their native language and then hurling the item in their hand towards the bin finishing with that universal word that begins with f understood the world over as “No longer serviceable”.

I hope I was able to present that in an acceptable way.

dckrsn Thu Oct 23, 2014 4:20 pm

I thought your explanation was both acceptable and succinct Dave.

Potty mouth Bob. lol!

1/2A Nut Fri Oct 24, 2014 1:38 am

Jim Walker 1/2A Hydro

http://www.americanjuniorclassics.com/movies/Boats.wmv

The Famous Jim Walker starting the Miss Thritway and a run on the pond. Clapping

1/2A Nut Fri Oct 24, 2014 2:05 am

http://www.dumasproducts.com/product_info.php?cPath=39_80&products_id=444

Cox 049 powered race boat 2314-210

For those wanting to try a 1/2A boat.

OVERLORD Fri Oct 24, 2014 2:21 am

The German boat has a flexible drive shaft. Looking a the prop, which has an M4 thread, the flex drive must be 1/8" diameter. It seems that it is not supported much by a brass tube, except maybe where it goes through the hull. Isn't there any risk of wobble? Or is the 1/8" flexible drive thick enough to remain in place. What if you would use a .098 (2,5mm) flex drive?

1/2A Nut Fri Oct 24, 2014 3:36 am

Yes the reality if used with even a TD engine a 2.5mm flex drive is enough to do the job. You could use wire drive too as an option. I prefer no drag straight drive shaft longer than what dumas sells to minimize the angle of attack.
2mm to 3mm or 1/8th in should hold up.

You can use teflon tube to protect the cable with some brass stock to protect the teflon and reduce vibrations / wobble.

roddie Fri Oct 24, 2014 6:00 am

I had seen that vid before.. and marveled at it! There aren't many Cox powered "submerged-drive" boat vids out there. I've had an outrigger in the works for a while.. Shocked

.. I have a similar Dumas kit to the one shown above. I'm trying to come up with a transom-design that allows for adjusting the height of the drive. I'm leaning toward a vertically-slotted transom.. with a guide-plate for the output shaft-tube, that can be raised/lowered. This is an important aspect for tuning the drive/hull. Flex drive cables are nice.. but if you make your own; you need to note the direction of the "twist" in the cable, so it doesn't "unravel" when loaded.

1/2A Nut Fri Oct 24, 2014 7:32 am

Just a quick note - as about to leave to the office for the day the hydro is low lying by design and submits itself to more water tension the prop runs on the hub here is the likely on plane water line when not hoping over water ripples. Its light big plus and hops level when it does. Would have been faster if the rudder was reshaped as shown the rooster tail lets you know the prop is airing out a blade.

Cox 049 powered race boat Germhy10

OVERLORD Mon Nov 10, 2014 10:33 am

Interesting information, thanks guys. When reading different building threads of outriggers and other hull-shaped race boats, they are all finished with resin and sometimes also with fibreglass. In case of 049 driven boats, would iron-on covering do the job?

1/2A Nut Mon Nov 10, 2014 3:32 pm

I have used iron covering if you overlap the seams well perhaps use balsarite to make it more sticky would be helpful otherwise the golden rule is a epoxy coat final finish as boats typically use high nitro mixes. If there is anything in the water such as twigs, sticks and the like could compromise the wood.

ian1954 Mon Nov 10, 2014 3:40 pm

Don't use iron on covering. It is not tough enough and will easily tear, scratch or abrade away! It will leave you with soggy balsa.

You can get very light glass cloths 18g per Sq M. That and resin with judicious sanding won't add that much weight.

Unless you can seal the balsa very well, iron on covering is not a good choice. Even then - it is not very strong.

As in the previous post - you would me suprised what any sort of float debri can do to a balsa hull!

1/2A Nut Mon Nov 10, 2014 4:42 pm

On a side note I only use aircraft ply for all my boats these days. Back in the day I had some micro balsa boats that held up well with monokote only because they are so light covering to scale and weight was robust. You can use spar urethane with ply construction and only epoxy the inside of the hull but epoxy is king. If you make a balsa boat you should consider glassing the bottom of the hull for RTR boats weighing more than 10oz. There is one other trick with balsa boats applying a thin sheet of plastic to protect / same stuff used for protective covers for documents.

anm2 Tue Nov 11, 2014 5:16 am

ian1954 wrote:Don't use iron on covering. It is not tough enough and will easily tear, scratch or abrade away! It will leave you with soggy balsa.

You can get very light glass cloths 18g per Sq M. That and resin with judicious sanding won't add that much weight.

Unless you can seal the balsa very well, iron on covering is not a good choice. Even then - it is not very strong.

As in the previous post - you would me suprised what any sort of float debri can do to a balsa hull!

Ian, What constitutes well sealed balsa? Will standard dope applied in enough coats do the job? Thanks, Andy

ian1954 Tue Nov 11, 2014 6:24 am

I would use "sanding sealer". It is dope with fillers and additives. It sands to a nice finish.

I would apply the first few coats thinly so that it can soak a little further into the balsa.

Polyurethane varnish will also work but it can be a little thick.

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