Re: Tee Dee Performance Crank

1/2A Nut Sat Nov 22, 2014 9:10 pm

I have some different cox powered options for the Skorch.
In the pic:
- Galbraith head
- Nelson plug
- Tornado carb with air bleed
- Red anodized aluminum carb body
- Tatone muffler with pressure tap
- Tornado grish 5x4 prop with TD .09 spinner
- Phenolic thrust washer
- Non SPI .051 cylinder

I sourced some finishing supplies online:
I have applied 7 coats of fuel proofing gloss clear coats over the ply fuselage. I first filled in the grains with 2 part Z-poxy finishing resin squeezing off all excess resin off the fuselage so primarily only the grains were filled in then applied the gloss thinner coats using LustreKote by Top Flite. This method allows for a lighter finish without the need of fiberglass and a thick coat of the more heavy epoxy resin. With the drying / curing times involved the whole process took about a week to finish.

I have some other hopped up cox engines and a stock TD 050 RC that will get a pressure tap on the muffler to try for the fun of it but the reality is the modified engine in the pic will provide statically additional
rpm 1.2k to 2k and serve the plane well as it can idle low for stunt flying and with pressure maintaining great fuel delivery at full throttle.

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**Cribbs74** Sun Nov 23, 2014 4:15 pm

I like the natural wood finish. Good job Nut!

1/2A Nut Sun Nov 23, 2014 9:35 pm

Thank you Cribbs!

Agreed I just couldn't bare to cover up all that lovely wood grain.

balogh Sun Nov 23, 2014 9:37 pm

Do you fuel-proof the tank compartment as well just in case leakage occurs? The plywood will absorb castor and get stained.

1/2A Nut Sun Nov 23, 2014 10:03 pm

Yes good point, I fueled proofed the inside just past the landing gear former.

- First with Z-poxy resin pressed into the grains
- After 24hrs wiped clean of residue
- Finished up with 7 thin coats of the LustreKote.

The process seems to have kept the weight down nice glossy hard finish. After the 6th coat I fine sanded everything smooth and applied the last coat.

The Lil Speedy TD .020 version did not get its grains filled with Z-poxy a mistake on my part. The fuselage had 4 coats of the LustreKote yet the sneaky castor oil has stained the front end thru migration or time, lucky for me I have used ply so its still very strong. The inside was clear coated the oil appears only on the outside surface.

1/2A Nut Tue Nov 25, 2014 12:29 pm

I am continueing the Skorch build adding new posts and photos here:

http://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/11602404-ply-rolled-fuselage-part-deux-1-2a-mini-skorch-6.html

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1/2A Nut Thu Nov 27, 2014 4:05 pm

Woooot pass the gravy!!

Turkey

Happy Gobble Gobble Day.

1/2A Nut Sat Nov 29, 2014 1:35 pm

balogh Sat Nov 29, 2014 5:07 pm

Congratulations 1/2A Nut, a beautiful one..is this powered by a 049 TD?

1/2A Nut Sat Nov 29, 2014 5:45 pm

Yes just very modified TD .051.
Im down to covering the wing with white monokote adding racing numbers and installing the wing servo's will knock that out this weekend.

getback Sat Nov 29, 2014 10:30 pm

SWEET !! That looks shricking wit a 051 mod should knock down some good numbers Damn!

Another fine build to play with There 1/2ANUT . Eric

1/2A Nut Sat Nov 29, 2014 11:58 pm

Thank you Eric!

With a carbon/plastic 4 x 4.5 should see 80+ mph level with 40% nitro and with some diving should do nice passes around 100mph. This one only has 88 Sq.In of wing so less than a larger 1/2A pylon class wing. Current weight less two 9g carbon geared servo's 263g ready to fly with wing covering should be about 10.8 oz. I have a some open exhaust modified TD's also running on nelson plugs to test out which may eek up to 90+ mph 4.5P prop with a exhaust throttle. Small Cox Logo

Still eating Turkey sammies and left over fixings

Turkey

1/2A Nut Sun Nov 30, 2014 1:04 am

András,

Something to consider I know you like the cox 5 x 4 perhaps you should try the APC 4.75 x 4 pylon / combat prop?
I have bought a set of 3 to test they do look good and will hold their pitch. One shown here mounted with a Queen Bee spinner or a .09 spinner will work also can use the cox 1/2A small rubber spinner and adapter as shown in the second pic. Down fall of the rubber spinner you will have to use a spring starter.

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balogh Sun Nov 30, 2014 7:16 am

Thanks 1/2A Nut I will try. APC props are sold here though larger than you suggested.

I had a mid-air failure with a new 5x4 nylon Thimble Drone yesterday. One blade broke in the stem for probably internal material defect or fatigue reasons. Makes me more cautious in future to stay away from the plane of the spinning prop.

Surfer_kris Sun Nov 30, 2014 12:26 pm

The new production black cox props have had some problems, the 5x3 ones can also shred their blades around 20000rpm.

The APC props can be bought directly from APC, and the 4.75x4 is a very good prop. They need to be protected at landings though. The Norvel .049RC will spin these at around 20500rpm (10% nitro and stock muffler), while the .061 will give you an additional 2000rpm (approximately).

Here is my little speed plane, also made from sheet balsa, it just needs an engine cowl before I maiden it;

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Surfer_kris Sun Nov 30, 2014 12:33 pm

Here is a link to the reported problems on the 5x3 props; RCU thread

The test is easy but destructive...

Ken Cook Sun Nov 30, 2014 12:48 pm

I spin the standard non safety tip Cox 5x3's at a consistent 32-34K rpm's. I have the prop cut down to 3 5/8" and never once had one shed a blade even after many ground strikes. Even my Norvel's are running them into the 29K range. I inspect around the hub for stress cracks which a simple flex test will reveal. I did have the safety tip prop 5x3 break on a Bee and never used them since. I do recall Bernie explaining that there may have been issues with them and he would generously replace them. Ken

1/2A Nut Sun Nov 30, 2014 12:55 pm

Great looking plane Kris well done!
What is the all up weight without a cowl, do you have a pic of the underside?
When ready post a videooO

Airplane

Ken Cook Sun Nov 30, 2014 1:02 pm

One thing to note with APC is the white stress marks that can form on the blades. I've seen this on high powered engines but never on Cox related items. As far as bushings are concerned, a piece of fuel tubing is all that's needed. I had designed APC bushings that Mike Parkin was selling on Ebay. These work very well, but prior to that, all of our high performance engines were utilizing tubing on the prop screw which was all on Cyclon's, Fora's and Profi's. Ken

1/2A Nut Sun Nov 30, 2014 1:09 pm

I see the vid was posted back in 2009 back when the 5 x 3 props with the safety tips where marked
Cox Hobbies. Seems like a past issue yes? These days Im sure Bernie has his efforts checked. I did a flex check just now with 2 props bought under Bernies watch a black 5 x 4 and a yellow 4.5 x 4 flexed just fine no signs of brittle plastic. Small Cox Logo

1/2A Nut Sun Nov 30, 2014 1:22 pm

Kris I remember this pic posted back in August I had zoomed in on it appears to be painted? What type of paint did you use in regards to protecting the plane from nitro? There is a special epoxy paint sold in the US for cooking ovens it only comes in a few colors I have had great success with high nitro use, very tough finish.

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balogh Sun Nov 30, 2014 1:23 pm

Surfer_kris wrote:Here is a link to the reported problems on the 5x3 props; RCU thread

The test is easy but destructive...

Shown here is a safety tip 5x3 black nylon prop of which I bought a few from COX Int'l a couple years ago. They were dead on arrival, I have never used them since I noted the fine tangential cracks on the blade.

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The 5x4 black nylons, except from the mishap yesterday, never broke, when spinning 24k unloaded.

balogh Sun Nov 30, 2014 1:32 pm

Surfer_kris wrote:The new production black cox props have had some problems, the 5x3 ones can also shred their blades around 20000rpm.

The APC props can be bought directly from APC, and the 4.75x4 is a very good prop. They need to be protected at landings though. The Norvel .049RC will spin these at around 20500rpm (10% nitro and stock muffler), while the .061 will give you an additional 2000rpm (approximately).

Here is my little speed plane, also made from sheet balsa, it just needs an engine cowl before I maiden it;

Beautiful plane, Kris..looking forward to seein a vid on the maiden..weather permitting, I guess? How much does it weigh? Do you have dihedral in the wings?

1/2A Nut Sun Nov 30, 2014 1:53 pm

I dug through my cox props and found a 5x3 with safety tips I had bought 2 by mistake this year. It says Cox Hobbies Inc. and bent it over stress cracks appeared on the skin right away then bent some more and it snapped right in half what a waste of money. Good job I never used them, could have taken out an eye out!!

Has anyone had a response from Cox why they still sell these??

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Surfer_kris Sun Nov 30, 2014 5:17 pm

Here is a picture of the bottom side too. The wing has a square carbon fibre wing spar for strength, so no di-headral in the wing, only wash-out at the wing tips.

The weight ready to fly (but without engine cowl) is around 8.5oz. That's with a clunk tank and regular 400mAh NiMh battery, I'm a little tempted to try a balloon tank and a lighter battery though (e.g. a 500 mAh smart Lipo). That could save another oz or more of the weight I think.

The colour is a regular spray paint for cars, I have used that in the past and it has been okay with low nitro fuels, the paint will mostly see exhaust residue too. I have even once painted a plane with regular, oil-based, indoor paint. Still looks okay about 30 years later...

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