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Archive for November, 2010
Posted by SkyCadet | Nov 29, 2010 @ 03:37 PM | 3,562 Views
I recently trimmed my Dubro 830 skis I mounted on the Super Decathlon BL.

While the stock skis were fine, they were a bit large I felt, and added extra unneeded drag and frontal lift. The pane flew fine with them, and the snow on TO tended to collect in the grooves where the tracks were, making the skis very nose heavy until flying for some time. (wet snow, not powder).

I cut along these grooves, and now the skis are 6.25"x1.25" each, having trimmed 3/8" or so off the rear as well. Dremmels are great tools for this!

Attached are the photos of the new improved setup. These work better on the plane - more nominal trim, less frontal lift affect when flying (flies more like with wheels), and better cruise performance as well.

They still glide nicely in the snow!

Two flights were hugely successful at -5C: 12 minutes each!

Good to go! The Super Decathlon BL makes a superb winter aircraft!

SkyCadet
Posted by SkyCadet | Nov 29, 2010 @ 03:12 AM | 3,361 Views
I just finished a set of small skis for my Micro Champ.

These were made from a popsicle stick, cut in half. this one was slightly curved lengthwise, so it made a great ski shape! I then used a Dremmel tool to taper the front ends and the rear. Used two Nylon clamps I had surplus from a spare plane (rounded rectangular pieces with one hole on each end, about 1" long).

I had two 1.5mm ID collets from my Dubro 830 ski set, perfect to use with the micro champ wires. The Nylon clamps were cut flat on one side to act as ski pylons, and I used graphite epoxy to hold them square to the ski. The collets were also GE'd to the nylon.

Painted to match - got pretty close. Undersides coated with 30% dilute white glue to seal the ski bottom and make smoother for running on the snow.

Adds about 1.3g or so more than the Dubro 123 sport wheels I put on. The total ski area is around 1.9 sq. in. Using 0.875 sq. in/oz. (14sq. in/lb guideline), this can handle around 47-50g. Perfect, since my AUW is around 47g!

Keeping the skis fairly small allows to minimize weight, drag and frontal lift tendencies with the skis. Angled about 5 up from flat. Prop clearance is around 6-7mm, so the plane is similar to stock wheel clearance for the prop.

See pix below...

SkyCadet
Posted by SkyCadet | Nov 28, 2010 @ 01:49 PM | 2,817 Views
While the Dubro 830s are very suitable for smaller park fliers to 34oz or so, I feel my set on the Decathlon BL are too large for the plane. I am cutting mine back a bit to get more performance from the plane, and it will also reduce drag.

My plan is to use a Dremmel tool and cut the skis along the inner track slot, and trim 1/2 " off the back. This will make the skis' total surface area (both) around 18 sq.in. Plenty for my Decathlon. Should reduce weight by 30%, and also drag.

The plane flies well with these as is, but I have a lot of extra surface than really is not req'd.

SC
Posted by SkyCadet | Nov 26, 2010 @ 12:22 AM | 2,951 Views
Well, I had a one-flight window today before dusk, when the wind died off. We had a "Chinook" that is, a warm westerly wind typical off this time of year.

Temps the last few days have been below 0F/-20C, so no flying in THAT weather - just too darned cold, esp. with micro flurries and winds.

Today was sunny, mild [for winterish weather], and so I maidened the Decathlon BL on skis. It it flew superbly! I needed 3up clicks on the elevator trim on my DX6i to get it level at 55% throttle, but the plane flew nicely. With only a light breeze, the skis did show some drag and nose lift, especially in turns - my Dec BL usually noses down without up elevator on a turn, being a 3ch plane, but turns seemed flatter with the ski-induced lift, requiring very little up elevator to coordinate.

Landing was AWESOME! I settled the plane in after an 8 minute run, and it glided in for a VERY smooth TD and glided on the skis, virtually balancing on them for about 7 feet, before the tail slowly settled in - 12 feet total.

This was so much fun! I am looking forward to flying every mild winter day [-6C or warmer] I can.

SC
Posted by SkyCadet | Nov 22, 2010 @ 12:37 PM | 3,946 Views
These are the units I installed on the two planes below:

http://www.horizonhobby.com/Products...?ProdID=DUB830

Pic of the set uninstalled is attached. I used graphite mixed with 6-minute epoxy [1:1:1 mix of graphite:resin:hardener - I call this GE] inside the hollow underside of the mounting section to make the structure more rigid and allow for more secure mounting to the planes' landing gear. The hollow underside is filled approx 1/2 full of the black-gray GE, with the ski sitting flat upside down. Flexure is retained somewhat, and the stuff won't get brittle even at -18C or 0F.

It takes about 8-10 minutes for "shaping" cure (at which point the material won't flow anymore at all, but may still be sticky), 20-30 minutes for 90% strength cure, at which point one may drill into the marks on the sides to match their gear wire/bolt diameter. After 1h, the GE is fully cured (graphite slows down the reaction a bit, but enhances the flow characteristics of the material to make it fill in gaps and crevasses). it takes 3-4 minutes for the stuff to get sticky or stringy, so mix well fast, and start applying in the gap ASAP. GE flows very well when first mixed, so just scoop and lay in. I used a popsicle mixing stick to apply it. The material will draw down like syrup into the crevases. Any drips on the ski underside can be cleaned up with an alcohol-laden Q-tip if done within 10 minutes or less.

#830 skis come with smaller collets to hold onto thinner wire...Continue Reading
Posted by SkyCadet | Nov 21, 2010 @ 04:41 AM | 2,929 Views


Well, I am ready to go this winter with two planes: My Pilot-1, 1/8 Scale 7AC Champ, and my Super Decathlon BL!

I used Dubro #830 Park Flyer Skis for both planes. I think that the Champ will still run well on snow with these skis also, given what I have seen on full scale planes. It should warm up to around just below freezing later this week, and we are expecting some snow, up to 6-8cm. Should be perfect conditions to fly the planes in.

I'll start with the Dec BL first, to get a feel of the plane in snow, since I am more familiar with that plane. Then, the Champ!

Below are some photos of both planes with the skis installed.

SkyCadet
Posted by SkyCadet | Nov 08, 2010 @ 12:26 AM | 3,275 Views
Well, on Wednesday [Nov. 4], my Super Decathlon BL had a mishap.

During a turn downwind, I suddenly lost positive control of the plane. I was shooting on-board video during the flight, but upon inspection of the footage, it was unclear exactly what happened. The plane turned away from me and then went into a spiral dive, and then a spin.

It ended up in a prickly thorny tree, and was basically a write-off when removing it from the shrub; the fuse was heavily punctured, the tail ripped, and the gear mains were cracked during impact into the tree. To repair it would have taken more time than building from scratch...

So, using a second spare wing, tail, fuselage, and two new servos and ESC, I rebuilt the plane from the ashes! I used my original motor, which I had to repair with a new shaft during Flight #101 [nose in crash from 10'], and placed a new motor in the Dec #1 after flt. 101 until the mishap.

White glue [40%] coating done on ALL lifting surfaces [exc. on hinges on tail]. Graphite epoxy [1:1:1] done on tail, while squaring to the fuselage. Painted with Cadmium Yellow acrylic enamel - near perfect match.

Used another Dubro micro tail wheel, epoxied a 0.020" wire connection off the rudder control horn to the wheel strut [see pix below]. Makes a superb steerable tail wheel system, low profile, but effective, and far superior to the stock skid system. I used graphite epoxy [GE] to affix to fuselage underside after tail placed on plane. The wire is a &...Continue Reading