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Cox Pica Dualist ARF

Old 12-29-2006, 08:59 AM
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bhdutch
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Default Cox Pica Dualist ARF

I just got the new Cox Pica Dualist twin for Christmas and I am considering engines. It calls for 2 40 size two strokes but I've run 4 strokes since the 1990's. My friend always used 60 two strokes on the Dualists he flew and it was a rocket! I've never had a twin cylinder 4 stroke so here is my plan.... I am considering twin SAito 60T's. I will go with standard gear instead of retracts because of the engine weight (trade off I hope). But am wondering if I should go with the 90T or 100T? The 100 is shorter (base to prop) and either one would only cost me 2-3 oz in weight each over the 60T. But the 60T's should fly this plane just fine. My concern is that the 90T or 100T will be just too much engine for the dualist. I've flown GP's Super Sportster 40's converted to twins in the past. Any thoughts here and am I missing anything obvious by going to twin cylinders in this model? I do know this will probably be the sweetest sounding twin engine ever!
THanks,
Ed

I saw a post on another thread that said their covering wasn't good. Mine has a nice covering job. But they are right, the decals are installed already and I would like to see those separate.
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Old 12-29-2006, 01:51 PM
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Rickles56
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Default RE: Cox Pica Dualist ARF

Don't the twin cylinder Saito's have considerably less power than the singles of the same size. Check out the specs.
Old 12-29-2006, 02:29 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

You have a good point. The FA 62 can swing a 13x6 prop @ 9900 and the 60T can only swing a 13 x 5 @ 8000.
The next step would be the new 90TS or 100T. They swing a 14 x 6 prop @ 9900. But wouldn't the real question I need to ask be will the two 60T's equal or surpass the power of a 40 size two stroke that swings a 10 x 6 @14,000. Saito does not have HP ratings so I'm not sure how to make that comparison. Do you?
Thanks,
ed
Old 12-29-2006, 04:43 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

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Old 12-29-2006, 06:03 PM
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boingram
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Default RE: Cox Pica Dualist ARF

Hi...that post re: the covering was probably mine, but I called it a Sig kit so I may not be receiving this thread. This is my third Duelist, the other trwo being old PICA kits by Dave Platt. This is a very quick design, and is very pretty with retracts..

My thoughts on the engine situation:

1: One of the reasons for a twin is the sound and it is my feeling that nothing sounds nicer than two 2-strokes in sync.

2) The weight of the 4-stroks is gonna be higher that two AX 46's. A twin by it's nature has a higher wing loading due to one more engine, one more servo, and another tankfull of fuel.

3) The engines are sidemounted and I don't trust 4-strokes to stay lit like a 2C.

4) I currently have a Seagull Dual Ace and a Cedar Hobbies Twin Stik. Both have OS 46AX's and I've never had a burp.

5) Dot all you "i's" and cross all your "t's"...twins are a hoot!

Bo
Old 12-29-2006, 06:08 PM
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sewflynwa
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Default RE: Cox Pica Dualist ARF

BHDutch,

The biggest problem I had (and still have) with my kit built Duelist was ground clearance for my props. When I fly off grass, it must be close cut to allow me to take off without the props cutting furrows. This is the one thing that has prevented me from ordering the ARF. Until I know I can put the right size prop on my engines without having ground clearance issues, I am reluctant to have this headache again. What is the distance from your engine's driveshaft to the ground?

Thanks,

Cary
Old 12-29-2006, 06:22 PM
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BillS
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Default RE: Cox Pica Dualist ARF


ORIGINAL: bhdutch

You have a good point. The FA 62 can swing a 13x6 prop @ 9900 and the 60T can only swing a 13 x 5 @ 8000.
The next step would be the new 90TS or 100T. They swing a 14 x 6 prop @ 9900. But wouldn't the real question I need to ask be will the two 60T's equal or surpass the power of a 40 size two stroke that swings a 10 x 6 @14,000. Saito does not have HP ratings so I'm not sure how to make that comparison. Do you?
Thanks,
ed
To make an intelligent decision regarding engine size you need to know the all up weight of the airplane (without fuel) and the wing loading in oz per sq ft.

Generally 4 strokes are expected to develop about 15% or so less power than 2 strokes. However a 4 stroke also turns less RPM, which can influence the flight envelope on the top end.

Bill
Old 12-29-2006, 06:40 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

Sewflynwa,

The best I can measure the distance between the centerline of the engine and the ground will be 7"- 7.25". Not an exact science because the kit is still unassembled but that should be close.

Dutch
Old 12-29-2006, 07:20 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

I got these off the web sight:
Wingloading:
26-32oz ft2

Weight 9-11 lbs.

I would be building mine without the retracts which will save some weight. I am a bit concerned about balance with the heavy engines.

Dutch
Old 12-29-2006, 09:21 PM
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BillS
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Default RE: Cox Pica Dualist ARF


ORIGINAL: bhdutch

I got these off the web sight:
Wingloading:
26-32oz ft2

Weight 9-11 lbs.

I would be building mine without the retracts which will save some weight. I am a bit concerned about balance with the heavy engines.

Dutch
Both wing loading and all up weight are respectable. Forty size 2S engines will be sufficient and a .50 2S would be overkill. Power is often not your friend with a twin. I have flown a 10 1/2 pound twin with .25 engines and there was not enough reserve power for safe flying. I fly an 8-pound twin with .25 engines and the power is about right. I also fly a 10-pound twin with .40 plain bearing engines and the power is slightly more than needed. I also fly a 6 1/2 pound single with a .50 and would not hesitate to use .50’s on a twin up to 16 pounds.

At the upper end of the wing loading the stall speed will be in less than 30 mph and propping for a top speed of 70 or so mph will give adequate flight envelope.

Hope the information helps.

Bill
Old 12-29-2006, 09:27 PM
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boingram
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Default RE: Cox Pica Dualist ARF

Yes, prop clearance will be a big factor. On my other Duelists I ran 10/6 on old K&B FP 40's.

My Dual Ace has 11/4's on my AX 46's, but if I do not grease the landings, I get prop strikes. 10/6's make it too fast and I worry about flutter due to the speed...even with fixed gear.

Bo
Old 12-30-2006, 12:34 PM
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sewflynwa
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Default RE: Cox Pica Dualist ARF

Dutch,

Thanks for the information, 7"-7.25" is great news for me but not sure if the info helps you very much. All I can do is relate the tremendous frustration I encountered with broken props due to minimal prop clearance.

Cary
Old 12-30-2006, 07:32 PM
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Default RE: Cox Pica Dualist ARF


ORIGINAL: sewflynwa

Dutch,

Thanks for the information, 7"-7.25" is great news for me but not sure if the info helps you very much. All I can do is relate the tremendous frustration I encountered with broken props due to minimal prop clearance.

Cary
I hate breaking a prop due to minor ground contact and don’t hesitate to use bigger wheels and/or longer gear when ground clearance is a problem. Appearance is only slightly compromised and usually longer gear exists somewhere in the collected junk.

Bill
Old 12-31-2006, 10:11 AM
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boingram
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Default RE: Cox Pica Dualist ARF

Hi all....

Anybody notice on the cover lid of the box that the Robart part number for the suggested air kit is Robart # 118. I can not find that on Robart's web site, but they do have a # 188. Transposed numbers?

Also, any one have a suggestion how to remove the applied graphics. I really wish thay had left that for the builder/assembler.

Bo
Old 12-31-2006, 12:53 PM
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boingram
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Default RE: Cox Pica Dualist ARF

Hi all...

In response to my own ??, I just removed the graphics. Not too much trouble. They are simple vinyl appliques.

I simply slid a single edge razor blade under a graphic over a supported area so if I cut the covering, I could iron it back down to the wood airframe. Started with the horizonal stab as it looks like it is symetrical and if I screwed up, I could just install it with the numbers down.

The only area of concern is the "I" and the "s" as they are over unsupported areas.

Just take your time...no big deal.


Much prettier airframe with those graphics gone! (IMHO)

Bo
Old 01-01-2007, 11:31 AM
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bhdutch
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Default RE: Cox Pica Dualist ARF

Thank you everyone for your responses!

With your help and suggestions I've checked engine weights, HP ratings, fuel consumption, fuel capacity (10 oz and not much room to do anything else), prop size and ground clearance, overall weight and wing loading, retract weight, engine physical size and fit and numerous other things. I'll post pictures when I make decisions and get things installed.
Thanks again for the input.

Dutch
Old 01-01-2007, 11:37 AM
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bhdutch
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Default RE: Cox Pica Dualist ARF

Bo,

How about some after pictures?

I think your air kit is probably what you said. The standard air kit which is #188VR or 188VRX.

Dutch
Old 01-01-2007, 01:35 PM
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boingram
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Default RE: Cox Pica Dualist ARF

Dutch,

I don't know about you, but my kit quality is not representative of the price. I know that bright yellow is probably a hard color to get right, but Cox has a reputation to develope.

The covering around the nose (squared off and not finished), the concave area around the turtle deck are pretty pitifull. And two of the f'glass nacelle rear fairings fell off and riped the covering on the top of the wing.

I also have a framed-up Pica Duelist ready for final sanding and will take some comparison shots. Looks like the rudder on the Cox kit is not as big as the original, but it is balanced where the Pica kit is not.

This would be a great $200 ARF, but the flying community is paying a premium price for a new kit that will be quite popular. I only hope the QC improves.

Bo
Old 01-01-2007, 02:20 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

Bo,

Whoever did mine did a much better job, however, the fiberglass fairing on one of the wings did come loose like yours but has not ripped the covering. The covering around the nose and turtle deck on mine looks fine. If I find additional items as I'm assembling I'll report them. Have you contacted Cox regarding these issues? If I had as many issues as you're describing that's what I'd do.

Dutch
Old 01-01-2007, 02:37 PM
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Default RE: Cox Pica Dualist ARF

Dutch,

Just tried to send them an e-mail re: my concerns. The input fields on their site do not work.

Having been an accomplished modeller for over 40-years, I am NOT impressed!

I'll try again tomorrow....

Bo
Old 01-01-2007, 05:07 PM
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Default RE: Cox Pica Dualist ARF

I really like the looks of the Cox Pica Waco YMF ARF, in the photos it looks like a beauty. I hope that it is a quality product as i would sure like to buy one of those, preferably the bigger version.
Old 01-09-2007, 08:31 AM
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Default RE: Cox Pica Dualist ARF

After a lot of research I purchased two Saito 90TS's for my Dualist. The reason I purchased the 90's vs the 60's was two fold.
I think the 90TS will be an easier resell down the road if I resell them and they only weigh about 1.2 oz more than the 60's and have a lot more power....hopefully not too much power. Now my challenge is to find larger fuel tanks or carry a stop watch with a count down timer so I don't run out of fuel!

Thanks for all of the input everyone. It's been very helpful.

Dutch
Old 01-12-2007, 12:34 PM
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Default RE: Cox Pica Dualist ARF

Dutch,

I received mine in great shape and the covering is well done. I will be running OS 46 AX's in mine with spring air retracts. Look forward to telling everyone how it turns out.
Old 01-12-2007, 07:16 PM
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bhdutch
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Default RE: Cox Pica Dualist ARF

Looking forward to how yours turns out. I opted for four strokes instead of retracts. As it is, I'm gonna have more $ in it than my Helicopter.
One post I saw the individual was removing the decals. I've had success doing that with the heat gun I use for shrinking the covering. I'm gonna put checkerboard on the bottom of the wing but don't know what I'm gonna do with the rest of the color scheme tho. Picked up some dye so I can tint the canopy last weekend.

Dutch
Old 01-18-2007, 08:21 PM
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Default RE: Cox Pica Dualist ARF

Engines are in........[img][/img]
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