subarubrat

My Feedback: (1)

I made a call the other day to Kress jets and left a message asking them how many orders would they have to have to make a production run of the RK049 ducted fan kit. I am curious what iterest there is in buying this fan if they made it again. They easily go for $100 or so on Ebay. 1/2 A ducted fan was a marginal success in the early 80's in some cases and a failure in others. With todays entire 4 channel system weighing less than one servo in the old days, and construction materials being so much lighter 1/2 A ducted fan is viable now as has been demonstrated by Kamdax. And of course there is the Norvell instead of that fussy cox teedee. The Kamdax unit is a great unit, I have a few, and probably better than the RK049 on a thrust to weight comparison but it is still an awesome unit. So, if Kress said they would make a production run how many would you buy?

EASYTIGER

My Feedback: (119)

You know I'm a 1/2a jet nut. I own both Kamdax and Kress units. Since the Kamdax one came out, there is absolutely NO reason to use the Kress. The kamdax is everything the kress is not. Simple, reliable, and thoughful.
The Kress one is what happens when engineers design something without really talking to PEOPLE. It consists of about 75 discreet parts, has verry difficult assembly procedures, has no provision for throttle, and heavier and less efficient than the Kamdax one.
Let me ask you this:
WHY would you want a Kress 049 fan?

subarubrat

My Feedback: (1)

Because it has those 75 parts and is overly complex to accomplish the task, a bit of nostalgia for that classic unit, and because it is a visually impressive unit. My Turbax has like 3 parts, but I just built an F4 from plans to use the 1978 RK40 I got on Ebay. So you could add on a healthy dose of just because. Sort of like buying a Morgan car, they use wood in the chassis and a big fat 8cyl making less than 200Hp, but it is unique and just a neat looking piece of machinery.

EASYTIGER

My Feedback: (119)

Fair enough! My Moggie makes no sense, it doesn't even HAVE eight cylinders!
But I think the limited handful of guys who would be interested in an RK049 for nostalgia purposes would already be well-served by just ebay and swap meets, and that if you had 100 of them, the price would drop to $15 and you would STILL be sitting on 80 of them!
If you want one, I have one of the originals...the actual one built by Walt Musciano for his F-84 and shown in several books and magazines. No engine in it, and it is dissasembled to some degree(to get the engine out), but you can have it. Walt would be happy, I'm sure. He gave it to me.

subarubrat

My Feedback: (1)

Your probably right.

pecojets

the NEW kress 709 its only a bit bigger than the rk 049 , and with a cox tee -dee 09 has twice as much power , less parts ; AND with the kamdax retail price of 40.- dollars theres no sence for kress to produce the rk-049 FOR AROUND 100.- ; but ,how about the kress impeller in the kamdax fan ? maybe we can use only the impeller from kress ; i have the kamdax mig-15. also i have the kress .049 impeller ; let see if mr time allow me to do some test

EASY TIGER , DID YOU ALREADY TEST IT ?????

pecojets

subarubrat

My Feedback: (1)

Either he did, or someone did, I read the thread a while back. Less thrust as I recall. I would like to see a re-issue is not for practical reasons to compete with Kamdax. I would like to see it lower the going rate a bit that is for sure. Very much like there is no reason for Tamiya to rekit the grasshopper, it has been made obsolete, it is just for the sake of it's unique approach to the task.

EASYTIGER

My Feedback: (119)

I did test the Kress rotor in the Kamdax, I got 11 ounces of thrust instead of the 14 from the Kamdax.

The Tamiya Grasshopper, well...apples and oranges. There must have been three hundred grasshoppers bought for every RK049. And the Grasshopper WORKED! Which is why so many people have fond memories. Maybe if Tamiya still has the tooling, they could do a run, but they will probably find out that the market for such a thing will get saturated VERY soon. They are worth a bundle now because there are not that many around. Add 500 new kits to the mix, and they won't be able to GIVE them away!

Thomas B

My Feedback: (4)

I have some nostalgic feelings for the RK-049 unit, but lets face it. It is just plain obsolete.

EDF units in this size range are far more reliable and user freindly than a glow df in this size range.

The practical upper limit for an RK-049 is about 16 oz of thrust.

People are taking almost double that from a MF 480 EDF and brushless motor on a regular basis.

If you have to go small glow, the Kamdax unit is a better way to go.

Interestingly enough, the 3" RK-049 impeller works VERY well in the Kyosho EDf shroud using a suitable brushless motor.

I seriously doubt that even the new Kress 709 impeller works as well as is claimed. I ran some tests on the old one and it fell FAR short of claims, even with a great running Tee Dee .09

EASYTIGER

My Feedback: (119)

Yup. Overrated efficiency, I think. The fact that it would not beat out the Kamdax rotor is telling. I NEVER got the thrust advertised out of ANY kress unit. Never saw, or heard of anybody, who ever got a pound out of the RK049.
All you say about EDF versus baby ICDF is true. EDF makes more thrust. It's just not the same thing, though!

subarubrat

My Feedback: (1)

EASYTIGER, Tamiya IS re-kitting the grasshopper! I have on on pre-order at Tower, not a bad price either, although I remember them and their clones going for as little at $39 in the day.

Part of the draw for me is making the older more creative (IMHO) ideas work with modern technology. I built a COX Cessna with a Norvell, and then full housed it, flaps, ailerons, brakes etc. It weighs signifigantly less than OEM and is an absolute wonder to see and fly. I also took a MRC Desert Thunder buggy which was one of MRC's "world scale" cars. These things were tough, handled great but were a bit sluggish due to their rhobust construction (weight). So I stuck two brushless motors on it and WOW.

jrpav1

My Feedback: (17)

I came across this old thread while I was looking for an EDF to replace an RK-049. I actually have a Midwest A4 and an RK-049 that I bought way back when it was new. Luckily I never finished the project so I now I have a good chance of success. As cool as the old RK-049 is, I realize that an EDF will work much better. So the question is - what's available now? I know enough about how fans work to realize that even though a smaller diameter EDF will generate as much, if not more thrust than the old RK-049 that doesn't mean a smaller fan will work properly without major mod's to the shape of the fuselage ductwork (i.e. adding weight). Does anyone know of a good EDF substitute for the RK-049?

Bob_B

My Feedback: (11)

What diameter is the RK 049? There are edf fans from 30mm 215mm
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