R/C 2x Upscale Rokitflite Fake Wulf rocket glider

[burkefj]

I saw a posting on FB the other day and it got my mind working. I decided to do a pure R/C 2x upscale using BT-80 tubing, and doing a complete swag on the dimensions/sweep etc just looking at the photos in the Fake Wulf Gallery as I've never had or seen one in person. I tried to keep it under 6 oz, and indoor test glides showed real promise. I wanted to keep the nose/transition for the looks as I really like them. I wound up using openrocket to print a 1.5" long transition from 2.6" to 1.6" on thick photo stock and then cutting the forward part of the body tube into little pointy fingers, about 16 of them so when I slid the transition over the fingers they would center and allow me to glue it to fingers and not have to add the weight of a tube and centering rings. Worked great. I also used the template to cut vinyl wrap to go over the transition after it was installed.

I was a bit worried about wing flex, I went light on the carbon for weight and they did turn out to be a bit floppy, on the 9th flight this morning I overstressed it and bent the wing slightly, so I pulled it off and made a new wing with less dihedral, less wingtip toe in(to reduce pitch up effect) and doubled the spars. Flew great, hands off glide, just touch the ailerons for a turn, no elevator needed, just a slight flare before touchdown. The new wing is a bit heavier so flight weight is 6.5 oz now, glide weight around 6, but you can see glide is very nice. 35" wingspan.

I decided to leave it in the white winter scheme to save weight and hand cut some vinyl trim for markings.

 

[burkefj]

 

[tab28682]

Simply awesome!!

 

[Tom Flint]

Awesome! I want one.

 

[Ez2cDave]

Frank,

Now, THAT is VERY COOL !

Any chance of adding "flaps" to create some undercamber to increase lift and glide duration ?

Dave F.

 

[burkefj]

Frank,

Now, THAT is VERY COOL !

Any chance of adding "flaps" to create some undercamber to increase lift and glide duration ?

Dave F.

I has full span elevons, I don't know what it would do to pitch if I tried to run them as flap/elevons, I already need up elevon for glide due to the CG shift, so I can't really put down flap...The problem is not the glide duration, it is pretty good, the problem is boost altitude due to weight, if I went to a bigger motor it would go higher, but would not be stiff enough and flutter would be an issue and then CG shift would be much worse and glide would suffer, it's just a sport flyer.

 

[Ez2cDave]

I has full span elevons, I don't know what it would do to pitch if I tried to run them as flap/elevons, I already need up elevon for glide due to the CG shift, so I can't really put down flap...The problem is not the glide duration, it is pretty good, the problem is boost altitude due to weight, if I went to a bigger motor it would go higher, but would not be stiff enough and flutter would be an issue and then CG shift would be much worse and glide would suffer, it's just a sport flyer.

I was just thinking that it looks capable of a lot more . . . The ability to "work thermals" would be very cool !

Dave F.

 

[burkefj]

I did a flight today where it boosted really straight and right of the top it started to roll and yaw quite a bit and I switched to glide trim and it didn't really react it just kind of went into a big spiraling circle with a little doink at the end. Both of the wings had torn about halfway just inboard from where the elevons are cut, that happened on my first rendition of the wing and I made a new one but stiffer but apparently flex was still an issue even with the fairly slow boost. Everything was functional on the model I think it was just flexing the wing at the tear instead of deflecting the elevon, so I tore the wing off and made a new one out of 9 mm and just kept it flat so I could use straight spars, so no dihedral and no tip droop, I also extended the services to full span. I'll try it out tomorrow. Weight came out exactly the same.

 

[Ez2cDave]

Frank, are you thinking Wing Flutter?

Sounds like a likely culprit to me.

 

[lakeroadster]

Frank, are you thinking Wing Flutter?

Sounds like a likely culprit to me.

A thumb drive camera would help drill down on what's happening... and would be very fun to watch.

 

[burkefj]

A thumb drive camera would help drill down on what's happening... and would be very fun to wat

A thumb drive camera would help drill down on what's happening... and would be very fun to watch.

Not in a 6.5 oz model that is already on the edge for that 18mm motor, any extra weight would kill it and using a more powerful motor would definitely cause more Wing flex and flutter.

 

[burkefj]

Frank, are you thinking Wing Flutter?

Sounds like a likely culprit to me.

I did see just a bit of flex on the boost I didn't really see flutter normally I can see it if it's bad this could have happened in a previous flight and I just didn't notice the cracking. I have noticed a tendency whenever I have wingtips and I've tried many different iterations that those tend to exacerbate flutter problems in the thin wings, so it could be that those cranked down wingtips were causing an issue. I thought about gluing the crack and taking the wing tips off and seeing how it did but I felt it was just better to pull the entire wing and put a thicker one on that was just flat since I've got elevons I don't really need the built-in dihedral anyway. It did look cool with that gull wing sort of like a romulan bird of prey. I knew that the wingspan and the stiffness were a little lacking but I was banking on the fact that it was kind of on the edge for that motor so the boost speed wasn't very fast, but you don't know till you test it.

 

[Ez2cDave]

I have wingtips and I've tried many different iterations that those tend to exacerbate flutter problems in the thin wings, so it could be that those cranked down wingtips were causing an issue.

Frank,

The "Dihedral Break Lines" on those Wing Tips are not perpendicular, are they ?

They look "angled" to me, in the pics . . .

If that is the case, they would create "Wash-in" or "Wash-out" ( In this case, I think it is Wash-out ), right ?

Could that be be source for inducing Wing Twist & Flutter ?

Dave F.

 

[aerostadt]

I have been thinking of making a new Double Shuttle using Depron reinforced with adhesive paper on both sides, but I am not sure that the wings could take the stress. The main reason for doing so is that it takes so much effort to build the wings from balsa reinforced with paper and white glue.

 

[burkefj]

Frank,

The "Dihedral Break Lines" on those Wing Tips are not perpendicular, are they ?

They look "angled" to me, in the pics . . .

If that is the case, they would create "Wash-in" or "Wash-out" ( In this case, I think it is Wash-out ), right ?

Could that be be source for inducing Wing Twist & Flutter ?

Dave F.

They're angled inward slightly as in the original design which I intended and thought gave a little bit of wash out as well as a little bit of drag to help with yaw stability but that may have been causing the issue.

In any case the test flights this morning were good I was just slightly tail heavy on the first flight and a nickel and a penny fixed that and I reduced the throws since the full span controls are more effective nice easy boost and reasonable glide getting about 30 to 35 seconds of glide on about a 300 ft boost

 

[sr205347d]

made a new one out of 9 mm

Or you could stiffen a 6mm wing with packing tape with minimal weight gain.

 

[burkefj]

Or you could stiffen a 6mm wing with packing tape with minimal weight gain.

I thought about that but the double spars I used in the 6mm Wing made it weigh the same amount as the new straight 9 mm wing plus I think the wingtips were causing some twisting flutter and I would have had to do something with those as well.. I also wanted to redo the controls to be full span also.

 

[Ez2cDave]

I have been thinking of making a new Double Shuttle using Depron reinforced with adhesive paper on both sides, but I am not sure that the wings could take the stress. The main reason for doing so is that it takes so much effort to build the wings from balsa reinforced with paper and white glue.

That sounds interesting . . .

I got a "mental image" of the COX "SPACE SHUTTLE AMERICA" . . .

 

[burkefj]

Test flights were great with the new Wing after a little CG and throws adjustment! 7 flights this morning, 300' boost and 30-35 second glide.

 

[Pepe Le Pew]

Many years ago I designed and built a small, twin boom rc plane and I test flew it on an estes E motor, my daughter is now 25! I may build another soon.

 

[BABAR]

Not your cup of tea, but would be interesting to go back to original design and fly this as a boost glider with a rear eject pop pod.

of course, since the center has to be “hollow” to accommodate the lifting pod fuselage, finding space for the battery and the electronics may be challenging. Without the motor (which would come out with the pop pod under streamer or chute) you’d have a somewhat lighter model.

as you say, however, it is a Sport flyer. The goal of sport is FUN. You have, in this case (ans currently built annd flown) and as always, achieved that in spades.

when was the original released? I think as old as it is, it is still too young to be a competitor in the Estes Classic Model category. An RC version flying on the original Pop Pod design would be very cool.

 

[kjohnson]

when was the original released? I think as old as it is, it is still too young to be a competitor in the Estes Classic Model category.

May 11, 2009, so not Classic Model qualified. For that event it has to have been released prior to 1990.

kj