Two Sheet No Waste Twin Tail Under Development

[dharkless]

Hi Guys & Gals,

I usually introduce my new designs in the article section but I thought I would give the Forum a try this time.

Earlier this year I introduced a series of One Sheet No waste Twin Tail designs. There are two sets of plans from which you can build 4 different versions, two long wing and two short wing.

This will be a two sheet version.

I am headed out for the maiden flight. Here is a the pre-maiden picture. Hopefully it will look the same upon my return.

 

[HawkMan]

Those look pretty cool and look like they would be great for FPV/camera, but is that just two barbecue skewers for the tail ?

 

[dharkless]

No. They are fiberglass plant stakes. They are flexible and that is one of my concerns. On the second prototype with swept wings I am going with 5/16 poplar dowels from Lowes. They are same weight but stiffer.

 

[HawkMan]

have you considered triangular foamboard struts?

 

[dharkless]

No maiden today! I got out to the field with about a dozen rain drops on my windshield. Within about 5 minutes the sky opened up and we had a cloudburst that lasted almost an hour. I spent an hour under the field shelter with a dozen people who were sure that I had brought the rain. The rain quit as quickly as it had started but everything was was too wet for flying foamies.

 

[dharkless]

The original concept for the one sheet version was predicated on having several 36" X 3/16" dowels on hand. When I discovered them in my old balsa supply chest I said to myself "Now , what can I do with these?" I decided early on to cut them in half for twin tail booms and the design grew from there. Therefore I did not consider other boom alternatives.

Although some readers suggested that I may get flutter, there were no stability issues. In fact the planes flew quite well. I have continued that simple approach for the larger design. I had some 3/16" fiberglass tubes on hand from some orchids I had gotten my wife. They were 24" long which worked out well for the larger design. They are also stronger so I thought they would be suitable (and they may still prove to be so). Only later did I decide they might be too springy and looked for alternatives. I got 48" 1/4 and 3/16 diameter dowels from Lowe's. It turns out that the 5/16 ones weigh the same as the fiberglass tubes and are considerably more stiff. The second build (swept wing prototype) uses those and I will probably re-do the one in the picture with them as well. I did want to try one flight with the fiberglass to determine whether the flexing causes any problems first.

If I went to foam booms and staying with the no waste concept I would have to reduce the wing and tail areas to make the booms. I was not eager to do that.

 

[aj308win]

I look forward to the report on how she flies.

One of your original twin-tail no waste trainer builds inspired this:

I started to lay out your plans, but then folded the wing on my bloody wonder. I stretched the Bloody Wonder wing out to 36" and kinda took your twin tail design and made it work here... I do get some tail flutter, but my rudders are not perfectly straight.

 

[dharkless]

That is a nice adaptation. What are your booms made of? If you hold by the nose can you make the tail bounce?

I tried the maiden again today but the hot glue did not hold the fiberglass well. Before I launched I noticed that they were coming loose at the trailing edges of the wing. I am in the process of switching over to the 5/16"dowels now. I just took a break to let the glue gun heat up...

Here are the wooden booms on the second build:

 

[aj308win]

My booms are made of 1/2x1/2" pine, that has a 1/4" hollow square removed from the center. I originally intended for them to be multicopter booms that I could run wires inside. To make them, I cut a 1/2x3/8" pine strip, and then reset the table saw blade to cut down the center 1/4" deep at 1/8 and 1/4" from the rip fence (poor man's dato blade haha). I then took a 1/2x1/8 strip and CA glued it to the top of the channel I created. I was worried about the strength of my improvised booms on my Tricopter, so they were sitting around when I was looking for boom material. They weigh more than I would like, but they have held up to some gnarly landings into soybeans and aggressive aerobatics.

If I shake the nose, there is no bounce in the tail. I get a funky "tail wag" in the air occasionally.

 

[dharkless]

The fiberglass tubes did not hold well with the hot glue. I have changed them to the 5/16 poplar dowels. I noticed them coming loose before launching for the maiden today, fortunately!

I am ready for another try tomorrow.

 

[dharkless]

My first build with the fiberglass was pretty bouncy. There is a little bounce in the second build and the re-work of the first one with the 5/16 dowels but it is MUCH less. I really have to shake it hard to get any. I think it will be pretty stiff in the air.

Your booms have a net cross section of .1875 SI. My dowels have a section of .0767 SI, so less than half. Poplar is also lighter than pine on average. My dowels probably weigh about 1/3 of your booms.

I did have to add a little nose weight because the wooden dowels used more glue at the tail section than the fiberglass ones did.

 

[dharkless]

I like the wire rudder braces and the cooling scoop.
Do you have a hatch on top or the fuselage? If not how do you access your gear?
You can add stability on twin tails by angling the rudders out on each side. Just make the connecting rod about 3/8" longer and then split the difference. It makes the tail self correcting.

 

[aj308win]

I cram a 2200 all the way up front inside the fuse. I cut a bevel on the back of the "Battery Pod" and use a bamboo skewer as a hinge at the rear of the fuselage. To hold everything closed, I have been simply been wrapping a velcro battery strap around the outside of the fuse and battery pod. It isn't elegant by any means, but it got me in the air. When I eventually scrap this plane, there are a bunch of ideas I have to improve the next one. This was engineered on-the-fly; I expected some compromises and shorcuts. The rudder braces are actually 2mm carbon fiber sticks. I was at my LHS and for $3.50 I felt like buying 4 feet of the stuff.

I will have to bend up a new connecting rod that is a hair longer, that sounds like a nice, easy solution to the tail flutter.

Have you had a chance to fly yet?

 

[dharkless]

Nice idea for the battery pod. You could probably use a second skewer toward the front to hold it up. If you reinforce the holes with gift card or plastic cutting board they will stay tight.

I did fly the prototype. I had a problem with the elevator not responding to radio input due I think to the control rods being too long and flexible. I did almost one full pattern and was trying to turn back to land when the rudder would not pull it around or keep it up. I ended up nosing in hard tearing up the fuselage and the middle of the wing behind the spars. I spent the last two nights putting it back together. I now have the servos at the tail and very short control rods. Had to go a little bigger on battery to balance. I am ready to try again next time out.
It was flying really well before the crash except for not having enough elevator.

 

[menachg]

people post some plans fore the benefit of the ones that prefer not to experiment if someone else did it already before them

 

[dharkless]

I will do an article with plans and step-by-step instructions once I get all the kinks worked out.