Collaborators - build 1 - 800 mm KFM flying wing

[FoamyDM]

This little guy is a TON of fun, so Ok...

I have to rebuild anyway. Last flight hit a bleacher, which cracked it in half, and sheared off the foam from one of the ailerons. It's what I get for not using Stranded packing tape.
I couldn't believe it!

I will get them together... or you can print yours at 55%. and just find the mid point between the top 2 layers... No, a new plan set is simpler.

 

[FoamyDM]

I have a question though about KFM wingfoils.

I made the first 445mm one with 2 layers per your suggestion, or 1 layer of lift. Which was enough for a moderate pass with a 3s 850mAh pack, 12a BLHeli ESC and the Tachyon 1408 3750 motor mounted on a bottle cap with two 3.7g servos - 110g of AUW weight. (2s 80g)

Q: Would three layers, or two lifting pockets. end up creating twice the lift, allowing slower flight?

 

[Hai-Lee]

Firstly the "Pockets" are not lifting pockets but rather the steps capture a roll of circulating air which smooths out the effective airfoil and hence provide a smooth airfoil section which provides the lift. ( A bit like what we call a 'Spoiler" does when used on the rear of a car).

An additional layer and step would have 2 effects. Firstly it would make the wing a lot heavier and secondly it would be like using a thicker airfoil section. You would get increased lift but also increased weight and drag. On a smaller wing the effect could adversely effect its performance. As an alternative you could make the top layer a shallow pyramid over a spar or similar to increase the wing thickness without adding too much weight or material! I could do a rough drawing if you do not quite understand what I am referring to.

If you wish to try the third layer on the smaller wing you could try using the middle layer WITHOUT its paper. FB with paper removed weighs around 40% of what the full FB weighs. The centre layer could also have lightening holes cut in it where the upper layer cover it.

Let me know which way you would prefer to proceed!

have fun!

 

[FoamyDM]

Thank you Hai-Lee. Your explanation tells it plain.

I might try a number of tests on this subject... 3 layers no paper with holes and a Cellophane shrink wrap. 3 layers with holes and strategic paper removal, and 2 layers paper on the inside. Either way you will see it in the other thread.
I will post a link here for those interested from this thread.

 

[Hai-Lee]

Thank you Hai-Lee. Your explanation tells it plain.

I might try a number of tests on this subject... 3 layers no paper with holes and a Cellophane shrink wrap. 3 layers with holes and strategic paper removal, and 2 layers paper on the inside. Either way you will see it in the other thread.
I will post a link here for those interested from this thread.

I still recommend the paper on the top and bottom surfaces just for strength but the centre layer can be paper free and the area covered with the top piece it can be like swiss cheese!

If you decide to remove ALL of the paper then you will definitely need some spars CF or similar!

Looking forward to your experimental build!

have fun!

 

[Hai-Lee]

Finally got a video of the wing flying. Not great quality and close to ridiculous wind speed but I took it up anyway!

See: https://drive.google.com/open?id=1lk00RuUQUvHPCt1XfYvNBIEU6iKC8FMW

Have fun!

 

[Hai-Lee]

It has been a while since I have added anything to this thread and so I will start off with a few posts in relation to making the wing even more collision resistant. The need arose when a couple of wings actually collided with solid structures including colliding with a steel light pole when going at maximum speed! After analyzing the damage caused further reinforcing was added and tested!

Here is a pic of the added spars/structure.



The picture shows a CF wing spar, (black), and a couple of bamboo skewers along the LE of each wing. The skewers are back from the actual LE to allow the foam to deform and absorb some of the energy before the skewer being impacted. The skewers actually spread the impact forces across a far great area of the LE and wing and thereby reduce the likelihood of a fracture ripping a wing panel off.

There are a couple of shorter Bamboo reinforcements to be added to the wing TE but they purpose will be explained, and locations shown, in the next post.

Have fun!

 

[OliverW]

It has been a while since I have added anything to this thread and so I will start off with a few posts in relation to making the wing even more collision resistant. The need arose when a couple of wings actually collided with solid structures including colliding with a steel light pole when going at maximum speed! After analyzing the damage caused further reinforcing was added and tested!

Here is a pic of the added spars/structure.

View attachment 142075

The picture shows a CF wing spar, (black), and a couple of bamboo skewers along the LE of each wing. The skewers are back from the actual LE to allow the foam to deform and absorb some of the energy before the skewer being impacted. The skewers actually spread the impact forces across a far great area of the LE and wing and thereby reduce the likelihood of a fracture ripping a wing panel off.

There are a couple of shorter Bamboo reinforcements to be added to the wing TE but they purpose will be explained, and locations shown, in the next post.

Have fun!

I may have to build one of these.. Lately I have been obsessing over mighty minis and small wings..

 

[Hai-Lee]

I may have to build one of these.. Lately I have been obsessing over mighty minis and small wings..

You will find it rather enjoyable but there is a down side.

Since building my first one It seems that I always have one or more being built. It seems that others like the simplicity and the rugged nature of the bird and you may be inundated with requests for you to build one for them.

So far I have built over 50 and STILL people are ordering them based purely upon their own desire to join in the fun with the others! Even the LHS has ordered them and I keep bumping to RC pilots who own one.

If you are a good pilot with a good radio build it very light but if you manage to test the solid structures around the flying field then fit the spar and other reinforcements. I still fly and love mine though I think an even more powerful motor is on the horizon!

have fun!

 

[mayan]

Along time ago when I just started flying wings, and had many issues with the FT designs, @Hai-Lee recommended I build a KFM Wing. At first I wasn't sure about this, honestly just because I didn't really like the look of the airframe but once I built it and flew it I was hooked. It is a great, durable, steady airframe perfect for learning to fly wings. I recently lost one at the field and never found it, one that was actually setup waiting for clover antennas to be able to fly FPV. No matter how much I searched I just couldn’t find the plane and eventually gave up hopes of finding it. I was bumped out about it for a while and refused to build a new one but then the clover antennas and a new camera arrived. I decided that it was time to try FPV so I built a new KFM Wing and set it up for FPV, however before I can go out and enjoy my new KFM Wing I feel like I never really got to grieve the loss of the old one. Here is a short video that I made to pay my last respects to a bird that was good to me for such a long time.

 

[andrej]

Is this wing well suited to flying between bushes and trees on FPV?

 

[vhandon]

Is this wing well suited to flying between bushes and trees on FPV?

Yes, I built several for FPV barnstorming and they work great.

 

[mayan]

Is this wing well suited to flying between bushes and trees on FPV?

Very has a great durability.

 

[andrej]

Thanks for the answer. Years ago I was made a kfm-4 profile, flying was quite slow, flying perfectly between trees. I hope this wing (here looks like kfm-3) will fly not worse. That's how my old kfm4 wing flew

 

[andrej]

put the motor 1806 2300k prop 5x6 battery 3S 1300mah. It flies pretty fast. If you put the 1400kv motor and the 7x6 prop, it will be slower? Reflex do you have how many mm?