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Old Dec 17, 2011, 09:08 AM
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Australia, SA, Henley Beach
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Folding Lazy Hawk

I thought Iíd start a thread about making my new Lazy Hawk fold up.

Followers of the Shrike 2 thread may have seen my Shrike with its quick release wing spars and tail. It fits very neatly into a travel box and Iíve decided to give the Lazy Hawk the same treatment.

The ferrules Iím making are essentially the same as my current Shrike quick release ferrules, but beefed up to Lazy Hawk size. This design with double brass tubes is probably over-engineered, but is strong and reliable and the result of some painful testing on the Shrike!

Iíve learnt a lot developing these quick release wing spars and despite being made by hand in a very basic workshop, the pair on my Shrike work very well. But they were preceded by several failures and Iíve a hint or two to pass on if anyone is serious about making their own. Iíve also spent a lot of time compensating for inaccurate drilling, and this time I decided to have the holes drilled by a machine shop.

The photo shows the blanks just after theyíve been drilled and an almost finished Shrike ferrule for comparison. The Shrike spars are 4mm and the Lazy Hawk 5mm.

As with the Shrike, the closest carbon fibre I could find to Seanís original spars was a bit thicker, but I prefer this because it gives me room to taper them. I have a couple of thicknesses and tapers for the Shrike, which I can swap in the field very quickly.

Because of my eccentric drilling of the retaining pin holes, I have dedicated left and right spars for the Shrike, but the Lazy Hawk spars are so accurate that the left and right are interchangable and a dream to locate. I canít wait to get them finished.


I havenít started on the tail attachment yet, but before you can fold the Lazy Hawkís wings you have to make another mod that wasnít necessary on the Shrike.

On the Shrike (yellow bird), the power plate bolts to the wing membrane in line with the end of the diagonal wing batten. Thereís sufficient gap for the wing to fold between the bolt and the batten. On the Lazy Hawk (cranberry bird) the power plate extends beyond the end of the batten, preventing any fold taking place at all!

After considering other quick-release ways of attaching the power plate to the wing dacron, and even experimenting with folding power plates, Iíve decided to go with the simplest solution. Iím going to shorten the power plate so it attaches where it does on the Shrike. This will actually make the Lazy Hawkís power plate smaller than the Shrikeís!

Iíve expressed elsewhere my confidence in Seanís design and acknowledged that my modifications will probably lessen the performance of the bird. (My wing spars are heavier for a start.) So Iím in a dilemma about the power plate.

Looking at its function to stabilise the trailing edge and tie it to the fuselage, I canít see the advantage of extending it beyond the end of the diagonal batten. Not by 12 or 15mm surely? But I do acknowledge that Sean does things for a reason and this mod might also diminish the birdís performance.

Anyway I look forward to feedback and comments.

Having fun,

Andrew
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Old Dec 17, 2011, 12:22 PM
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Hi Andrew,

I'm pretty sure your new LazyHawk has a slotted quick release tail rocker. I started putting those on all of my kits after reading your posts, not that I have had any other requests for any sort of quick release features but it was easy enough to implement so I went ahead and did it so that should help you some. I also have slotted spar ferrules for anyone who prefers them. They do allow a quick folding up of the wings in a car,etc., just maybe not what you were wanting for the travel case though.

Altering the power plate will for sure diminish flight performance. Is there any way you could fold the bird up and leave the power plate alone?
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Old Dec 17, 2011, 02:09 PM
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Have you flown your cranberry Lazy Hawk yet? I think flying it stock would be a good idea before you add any mods to it. Make sure it flies correctly out of the box first.

Please post some flight pics of it. That is a nice looking bird. I actually wanted to keep that color for myself after building it as that was the last of that polyester ripstop material.

The supplier (and only US supplier) of that particular fabric is closed down to due to storm damage and nobody knows if and when they will open back up so you've got a unique color bird for a while at least. The only other source of that material I can find is in Europe ( it's actually made in Japan where the factory there too experienced damage from the tsunami last Spring) but the cost is more than double in Europe not to mention the shipping charges and the fabric comes on long heavy tubes so it's costly to ship.

I do have alternate suppliers for good super lightweight ripstop in red, blue, and white, but the rest of my colors are from a slightly heavier fabric and my color selection isn't as large as it was. The super light fabric is typically refered to as "1/2 ounce" while the slightly heavier is referred to as "3/4 ounce". Both work well but the thinner material is better for smaller birds. The Lazy Hawk in my old gliding youtube video..the one with the yellow wing that glides for a long time has the heavier fabric so it does work just fine. Just thought I would mention my fabric situation.
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Old Dec 17, 2011, 10:58 PM
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Sean thanks for the material explanation. The florescent yellow material I have on my LH is a heavier rip stop that I have ever felt. Its has a nice feel. I know I should just fly it, but that's my baby.. kinda scared. Ill do it soon tho
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Old Dec 18, 2011, 01:08 AM
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Thanks very much for your comments, Sean. I'm very proud to be the owner of such a unique bird and I can't wait to see it in the air with the sun shining through the wings. The colour is fantastic!

I haven't been able to fly it yet because the tail still hasn't arrived, but I do intend to fly it in stock configuration first to get a true impression of how it goes. This is my dilemma with the power plate because my philosophy so far has been not to make any modifications that I can't easily remove and go back to stock. An obvious temptation is to disassemble your wing spars and use the rods in my quick release spars. That way I would be using standard spars with stock flexibility, but I wouldn't be able to revert if my spars didn't work out.

Theoretically, apart from a bit of extra weight, my spars and tail maltese cross shouldn't make any difference to flight characteristics, but the power plate clearly might. I'm playing with my old broken Shrike power plate to see what I can rig up.

I don't have any G10, or I’d just make another plate, but I think the best option is to drill the existing power plate closer in and make a direct comparison by re-locating the bolts. Obviously another hole in the middle of each arm will make it weaker, but I’ll find out whether there’s an unacceptable drop in performance. If I decide to revert to the full length I’ll just have to hope it’s strong enough, or make another if it breaks.

But like I said in my previous post, I can’t see how extending it beyond the end of the diagonal batten adds much stability to the trailing edge. Or maybe there’s something I’m missing?
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Old Dec 18, 2011, 01:19 AM
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Quote:
Originally Posted by Ubute View Post
I thought Iíd start a thread about making my new Lazy Hawk fold up.

Followers of the Shrike 2 thread may have seen my Shrike with its quick release wing spars and tail. It fits very neatly into a travel box and Iíve decided to give the Lazy Hawk the same treatment.

The ferrules Iím making are essentially the same as my current Shrike quick release ferrules, but beefed up to Lazy Hawk size. This design with double brass tubes is probably over-engineered, but is strong and reliable and the result of some painful testing on the Shrike!

Iíve learnt a lot developing these quick release wing spars and despite being made by hand in a very basic workshop, the pair on my Shrike work very well. But they were preceded by several failures and Iíve a hint or two to pass on if anyone is serious about making their own. Iíve also spent a lot of time compensating for inaccurate drilling, and this time I decided to have the holes drilled by a machine shop.

The photo shows the blanks just after theyíve been drilled and an almost finished Shrike ferrule for comparison. The Shrike spars are 4mm and the Lazy Hawk 5mm.

As with the Shrike, the closest carbon fibre I could find to Seanís original spars was a bit thicker, but I prefer this because it gives me room to taper them. I have a couple of thicknesses and tapers for the Shrike, which I can swap in the field very quickly.

Because of my eccentric drilling of the retaining pin holes, I have dedicated left and right spars for the Shrike, but the Lazy Hawk spars are so accurate that the left and right are interchangable and a dream to locate. I canít wait to get them finished.


I havenít started on the tail attachment yet, but before you can fold the Lazy Hawkís wings you have to make another mod that wasnít necessary on the Shrike.

On the Shrike (yellow bird), the power plate bolts to the wing membrane in line with the end of the diagonal wing batten. Thereís sufficient gap for the wing to fold between the bolt and the batten. On the Lazy Hawk (cranberry bird) the power plate extends beyond the end of the batten, preventing any fold taking place at all!

After considering other quick-release ways of attaching the power plate to the wing dacron, and even experimenting with folding power plates, Iíve decided to go with the simplest solution. Iím going to shorten the power plate so it attaches where it does on the Shrike. This will actually make the Lazy Hawkís power plate smaller than the Shrikeís!

Iíve expressed elsewhere my confidence in Seanís design and acknowledged that my modifications will probably lessen the performance of the bird. (My wing spars are heavier for a start.) So Iím in a dilemma about the power plate.

Looking at its function to stabilise the trailing edge and tie it to the fuselage, I canít see the advantage of extending it beyond the end of the diagonal batten. Not by 12 or 15mm surely? But I do acknowledge that Sean does things for a reason and this mod might also diminish the birdís performance.

Anyway I look forward to feedback and comments.

Having fun,

Andrew
Hi Ubute,

Just want to mention that brass is a heavier and less strong material than steel . You can save some weight and add some durability by replacing brass tubes with stainless steel ones.Please check Doctor Kakuta's " how to do it" videos.

Success!

Otto
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Old Dec 18, 2011, 04:49 AM
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good work andrew , i would fly it before modifications just so you can compare and i was just reading you are.You will be truly amazed how different and majestic it is good luck and regards brian
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Old Dec 18, 2011, 04:52 AM
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IMO shortening the power plate a little wont make a lot of difference cheers brian
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Old Dec 18, 2011, 06:08 AM
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Hi Otto, thanks for the suggestion. I have read about Dr Kakuta’s stainless steel tubes, but brass was what was available to me so I went for that. I did know that stainless steel was stronger than brass, but I didn’t know it was lighter, so thanks for that info.

Thanks also Brian for the opinion about the power plate. I’m making a short fibreglass one for testing. Fingers crossed, I hope to get Cranberry in the air by Christmas.

Andrew
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Old Dec 18, 2011, 06:24 AM
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great some video if you can i would love to see it cheers brian
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Old Dec 26, 2011, 06:07 PM
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Here are some pictures of my lazy hawk, Cranberry, which I finished building on Christmas day. Itís next to the indomitable Shrike for comparison. So far it has been too windy to fly anything, so I have to imagine how it will look gliding high above with the sun shining through its wingsÖ
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Old Dec 26, 2011, 07:20 PM
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Nice looking birds
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Old Dec 26, 2011, 11:41 PM
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look great andrew cheers brian
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Old Dec 27, 2011, 02:14 AM
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Nice photos. Love that Ocean Spray Cranberry juice cocktail hawk.
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Old Dec 27, 2011, 04:21 AM
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comparing sizes the shrike looks the same size as my clipped wing PH
and they say size doesnt matter great colour andrew
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