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Hellcat Build with 250cc Radial

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Hellcat Build with 250cc Radial

Old 01-16-2009, 01:33 PM
  #51  
flyn2high
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Default RE: Hellcat Build with 250cc Radial

The hellcat has a very distinctive aileron hinge. You can see them in this full scale photo.
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Old 01-16-2009, 01:44 PM
  #52  
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Default RE: Hellcat Build with 250cc Radial

I tried to lay out the aileron so that I could have the same hinge arrangement as the full scale Hellcat. The geometry gets a little complex due to the aileron getting shorter and thinner at the wing tip. Also shown are the drawings of the hinges and the ones I cut from 1/16” 304 Stainless Steel. A 2-56 screw and lock nut is used in each one to secure them. The corrugations on the hinge are so that the epoxy will be able to secure them better. I plan to have them fit in a pocket so that I can slide them in and out and glue them in when they are all in alignment. There is no reason they can not be made from G-10. I was worried that the glass fibers would fowl up the coolant pump on my milling machine.

There is also nothing wrong with hinging it per the plans. It will still look and fly very well. You will have to get under the wing to see the difference.

By the way full size PDF drawings are available for the layouts and the aileron and flap hinges at:

http://www.liskyhawks.org/images/hellcat/wing_parts.zip
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Old 01-17-2009, 01:10 PM
  #53  
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Default RE: Hellcat Build with 250cc Radial

Okay, I read this last night, and now that I have picked myself up off the floor...........

Man, I just love you guys who have talent as well as cool machines to spit out these awesome components in your builds. Just those hinges are amazing!! [sm=thumbup.gif]
Old 01-17-2009, 01:47 PM
  #54  
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Default RE: Hellcat Build with 250cc Radial

Great work Lou. I just got some miniature 2/56 locknuts from Robart for my current project. They're really tiny and would look scale on the hinge pins. Mitch
Old 01-17-2009, 03:10 PM
  #55  
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Default RE: Hellcat Build with 250cc Radial

The milling machine is really cool. This is my second one. It was not as expensive as you may think. The first I got off of eBay and it was too small to do anything useful. This one in the photo below I got from a small company in China. I think I was their second customer and I had to do all of my own R&D work to get it to run properly. It is well designed and the electronics is great but they did not know how to get the mechanics and electronics working together. Anyway I made my own bench and the big enclosure around it. Coolant fluid sprays out on the endmill and drips down to the base, when it is cutting metal. This coolant is 85% water. Then it drains into a bucket that has a pond pump to recirculate it. I covered the inside of the enclosure base with two layers of 6 oz glass cloth and resin to make it water proof. My main business is with computers and mechanical engineering so the electronics and software was not too much of a problem. Attached is a photo of it when it first arrived and after I got it set up. It was still nice and clean. The part shown is for the tail wheel assembly that I made for a friend. This required 3D machining where the tool is moving in three axes the same time. If you design the part using a 3D cad program, there are other programs that can create the complex tool paths almost automatically.
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Old 01-17-2009, 09:14 PM
  #56  
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Default RE: Hellcat Build with 250cc Radial

Back to the wing. . .

I will try and describe how I am going to hinge the flaps. It will be done similar to the Ziroli plans at least in respect to the location of the hinge point. However I will use a 1/16 dia music wire hinge shaft. For the hole I will use 1/8” OD x .074 ID nylon tubing that I will glue in a slot. Attached is my layout to help clear it up. Originally I had planned to build up the location of the nylon tubing with balsa stick but it would be more accurate to take the flap over to a table saw and cut a nice straight slot with the leading edge of the flap against a the saw fence.
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Old 01-17-2009, 09:19 PM
  #57  
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Default RE: Hellcat Build with 250cc Radial

The full size Hellcat had an extremely complex flap mechanism. As it went down it also moved toward the rear. My plan is to make it look reasonably scale without the complex movement. After all this has to fly. Attached is a bottom view from the 3views showing the locations of the flap hinge. There are two flaps on each wing. The flap that is outboard of the strut has three hinge points. The other flap that is inboard of the strut only has two. This inboard one is no problem. I will put two hinges with a single servo. Since I have a wing break on the outboard flap that is in-between two of the hinges that will leave the flap on the removable wing tip with two hinges, which should be fine. The problem I see is that there is a short section of the outboard flap with only one hinge. This is where I am going to add a hidden hinge. It will work just like the others but the slot in the flap will not be visible from the top or bottom. See the drawing and machined flap hinges below.
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Old 01-17-2009, 09:39 PM
  #58  
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Default RE: Hellcat Build with 250cc Radial

Well I got both wing tips and the center section framed out. Today I added the anti rotation pins and mating holes to the wing. This would have been easier if I had thought about this when I had four of rib # 7 all stuck together and was cutting it out. I would be guaranteed to have it in alignment. I was able to clamp the center section and wing tip together and use the Dremmel with a right angle drill to make an 1/8” pilot hole. I increased it to 3/8” dia with a hand drill and a lot of care. No problem with the alignment. It is nearly perfect and I can always do some slight adjusting later if necessary.

Attached are some photos of the framed wing tips attached.
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Old 01-17-2009, 10:52 PM
  #59  
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Default RE: Hellcat Build with 250cc Radial

Hi Mitch:

Those locking nuts sounds great. I may just do that. Mine are 1/4" hex. I would still use locktite on them though. I have a Balsa USA Spad with the Robart horns on the elevators. I had them screwed on properly but on one side the lock nut came off all by it self. Lucky for me I had a separate servo on each half or I would have lost the plane.
Old 01-18-2009, 12:23 AM
  #60  
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Default RE: Hellcat Build with 250cc Radial

Lou,

Your work is simply fantastic! Don't know if you have ever seen these photos, but it may get the head churning. True slotted flaps would be da bomb.
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Old 01-18-2009, 12:24 AM
  #61  
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Default RE: Hellcat Build with 250cc Radial

Lou, Great stuff. I cant believe how far you have come in one week since I've been over.

Whatching, with interest.

Gunny
Old 01-18-2009, 01:47 AM
  #62  
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Default RE: Hellcat Build with 250cc Radial

Nice mini mill. And the build is mind boggling.
Old 01-18-2009, 08:58 AM
  #63  
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Default RE: Hellcat Build with 250cc Radial

Nice work again, lou like all your planes. so when do you sleep?
wish I had more time to play
tom
Old 01-18-2009, 12:55 PM
  #64  
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Default RE: Hellcat Build with 250cc Radial

Hi Country Boy that is really neat. I saw that once before but ruled it as too complex. The hard part is adding enough rigidity so that it is functional and then I would need two setups for each of my 6 flaps. It would look cool though . . .

Thanks Knot.

Tom it is easy just don't go to work. My business seams to run just fine with out me.

Hi Gunny: I am setting up to sheet the main wing control surfaces. After I get them cut out I will s post more photos.
Old 01-18-2009, 06:13 PM
  #65  
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Default RE: Hellcat Build with 250cc Radial

Coming together nicely Lou........I'll be watchin

Phil
Old 01-20-2009, 12:12 PM
  #66  
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Default RE: Hellcat Build with 250cc Radial

Hi Phil

Welcome to the forum. I had discussed with you my plan to use two spars as you did in your Skyrader. After laying it out it just didn’t make sense. The main spar falls in the center of the wing and a rear spar would have been too close to be useful. Instead I went a little heavier and used one spar with two anti-rotation pins. After seeing it done and handling the wing I am sure if I errored it was due to being too strong.

Right now I am installing the wing servo mounts and locating the hinge points. I will post more photos shortly.
Old 01-20-2009, 01:41 PM
  #67  
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Default RE: Hellcat Build with 250cc Radial

Hi Lou

Yea....what you have so far looks looks to have been built from the 'Bismarck School of Engineering'......so PLENTY up to the task

Phil
Old 01-21-2009, 10:04 PM
  #68  
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Default RE: Hellcat Build with 250cc Radial

Hi Phil. 'Bismarck School of Engineering' that is a good one. Right now the center section is 5 lbs. I have to think light.


I may go with 8 servos in the wing. There will be two for the ailerons, and three on each side for the flaps. I could join the two main flaps together but it will be easier with no chance of binding to have a separate servo for the outer flaps on the center section. Since the servos will be installed sideways I made some light servo mounts out of some scrap angle. It started out at 1” x 1” and 1/8” aluminum angle.
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Old 01-21-2009, 10:06 PM
  #69  
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Default RE: Hellcat Build with 250cc Radial

The following photos are bottom views. I plan to have access hatches for the servos on the bottom. The aileron servo shown is deep in the wing so that the servo arm clears the skin. There was actually not much room for a wood screw to attach the servo mount. I was worried that it would come out of the top side. I used blind 4-40 nuts on the far side with 1/8” aircraft ply for this servo. The aircraft ply is nearly flush to the top of the rib.

The other photo of the wing tip it shows the location of the hinges in red with the servos in place. I will be using Hitec digital servos. I plan to gang them together and use my Hitec programmer to set the travel and direction of rotation. I like set the speed in the transmitter so they all go the same slow speed.
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Old 01-21-2009, 10:08 PM
  #70  
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Default RE: Hellcat Build with 250cc Radial

The center section is shown with the servo mounts in place. The next photo shows the additional rib that I added. I did this for three reasons. First so that the servo is not exposed to the grime that may come off the wheel and second to provide a secure member to attach the servo mount. The third reason is that with out it there will not be much support for the bottom wing skin as most of the adjacent rib, W-5, will be cut away to clear the wheel.
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Old 01-21-2009, 10:10 PM
  #71  
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Default RE: Hellcat Build with 250cc Radial

The next photo shows a template I made to see where the wheel will come. This is the exact size of the wheel so I will need to have some clearance around it.

Next I am going to focus on the landing gear so I can cover the bottom of the wings and cut out the control surfaces.
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Old 01-22-2009, 01:30 AM
  #72  
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Default RE: Hellcat Build with 250cc Radial

Lou, how on earth do you move so fast on this when using the Probond? Doesn't each joint take several hours to cure?
Old 01-22-2009, 02:01 AM
  #73  
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Default RE: Hellcat Build with 250cc Radial

Great work Lou. Love watching and learning.
Tom
Old 01-22-2009, 10:06 AM
  #74  
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Default RE: Hellcat Build with 250cc Radial

Hi Knot and IIIat

We are really spoiled with CA. Don’t get me wrong it is great stuff but it forces you to work quickly. With ProBond I have time to make adjustments. A trick I learned is that if you screw up you can de-glue it by using a heat gun. It softens the dried ProBond and the parts can be removed. You can do that with epoxy with a little more heat as well. Some of the techniques to getting around the slow drying time which is about 30 -45 min is to try and do more then one area at a time. I also use a lot of small plastic clamps. For 4 bucks you can get 22 clamps Harbor Freight (part number 8826-2VGA). Also have a good supply of zip-lock plastic bags with a couple of pounds of lead shot in each. They make great weights that will conform to what ever. The plastic does not stick to any of the glues I use. If a glue joint wants to spring open and you can not use a clamp, and pins will not hold it try using some blue masking tape. I always use the tape when I edge join wing sheeting with ProBond. One characteristic that causes a problem sanding is that Probond dries to a hard rubber like consistency and it resists sanding. If you know that you will be sanding excess glue, Titebond Original Wood Glue (which is aliphatic resin) works well. It dries hard and sands very well. It is too brittle for general construction and not water proof. I don’t care for the premium types of Titebond as they are too rubbery for my taste.

Old 01-23-2009, 02:40 AM
  #75  
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Default RE: Hellcat Build with 250cc Radial

Nice build of a great looking warbird Lou. Good luck with the rest of it. I especially admire that tail linkage of yours!
Regards Al

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