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Hellcat Build with 250cc Radial

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Hellcat Build with 250cc Radial

Old 01-23-2009, 08:12 AM
  #76  
flyn2high
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Default RE: Hellcat Build with 250cc Radial

Hi Ali

I am glad to hear from you and thanks for your comments. I can't wait to fly this beast but it will be a ways off. Today I got my invitation to Top Gun so I hope to see you there. I will be flying my Stearman again.
Old 01-23-2009, 03:34 PM
  #77  
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Default RE: Hellcat Build with 250cc Radial


ORIGINAL: LouCetrangelo

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.
Looking good Lou. You oughta consider selling them servo mounts.
Old 01-25-2009, 07:17 PM
  #78  
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Default RE: Hellcat Build with 250cc Radial


Hi Mr Bigg:

Thanks for your comments. My little CNC would be chugging away like mad if I tried to make the servo mounts in quantity. I would also be kept busy as it needs a lot of attention with each tool change and to reposition the stock. I will add servo mount detail drawing to the wing parts zip file which is at:

http://www.liskyhawks.org/images/hellcat/wing_parts.zip

An easy way to make a servo mount by hand is to just cut off 3/8” lengths off of a 1” x 1” aluminum angle and on one leg drill two holes for the servos and on the other two mounting holes. Then just make two per servo.
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Old 01-25-2009, 07:24 PM
  #79  
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Default RE: Hellcat Build with 250cc Radial

I did not want to install the landing gear by trial and error so I laid it out in Solidworks. I drew the landing gear accurately and a segment of the center section of the wing. It turns out that the gear is a very close fit in the wing. The front of the gear only clears the top and bottom skin by 1/32”. I tweaked and adjusted in Solidworks to control the clearance the wheel has to inside of the top skin when it is retracted. This can not be done on the model with out chopping out the rear spar and W5 rib to clear the wheel. The photos below show what I am describing.
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Old 01-25-2009, 07:33 PM
  #80  
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Default RE: Hellcat Build with 250cc Radial

The position of the gear mounting rail needs to be carefully positioned. The photos below show the tight clearance. After all that I needed to use 1/32” aircraft ply as shim stock on top of the gear mounting rail.

I used 10-32 T-Nuts on the other side of the mounting rails and attached each gear with eight 10-32 socket head cap screws. Before drilling the holes I squared up the gear with respect to the main spar.
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Old 01-25-2009, 07:39 PM
  #81  
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Default RE: Hellcat Build with 250cc Radial

I am having such a good time building but I need to hold up here for a month. We are going on annual pilgrimage to Florida to escape the cold in February. It will give me a chance to finalize some of the changes I have made to the drawings and send them off to Nick Ziroli Jr.
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Old 01-25-2009, 10:53 PM
  #82  
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Default RE: Hellcat Build with 250cc Radial

Snowbird, huh?

Man, I would like to find an Adult Education school or something near me where I could learn Solidworks or some other sort of CAD system. I envy those drawing so much!

Have fun in the sun Lou.
Old 01-25-2009, 11:53 PM
  #83  
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Default RE: Hellcat Build with 250cc Radial

Hi Knot:

More like a snowflake. ha ha. We just go for a month but I bring a plane along for thoes days when it is not too windy.

I used AutoCad a lot and it wasn't too difficult to learn Solidworks I just used a book from Amazon. They have a good selection.
Old 03-10-2009, 11:24 PM
  #84  
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Default RE: Hellcat Build with 250cc Radial

Hey Lou, Are you back from FL yet?

Tom
Old 03-14-2009, 08:21 PM
  #85  
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Default RE: Hellcat Build with 250cc Radial

Hi to all:

I am back from Weston in southern Florida where my wife and I spent the month of February. I brought one of my 35% aerobatic planes and flew whenever the wind was below 15 mph. The weather was beautiful but the wind was not what I am used to up north. At the nearby municipal field, Markum Park, there is an excellent 700 foot paved runway. However, the locals call it Mayhem Park for a reason. The only requirement is an AMA card. Knowing how to fly is optional. Midair’s are quite common and you can expect at least one crash per day. I really had a great time though with good friends and my plane is still in one piece.
Old 03-14-2009, 08:23 PM
  #86  
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Default RE: Hellcat Build with 250cc Radial

Now back to the Hellcat. I was saving this next procedure until now because I was not sure how it was going to turn out. That is the single bolt hole to join the wings. The hole is going through about 3” of hard wood and must exit precisely in the correct place. I gave this a lot of thought and purchased a 6” long drill .166 dia. This is a tight clearance for the 8-32 x 4” long socket head cap screw used to join the wings. Both are available from McMaster-Carr.
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Old 03-14-2009, 08:26 PM
  #87  
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Default RE: Hellcat Build with 250cc Radial

I used my drill press to drill the two holes at each end of the center section spar. I propped up one end on boxes and rested the other end on the drill press table. I locked the handle to move the spindle all the way down with the drill bit in the chuck. Then I eyeballed it from the front and side and made all my adjustments to make sure it was aligned. I drilled short depths pulling the bit back out often to clear the chips. The hole actually came out very close to where I planned. I was only about 1/32” off, and I was able to adjust the stainless straps to compensate. Below are some photos. Now with all the straps in place and the wing tips attached all is very tight. There is no noticeable play in the wing tip joint at all. I needed to hold off sheeting the wings until this was done but that is the next step for me.
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Old 03-14-2009, 09:58 PM
  #88  
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Default RE: Hellcat Build with 250cc Radial

While I was away I drew up the vacuum mold tooling for the canopy and the drop tank in Solidworks. See the attached photos below. Nick Ziroli Jr was kind enough to offer to machine the tooling on one of his large CNC machines. He also sent out my cowl plug to have a fiberglass mold made. Wow that really is a huge help. Thanks Nick.
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Old 03-14-2009, 10:40 PM
  #89  
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Default RE: Hellcat Build with 250cc Radial

Lou is back!
It's great to see you back at it Lou. It'll be great watching along and learning again.

Tom
Old 04-11-2009, 11:52 PM
  #90  
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Default RE: Hellcat Build with 250cc Radial

Last week I was able to get back to work and made a little progress on the hellcat. First I glued up 3/32” x 4” x 36” wide balsa using pro-bond wood glue into wide sheets. I sheeted the bottom surface of the outer wings while cutting out a slot for the 1/16” thick stainless joiner.
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Old 04-11-2009, 11:54 PM
  #91  
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Default RE: Hellcat Build with 250cc Radial

It is usually recommended to sheet the top surface of the wing first so that you can keep it straight using the same supports used for the ribs and spars. In this case I felt it would be much simpler if I sheeted the bottom first. This way I could install the aileron and flap hinges which lie on the bottom surface. A second reason is that I did not want to have the hinge hardware installed until the surface was glassed. I am going to glass the bottom of the plug in wings and center section then install the hinge hardware and then sheet the top.

After cutting out the ailerons and flaps from the wing, I made 1/8” light ply brackets to support the hinge hardware. Using a fine toothed scroll saw blade and a 1/16” file I cut through the trailing edge spars to make a clearance slot for the hinge hardware.
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Old 04-11-2009, 11:56 PM
  #92  
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Default RE: Hellcat Build with 250cc Radial

I rounded the leading edge of the ailerons as per my layout. Then I sheeted it using 3/32” balsa soaked in Fantastic cleaner. Ammonia works very well to tightly bend balsa but Fantastic is almost as good and it doesn’t smell so bad. For the aileron control horn I decided to go with a G10 bracket with a Sullivan 4-40 metal clevis that has a locking clip. The clevis will be buried and non removable. I used gorilla glue (not shown) to mount the horn to the aileron. I marked the leading edge where the control rod would enter with a making pen. After fiber-glassing it will get a slot.

I cut out light-ply brackets for the hinges in the ailerons. Before sheeting the top of the wing I will epoxy in the hinges in the slots I made. It will need to carefully aligned so that they are all in the same plane and I have the correct gap.
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Old 04-12-2009, 12:01 AM
  #93  
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Default RE: Hellcat Build with 250cc Radial

With one huge sheet of 3/32” balsa I sheeted the straight part of the bottom of the center section. A narrow strip was fitted to the two end ribs that are on an angle. I then sanded the outside edges and made sure I could still attach the outer wing panels.
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Old 04-12-2009, 12:02 AM
  #94  
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Default RE: Hellcat Build with 250cc Radial

Gear Strut Covers

Using the 3 view drawings in the computer, I blew up the bottom of the wing in the area of the landing gear. With Adobe Photoshop I was able to layer it on top of sheet 5 of the plans showing the wing layout. With a little stretching and shrinking here and there I adjusted the strut covers so that it looks correct. The main gear is very close to scale but not exact. The wheel is slightly bigger and the strut is a little shorter and is closer to the leading edge a bit. I wanted to have the strut cover as close to scale as possible but at the same time it must line up with the center of the wheel and be functional.

I was able to print it out in sections on 8.5” x 11” paper and taped them to the bottom of the center section.
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Old 04-12-2009, 12:05 AM
  #95  
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Default RE: Hellcat Build with 250cc Radial

The strut covers on the Hellcat have a bump to clear the strut. I am using pink foam to create this feature. I will stretch polyethylene film over the printed strut covers then fiberglass over the pink foam forms with several layers of 6 oz fiberglass and West System epoxy resin. The pink foam form will be destroyed when it is removed from the finished strut cover.

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Old 04-12-2009, 12:07 AM
  #96  
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Default RE: Hellcat Build with 250cc Radial

Here the form is shown after an hour of sanding to shape.
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Old 04-12-2009, 09:12 PM
  #97  
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Default RE: Hellcat Build with 250cc Radial

Welcome back Lou. And Happy Easter! As usual, I'm very impressed with your work, and I'm learning!

Tom
Old 04-12-2009, 09:30 PM
  #98  
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Default RE: Hellcat Build with 250cc Radial

This is artistry in building. Very enjoyable to watch.
Old 04-12-2009, 09:40 PM
  #99  
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Default RE: Hellcat Build with 250cc Radial

Lou,

Will Ziroli provide plans for the Hellcat in the same dimension as the one you are building? If so, any idea when the plans may be available. Also, would it be possible to use 1/4 scale Corsair gear in lieu of having gear specially made? I asked because I am seriously considering another large project for a large radial engine once I finish the 1/4 scale Corsair, and in an attempt to reduce cost, I am looking for a project that would permit using some items from the Corsair. By the way, the gear is made by Seirra with 7.5 inch wheels, and it does rotate approximately 85 degrees.

David
Old 04-12-2009, 10:54 PM
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Default RE: Hellcat Build with 250cc Radial

Hi Tom: Happy Easter to you as well. Actually it is a leaning experience for me as well as a fun project.


Thanks for the kind words Knot. Watching it taking shape is a great motivator.


Hi David: I sent Nick Jr. the enlarged plans last month. They should be available. You can call at (631) 467-4765 or email to Sales@ziroliplans.com. The web site is http://www.ziroliplans.com but I wouldn't expect to see it up there this soon.

Darrell Tenney at Sierra Giant Scale also made the gear for my hellcat. He was planning to offer it as a standard product. As far as I know it should be available. My gear goes through about 95 degrees rotation. One of my fellow cub members purchased the Composite ARF Corsair with the folding wings and the same 250 cc radial engine but I have not seen his yet. At last years Top Gun I saw one fly as a demonstration. It was very cool. I know that Darrel made the gear and hydraulic wing folding mechanics.

Darrel made my wheels as well but they are 7" in diameter.

I suppose it is possible to share the engine between the two planes but you would probably need at least new side plates for the gear to be able to rotate the extra 10 degrees. The best bet is contact Darrel. His web site is http://www.sierragiant.com/ Let me know how you make out.

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