Wildcat Retract Installation Guide.
Hello to all of my friends and fellow Wildcat Enthusiasts!
By now most of you know who I am and the modifications I have developed for the Wildcat. I just wanted to get the instructions to the install as a blog entry since the thread I started has all but disappeared. Here are some videos of my work and the instructions are just after.
Retract Install Instructions
In this kit you should have:
1 Main Retract Unit with 2 1/4” wheels already installed
1 Tail Wheel Unit with Wheel already installed
1 Modified servo arm with adjustable clevis
1 HS-645MG Servo
4 Servo screws and servo mounting hardware.
1 Long servo mounting stick, beveled.
1 Short servo mounting stick.
1 0.01” Styrene
1 12” Strand of fishing line
Additional Parts you will need:
1 Control rod to run from rudder servo to tail wheel
1 Castle Creations 10 Amp BEC
Tools & Supplies you will need:
Dremel Tool with sanding components
New Exacto blades
Small Hand Saw
30 Minute Epoxy
Foam Safe CA
Loctite No Mess Adhesive - Walmart
Sand Paper or large emery boards
Optional Items (These will make you life easier)
2 1/8” door knob cutter
Step 1 - Parts Removal
Remove your prop, cowl, motor, esc, wings & battery hatch if you have not done so and put them in a safe place out of the way. Use a long screw driver or a tool that you have designated for prying and pry the plastic parts off. Do the belly pan first as it will be the hardest and if you go slow and steady you won’t discolor the plastic. The wheels come off real easy and the tail wheel will take a little pulling but will come off. Just be gentle enough to leave the foam and not rip it out. Keep your belly pan and main wheels we will use those but you can toss the tail wheel. It is glued together so you wont even be able to use it for a cover.
Step 2 - Foam Removal and Prep
Use a 2 1/8 door knob cutter to make this job easier. Center up on the wheel well and just twist. DO NOT attach a drill. It will make a mess and probably destroy the airframe. Ask me how I know.
Next, use your Exacto blade to cut out the top of the wheel well and leave enough room for the retract mechanism to work. Start small and only remove what you need.
Now use a pencil to draw in your gear door lines. Use a straight edge for a good clean line. Remove all the foam in this area. Once the foam is our we need to be careful with how we handle the fuselage because it gets real flimsy. It will be sturdy again once we glue the retracts in.
Take your belly pan and place it in its holes. The taller more bulbous end goes towards the back if you don’t remember how it went. Draw in your gear door lines and remove those sections from the belly pan. Once you get your retracts in you may have to go back and remove a little more plastic to make sure the retracts go all the way down. You will get a better idea of how it needs to be once you get through picture 16 in the build.
Lay your retract unit in place and try to center it as best as you can to your wheel well holes and draw around the mounting sticks. The more accurate you are here with your left to right placement the less trouble you will have with adjustments and tracking while taxiing.
Remove the foam about 1” down. This measurement may vary based upon the accuracy of your wheel well holes. Gently remove any foam that may cause binding of the gear when moving up and down. You will need some filler foam on the front mounting stick since it is getting up into the esc at this point. Use some foam safe CA to get it to stay put and make sure you constantly test fit and function before you epoxy. Once happy we can move on to the gluing. Images 13 -16 show the before and after of the foam filler needed to get the retracts to sit in the right spot. You will also want foam chunks cut to fit over the mounting sticks to fill the gaps once the retracts are glued in. See image 15 for an example.
Step 3 - Gluing in the Retracts
Now that your happy with the fit it is time to mix up some 30 minute epoxy. The reason I like 30 min epoxy it how far it saturates before it dries. It is very strong and durable. Smear 30 min epoxy all the way around the mounting sticks front and back leaving room away from the mechanism. about 1/4” should be safe from squishing into the working parts. Push it all the way in and then get the foam chunks you cut for filler and coat the contacting sides with the epoxy. Push them into place and place tape over the area so any excess does not drip. Put the belly pan on but don’t glue it. This is so that you hold the right placement of the fuselage and not introduce any weird thrust angles of fitting problems with the wings and such. Working ahead and making sure that the belly pan fits nicely with the gear extended will save some panic work here. Extend the gear down and place on a level table. If the table is not level, get it as close as you can and match the bubble from it to the plane. Another reason I like 30 minute epoxy is its work time. You can take your time and get this right and when it is dry it will be perfect.
Step 4 - Installing the Servo
Once the epoxy has dried on the gear it is time to install the servo. The servo placement should be 2 9/16” from the edge of the firewall, and 5” from the back of the hatch area. The servo wire goes to the back of the plane so you will have to notch a path for the wire to run in a manner so not to interfere with working components. You will also need to remove the plastic ring for the carbon rod. You will be cutting deep enough so that the servo sits flush on the lower part of the hatch. This means you will have to trim off the top edge of the plastic ring just down to the ring itself but not breaking into it. Remove the foam down to the hole left by the ring being removed and if you cut into the hole it will be fine.
At this point you will want to put in your port wing and mark the open area onto the plastic. You will use your saw and remove the plastic and foam from this area so that the servo can sit flush. You will also see that the front of the wing will cause conflict with your retracts working. Trace out the area and remove the foam there and on the starboard wing. Once done those can be put aside for a while.
If you haven’t mounted the servo to the sticks by now, do so. Mark your holes and pre drill them before screwing them in. Once done take some thin CA and put a drop in each hole. This will stiffen up the threads so that the screws wont strip out. Let the CA dry for a few minutes before mounting the sticks to the servo. The longer stick should be beveled to some degree. This stick will be mounted directly over the wing mount screw. Check to make sure you can still get the screw in and access it with a screwdriver. If not bevel the stick some more till you can. Rough up the foam where the sticks will glue and mix up some more 30 min epoxy. Rough up the plastic ring so the glue will stick to it as well. Put epoxy on the plastic ring and put it in place. Mount the sticks to the servo and put the epoxy only on the sticks where they will contact the foam. Make sure you get a good bit on the tooth pick posts too. Place it in its spot and tape down so it doesn’t slide out. Let it dry for a couple of hours. We will be apply some torque to this area next and you want it good and solid.
Step 5 - Making the Tail Wheel Work
Use the tail wheel to mark positions for cutting. Everything that the balsa wood covers needs to stay the same and you need to remove enough material so that the tail wheel moves freely in both directions. You will also need to shave out the curved material so that the balsa wood sits flat.
Use a sharpened brass tube to cut the hole for the control rod. Start it at the back but you will probably need to come from the front of the plane and run the same line that the rudder control rod uses. The control horn for the tail wheel should be on the same side as the rudder.
Connect the Z bend to the control horn and let the adjustable end be on the servo arm. Once your happy with the placement and movement, mix up some 5 min epoxy and glue it in place. Hold it in place for the 5 minutes so you don’t end up using tape and removing paint.
Once dry, sand down the edges to the shape of the fuselage and then apply some light weight spackle. Use foam chunks to fill in the bigger gaps. The spackle will take about 4 hrs to dry in a warm climate but over night if its in the cold of the garage. Sand to shape and fill again if need be.
Step 6 - Notching the Battery Hatch
Place the battery hatch on like you normally would and mark the areas where the servo and mounting sticks make contact. Draw a box in this area out to about half way across the hatch. Remove the side ridges and just a thin layer of the main foam. If it doesn’t quite fit snugly the remove a little more till it does.
Step 7 - Wheel Covers
Now its time to do the wheel covers. You may not wish to go to this length but I will show you how I do mine. You take the standard wheel cover and cut off the 4 tabs. Pull out any loose glue. Use an exacto blade to trim off the black tire part. Don’t use scissors because it will split the plastic. Once trimmed out, clean off any extra glue and use an emery board to clean up the edges.
On the wheels I used nylon lock nuts. You will have to cut down the axle bolt and lock nuts for this to work You can get some different nuts if you want and use some blue thread locker instead. I like the strength of the nylon lock nuts but my pictures show either way.
Once the thread locker had dried and the wheels spin freely you will fill the hub with Loctite No Mess Adhesive. Place it on the wheel and center it as best as you can. Spin the wheel a few times to make sure you have it centered up pretty good. When you happy with the placement, put masking tape over it and go do the other side. The glue will take over night to dry but dries clear. So if a little got on the outside it is no biggie but you can clean it up with a wet paper towel if you so desire.
Step 8 - Gear Doors
You should have a 12” strand of fishing line and a piece of 0.01” Styrene. Use this piece and make you a template on a piece of paper. Cut out that shape from the paper and lay it so that the thick ends are over the wheels and the narrow ends are in between the holes for the belly pan posts. Draw the pattern of the wheel opening on to the paper. Once happy with the shape, transfer it to the plastic and cut it out. The plastic will glue to the fuselage on the narrow tabs and should not bind with the belly pan we cut earlier. If it all fits and moves freely then We need to cut the 12” fishing line in half. Take each half and put a smaller piece of masking tape on it. Put a dab of CA on the inside of the gear door, centered about 1/8” from the edge. When you glue it make sure the line is going out from the wheel shape not in to the center of the plastic. Press the tape down on to the glue and let it dry. Careful not to glue your fingers to the plastic. Do the same thing for both sides. When done, use an emery board and scuff the plastic where the doors are going to be glued to the fuselage. Use some foam safe CA and glue them on. Once that is dry we can now hook the gear doors to the retracts. There are 2 holes on the front of the retract. Feed the line through one and out the other and back through the first one creating a loop. Retract the landing gear with your hands and easily pull the gear door out to where you want it on the fuselage. Let the line slip till your happy with the door placement and ease the gear back down till you can reach the 2 holes with the CA glue bottle. Put a drop over each hole and let dry before you do the other side. Once both sides are done trim off the extra fishing line and your doors are good to go.
Next you have the belly pan. You will need to trim it so that the gear doors can move freely and not bind in the down position. It will take some trial and error but you will get it. Once you are happy with the fit then you can use some 5 min epoxy and glue the belly pan back in place.
Step 9 - Making the Retracts Function.
I want to preface this step with the fact that this will be tedious. There is no perfect measurement. You have to get in there and work with it till it works. Everyones build is different. The ball links are preset to my measurements and you should be in good range to work from there. With that understood lets finish this sweetheart up shall we.
Putting the servo into operation will put a lot of torque on a thin flimsy area of the fuselage. At this point you will want to glue in your Port wing. I know most do not like this idea but for this to function appropriately you have to. You will want to scuff the plastic with 80 grit sand paper and wipe it clean with rubbing alcohol. Try to scuff the inside of the wing saddle as best as you can so the epoxy takes hold. Remove the servo from its mounts. You may need to put some holes in the starboard wing saddle if you have not done this already to get the screws out. With the servo out of the way and the surfaces of the wing and saddle scuffed and cleaned, mix up some 30 min epoxy and apply it to the contact areas. Plug the wing in and screw it down tight. Wipe off any excess epoxy that may have squished out. Looking in the servo hole if epoxy has not squished up into this area, apply a little to coat the bottom of that spot to make a good seal but not so mush that it will end up lifting the servo once dry.
Once the epoxy is dry, I would give it an hour, mount the servo back in. It should be rock solid at this point. In your package you should have a modified servo arm. The servo arm has a clevis on the end. This is a predetermined measurement based upon my F4F. The clevis should not move and any adjustment that may be needed should be done on the ball links. You will want to have your battery and radio equipment handy. Turn on your TX and make sure you have your Wildcat selected. Go into the program settings and go to the travel adjust area for the retracts. In there you want to set your + setting to 100% and your - setting to 70%. Once those are set, put your gear switch to the down position and plug in your battery for the plane. When the esc has set itself the servo should go to the gear down position. Take the servo arm and put it on the servo so that the arm is touching the carbon tube. If you have not put your carbon tube in go ahead and do so. Flip the gear switch to up and pull the gear in with your hands. You may need pliers here to get that clevis into the hole on the T-bar connecting the ball links. Once on there slide the fuel tubing already on the clevis just far enough forward to not interfere with the T-bar movement.
Once it is connected give the switch a flip down. It may not be perfect right out the gate. The wheels may hang on the wheel well sides indicating a little more foam may need removal or the ball links may need some adjusting to get the wheels to go all the way down. NOTE: We are now at the tedious part of the build. Play with the adjustments to get the desired effect. 1 turn on the ball links goes a long way. On the retract you will notice that there is a pin that goes all the way through the upper A-arm and connects to the upper part of the spindle. That pin should touch the lower A-arm when in the gear down position. That is the point of locking that will guarantee a reliable landing. If you have binding at the end of the retract extension where it does not want to lock down, the belly pan may need some sanding.
Well, now that you have it working you should be feeling pretty darn good. The RX now mounts in the back starboard side. You will want to route your wires so that they don’t interfere with anything moving. Don’t forget to install a BEC.
All that’s left now is to do your touch up painting and go fly.
Thanks for looking.
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