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JAS-39 Gripen Owners/Build Thread

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JAS-39 Gripen Owners/Build Thread

Old 09-05-2008, 01:51 AM
  #26  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

Build - Cockpit Options

Here are some links to the full scale Gripen cockpit:
[link=http://www.canit.se/~griffon/aviation/gripen/cockpit/gripen-cockpit.html]http://www.canit.se/~griffon/aviation/gripen/cockpit/gripen-cockpit.html[/link]
[link=http://www.youtube.com/watch?v=Bt8qVX-UKVA&feature=related]http://www.youtube.com/watch?v=Bt8qVX-UKVA&feature=related[/link]

Neither Skymaster or JetLegend produce a cockpit kit for their Gripens and various alternatives have been suggested in previous threads. I’ve consolidated some of the the info below to save the hassle of you having to research it for yourself and added a few other options.

Simple Cockpit:
- joeflyer used the cockpit tub that came with his kit then added an instrument panel decal and an [link=http://mgapilots.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=mga&Category_Code=topguns]MGA Top Gun pilot[/link]. Their website lists the pilot as 1:8 scale but can be made to fit. The [link=http://www.dreamworksrc.com/catalog/advanced_search_result.php?keywords=jet+pilot]Dreamworks Jet Pilot[/link] bust is 1:7 scale and is available in several color schemes.
- The SM ARF+ kit currently doesn’t come with a tub. However, the [link=http://www.bvmjets.com/Pages/kits/bandit_arf.htm]BVM Bandit ARF[/link] (scroll down to the photo showing the kit contents) cockpit platform, seat back, and dash decal fit the Gripen. The pilot busts listed above will fit quite nicely.

Modifying Cockpit Kits from other Models:
- Ray Davis started with a SM F-16, cut it in two to bring in the side panels under the canopy lip, kept the main/front panel whole, refit the center console, and fit the forward portion and gun-sight whole. He used only the seat back (not the cushion) which sits on a ply platform with enough clearance for the nose gear. For a pilot, he modified a Blue Box lady F-15 pilot (cut lower legs, shortened torso and arms)
- The Gripen and F-18 ejection seats and instrument panel are somewhat similar so an F-18 cockpit kit can serve as a starting point. [link=http://billr.org/just-the-pits/f18pit.asp]Just The Pits[/link] sells a cockpit for the YA twin F-18 (1:6.8 scale) but it needs the glare shield and cockpit “deck” from the YA kit. [link=http://www.centuryjet.com/webstore/moreinfo.cfm?Product_ID=1067]Century Jet Models[/link] sells a cockpit kit for their ANK (1:6.85 scale) F-18E.

Scale Gripen Cockpit: - Updated 10/3/08
A scale Gripen cockpit is now available from Dante and Monica at [link=http://www.camlex-rc.com/winginfo.html]CamLex Enterprises[/link]. I heard about it when it was still in prototyping (Sept 09) and exchanged emails and phone calls as I was pretty happy to hear that a manufacturer was making a Gripen cockpit. Dante and Monica are nice people and there was great communication keeping me informed on the progress of the prototype and my order. Here's portions of an email from Monica giving a bit of background on their cockpits.......

They are called the CamLex/Wingman JetLegend series and are being done by Wingman RC (Michael Hicks). He is custom making every cockpit. These are not perfect molds with every one being exactly the same. These have character and are hand painted individually by Mr. Hicks himself. We work together to make these cockpits as life like as possible. We can make any cockpit color scheme you want we can add names to the helmet…..

Kind Regards,
Dante & Monica
CamLex Enterprises
PHONE: (888) 837-7906

Below are photos of their Gripen cockpit:
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Old 09-05-2008, 05:33 PM
  #27  
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Default RE: JAS-39 Gripen Owners/Build Thread

Hello Gripen owners.

This is my old Skymaster Gripen (Gen 1)

30Lbs With a P-80, Lights and smoke system. Flew very well..

As requested, I’m posting pictures to help with installation of components.

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Old 09-05-2008, 05:38 PM
  #28  
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Default RE: JAS-39 Gripen Owners/Build Thread

Gripen
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Old 09-05-2008, 05:41 PM
  #29  
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Default RE: JAS-39 Gripen Owners/Build Thread

Gripen
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Old 09-05-2008, 05:42 PM
  #30  
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Default RE: JAS-39 Gripen Owners/Build Thread

Gripen
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Old 09-05-2008, 05:44 PM
  #31  
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Default RE: JAS-39 Gripen Owners/Build Thread

Gripen
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Old 09-05-2008, 11:05 PM
  #32  
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Default RE: JAS-39 Gripen Owners/Build Thread

Wow!!!!!
What brand and model number are those saddle tanks?????
They sit nicely on the C of G and even better I don't have to build them!!!!!

Also how have you run the fuel lines? Is it bubble trap then main tank on the floor then parallel into the to forward saddle tanks and then parallel into the rear saddle tanks?
A simple diagram would be awesome please.

Must have. ;-)
Old 09-08-2008, 12:09 AM
  #33  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

growingupisoptional,

The saddle tanks shown in Jeff's photos are for his smoke system. They are Sullivan ducted fan tanks [link=http://www.sullivanproducts.com/Fueltanks1Content.htm]http://www.sullivanproducts.com/Fueltanks1Content.htm[/link] and are 11oz each. I'm also using them for smoke. Joeflyer has one mounted under the duct (and between the gear cutouts) as an additional fuel tank.

As for the routing of the fuel lines... forward tank goes to a T fitting which connected to the two large saddle tanks on each side of the inlets, which in turn are T'd together and feed the custom tank I made which fits under the inlet duct (like Joeflyer except mine is about 28oz), this tank then feeds the UAT, which is connected to the fuel pump, shut off valve, filter, solenoids, and finally the turbine.

Diagram of fuel system added in edit 9/13/08.
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Old 09-08-2008, 09:57 PM
  #34  
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Default RE: JAS-39 Gripen Owners/Build Thread

Build – Tanks

Skymaster relocated the main landing gear relocated forward about 1-1/2” to assist the model in rotating during takeoff. In order to accommodate the gear in the retracted position, the saddle tanks were reduced in size (see photos below of the “old” and “new” tanks). I believe that the center tank was eliminated and replaced with a forward tank located between the inlets. Joeflyer measured the ARF+ tanks and found their capacity to be 72 oz total (not 78 as advertized) with 16oz in the fwd tank and 28oz in each of the two saddle tanks.

Building the tanks was a challenge because of the locations of the holes for the fuel stoppers. The saddle tank stopper hole is on the upper face towards the rear end of the tank. In order to get the clunk to reach the top of the tank when inverted, I annealed some 5/32” brass tubing and bent it to the shape using a [link=http://www.shopatron.com/product/part_number=786/101.]Dubro Tubing Bender[/link]. The stopper hole in the forward tank is also on the top face. This location gives you a similar clunk problem, but also the stopper & fuel tubing will interfere with the control horn for the canard. I used Hysol and a piece of [link=http://www.bvmjets.com/Pages/Catalog/poly-ply1.htm]BVM .020 Polyply[/link] to plug the hole and drilled a new hole in the front face of the tank.

The UAT was installed in a holder mounted at the back of the mid bay. It can be mounted in the nose if you think you’ll need the additional nose weight. A Velcro strap secures the UAT in the holder yet allows for easy removal. The fuel and smoke tank vent ports are [link=http://www.jetsnstuff.com/BUY_NOW_%21.html]JetsNStuff bulkhead fittings[/link] installed in the right wing root. Filing the barb off the exterior connection allows for easy attachment/removal of the tubing to the startup/overflow tank.

Auxiliary Tank
72 oz doesn’t give a lot of margin when using a JetCentral Falcon or JetCat P-120 so an additional auxiliary tank is needed for reasonable flight times and peace of mind (in addition to using a startup/overflow tank). Here are a couple of possibilities:
- [link=http://www.sullivanproducts.com/Fueltanks1Content.htm]Sullivan S380 ducted fan tank[/link] installed below the inlet duct and between the main gear cutouts. It’s inexpensive (about $7.50 retail) and readily available. Unfortunately, it only holds 11oz but that’s better than nothing. In order to get the tank to fit, you have to relocate/trim the wood support where the inlets meet.
- [link=http://www.bvmjets.com/Pages/fuelcells1.htm#SP]BVM MiG-15 saddle tank[/link] holds 28oz, would fit under the duct and between the formers. However, it’s 5.6” at the widest point. There is a 5.25” space between the retracted gear at the narrowest point (the axle supports). Perhaps it’s possible to make up the difference by trimming gear mounting rails.
- [link=http://www.angelfire.com/wi/jettech/page2.html]Jet-Tech[/link] – Gary can make a custom Kevlar tank using a modified mold for the Mark Frankel Skyray saddle tank. By reducing the tank width to 5” and the length to 5.5”, the 1.5” thick tank will hold about 22oz. Cost is $135 + shipping.
- Do It Yourself – I’d never molded a tank before so I thought I’d give it a try. It’s been a learning experience and I’ve done a couple of “trial” versions to fine tune the process. It has a 28oz capacity and is made by glassing a foam block cut to the shape of a flat-bottomed “U”. The layup is 3 layers of .75 oz/yd fiberglass and 4 layers of 5 oz/yd glass with West Systems epoxy. A shop vacuum and a “Space Bag” (available at a local department store) was a low cost solution for vacuum bagging the tank while the epoxy sets. The tank is then cut in two, the foam removed, the fittings installed, and then glued back together with glass tape. Many thanks to Wayne, John, Mark, and Gordon for their help. Overall I’d say that this route is lot of work, but those additional ounces of fuel may come in handy if an “extra” go-around is needed. The tank also had the advantage of stiffening the fuselage bottom which makes the gear doors fit a bit better.

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Old 09-09-2008, 02:33 PM
  #35  
invertmast
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Default RE: JAS-39 Gripen Owners/Build Thread

Jim,
build is looking good.. can't wait to see the color scheme your planning.
Old 09-10-2008, 01:09 PM
  #36  
Spencer K
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Default RE: JAS-39 Gripen Owners/Build Thread

looking good jim, now if my f-16 doors look as good as yours, ill be in business...
Old 09-11-2008, 11:05 PM
  #37  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

Yeah Spencer, but there is that little matter of a Titan that you need to actually start the business!!!!!! Hang in there bro, your -16 will be fan-f'ing-tastic and certainly one of a kind. Good luck in the flight training. Next stop CFI! Ciao to B!

I started up the installed P120SE for the first time today to do engine/fuel system tests. It was a night start (I had a couple of spotlights though) with the landing, nav, strobe, and AB lights working. It looked and SOUNDED mean and out came a couple of neighbors to watch the show. The P120SE is an awesome machine!!!! Taxi tests might happen this weekend. I'll post some photos of the front and mid equipment bays when I get them fine tuned.

Jim
Old 09-13-2008, 10:18 PM
  #38  
MattyC-130
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Default RE: JAS-39 Gripen Owners/Build Thread

I have a Skymaster Grippen ARF plus. The question I have is the Carbon Fiber main spar tube is one piece that extends through the Fuselage. Should this be cut in to 2 pieces that only extend flush to the inside of the mount plates. I am tending to leave it one piece for added strength, the airflow around it to the engine should'nt be a problem.
Thanks,
Matty
Old 09-14-2008, 07:51 AM
  #39  
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Default RE: JAS-39 Gripen Owners/Build Thread

the Carbon Fiber main spar tube is one piece that extends through the Fuselage. Should this be cut in to 2 pieces
ABSOLUTELY NOT ! It won't be strong enough if you cut it. It's intended to go through the fuse and won't interfere with anything. I made holes in my ductwork to allow it to pass through.

Joe
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Old 09-14-2008, 08:39 AM
  #40  
MattyC-130
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Default RE: JAS-39 Gripen Owners/Build Thread

Thanks Joe.
I will do the same with my duct work to accomodate the tube.
Matty
Old 09-15-2008, 02:00 AM
  #41  
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Default RE: JAS-39 Gripen Owners/Build Thread

Build – Mid Equipment Bay

I guess this would be the engine compartment of most jets, but not the Gripen as the turbine aft mounted. As such, you get a whole bunch of “extra” room to stuff the goodies.

Duct Extension

It needs to be cut to length depending on where you mount the turbine and should be removable without removing the turbine itself. I kept trimming away at it until it was short enough that when the rear end is placed against the FOD screen, the front end just clears the inlet ducts halves. Then it is slid forward about ¾” over the halves.

You have to cut a hole in each side of the duct extension for the carbon fiber main spar. Locating the holes was a simple matter of fitting the duct extension over the inlet halves then supporting the rear of the duct extension so it was centered on the turbine. Insert the carbon rod through the guide in the side of the fuselage, and draw a line around the rod where it contacts the duct.

I didn’t want the duct extension to flap around when the carbon rod was removed for transport, so I borrowed an idea from Joeflyer and added a cradle to support the duct. The cradle is a couple of lite ply arcs with ¾” long spacers between them and is glued to the top of the rear landing gear former. A Velcro strap (from Home Depot) holds the duct extension in place and keeps it aligned for easy reinstallation of the carbon spar. Good one Joe!!!!

Locating Components

There are a plethora of possible layouts and we all have our favorite way of doing things. Much of my layout was determined by to the planned installation of the [link=http://www.tamjets.com/original/product_info.php?cPath=23_22&products_id=94]Tamjets smoke system[/link] and wanting all the fuel components together and close to the turbine. Tam recommends keeping the pump at least 6” away from other electronic components. As such, I mounted the ECU just aft of the left main LG, the status board on a shelf over the left wing spar guide, and the smoke pump in the right wing root between the LG formers. The UAT is in a cradle to the right of the duct at the back of the equipment bay. The shutoff and kero-start solenoid valves and the fuel pump are mounted on the rear side of the rear LG former. This keeps the “liquids” on the right, and the electronics and servo and power wires on the left. I used a [link=http://www.jetsnstuff.com/BUY_NOW_%21.html]JetsNStuff tubing mount[/link] for holding the small Tetra manual valve for the JetCat and smoke system.

Smoke System

I wanted the smoke system to be easily removable for “non-smoke” flying days. The pump is zip tied to a small bracket in the right wing root and is powered via an Rx-type switch connected to the ECU power cable. Two [link=http://www.sullivanproducts.com/Fueltanks1Content.htm]Sullivan S380 ducted fan tanks[/link] are plumbed together and held to the duct extension by Velcro straps. I “teed” a fill port into the line from the tanks to the pump. The vent line runs to a bulkhead fitting in the right wing root (see post #34). Tubing from the pump runs along the right wing root to the engine bay. A single smoke nozzle is mounted to a ply shelf glued to support for the turbine mounting rail (see post #21) and is connected using a 4mm Festo union fitting. The nozzle exit is 2" behind the turbine exhaust and is centered in the exhaust pipe.

Removing the smoke system takes about 2 minutes and involves disconnecting the Festo (the nozzle can stay in place), cutting the zip tie to free the pump, releasing the Velcro straps to free the tanks, popping the Tetra fitting from the mount, and disconnecting the power and signal wire to the pump. Reinstalling it all takes about 5 minutes (less if you have small hands) for those spontaneous “Best Smiley Face” competitions.
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Old 09-15-2008, 02:23 AM
  #42  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

The build thread documentation is lagging just a bit behind the actual construction. The plane is mostly built but has a few things remaining (cockpit kit, Tx programming, and maybe painting) before the maiden flight. The bird currently weighs 22.4 lbs with empty fuel tanks but full UAT and without the smoke system installed. Adding the fuel and 1.5 lbs for paint gives an estimated takeoff weight (without smoke system) of 28.5 lbs. Adding the smoke system & fluid brings the takeoff weight to 30.6 lbs. It should be quite the performer with a 28 lb thrust turbine.

I had it out at the field today for a bit of testing (range checks, engine tests, smoke system tests, lights, and taxi testing). The Tamjets smoke system worked very well even with only one nozzle at 0%ATV (off is -150%). The JetCat P-120SE was amazing; gone are the days of scuba bottles, propane/butane, and leaf blowers.

With the narrow stance gear, some claim that the ground handling leaves a bit to be desired. However, with the Skymaster tires inflated to 45psi (thanks Vin) and the NWS dual rates on about 25%, the ground tracking on practice take off runs was quite good. We'll see how the landing gear really performs in upcoming flight testing. In the mean time, there's a new "Cloud Maker" in town!!!
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Old 09-17-2008, 01:23 AM
  #43  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

Thomas (invertmast),

I was originally going to go with a modified Swiss scheme (like the Chilean Gripen from JetsRC) with an added checkerboard on the bottom, but decided that I would ressurect an old scheme from a Viper built in the mid-90's. I still have some of the paint left over; I wonder if it is still good (not)! You have to really love a checkerboard to do it since it is a b*tch to mask.

I'm still waiting for your F-18 and that F-100. Tick, tock!!!! I need something to practice with until I get this baby in the air.

Regards,

Jim

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Old 09-17-2008, 04:03 AM
  #44  
NickC5FE
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Default RE: JAS-39 Gripen Owners/Build Thread

jIM, LOVE THE SCHEME! Glad you got ol girl going good on the taxi checks, she looks great. Currently in Guam, next stop Okinawa. Take care bro, Nick

Tamjets smoke pump puff goooooot!! ;-)
Old 09-17-2008, 09:04 AM
  #45  
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Default RE: JAS-39 Gripen Owners/Build Thread

Jim,
that color scheme looks AMAZING! i love it! Will definately be one of a kind. I'm back to work on the big F-18 now. Turbines, bypass' and pipes are all mounted, now just working on finding the last of the air leaks in the brake systems, and finish some linkages. Then its off to get clear coated and final installation of everything (once i can afford the autostart upgrade and fuel system stuff). Shouldn't be much longer, as long as i can get work to co-operate w/ the finances. haha

Thomas
Old 09-17-2008, 10:29 AM
  #46  
Ray Davis
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Default RE: JAS-39 Gripen Owners/Build Thread

A few things:

I added a spacer on the nose gear (and fabricated a new, longer 'pin') to raise it 3/4", which made rotation much smoother, no longer neededng full elevator and the subsequent 'jump' into the air on TO; I stiffened the main strut springs and greatly increased the oil viscosity (finally using chain lube oil); and filled the tire cavity w/ Gorilla Glue PU. Oh yeah, and a gyro. Now runs straight and true, w/ beautifully damped landings no matter how hard your 'carrier' landings might be.

Struts/gear/tires very nice stuff.....but a good solid tire would be better in every way. C'mon SM!

Check your 'live hinges'...mine (ARF-Plus, purchased 16 months ago) deteriorated before even my first flight, by just flexing them through their range. They became loosened and 'screen door-like' w/ an increasing gap; some of those threads began breaking. I notified SM, they were more than happy to replace the wings, but I chose to repair w/ Robart hinge points (the knuckle just shows through the top wing surface. Looks good.)

Six flights, then my 8-year old engine seized on TO, minor damage. But, I noted the rudder hinge is now 'loose/sloppy' as well. Repairs, lights, ordinance, weathering over the winter....

Check your hinges!

Ray
Old 09-17-2008, 01:43 PM
  #47  
NickC5FE
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Default RE: JAS-39 Gripen Owners/Build Thread

Hey Jim, whatever you used to create that scheme on the computer, can you tell me what program!! I wanna get a scheme "on print" and outta my head. Thanks, Nick
Old 09-17-2008, 01:55 PM
  #48  
Vincent
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Default RE: JAS-39 Gripen Owners/Build Thread

Ray,
I used large nylon rope in my SM F-86 tires to firm them up. I agree, this blow up tire stuff is BS and also the tire rubber itself is very thin material.
V..
Old 09-18-2008, 08:42 AM
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Ray Davis
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Default RE: JAS-39 Gripen Owners/Build Thread

Vinny.....yeah, I expect within a half-dozen flights next season, I'll be running on my GG PU 'liner' . Maybe by then SM will have solid replacement tires.

Ray
Old 09-21-2008, 04:30 AM
  #50  
rcjets_63
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Default RE: JAS-39 Gripen Owners/Build Thread

Build – Main Gear Doors

The “standard” installation on the Skymaster (and likely JetLegend) Gripens is a one piece main gear door and one piece nose door. Unfortunately, this isn’t even close to scale as the full size Gripen has a two piece main (inner and outer) and a three piece nose (fwd, left, & right) as seen in the photo below. So, for any “purists” out there, here’s how you do the two piece main doors. (The nose doors will be in a later post.) Note: The gear doors come with 10 hinges total for the standard installation; you will need to order another package of hinges if you want to do scale doors. You’ll also need either an [link=http://www.up-1.com/uptwo.html]Ultra Precision UP-2[/link] or dual valves with a sequencer since the outer doors only open to allow the gear to swing up/down.
- The Skymaster doors have an “S” shaped channel molded into the inner skin of the doors. Cut the door in two along the FORWARD edge of the channel.
- Squeeze a bit of epoxy & milled fiber between the inner and outer skins to seal the gap.
- Install each outer door with three hinges in the molded pockets. The inner doors use two hinges each. You’ll have to trim the sides of some hinges in order to get them to fit into the pockets yet clear the fuselage formers (see photos).
- The outer gear door should open 90 degrees such that the bottom of the gear door is vertical when the door is open. I couldn’t find a good photo showing the angle on the inner door so I also installed it to travel 90 degrees.
- An air cylinder drives the outer gear door. I used [link=http://www.bvmjets.com/Pages/Catalog/air.htm]BVM #5751 1" stroke cylinders[/link] as I found them to be a better fit than the Skymaster cylinders. I exchanged the rod end with a ball link clevis and installed a [link=http://www.shopatron.com/product/part_number=190/101.0]Dubro #190 1/16" threaded ball link[/link] on the hinge. The cylinder was mounted on a ply mini-former Hysol’d to the upper fuselage immediately outboard of the hatch opening. This geometry results in the fully extended cylinder holding the door open 90 degrees but, upon retraction, the door is closed before the cylinder retracts fully which keeps the door held tightly closed.
- Here comes the fun part….the inner gear door is driven by a mechanical link to the retracts. It took a while to sort out the geometry at first, but once I did, I copied it to the other door and it worked on the first shot. Hallelujah!!!
- Drill and tap a 2-56 threaded hole on the INBOARD side of the aluminum strut block. The hole should be 1/8” forward and 1/8” up from the edges of the block (see photo). The hole only has to be deep enough to intersect the hole for the strut. Cut about 3/32” off the threaded portion of a [link=http://www.shopatron.com/product/part_number=181/101.0]Dubro #181 2-56 threaded ball link[/link] and install with Loctite into the tapped hole.
- Drill a 1/16” hole in the inner skin of the inner door at the dimensions shown in the photo. Install a 1/16” threaded ball link in the hole with Hysol (squeeze some through the hole to help “pot” the ball into the door).
- Make a linkage using two ball link clevises and a length of 2-56 threaded rod. The link should be 1-15/16” from center of ball to center of ball. Bend the link about 10 degrees at its midpoint to form a slight “V” shape. The ball hole in the clevis to be attached to the retract strut block points towards the INSIDE of the V. The ball hole in the clevis to be attached to the door points towards the OUTSIDE of the V.
- Trial fit the link onto the strut/door. Retract the gear and adjust the length of the linkage such that the door closes fully when the gear is retracted.
- Frankly, I hate installing gear doors, hinges, links, messing with gaps and clearances but dang they look good when they’re done and it’s easily worth all the effort!!!!!!!!

Regards,

Jim
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