rcjets_63

My Feedback: (4)

Looking good Sebastian,

I would caution you about extending the gear length though. The gear will need two springs to work properly. One spring needs to be weak enough to fully collapse under the weight of the empty plane but strong enough to fully extend the strut against the oncoming airstream. The second (stronger) spring provides shock absorption on landing.

Regards,

Jim

sysiek

My Feedback: (176)

I'm usually using Tygon or silicon tube in the spring to make the shock two action soft with the spring and when the rich the silicon it's hard and not bounc back just like oil shocks.

sysiek

My Feedback: (176)

OK so I did new nose gear doors .now in scale length and did some hinges planning for the main doors.

rcjets_63

My Feedback: (4)

Nose Gear Doors - Cylinder Installation

Back wrenching on the Gripen after a couple of days of sorting out details with the graphics for the tail and canards. I did a layout of the nose gear cylinders in CAD (far easier than the trial and error method) and came up with a pretty clean installation. Here are some pics of the install and a comparison with the full scale.



The geometry is pretty simple, I used .060" G10 to make control horns installed in the doors. The cylinder rod attachment point is 3/8" inboard and 3/8" above the hinge line. The cylinder is mounted on a wood bracket such that the cylinder rotation point is 9/16" inboard of the fore/aft plywood longerons. The bracket is installed 8-1/2" aft of the longeron front former. BVM 5751 cylinders (5/16" diameter, 1" stroke) were used. The door rotates 95 degrees.

I received a fantastic email today. I've been invited to a take a tour of a full scale Gripen airbase after the Jet World Masters. Oh yeah, I accept that invite. Should be lots of fun and I hope to take a selfie while sitting in the cockpit. I suspect a ride is too much to hope for (even if I ponied up my Visa card to pay for the fuel) but I will keep my fingers crossed.

Regards,

Jim

sysiek

My Feedback: (176)

I wish you actually have chance to have flight in the gripen you making the model off or eny gripen,and do not worry about the visa charge for this one flight it's worthit to go bankrupt or take long term pay back plan ,I will .

rcjets_63

My Feedback: (4)

Lights

I received most of my lights from Details 4 Scale and I'll install them once I get the plane in the air (but before painting). Another division of my company actually makes the lights so I was able to get copies of the drawings and provided them to Dan so the model lights should be quite accurate. Here's how they look:

Fin Anti-Collision Strobe: Obviously the aft side of the fin and fairing need to be reworked a bit so that the light will fit.


Aft Navigation Lights (2): The Lexan light cover needs to be trimmed down a bit. Notice how the light is mounted on an angled base on the full scale.


Left/Right Navigation Lights: The -39A & B variants had colored lenses. The C & D variants had color LED's with clear lenses. I'm doing a -39C



Wingtip Light: The small incandescent light on the mounted on the aft inboard side of pylon 1 (wingtip) was replaced by an LED light on the C & D. These are just too small to do with an LED on the model but here are some pics for reference. I think that they are maintenance lights controlled from the ground because the white dial on the A/B incandescent light is knurled and has ->ON OFF<- markings.


Taxi Light: this light is mounted in slightly different locations on the A & C variants (on a bracket attached to the forward nose gear door) and the B & D variants (mounted on a trapeze near the retract cylinder). These lights and the landing lights (attached to the main landing gear struts) were not made by my company so I couldn't get drawings. Fortunately, I had a high enough resolution picture that I could read the manufacturer's part number off the ID plate. The light was made by Grimes, which was bought by Honeywell. So I phoned up Honeywell customer service, gave them the part number, and they gave me the overall dimensions of the light assembly. I asked for a copy of the drawing but no joy. I haven't received my taxi light and bezel but they are supposed to arrive Saturday.


Landing Lights: These are also made by Grimes and are mounted in frames to the main landing gear strut. They are a bit bigger than the taxi light. I'm supposed to get the lenses Saturday.


Regards,

Jim

sysiek

My Feedback: (176)

Hi Jim do you have close up pictures of the maim gear doors ,I have problem with positions the hinges and actually might use one long piano hinge the off set hinges don't work with out complications .

sysiek

My Feedback: (176)

I did some pictures on rcu it's dificuld to do on my jet but possible .

rcjets_63

My Feedback: (4)

The hinge pin line is actually outboard of the door. You can see it quite well in photo 2 of your post above (#1083). Here is a high resolution pure bottom view that you can use to scale the location of the hinges. I suspect that the lever length on the hinge is much longer than on a typical offset hinge. You might have to make your own (like I did) out of G-10. The hinges rotate into the slots you see immediately outboard of the main gear door.



This photo gives you a pretty good look at the forward hinge. In the next photo you can see the rear hinge.

Regards,

Jim

sysiek

My Feedback: (176)

Thanks Jim ,good I have a lot of g-10 material to make the long hinge .i might try long piano hinge my jet it's little off .

rcjets_63

My Feedback: (4)

You don't need a lot of G-10. Only 3 pieces per door, each about 3/8" wide and 1" long with a 1/16" hole for the music wire hinge pin.

Jim

sysiek

My Feedback: (176)

I know Jim just hou know how many pices I'm going to cut before doing right

rcjets_63

My Feedback: (4)

Airbrake Cylinder Installation

The airbrakes don't have any molded-in obvious attachments for an actuator so it really is up to the builder to decide how to drive the airbrakes. In the other Airworld Gripen thread, festus01 installed a G-10 plate as a lever and used BVM cylinders. Here are his pics:

Fundementally, the idea is sound but I didn't like the that so much of the rear former was cut away (and the CF rod installed). Also, it would be difficult to remove/reinstall the BVM cylinder from the model if any maintenance was required. As such, I made some changes to the design as follows:

- The G-10 lever arm was positioned 10 degrees off the fore/aft axis. The arm is 1.5" long and was installed in a slot I made in the speedbrake by using a large cutoff wheel
- The BVM cylinder bracket was modified but cutting a clearance slot for the extension nipple.
- The cylinder bracket was screwed to the aft side of a 1/2" thick plywood laminate. The plywood was then match drilled/tapped to a 1/4" thick sub-former installed in the fuselage (approximately 4" behind the elevator hinge line. The two 8-32 SHCS used to mount the plywood laminate to the sub-former can be easily reached should I ever have to remove the cylinder.
- The cylinder was modified by solding a 1-1/2" extension made of 3/16" brass tubing. The head of a 4-40 SHCS was sanded down until it fit into the brass tubing and soldered in place.
- The rear former only needed to be slightly grooved to allow clearance for the G-10 lever arm when the airbrake is in the open position.

Here are pics of the installation showing the door in the closed and open positions:


Regards,

Jim

rcjets_63

My Feedback: (4)

Gearbox Exhaust - Scale Detail

The gearbox exhaust feature which has been molded into the rear left upper fuselage leaves a bit to be desired in terms of it's accuracy to scale. It really isn't all that surprising that it isn't a good match for the full scale, because it is hard to get a good picture of feature due to its location on the aircraft. The typical photo is something like this:


Yep, a bit out of focus, and so small that you can't see much. I was pretty pleased when I came across this photo in a book:


But that really isn't a lot of help either. In order to get a good photo, you have to be able to stand on the aircraft; something generally frowned upon at airshows and museums. However, I know a guy who has that sort of access and was nice enough to take some pics for me with dimensions (mm). If you are a Gripen fan, you'll want to save a copy of these:


Having that pic made it easy to make a new gearbox exhaust detail out of G-10 and basswood. I've still got a bit of finish sanding to do of the reddish seal area, but all-in-all, I think it looks like a good match.


Regards,

Jim

RCISFUN

My Feedback: (44)

Jim with all the great work you're putting in on this project, how do you have time for your day time job?

roydefiant

Incredible attention to detail

Roy

sysiek

My Feedback: (176)

I was not able to do proper hinges for the main gear doors my fuselage have wird angle and don't matching the gear doors ,right now I'm glued pice of wood from inside to match the curve to the gear door and going to do the install with ss steal piano hinge this will not look to scale but will make the door work will post some pictures tomorrow ,Jim the details on your jet just grate,where is the gear box situated post picture from away thanks ,do you going to use some ss steel tubing to make the exhaust pipes ?

rcjets_63

My Feedback: (4)

Top Details - VHF & IFF Antennas, Gearbox Louvered Inlet

I thought I'd have a bit of fun today by adding some scale details. Nothing adds zing to a plane like antennas and the Gripen has several of them on the dorsal, more under the nose, and the beacon on the bottom aft centerline. The dorsal antennas are most visible so I thought I'd do them first. In this pic of Swedish Air Force JAS-39A #131 (done in splinter camo) you can clearly see the large VHF antenna, and the two smaller IFF antennas. Note that between the two IFF antennas, there is a blanking plate. The Czech Gripens have the same antenna configuration and the blanking plate on their JAS-39C's is circled in red. The JAS-39D (as shown below with the yellow covers installed) doesn't have the plate.


The large VHF antenna was made with .060 thick G-10 laminated on either side with 3/32 balsa and a .020 base. The G-10 central piece fits into a slot cut into the dorsal. The IFF antennas are also made from .060 G-10 with a .040 thick base.


Seeing as how I did the gearbox heat exchanger exhaust the other day, I figured it was time to fill in the nearby cutout for the inlet air to the heat exchanger. The inlet is louvered so it takes a bit of work. I laminated alternating layers of .020 thick G-10 and 3/32" balsa using canopy glue. Once the glue was dry, the laminate was sanded to size, and side plates added with thick CA. The balsa was then carefully cut out from between the G-10 (thus the choice of canopy glue), and the finished set of louvers were installed in the model. It looks pretty cool.


Regards,

Jim

rcjets_63

My Feedback: (4)

APU Blister - Corrected Shape

The Gripen A & B variants were fitted with an APU made by Microturbine but their high failure rate led to their replacement with a Sundstrand APU on the C & D variants. The layout of the inlet & exhaust changed and the cover over the Sundstrand APU has a different shape. Here are photos of a B Gripen and C Gripen 9245 which illustrates the shape change.


I'd previously added the blister to the model by gluing a piece of blue foam in place, sanding it to shape, and then glassing it (covered in a previous post). The more I looked at it though, the more I knew it there was something wrong. The curvature at the front didn't seem to match the full scale, and the blend into the fuselage on the inboard side of the blister just didn't look right.


Finally, after looking at a variety of APU blister photos and interpreting grey shadows, I figured it out....the upper surface of the blister doesn't blend directly into the aft fuselage on the inboard side. There is a slight step down and this is what results in the curvature you see at the front of the blister and why the countersinks for the screws on the inboard side of the blister appear to be at a weird angle. I send off an email to a buddy at a Gripen base and asked him to send me a dead on end view pic so that I could confirm the shape of the blend on the full scale. Sure enough, there is a trough between the blister and the curvature of the aft fuselage.


The good news was that I had found what was wrong with my APU blister; the bad news was that I needed to rip away the earlier effort and try it again. This time it is much better. I just need to fine tune the size/shape of the trough with some spot putty.


Regards,

Jim

sysiek

My Feedback: (176)

OK finely the main gear doors .so after multiple times of trying make scale hinges I decided to use piano hinge .the was a big gap between the fuselage and doors so bond was the fix .

sysiek

My Feedback: (176)

OK bondo off

rcjets_63

My Feedback: (4)

Sebastian, the gear doors are looking pretty good; well done. Here is a top view of CzAF JAS-39C Gripen 9244 showing the location of the gearbox air inlet and exhaust. If you look closely or zoom in, you can even see the blanking plate between the two small IFF antennas on the dorsal.


Once I paint the model, I will install stainless tubing to complete the details of the gearbox exhaust. There are also a few other areas of the plane that will need short pieces of stainless tubing.

Regards,

Jim

sysiek

My Feedback: (176)

Thanks for the picture .The biggest thing it shows how much the racket rails stick out of the wings .I'm going to add some extra details to my model after the complete repair .

rcjets_63

My Feedback: (4)

Sebastian,

I was looking over the photos you posted of your plane. I'm afraid that the wingtip pylons are mixed up. Whoever built the kit glued them on incorrectly. They glued the outboard flat surface to the wingtip rather than the inboard rounded surface. As such, the fairing for the maintenance light is on the outboard side. You will need to cut off the rails and correctly install them.


Adding some other scale details will really dress up the jet. The biggest and most obvious features missing from the model are circled in the photo below:


Regards,

Jim

sysiek

My Feedback: (176)

Great catch Jim will cut them out when back to work on the wings .for now waiting for new main struts and new gear doors actuator and when finished the fuselage part then wings and some extras to make it looks better.