IS-4 Jastrzab

[mlachow]

There are several pieces to glue in around the wing root. These pieces support the sheeting around the root area. One piece supports the place the rounded fuselage shape intersects with the airfoil. Then two pieces support the sheeting around the root rib. These pieces curve on the fuselage they have to be glued one one at a time. The piece closest to the center had some wide grooves so I added some cotton flox to fill in the slot. The side pieces under the root rib needed some thin shims to make the ply close to even with the bulkhead.. When it does get sheeted, the sheeting will extend a little beyond that ply. I might also need some shims added to the surface of the ply at the trailing edge to get that surface level with the bulkheads when I install the fuselage sheeting.



After that was done, the wing root ribs are added. I used some flat stock to keep the ribs flat while the epoxy was curing. The holes for the wing alignment pin lined up just fine.


When you run out of clamps you wait for the glue to dry.

[mlachow]

Two by two, gluing the stringers to the fuselage. I now have the middle two glued in place. I still need to glue the top and bottom stringers in place. There is also another one in the front along the bottom that extends from the nose to the wheel.



And since things are starting to get a little stiffer, I put on the stab and the one wing panel that is framed out to see what it all looks like. A long way to go but it is starting to look like a sailplane. While waiting for some of the fuse parts to dry or cure, I also did a little work on the stab adding the blocks for the hinges and the framework around the servo openings. It is almost ready to be sheeted. Things look OK on at this point. When I get to sheeting the fuse, that is when I have to make sure things are straight, The fin is still pretty flexible.

[lenb]

Hi Mike,.

Great progress on the plane. The fuse is particularly interesting. Be sure I never lift it up for you, since they call me Old hammer hands. ( not sure why OLD ? )

[mlachow]

The fuse still gets covered with 2.5mm balsa. After that I usually finish the fuse with fiberglass. Maybe two layers on the front end plus some strategic strips of spreadtow carbon It is a 30% model so the fuse around the wing is pretty hard to get a grip on.

[mlachow]

I finally have all the stringers except those on the bottom near the nose done. It doesn't look much different. The front ones can be tricky to get curved around to the nose. My pine strips were not long enough to make it all the way so the front pieces are spliced around the second and third bulkheads. This helps with the curve. I did clamp four carbon rods from the nose back to the fin to check for twist. I did end up with a little twist from the canopy area forward. That should be fixed when I sheet the fuselage.

I also had an email exchange with Oldgliders. I had a few "extra" parts. There was a set of ribs that were almost like the fuselage ribs. They were slightly smaller and the two notches around the joiner were for a single thickness former. They were most likely left over from an older fuselage revision I could cut them up and glue them to the existing rib to make the wing root rib thicker. The root rib on the wing has a doubler.

[mlachow]

Other things still need work on the tail. The stab needs to be sheeted. The bottom is done in pieces and the real strength is in the spars, not the sheeting. For the sheeting I am ironing on the sheeting. I thin some wood glue with water and put that in a syringe. A nice bead is applied to the structure and then the sheeting is dropped in place. Then it is removed. I use a q-tip to spread the glue a little along the glue lines on the sheeting and the framework. If there are any dry spots, I add a little glue. After the glue is dried, the sheeting can be ironed on with a hot covering iron. The 2mm sheeting is thick enough that you have to move slowly to make sure the heat melts the glue.



The fin needs some balsa added to the LE. It is curved a little at the top and bottom. The plans call for 2mm then 3mm balsa strips but I am using multiple layers of 1mm balsa. Most of the fin will get sheeting with vertical grain but the fin near the stab might need a bit of solid balsa or a different grain direction to match the curves. I have two bars clamped to the fin to keep it straight while doing the lamination.



And the next fun step is going to be lots of trapezoids and scarf joints. Sheeting the fuselage.

[mlachow]

Let the fuselage planking begin. The first pieces are installed on the fuselage and it is starting to look more like a sailplane. Stab has also been sheeted and the fin partially sheeted. This part can be a bit tedious since all the pieces are custom fit. Some places can be fit with longer strips across multiple bulkheads but then there are places like the nose that require all individual pieces. It should be less than 200 pieces....

[mlachow]

I figured you all need some more pictures. This is probably about 1/3 of the work sheeting the fuselage. It does cover a bit of the surface. The pieces towards the rear might be smaller. I guess if you edge joined the sheets and edge joined at each bulkhead you could reduce the number of pieces being glued and get the sheeting on faster. I do pieces that are longer and stagger them so that there is some sheeting that spans two bulkheads. A little extra time but it should be stronger.

[lenb]

lol . getting old.

[mlachow]

Len, either the software is duplicating things or you are repeating yourself. Same message as 5 days ago.

[mlachow]

Continuing with fuselage sheeting. I completed the sides except for the bottom of the fuselage and the area around the tail. I also did a little sheeting in the wing intersection area.


The intersection between the fuselage and the airfoil is a little funny on the model. The real one is a pretty thick root rib airfoil so the bottom airfoil surface intersects the fuselage a bit lower. The model airfoil has the TE almost at the top of the fuselage so it is a really weird intersection. The real one does appear to have root fillets that somehow were attached after the wing was put on. I will do a fillet at the root to make a better intersection once the wing is completed and the wing joiner box is glued into the fuselage..

Some tape to hold the tail surfaces. Place the canopy frame pieces on the fuselage and this is what it looks like.




The next steps on the fuselage are making a nosecone and tow release, finishing up the landing gear mount, and getting the basic radio installation setup planned.
I need to frame the second wing panel in order to complete the wing mount. I have two work areas to build in but not enough clamps and pins to work on both the fuselage and a wing panel.

[patte de loup]

herewith 2 interesting topic about IS4 building :
- RETROPLANE.net :: Voir le sujet - IS-4 Jastrzab Thomas G.
- RETROPLANE.net :: Voir le sujet - IS-4 Jastrzab M1:3
Pat'

[mlachow]

I've seen them. They are a bit older and the OldGliders construction has been updated a little since then. The wing mount is definitely stronger. The bulkheads in that area are now doubled. The cockpit frame has been changed to a wider piece of plywood interlocking with everything. The number of stringers on the fuselage is lower but the slots are for 6x6 and the pictures of the 2013 vintage build appears to be maybe 5x5. There are also some doublers the full chord of the wing on the top ply piece on the fuselage.

[mlachow]

The plans call for an aluminum bracket bolted to the wheel well for the wheel. I made two of them to support the landing gear. I think it will be glued and bolted. It still attaches to some of the lite ply they use for everything in the kit. Not my favorite material for high strength. On the Bocian I laminated the gear box with some carbon fiber cloth.

I also need to make up a nose block. One of the sheets of 10mm balsa was really, really dense stuff Something suitable only for a nose cone. To make a pattern for the lamination, I pulled out one of the foam cutter bows. I sliced up some pink foam into 10mm sheets and taped 6 pieces together. I also squared them up into a foam block. I made a pattern for the side view and traced that line o the side of the block. I also used the fuselage to trace a line on the back of the block. I cut the foam block on those two lines on the band saw. Then I used a hand saw to do a little more shaping of the corners and sanded it a little. It is still a bit oversized. The next step is to take the 6 sheets apart and transfer the patterns onto the 10mm balsa sheets. I will also cut out some of the inner sheets for some space for nose weight. I should be able to make two nice 25 x 25 x 40mm cavities in there for nose ballast.

[SMYK]

Michael
Did you ever go to this picture Bonanza about Jastrzab?
all Polish ships are covered with pictures with separation for serial #. You can observe differences

http://szybowce.fotoedytor.com/galeria/index.php?cat=16

Mike

check the wheel location
I am not sure how your former placing lines up with factory setting. There was 29 bulkheads (LOL)
important is Main wheel location against CG It was placed right after bulkhead #10
there was two sets of wheels. Larger with brake and smaller with no brake ( depends of serial #). Different brackets
One thing for sure IS4 was piece of work
Metal nose cone cover was very fractional ( 73mm) . In your case it should be around 1" I think first former in Binio fuse is too far back to work with. It was removable cover with access to TOST towing hook
There is also interesting detail in the nose. Right after front former there is compartment for additional nose weight. Shape and installment on the drawings

[mlachow]

I think I have seen that site.

Binio definitely does not follow the original structure, And based on the retroplane.net photos the kit structure has evolved over time. I would say the front bulkhead is closer to where the second bulkhead is on the plans. And his photos with the kit show the tow hookup location a little higher and closer to the nose. The nose weight thing on the model is interesting. If I made it with 25mm tungsten, the thickest part would be at least .8kg. Which would be a good start in balancing the model.

[SMYK]

Michael
Place the towing hook in Factory location. There is a reason for it. Do not play games with physics. Our towing style needs more lower location then full scale. We fly above towing plane, not under like traditional full scale tail towing. All long nose slippers should have the belly tow hook location like most of the real modern gliders. This was subject of many mishaps while back when I was towing and probably still exist especially in deeper grass. High tow hook location also makes glider to dive behind the tug unexpectedly, sometimes, making that process nerve wracking.
I got tons of pictures proving that point, but this thread is about IS4 . I can make separate thread about it if any interest

[mlachow]

Well that is why I use a separate flight mode for towing. IS4 has a high wing location so almost anywhere in the nose should be fine. The structure does have a front servo tray locked into the front bulkheads. A scale location is about as low as you can go without offsetting it left or right of the skid.

The standard skid is just 3 layers of ply. I haven't decided if I am going to do that or build a functional skid. I used EOP foam inside the skid on my Pirat. The Orlik is just layers of ply.

[mlachow]

If anyone was wondering what is going on.... Second wing panel is on the bench.

[mlachow]

Time to test fit the wing before gluing in the second joiner box. Everything looks reasonable. Root ribs match fuselage, distance from front of stab to ailerons is pretty close, same for LE dihedral break to the front fuselage former centerline. The dihedral angle gets set on the building board when the box is glued in. And the angle relative to the root rib is also set off the drawings and root rib, The only thing harder to check there is the spacing from the joiner to the alignment pin. This assembly says things fit OK and I should not have to open up the holes for the alignment pins. The only place I might have to file a little in the fuselage will be maybe back edge of the ribs to match the joiner box alignment. The wing joiner box is at the back edge of the hole in the root ribs.

Next step will be to tack glue the joiner box on the bench and then double check before a full glue up with the System Three T-88 epoxy and fitting all the filler around the joiner box, spar, webs, wrap, sheeting, etc. I think I just have a very minor angle. The 3-views appear that the LE of the the two tips might be straight across the wing. It is really hard to tell in those drawings. I have about 6mm sweep on the tip LE's if it really was straight across the wing..