Tag Archives: Fin

Building 4 Star 60 Day 48: Stabilising Wires Installed

Stabilizing Wires Installed

Though my plane according to the plans was complete, Monday I truly completed my aircraft!

Outside of the plans, based on club members experience, I added support wires to the tail.  You can see them installed in the featured image above.  The reason for this addition is that a known flaw in the design of the aircraft is the weakness of the fin.  If you were just flying in circles and figure eights you would be just fine but as soon as you started performing loops and rolls you would have a problem.

That problem is that the forces applied to the fin during these maneuvers would cause the tail to twist making the aircraft unstable in the air.  This instability, and perhaps damage, leads to a lack of control and I believe even the potential for the fin to break.

The wires were created by John based on the ones installed on his 4 Star 60.  He sautered the ends to bolt to the surfaces onto the wire.  The are adjustable for length as you want to make sure they are at about the middle of the top of the fin as well as the middle of the outer edge of the stabiliser into solid wood, but not to close to the edge to ensure a firm hold.

Doing one at a time you line it up and mark where the holes need to go into the stab and the fin.  Adjustments needed to be made on the ends to ensure they sit flush with the surface of the aircraft.  You then drill out the holes, ensuring you go through in a straight line as you don’t want to be at an angle.  Next you put the screws through (screw it in once required) and then put a locking nut on the screw through the stab.  Can leave the one through the fin for now.

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Building 4 Star 60 Day 37: Covering, Fuel Tank and Rudder Hinged

Cockpit Painted

On Saturday I got to work on my plane again and made some more progress on covering and installation of the fuel tank.  One of the discussion Peter & I had in a previous session was what I’d like to do with the cockpit, use covering or paint it.  I decided to go with painting it as I felt under the heat of summer with no airflow under the canopy that covering would wrinkle and be a waste, so Peter stained the cockpit green, seen at the top.

I continued where I left off last session by completing the covering of the fin in white.  I was able to utilize the knowledge I learned from John in my last session about covering.  I was impressed with the result.  I didn’t quite get it right the first time so had to switch around the covering and start again (as the glue along the one edge was no longer good after pulling up the heated covering).  Throughout the process I had to make some incisions at the top and bottom to allow the covering to come around properly, which includes removing excess when I could.

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Building 4 Star 60 Day 36: Tail Covered

Top of stabilizer covered

Tuesday was an excellent covering session and nice to get in back to back days working on my plane.  Covering is definitely a time consuming task and the tail with all its intricacies took a lot of concentration and patience.  Throughout the process I learned how to do things better, namely so that I do not get the wrinkles when rounding corners causing a jagged/rough looking edge with wrinkles in the fabric.

I started with covering the bottom of the stabilizer in orange and the top yellow to match the colour scheme of the wing (picture below and above, respectively).  Measuring the surface at its widest point and longest point to cut a piece at those dimensions plus three inches to have play and room to grab.  For each piece the process I went through was (see bottom of article for better approach):

  • Woodpecker the surface
  • Line the piece up at the fuselage
  • Tack it down starting at the centre and working my way out
  • Start up by the fuselage and apply heat from trailing edge to leading edge (width of iron)
  • Repeat moving down the stabilizer
  • Ensure all edges are fully ironed down
  • Cut excess from trailing edge and tip
  • Fold leading edge (as have excess) around the entire edge, pull tight & iron it down
    • This is where the wrinkles really come in!
  • Trim excess from trailing edge
    • Doesn’t necessarily look pretty as the wrinkles cause the blade to catch preventing a clean line and instead you get a jagged rough line
  • Do your best to iron out all them wrinkles

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Building 4 Star 60 Day 35: Tail Covering Started

Fin-Stabilizer Transition Covered

Being Family Day in Ontario I got over for an afternoon building session with Peter.  I started off where I left off, the rudder.  I used the heat gun to shrink the covering over the ‘holes’ in the rudder and then using the markings on the fin figured out where the hinge marks were hiding under the covering that was over the leading edge.  I then used the back tip of an x-acto knife to open up the hinge slots, hard to see below 🙂

Rudder Hinge Slots Exposed
Rudder Hinge Slots Exposed

After that was finished up brought the fuselage up onto the workbench as I’m now on to covering the fuselage!  As you’ll notice from the pictures I am doing the fuselage and fin white.  Because you want your seems to be such that the covering is overlapping from front to back, prevents the air from getting under and peeling back the covering, we start at the table and work our way towards the nose of the aircraft.

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Building 4 Star 60 Day 25: Fairing Blocks, Covering Wing Tip, Patching, & Sealing

Glued Balsa Tail Fairing Blocks

Had another great building session with Peter today.  I started with covering the other wing tip in green, which again took a lot of time and due diligence!  I was able to do this one by myself as I remembered what I learned from working with Peter & John while covering the other tip, bottom of this post.

Afterwords I glued the balsa tail fairing blocks into place.  In order to do this I cut two 3″ lengths of 1/2″ balsa triangle stock to serve as tail fairing blocks.  I then marked one for each side of the fin.  Peter showed me on the first one how to angle the back so it tapers from front to back.  You mark a line for the max you can go for your tapper as well as marking where F6 (Former) rounds against the block as you then sand to achieve the desired taper at the back and to get it to be ‘aerodynamic’ with F6, as you don’t want it to be squared up above creating unnecessary resistance.  The reason for these two blocks is that in the design the fin is not sturdy enough without them and can cause the fin to flutter or break off during flight.  These two fairing blocks provide additional support to the fin to help prevent side to side movement.

Patched Imperfections on Top
Patched Imperfections on Top

After that was completed we poured some glue into a small container and mixed in another compound with the glue in the original container.  The compound makes the glue thicker, so you keep adding and stirring until you get the consistency you are looking for.  We then went over the sheeting on the wing and found any little whole, indent, ding, ‘non-smooth surface’ we could find and filled it with the mixture.  We then left it to dry.  The beauty of this mixture is that it is easy to sand, so next time I’ll sand for a smooth finish.

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Building 4 Star 60 Day 4: A little bit of everything

Today was another great day of building.  I lucked out today with some extra assistance to keep things moving along.  John cut the find down to size and sanded the edges for me.  Even sanded the sheeting.  Apparently this is one of the reasons why we don’t use the 1/16th that comes with as wouldn’t be able to sand.  We don’t do all the final touches on anything until ready to install due to hangar rash, that is the potential for bumps and what not while around the workshop.  We’ll want to make sure that sheeting surfaces are sanded smooth, excess glue gone, etc. Before applying the covering to prevent wrinkles, bumps etc. in the covering.

I marked the centre on the trailing edge followed by where the hinges have to go using the plans.  After practicing with scrap wood I made the slots for the hinges.  The other thing I had to do was start rounding the leading edge for aerodynamics.  This involved again first marking the centre, marking with a pencil so far from the edge on both sides as to how far to sand for starting the rounding, and then sanding the side edges at a 45 degree angle up to the line to get the rounding effect.

Sheeting cut, fin sanded, hinges marked
Sheeting cut, fin sanded, hinges marked

I repeated this process for the stabilizer as well, using the plans to mark where the hinges had to go, the centre position, and making the slots for the hinges.  Here I started rounding the leading edges using the same technique.

Peter showed me with the fin how to use sandpaper to finish the rounding effect using a finger on each side to apply pressure while moving the sand paper left to right over the edge as well as up and down the length of the edge focusing on one side or the other as needed to even it out.  You use the marked centre line as your guide since without it you’d have a hard time knowing what was the centre once you’ve started sanding.

Stabilizer hinge centres
Stabilizer hinge centres

On the stabilizer I marked the centre lines on all three sides (not the flat top as no hinge goes here and it won’t be rounded, actually want it to be flat and level for connecting to the body of the plane later).  Where you see the pencil marks that is the centre of my hinges, 6 total – 3 per half.  These markings with the long line is to help find hinge placements once covering is applied first to the edge so we can cut out the hinge location before covering the rest and putting the hinge in (dido for the fin).

Here’s a closeup of the edge where two hinges are marked and cut.  The cut into the wood for the hinge is very hard to notice which is where the markers are very helpful.

Stabilizer hinge placement cuts
Stabilizer hinge placement cuts

To continue prepping the fuselage today I glued the fuselage doublers to the corresponding fuselage side as we labeled yesterday.  We first traced them to guide us where we need to place it and to know where we can’t allow excess glue to remain.  I used a different kind of glue, titebond wood glue, for this as slower to set so absorbs in and creates a stronger bond.  As I glued each one we weighted it down to hold it in place and ensure contact is maintained throughout the drying process.  We had to ensure we wiped away excess glue from the slots and other areas where future pierces will go.

Weighted down glued doublers and tail wheel mount
Weighted down glued doublers & tail wheel mount

Another big thanks to John and Peter for the work they did on the firewall starting with marking the centre and where the engine lies on the firewall.  Peter explained to me how they used Johns Saito 100 4 stroke engine (same engine I’ll be buying for mine) to mark out where the holes have to go to on the engine mounts (they already drilled them for me) and made the small wholes where they’ll be attached to the firewall.  They also already had the whole drilled for where the fuel lines will pass through the firewall to the tank.  Today I drilled out the 4 tiny wholes to their proper size, 1/16th I believe it was and special tool was used to determine the size of bit required.  I then placed Vaseline into the blind nuts to prevent glue from getting in as glue was applied around the four holes and then the nuts were pushed into place.

Firewall, four small wholes are where the engine mount goes
Firewall, four small wholes are where the engine mount goes

 The last thing I did for the day was glue the tail wheel mount to the back of the fuselage bottom plate.  You can see the round weight over the top holding it down at the right of the pic with the weighted down glued doublers.

Building 4 Star 60 Day 2: The fin starts

Today I got over for another great building session with Peter.  Peter kindly had the sheeting for the (tail) stabilizer of my plane glued together.  We marked out one side of the sheeting tracing the framework with a pencil to know where the stabilizer framework had to go on the sheeting and then flipped over the framework.  I placed glue along the entire surface that was coming in contact with the sheeting while Peter spread it.  I then flipped over the framework, placed it on the sheeting, wiggled for good glue disbursement and then temporarily pinned in place while I glued the other side.  I removed the pins and placed the other set of sheeting onto the tail.  Peter then placed weights to hold everything snuggly together while it dries.

Sheeting glued and wrighted
Glued sheeting to both sides of the stabilizer I did on day 1.

The next step was buidling the fin.  Found it on the plans, pinned it in place followed by pinning wax paper over it.  The next step was to find the pieces and line them up on the plans followed by gluing and pining.  I then measured, cut, and sanded the rectangular ‘centre pieces’, need to remeber what their called and will update, until they fit snuggly but not to tight such that they are pushing out / warping the pieces already glued and pinned.

After completing this phase I had what’s below.  The long piece, trailing edge, is not attached yet however the bottom part has been sanded to give the desired angle and will be cut at the top when the time comes.

Fin framework glued and pinned
Tail fin framework glued and pinned.

The last part for the day was to prep the sheeting for the fin.  You always want to go oversized to ensure you cover everything and then can (what I imagine and will learn how) cut it down to size.   This time Peter and I did it together.  Peter tapped the back side using special tape (leaves no residue) and then folded the pieces back so I could run glue down between, top to bottom.  Then we layed them down flat, on glass, and wrighted them down while the pieces dry together.

Fin sheeting taped and glued
Fin sheeting taped and glued

That wrapped up another fun building session!  I’m definitely learning little by little.

Update 10/22/2016: I couldn’t remember the name for the ‘centre pieces’, it’s ribs