|Oct 20, 2011, 11:37 PM|
A few last thoughts on tape hinges,
I know it is easy and convenient and many like it after all it is less work. . . .or is it?
I've tried many kinds because of friends that say it's the "best", none have caused a crash but they all have caused field repairs when I want to fly.
I suppose it is good for disposable models after al,l many ARF's from China come with it installed.
Here is the way I see it.
Foam has cells , so many that extruded foam may be 80% air.
Tape , no matter the type, does not stick to air. If you have to fill the cells for it to stick good you may as well use real hinges.
I know foam sheets has a crust and most of the cells are closed but it is not smooth if you look at it closely.
Now add paint to the mix.
paint has solvents , that's how it gets from the can to the model and why it has to dry.
If the tape breathes or has a texture some of the solvent gets to the adhesive changing it's sticking quality.
I have never seen it get better.
Now add the sun
Here in Texas the sun tends to get really hot. You may not have this problem where you are but I use a hair blow dryer to loosen the tape when I peal it from depron because I know for a fact that it makes tape not stick.
Now paint the tape a dark color (if you can get it to stick) like olive drab
How hot do you think the tape will get on a summer day?
Sparky, why don't you use tape hinges?
"I have my reasons, mostly because I like maintenance free models."
|Oct 21, 2011, 12:01 AM|
Place the fuselage on the wing and slide sandpaper rough side up in-between them for a perfect wing to fuselage fit. Mark the center of each part after the test fit for easy alignment
|Oct 21, 2011, 12:03 AM|
Cut the horizontal stab using the pattern from the plans. Cut the elevators free and hinge them. Bend the crossover wire and use it to mark its position on the stab. Don't think you can get away with a stick to join the elevators, even at 6mm thick the stick will not be strong enough.
Use a heated wire to make slots in the elevators and bond the wire in place with epoxy. Fairly basic stuff but practice the heated wire thing; a butane lighter will provide all the heat you will need.
|Oct 21, 2011, 12:08 AM|
Installing the stab
To install the horizontal stabilizer a slot will have to be cut in the fuselage sides.
To prepare for the cut, support the model on a flat surface by the wing , two blocks of equal size under the center section front and back.
To set the incidence shim the aft end with a 3mm foam strip.
Place the aft turtle back in place and mark its lowest point.
Measure this point to the work surface and mark a line parallel to the work surface on the side sheeting. . . .both sides.
Measure from the mark to the table top and cut a cardboard strip this width. Use the cardstock to draw a line on both sides of the sheeting the length of the horizontal stabilizer.
Draw another pair of lines 6mm below the marked lines.
Cut the slot with a razor and bond the stab in place making sure it is centered and 90 degrees to the centerline.
You may want to skip bonding the wing next and put the top turtle deck on first so the fuselage is eaisier to handle but I did it with the wing attached.
|Oct 21, 2011, 12:13 AM|
Wing to fuselage bond
By now you know the polyurethane glue foams then hardens. For this step you must check the bond every 5 minutes or so to check for "foam blow outs" If the foam appears at the joint either rub it down with a Q-tip or something round and soft or scrape it away with the corner of card stock.
B back tomorrow with the plastic parts bonding, this is where it really starts looking like a cartoon Spitfire.
|Oct 22, 2011, 01:44 AM|
Turtle deck / Belly pan
Trim the flanges away from the plastic parts leaving as much plastic as you can
Place the plastic part on the model and hold it to a bright light.
(See this is where the wing got in the way)
Mark the plastic so about a half inch to three quarters inch overlap will remain when the part is final trimmed.
Sand the inside of the plastic .
Bonding. A very small amount of polyurethane glue is needed to attach the sides of the plastic to the fuselage sides. This bead should be right on the edge of the fuselage foam sheeting to avoid the glue reaching the outside edge of the plastic. A heavy bead of glue is alright for the former to plastic bond. any glue foaming here will only close any miss match gaps.
When you are happy with the fit make small marks along the fuselage edge so the alignment can be easily repeated. Apply the small bead along the edges then on the formers. Place the plastic on the fuselage being careful to not smear the glue on the sides.
( spreading the plastic a bit helps.)
Apply narrow strips of plastic tape to the side seams to hold the plastic against the foam sheeting. Running your fingernail along the edge will improve the tape to foam contact and better seal the plastic edge.
Place the fuselage with the plastic down to allow any excess glue travel toward the plastic. Remove the tape when the glue cures completely; about 2 hours.
Narrow plastic tape strips: Shipping tape used to close cardboard boxes did the best job at holding the plastic parts down. The plastic tape has a smooth surface and makes the best seal between the two forcing the glue inward when it foams so don't use masking tape.
Bond the forward turtleback piece in place with (IMPORTANT) the step in the plastic just aft or parallel with the back of the F-1 former.
Go ahead and see how the canopy looks on the model.
|Oct 27, 2011, 12:18 AM|
Bond the cowl in place.
To trim the cowl you lay a pencil flat on the work surface and mark back of the cowls edge, trim line.
Cut the flange off first then the trim line with scissors. Fit the cowl to the fuselage aligning the aft edge with the aft edge of former F-1.
This sets the thrust line.
Make a mark on the cowl about 1/4 inch above the bottom edge of the fuselage side sheeting, remove the cowl and lightly sand the inside aft surface of the cowl to prepare for the bond.
Apply a small amount of polyurethane glue to the inside of the cowl but not beyond the marks made.
We do not want the cowl to be bonded to the bottom edge of F-1.
Slide the cowl in place and hold it there with plastic tape to seal the cowl edge to avoid glue blowouts.
|Oct 28, 2011, 11:35 PM|
Bond the belly pan in place.
If you are going with the landing gear option bond the 6mm tail gear plate in place. Note that is over sized a bit and will need sanding for the belly pan to fit well.
To bond the belly pan in place several test fits are needed. The scribe lines should get you very close but to be on the safe side allow 1/8 inch extra for the first test fit. Align the belly pan to the fuselage using the aft end of both parts. Trim the plastic so there is about a 1/2 inch overlap to the fuselage sides. Seal the edge on the outside where the pan meets the wing and allow Gorillia glue to run down the inside edge . allow it to foam and the pan will be bonded to the wing.
|Oct 29, 2011, 11:05 PM|
This hatch will give you access to the front bottom portion of the of the model, This is where the radio , ESC, and battery is mounted. The front end of the hatch slides in-between the cowl and the F-1 former while the trailing edge is held in place with magnets. Start with trimming off the flanges. . . .
The hatch is formed oversized to make up for any fitting ill regularities. Start the trimming job at the step needed to clear the wing. Align the front edge step over the aft edge of the cowl and mark the point that the hatch meets the wing leading edge. Cut a small portion away and test fit. Continue trimming until the hatch aft edge touches the front end of the belly pan and the front edge rests on the cowl.
|Oct 29, 2011, 11:07 PM|
Your last test fit should be made with the hatch front edge under the cowl trailing edge. To make installation easier the width forward of the formed step should be about 1/2 inch with the corners rounded. If the gap between the cowl and F-1 is too tight adjust it by sliding a piece 180 sandpaper between the two and remove a bit of the former. Useing the sanding trick you can make the hatch fit just right to the wing.
The last trim task is to cut the aft end of the hatch to match the formed step in the belly pan.
|Oct 31, 2011, 11:56 PM|
Tape can be used to hold the hatch closed but I like magnet latches. To install a latch we need some meat to bond the magnets to. Bond scrap 6mm foam to the hatch sides be sure that it clears the aft plastic piece and that you sand the plastic for a good bond.
Install the hatch. Make a mark on the wing skin along the edge. Remove the hatch and bore a hole equal to the diameter of your magnet just inside of where the hatch outer edge touches the wing. Bond a magnet flush to the surface in the hole. Packing tape will keep the magnet from bonding to the steel and the steel will hold the magnet flush.
Mark the magnet position on the hatch side. Drill a hole slightly larger than your magnet diameter to match the other magnets position. Going over sized with the hole gives us some wiggle room. Drop the magnets on the taped magnets in the wing. Fill the magnet hatch holes with epoxy and install the hatch holding the model upright to prevent pouring the epoxy out of the holes. tape the hatch in place until the epoxy cures.
|Nov 01, 2011, 12:00 AM|
If you wanted the landing gear option you have put the gear plates in place already. now is the time to bend the wire, the wire is small enough to be bent with pliers so start with the base. Bend the wire to match the pattern on the plans. then bend the "leg" portion then axles.
Place the gear wire on the wing center section with the axles parallel to the wing leading edge and centered. mark the wing with a pen. Heat a smaller wire with a lighter and melt the foam in-between the pen marks. The glue that is holding the gear plate melts at a higher temp and will help to ensure the depth is equal across the groove.
Fill the groove with epoxy and install the gear.
The tail wheel is installed by cutting a slot in the plastic with a cut off wheel then cutting a slot in the tail wheel support foam plate installed earlier. dip the wire in polyurethane glue and slide it into the slot and allow it to set up.
|Nov 01, 2011, 12:04 AM|
Lets power this puppy up!
Now we need a motor but to align it with the cowl we need a spinner.
There is a video on the web site but for reference Ill post the steps.
This is a mix of all the cartoon model spinner work. Your spinner may look a bit different but the steps are the same.
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