Robert's Skywriter Build

[piker]

I was going to post this as a reply to Ben's thread, but figured I'd start my own build thread with this:


I'm building my tail feathers as open structure as I agree with Frank that the design is over built... especially in the tail area.

However, the original/plan/kit design tail feathers will be more rugged for every day use, should be less likely to warp, and will handle some hanger rash better than mine.  And with the efficient power systems we enjoy these days, we can enjoy the luxury of ruggedness.

My version is based on more traditional methods, heavily inspired by older Sig kit designs.  I'll post pictures tomorrow, and I'll bring my parts to the build class tomorrow evening.

[piker]

O.K. my tail "feathers" are done.

I used the laminated outer perimeter technique that I like to use for rounded shapes like these parts.  I created these shapes around foam forms, then pinned them to the building board and filled in the rest of the structure.  Then, last night, I sanded the parts to final shape.

BTW, I won't be using a metal elevator joiner as I prefer to keep the elevator halves separate and either run each side on it's own servo, or a split push rod, which I'll be using for this plane.  I prefer this as it offers individual adjustment for ensuring the two sides are in-plane, and I feel it gives a more direct and positive control to both sides of the elevator.

The first two pictures show the foam forms, the next picture shows the 1/4"x1/16" balsa strips that have been soaked in water to help them wrap around the shape without breaking, and were used to build up the laminate.  I've also included a picture of the 1/4" sheet that I stripped to the width I wanted for the rest of the framing, and then the finished product.

[Papa]

Somehow traditional always looks "right".


I try not to be old fashioned but when you see something like this, it's hard not to be.



Did you get a chance to weigh them? if not I'll bring a scale tonight.


Jack.

[sihinch]

Would love to know more about the soaking-bending-laminating technique. I've never heard about that or seen it.

I hate to say this but it looks great! I'll swap you for mine?

[piker]

I'll tell you all about it tonight.  It's really quite simple but makes fairly rugged structures. 

Weights:

Fin:          5g
Rudder:    4g
Stab.:       14g
Elev.:        10g

With no stab joiner as mentioned before.

[piker]

I went shopping for wood with Michael, on Saturday, and was able to start on my lower wings last night.

So, last Wednesday, I went into my local (to work) Staples, to see if they could scan and then print a mirror copy of the plans, so I would have the left side for building.  They couldn't.  Then, this weekend, Michael shows me his mirror plans that he had done at the Staple near his work... the SAME Staples I went to the day before he had his copy made!  I think it was even the same person doing the copy.  Sheesh!  I figure after I requested the mirrored copy, she may have looked into it further and figured it out... just in time for Michael to stroll in.  I was going to go back and get the copy I deserved, but couldn't wait, so I took a different approach last night...

When I had the plans copied, originally, I had a spare set made to use as templates for cutting parts (building from scratch).  Well, last night, I took the copy of the right, lower wing, taped it to my sliding door glass with the front facing the glass , turned on the outer light, and traced all the necessary lines onto the back of the paper, and then used this as the plan for my left wing. The same could be done with a blank sheet of paper over the plans.

I then cut out all the ribs I'll needed for the lower wing using the stack and band saw method, stripped my 1/4" square spar pieces from a firm 1/4" sheet, because the LHS was all out of 1/4" sticks (too much building going on around town  ), then started building both sides of the lower wing together.  I'll get the rest of the building (sans sheeting) done tonight.

BTW, I realized after I had built the wing to this point that usually, the bottom sheeting would be laid down first, with the structure built over top, ensuring a nice, flat, stable structure before removing it from the flat, building board.  Doesn't really matter, but I recalled that as a usual technique for building sheeted wings.

Another little tip that occurred to me last night was this:  It's difficult to cut through thick, hard balsa with the balsa stripper because it wants to cut the full depth with one pass, which can cause the thin, #11 blade to wander, and cut 'off' square.  I guess the blade depth could be adjusted, but that would be a pain in the butt for every cut.  Instead, I simply laid a 1/8" sheet beside the 1/4" sheet that I was cutting, that the stripper could run on top of for the first pass, then the second pass could be made with the 1/8" sheet removed.  A simple tip. but it worked very well and was easy to implement.

[Michael]

Servo wire holes cut ahead of time. Nice! 

[piker]

I think I've gone as far as I can with the lower wing build before the sheeting class tomorrow evening.

I don't want to attach the wing tips until after the sheeting it on, but I'll probably laminate them up tonight using the same construction as the tail pieces.  I'll also add the TE pieces, and the LE after sheeting.

I used 1/16 ply for the dihedral braces (the good ply) and made the rear brace a little shorter.  I made the servo mounts out of the same 1/16 ply, and imbedded good, 1/8 ply into the ribs for the inter-plane strut attachments.  I've decided that I won't be installing the angled aluminum pieces in the wing, as shown in the instructions, but rather use the ply hard points as a place to screw the struts to, with the angles aluminum pieces as part of the struts.  This will make for a cleaner fastening method, and an easier wing to cover.  Just another personal preference.

Oh, and I've added the false LE to support the sheeting.

The wing at this point is a delicate little structure.  For those who are at the same stage of the build, but are fairly new to this style of construction, rest assured that the sheeting to be added will add a LOT of stiffness to the structure.  You'll be surprised.  Also, don't forget that the covering (film covering) also adds a fair amount of strength and stiffness to these open frame structures.  Resist the temptation to add extra structure at this point as it will just end up resulting in unnecessary weight gain.

[piker]

Sorry.  No pictures today.  Just a progress report:

My lower wing is finished, sanded, and ready for covering. 

Last night I built my upper wing to the point of sheeting, which I'll hold off until the next Skywriter build class so I can demo the sheeting process for the class.

Let's set a goal for everyone (except Michael who is already finished his plane) of having both wings build and ready for sheeting.  That way, after the class (in just over a week), we can finish off the wings and be ready to start the fun part... the Fuselage!

Who's in?

[sihinch]

I think that's a bit much to aim for.

My bottom wing is nearly finished but don't think I'll have the top one done before the next class.

[piker]

The next class is a week and a half away!  I built my entire top wing in one evening (about three hours), AND I had to cut out all my ribs from sheet balsa.

You can do it.  It's not hard.  In fact, the top wing is easier than the bottom because there are no servo mounting requirements or dihedral, so the whole wing can be built flat on the board in one shot.

Here's the process:

Lay out plans, mirror to create other half, and cover with wax paper (10 minutes)
Lay down the bottom spars (2 min.)
Glue the ribs to the spars (10 min.)
Glue in the top spar (5 min.)
Glue on the trailing edge (5 min.)
Glue on the leading edge (5 min.)
Add shear webs (20 min.)
Fill in at root TE for curved section (5 min.)
Remove from board (1 min.)
Add hard points and AL pieces for strut attachment (20 min.)
Sand to blend parts nicely (10 min.)
Cut out curved section and sand smooth (don't round top and bottom edges until after sheeting) (10 min.)
Admire great work (9 days)

That's 103 minutes (1.7 hours... about one movie on Netflix) to build the top wing to "ready for sheeting"

You could even leave the rounded cut-out until after sheeting if you want.  That will save some time.

We all need to keep moving if we are to ever get onto the fuselage!   

[sihinch]

Remember, this is a build class.  We are meant to be learning and enjoying ourselves.  Not racing to the finish and putting pressure on each other to rush!

What takes you 5 mins may take me or others 15.  Plus, we all have other commitments and cannot build all night, every night. And the glue that Frank & Jack recommend is not a fast drying glue - at least 1 hour. So there is time in between steps.


And we also need to complete the bottom wing first.

Remember - fun!  If it becomes a race or too much pressure, people could chose to drop out.

[Michael]

Take your time, Simon, but Robert does have a point.


Despite what some may think, I never spent more than 20 minutes straight working on my Skywriter without taking a break to eat, watch TV, surf the net, or just do other stuff.

[piker]

You're right.  It's not a race.  That's not what I was implying.  (I don't know why YOU would be opposed to racing even if it was... you LOVE racing  )

I'm not trying to pressure anyone.  I'm trying to encourage.  It will be a lot of fun for everyone if we can move along at the same pace (the rather casual pace that it is) and finish at the same time for a group test flight in the Spring.

As Michael says, a bit here and a bit there results in impressive accomplishments, and the satisfaction we enjoy along the way makes it all worthwhile.

But, of course we are all free to build at the pace we choose.

[piker]

So, I'm back onto the Skywriter after taking some time off to work on the Morphine design and multiple copies of the plane for next summer.


With the top and bottom wings finished, it was time to figure out how I was going to approach the design of the fuse.  Since I'm building from scratch, I thought I'd try some different ways of achieving the same outside look of the plane while saving some weight with the structural design and material choices.  So here's my approach... right or wrong... we'll see how it turns out.  So far I'm happy with it.