WEDJ

The epoxy thrust wedge popped out just fine. Now I have to sand off the meniscus that formed around the edge.


FYI - http://en.wikipedia.org/wiki/Meniscus

Free Bird

Now that sounds like a plan!

WEDJ

Progress, no matter how small..........

Yes, try to do something all the time, even if it is just a little. Here's the epoxy thrust wedge, came out fantastic. Free Bird, I still want those wedges, in case I have to make adjustments. Doesn't look like much, but it is a solid two degrees of downthrust. I put an indent mark at the low point, it came out in the cast perfectly.

WEDJ

More small progress:

Decided to use 1/16 ply to double the LE former. I think after cutting out for the tank, it doesn't add any weight at all. Still need to drill for the wing dowels.

WEDJ

So here's the LE bulkhead, all cut out and ready to go. Notice the cut-outs for the throttle and the nose steering.

WEDJ

Now the Firewall. It is without a doubt an important piece of a plane. Notice the 8 holes, 4 for the motor mount, 4 for the nosegear mount. I also trimmed the epoxy thrust wedge, added the cut-out for the fuel tubing (I know it's not straight, it doesn't have to be)

And yes, Bob, there's the ring of plywood for behind the spinner.

I consider this part of building the PITA phase (Pain In The A**)

WEDJ

I thought I'd share my choices of glues and adhesives. Yes, I still use Ambroid. I am about to use it to secure the triangle stock on the fuse top & botttom. Yes, I double glue it. That's where you smear some glue on each surface, and let it dry. It seals the pores, and lets the glue you re-apply do its proper job. I like it for the tri-stock because it has to bend so much, I needed a glue that would not set up right away, yet be easy to sand. Epoxy would leave a ridge when it is sanded.

I use the quick and the thick CA for a lot of the building. The Titebond and Elmer's are sort of interchangeable, I like that where balsa to ply is involved. I used Titebond to laminate one side of the doublers on the fuse, and the moisture warped it so bad I had to make a T-pin forest. On the other side, I used 30-min epoxy, it was much tamer, and just some weight kept it flat while it cured.

The 20-min epoxy is a thin mix, good for fuel-proofing, see the firewall in a later post.

Based on what people said they wanted (Thread - what do you want in a build thread) I have tried to explain a little about problems, solutions, and tools.

Planning is a big part of the build process. Where does each pushrod go? Is there enough clearance for foam around the fuel tank? Where will the servos go? Which side will the steering be on?

WEDJ

Fuelproofing the firewall is a serious business.

I make sure I have every hole and access finished, then coat it in 20-minute thin epoxy all over. Since you have to hold it, it is a two-step process. I even coat the inside of the holes before I put in the blind nuts. Load the hole up, then stick a toothpick in there, swish it around, and wipe up the excess. Paint both sides and all the edges, then wipe them down lightly with a paper towel. This makes a super thin coating that is absolutely fuelproof. In the past, I have seen the screw holes be the point of failure because they are not fuel-proofed. BTW, after you put in the blind nuts, give their piercings a dab of epoxy, too.

Details, details.

WEDJ

So here's the right side of the fuse, as complete as I can get it tonight, waiting to finish the firewall and install. Notice the tri-stock and their multiple T-pins to make the curves, and the rest of the bulkheads, and the rear stiffeners are all in place.

Didn't Tom Brett own a straight edge? Or just french curves?

Actually, I still think all the flowing lines are beautiful.

BobHH

My Feedback: (18)

Nic, looking good! Glad to see someone else using Ambroid too!! Actually I have been using Sigment as I have not found a local supplier for Ambroid!

Bob

WEDJ

So far today I have epoxied the other half of the firewall, and made the rear wing hold-down. After looking at that 1/16 TE former, I decided that it is adequate, so long as I tie my 1/4 ply firmly to the ply wing doubler. The best way, which I used to use in the past, is to use tri-stock. I glued the ply with thick CA, so I could position it with my fingers, but the tri-stock is done with titebond. Notice I left about 1/16 inset on the plate. This is to allow for the wing center F'glas tape.

I will tap the ply itself for the 1/4-20 bolts.

rainedave

My Feedback: (1)

Nic, call me paranoid about wing bolt plates pulling out, but if the 1/4" ply plate isn't keyed into cutouts in the saddle doubler I would -and this is just me - drill 1/8" holes through the outside of the fuselage sides into the 1/4" ply plate, fill the hole with wood glue and drive in 1/8" dowels.

I really like your plan to combine the fabric-covered look with paint. Are you going with the original color scheme?

David

WEDJ

Hi Dave,
Yes, original color scheme. Maybe a shade lighter on the blue.

This method of attaching the ply plate has worked for me with all my .60 PP's 30 yrs ago, and this is only a .45 ship. Those ships had thousands of flights on them, never a hint of failure. I'm not worried at all. The key is to get a good glue joint with the tri-stock onto something solid. My .60 ships had 1/32 ply doublers that the ply was glued to.

If you want to play with the math, the .60 ships were 7.5 lbs of which 1.5+ was the wing, In a tight outside loop or outside square corner, perhaps pulling 10 g's, That's only 60 pounds trying to separate the wing from the body. You have dowels in front, and the screws in back. Figure half and half forces, a good glue joint on each side for the screws is only 15 pounds, minus the glue across the bulkhead, and the structure is much much stronger than that. Double that to 20 G's, and it's still only 30 pounds on the side joint.

However, I appreciate your concern, thanks for bringing it up. Did you ever have a wing bolt plate failure yourself? It's discussions like this that make forums so useful. We all learn from each other. I'm very glad you brought this up.

WEDJ

OK, the firewall is in!

Since this is such a critical part, because of the thrust angles, I like to make sure it's correct. I attached it with thick CA, but after it set up, the real strength is the tri-stock, which is applied with 30-min epoxy.

Now I have to put the tri-stock on the other half, and then it's time to match the sides. The real important part next is to join the rear end, and keep the sides tapered symmetrically. otherwise, it is a banana, which needs rudder offset to fly even close to correctly.

Don't ask me how I know...............................

Free Bird

Nic: Your Perigee is shaping up nicely and looking good! Can't wait to see it in person...
Being we're from the same school of building, our techniques and thought process are very much alike. It's scary that there's someone like me out there!

BobHH: I also use Sigment and Titebond for a lot of building. I try to minimize using CA glues when ever possible, I mostly use it for tacking parts together. CA glues are very hard to sand and impossible to eliminate seams. Especially when edge joning sheets or carving fuselages to shape when you start to get into the tri-stock. Old building techniques work best for me, especially on these classics.

FB

hrrcflyer

WEDJ,

Keep up the good work!![sm=thumbup.gif] I really like your tip on "double glueing". I would have never thought of it in a million years, but it makes all the sense in the world.

Happy Holidays

WEDJ

Tonight I joined the two fuse halves. Even just joining the bulkheads that are all the same width, it is important to keep the halves aligned, so they are true to each other (ie: both thrust lines are in the same plane) If you don't, the you will have a corkscrew body. That one I never did.........(unlike the banana)

That said, it is a pretty easy task. I first used thick CA to put the firewall onto the other half, and lined up the tail. That keeps both sides parallel. Then it is easy to spread the halves and glue up each bulkhead, using thin CA. The 1/4 ply for the wing screws is epoxied. The tri-square is then added to the firewall and the 1/4 ply wing screw plate, using 30-minute epoxy. Later, when I fuelproof the tank compartment, I will paint a liine of epoxy against all bulkhead joints.

WEDJ

Lastly tonight, I don't like that the bulkhead at the wing TE is just a bottom stub. The top of the fuse needs to be stabilized, so I put a small piece of strip stock at the top, so the fuse will not bend in or out during assembly later.

WEDJ

Today's small progress:

Moment of truth - Time to tie the aft end together. The photo doesn't show well, but the fuse is laid upside down on the top view, and the firewall and front sides lined up to the plan. then I pinned the front end. I pulled the back end together, and held it with a couple of clothespins. It was off center. Remove, adjust, replace. Repeat. Now it is centered. Look carefully from all angles, measure as best as you can, then hold your breath and put a drop or two of CA in the joint. Pray. Cross fingers. Cross toes. Take shallow breaths.

I THINK IT'S STRAIGHT (cue for applause, streamers and confetti, champagne cork pops in the background)

Phew! OK, now to insure it doesn't move, quickly put some of the bottom sheeting in place.

More to come tomorrow. Or the next day.

WEDJ

OK, I couldn't resist.

So who here has NOT done this? It is an essential part of building a model, I think...........

WEDJ

So if I back up a little, you can see the doll house I am doing with the 10 1/2 yo daughter. Man, do they have accessories for this stuff!

Update on the 14-yo's rc car - he also broke the connecting rod, parts are on order. I think learning how to re-build an engine is a good thing.

rainedave

My Feedback: (1)

I always get out the masking tape and tape on the control surfaces to get that first true picture of a model.

The Perigee is looking fantastic. This thread is getting better each day.

David

Atlanta 60

My Feedback: (18)

Man that is one beautiful airplane...Sexy lookin'!!

Agree with Dave...Getting better every day...

Chuck

WEDJ

Thanks, guys. I'm having fun.

BobHH

My Feedback: (18)

Nic, you forgot to mention that one must make engine and flying noises when you pre-assemble the model this way. It will insure the model will fly properly!!!!!


Bob Harris