CTDavies

Allan & Charles, sometimes this happens to me as well. The images can be removed again later with the edit function. So I usually wait a day or two before I remove and then upload them again. That usually fixes the problem.
Chris

Charles_e_bates

My Feedback: (90)

Thanks CTDavies:
I'll work on it
Charles

allanflowers

The first pix shows the baffles more clearly. The side ones are epoxied onto F1 and are permanent. The lower ones cover holes which I might want to open up later if cooling issues require, so they are screwed on.
Second pix shows the fitting and epoxing of the upper brass tab on the foiled cowl that I made. This, with the bottom wood block (and its screw), add two more attachments to the cowl along with the two on the sides. This should make it better for withstanding engine vibration, etc.
Then it was on to trimming the new cowl from Chris. The cut away part from the first cowl made it easy to layout.
Chris’s fiberglass work is thinner and lighter than mine so I had to add a strip of glass cloth around the perimeter for a snugger fit to the F1 former. It adds some stability to the part too. The waxed paper pushed onto it gives it a smoother finish when it sets.

allanflowers

Final assembly time!
First I reinstalled the dummy engine, which is difficult to get in over the needle valve area. The needle valve itself has to be installed after the dummy is in place.
Next is the spider installation, followed by the cowl.
Last, the propeller with its aluminum base plate and fiberglass spinner, is added.
The turnbuckles on the drag wires needed safety wires too. All the other turnbuckles had been done previously. I use Locktite on all the machine screws, including the 1-72x1/4� bolts that fix the spinner to the 1/8� thick aluminum base plate.

THEN I discover that the little spring steel clip that prevents the needle valve from vibrating loose from its setting got bent and is not functioning. So I had to tear it all back down again to get at that critical part and fix it.
%#@$&

abufletcher

Wow, that looks as complex as the actual aircraft! And I know what you mean about the retaining clip for the needle valve. I bent the one on my RCV90 when I took out the needle valve to (test)install the engine.

Teus

It's almost a shame to hide that beautiful dummy engine behind the spinner!

abufletcher

I don't see the cooling baffles you mentioned.

FokkerAce

I think they're the dark grey parts at 9 & 3 o'clock on face, and the 2 screwed on ones at 5 & 7 o'clock.

not large parts, but probably big enough to block air from escaping

FA[8D]

abufletcher

I thought "baffles" served to channel air closely around the cylinder head. These seem designed to close off possible air outlets. It this a good thing?

allanflowers

I am probably misusing the term. The side panels don't even block ANY air flow. The bottom ones do cover holes in F1 through which air could flow into the cavity behind the engine, which is vented to the outside by the louvers on the bottom of the belly pan. I am assuming that any free stream air coming from the front might compete with the air which is directed through the center duct - which is actually cooling the engine. I want ALL air leaving the cavity through those louvers to have passed through the center duct. The louvers are of limited capacity.
Access to my field this morning was muddy so I will have to wait until later in the week to do my taxi-cooling tests. The plane is ready...

eagledancer

make sure you take video!!! i really wanna see this one fly!!!!

abufletcher

Be careful on that taxi test. If all you plan to do is see if it will turn, there's not much danger. This is also a good way to build confidence that the engine isn't going to quit on you. I figure if the engine quits while taxiing out, there's bound to be trouble in the air. My Saitos will idle all day long with no problems. I'm not yet sure about how the RCV engines will do, though my RCV91cd was idling on the test stand down to 1800!

On the other hand, if you have the idea of trying to get a feel for how it might track on a take-off run, that's where you run the risk of seriously damaging the model, before it even has a chance to fly. Basically, once the tail comes up, you might as well be committed to flying. And chopping the throttle is almost guaranteed to result in a nose over and/or ground loop.

I speak from bitter (and recent) experience!

allanflowers

That's good input. I will try to resist the urge to high speed taxi.

abufletcher

Also make sure that the bungees on the undercarriage are as stiff as possible. That helps tremendously. If you've getting much "spring" just on taxing, then it's probably too loose.

allanflowers

I did some field tests today but it was mostly about cooling. The engine quit once (at idle) but generally seems to be fairly reliable. It doesn't have a great top end because it is set rather rich. The three quarters throttle setting probably gives higher rpm.
With the onboard glow, I am running a little richer than normal and I think that will prevent overheating. This does require a little higher idle setting though.
With other guys flying, I couldn't do much taxi testing - other than in the pits which is questionable etiquette. On the other hand, it proved that the spinner mounting is pretty sound - and nothing came loose on the plane. I did find a split rudder post (even before engine starting) because the cables were too tight. They may have even shrunk a little and pulled on the bottom of the rudder. This has been repaired and the plane is ready for its maiden flight which is scheduled for next Friday. In the meantime, I will get as much time on my Pup and Camel as possible.

allanflowers

Here are some final measurements for this model.
The total weight will come in at 133oz. or 8lb-5oz. This includes 2.5oz I am about to add in ballast, to bring the cg to 100mm back from the leading edge of the top wing (25%MAC).
The photos show the balancing setup, with the plane hanging from the ceiling.
With 777 sq inches of wing area, the wing loading will be 24.65 oz/sq ft.
The model has a fully skinned fuselage and fairly heavy fabric on the wings and elevator. The tailskid is from 6mm plywood and has a hard steel rub strip. The hinges on the wing and tail are brass and to scale.
Because of these things, I was concerned about it being tail heavy and requiring a lot of nose ballast, like my recent Pup and Camel, each of which required about a pound of lead.
In this case, the ballast will go in the little hatch in the TAIL, where the rudder linkage is concealed.

abufletcher

Two thoughts on the balancing:

1) It's always hard to see in photos but I've found that on all my models the nose has to be visually DOWN to really count as being balanced. Every time I've made it truly "level" the model has been a serious handful on the maiden. I assume you're talking about a 25% combined MAC, which sounds safe.

2) If it were me, I'd also double check the balance with the good old "finger balance" technique. While I have a Vanessa Rig setup, I don't entirely trust it.


And an additional thought or two on the upcoming maiden:

1) Assume that it WILL be tail-heavy and be mentally ready (if you have RealFlight, practice some seriously tailheavy flying)

2) Assume that it WILL be seriously out of trim and be prepared to fly even with uncentered sticks (as I had to do on my Snipe's first flight).

3) Keep the first flight short and sweet. Take off, fly around a few time, and land. No need to try to "prove" everything on a first flight.




Best of luck with your maiden. And have fun with it!

abufletcher

Again, if it were me, I'd prefer to see the model "balanced" more nose-down as in the blue line in the following photo.

abufletcher

This closer to how I like to see my models visually balanced. Again it's hard to judge this in photos. But here I've rotated the image a full 5 degrees forward!

allanflowers

I think the model was true level while balancing. I had measured it with a bubble level. If you look at the vertical lines on the thing in the background, you can see I had the camera tilted a little.
I prefer to balance at true level. It's just more scientific and less arbitrary than "slightly nose down". Of course I then am more strict on the balance point I use.
On this model, I am actually also concerned about a nose heavy situation because DJ reported a lack of ELEVATOR response at his landing flair. In any case, a few ounces for ballast is good news and I should be happy in spite of my tendency to fret about ANY extra weight.
I had been doing the finger tip balance (there are little pieces of tape under the wing at the balance point) but actually the Vanessa rig is so much more accurate. I did not pick up the discrepancy with the finger tip approach.

Your points on the maiden flight are right on. I will do just enough to get some photos, then land and go over every inch of it. Now if the wind is just nice and cooperative...

abufletcher

I agree, this tradition in modeling of calling a model "balanced" when it's actually nose down is definitely annoying. And as long as you have factored that into the choice of the balance point, that's great. I guess mostly I've had problems when a kit gives a CG and then sort of assumes a nose-down attitude. However, on my Snipe I did follow Frank's calculation for the CG but also with an ever so slight forward angle.

I sure wouldn't take ANY chance with having a tail-heavy model on a maiden just to address a POSSIBLE problem on landing. I've experimented in RealFlight and you can make a model seriously nose-heavy and it will still fly (and land) but just that little bit of tail heavy can make the maiden a nightmare. But it might be good to get DJ's opinion on this since he's the expert. How did DJ balance his model?

Despite being a portly 4.5 kilos, my Snipe few very nicely with the Saito 72. I've come to believe that is you AREN'T adding signification nose weight on an aircraft like this, there's possibly something wrong. Anyway, you have as much (if not more) experience maidening scale models as I do!

I guess I just don't completely trust the Vanessa Rig method after the "wild ride" maiden of my Puppeteer, which seemed right on the rig. I'll just always do both.

abufletcher

Just one more photo manipulation to think about. In your photo, the plumb bob shows absolute vertical. And this is absolutely perpendicular to the line I've drawn through the center of the spinner. And the tail on your model appears to be below this line. Of course, camera angles do play tricks but it looks to my eye line your model is actually tilted back just slightly.

I'm just worried about ya, man!

udet1918

Allan I have used the same balancing rig and balance level at 25% MAC. I have had no tail heavy issues doing it that way.

25% MAC is already forward of what is normal for full scale so in reality you are "slightly nose down" to begin with!

You stated DJ reported a lack of rudder response when nose heavy! Are you sure it was not elevator response that was meant? In a nose heavy model you WILL have less elevator authority, rudder is not affected.

I have found in most cases what seems to be a tail heavy situation is in reality to much elevator throw. If not dampened with EXPO a short coupled aircraft can become a handful with excessive elevator control. You already know about the rudder dealing with the Camel. It'll be similar with the SSW DIII.

I use the Mk 1 eyeball to give me a heads up on what to expect when doing a maiden, nothing better IMO. Pick up the tail and position your head in line with the rudder/fin. Just moving your eyes left and right take note of the position of the wings in relation to each other. Are there any warps, wash in, wash out, etc. A twisted wing will act as an aileron and cause the model to bank when it breaks ground, hence wing warping control. If you see any, even a slight variation you will know to expect a possible bank when in the air. Saved me from surprises many a time.

Abu is certainly not wrong he has developed a method that works for him and I'll say the same for me. You have built a stunning model and should be proud, we all of us who have followed along wish you an uneventful maiden and many future fun filled flights.

Ron

allanflowers

Thanks Ron. I appreciate it. By the way, you are correct - I meant elevator, not rudder.

I hear ya, Abu. No maiden flight is in the bag.
The cg recommended by D. Johnson on his ¼ scale D.III (as translated to this size) is actually a little rearward of where I am – so I should be okay. Also, 25% is pretty conservative. Nonetheless, I appreciate the concern of you and the other guys on this site – all of whom know the stress of facing a maiden flight.

On the pendulum being vertical, I think you are right. The plane may have been level but probably had gotten a little out of whack as I screwed around with it.

Wait a minute… This is CALIFORNIA. Everything leans a little left here, so….

The weights are epoxied in the tail and supported by a little wood cross bar. There is still plenty of clearance to the rudder mechanism. Now I can start to worry about the engine crapping out on me.

Charles_e_bates

My Feedback: (90)

Allan:
Looks to me that you have it all covered good luck and have fun.
One GREAT aircraft.

Charles