WH-300 3-Amigos build thread (3 ways of doing the same thing)

[KrisW]

continuing pics

[KrisW]

THEN. . . .I decided I didn't like all that extra materail on the front of the motorbox. It's silly overkill ! !

So I grabbed my Dremel cutoff wheel and begain slicing about 2/3 of the "lip" off the front of the box, in front of the motor plate. After that was done, I grabbed my belt sander and smoothed things up a bit, then finish hand-sanded with a block and 100 grit paper.

Not satisfied, I used a hole saw to make 4 holes through the motor mount spacer, then removed all the materal in a square shape. Again, everything was hand sanded and smoothed.

Finally, to make sure this motor box was NEVER coming apart, every seam was reinforced using 1/2" #4 screws. They add almost no weight, but are a lot stronger than dowels, and go into the wood in about 5 seconds each.

After that, the holes for the ignition leads were bored, the ignition mounted, and engine final mounted in place. The headers for the KS-1090's were trial fitted (need to be heated and bent up slightly. . .I'd already bent them DOWN to fit another airframe. . now I'll reverse the process ).

So, for now. . things are going splendidly.

[RC_Pattern_Flyer]

Tom, if you are reading this.. it would be simple to laser mark the holes for drilling either a 3w150 or Da150 onto the fire wall or make a quick template out of thin lite ply. This would allow those without great building skills who may have picked an ARF for this reason one added bonus to aidin building the Extra properly.

Just my 2 cents. a thought.

Well Kris, i can tell my building skills will be easily outclassed by you! HAHAHA, i am pilot not builder for sure. Hope i am one step behind you on this plane so i can learn as i go as well!

Looking Good.

Chuck

[airborneSGT]

Dang you guys are fast! I had distractions of G/F, Bar and gym tonight. I also had to pick up the rest of my 5955's. I should finish the plane by Friday.

[OverTemp]

Looks good.What are you going to use for the rudder control horn?Also, is a full ply block behind the motor required, or can I use stand-offs with the DA-150? I'm thinking of just using 4 x 1/2 thick, 1" diameter ply discs. Want to make sure nothing bends/breaks.RC Pattern Flier,A distant friend has this plane. I don't think you'll be able to put your servos in the tail with the stock exhaust. He had to space his motor out a little more to get it to balance with pull-pull.

[KrisW]

	Quote: Originally Posted by OverTemp
	Looks good.What are you going to use for the rudder control horn?Also, is a full ply block behind the motor required, or can I use stand-offs with the DA-150? I'm thinking of just using 4 x 1/2 thick, 1" diameter ply discs. Want to make sure nothing bends/breaks.RC Pattern Flier,A distant friend has this plane. I don't think you'll be able to put your servos in the tail with the stock exhaust. He had to space his motor out a little more to get it to balance with pull-pull.

The firewallis 1/2" thick, and very good quality plywood. I'd use a steel fender washer under the aluminum standoff, to spread the load, and not worry about it much past that. You only need about 1/2" of standoff, so the lever moment arm is
going to be very short.

Tom, Rcpatternflyer has it nailed. Since these parts are all lazer cut, adding "X" marks for BOTH 3W and DA, as well as ZDZ (with a shaped cutout line for the ZDZ carb to pass through) as well as some square standoff-plates with an included paper drill guide, would go a long way to helping the less-skilled builders with this engine installation. One other thing. . I'd move the end of the motorbox back about 1/2" and increase the thickness of the standoff, because the lip on the box REALLY gets in the way of a DA-150 installation due to the right cylinder being so close to things. You need a little air movement room behind the cylinders, and this would help. As you can see I removed about 3/8" of materal from the front and sides of the box. This is unnecessary material, and IMHO the entire "reinforce the motor box" frenetic reaction is unfounded with this design. It's very good wood, very strong, and very well put together. Merely chasing all the joints with thin CA is more than enough, especially if you sink some #2x3/4" screws through the plates into the edges of the ones they join to, as I illustrated. 95% of failures with this motorbox will be from the wood sliding apart where the tab/slots are. That will never happen with a proper glue joint, and a few strategically placed screws to help make sure there is no separation at these points.

This motorbox is SO overbuilt I am seriously considering swiss cheesing it to remove some more weight. Ditto for the sides of the firewall where the cowl mounts. It would be very easy to "Dalton" those area while lazer cutting them, to remove a few ounces of AUW. I have a 1/2" and 3/4" hole saw sitting here. . they are BEGGING me to get a bite on those areas. . . .

RCpatternflyer. . there are MANY who would disagree with you concerning my "Building skills" They like to throw my slightly off-beat way of attacking problems by saying I'm a klutz or that everybody laughs at the things I do. (Like I really care. . . . )

AirborneSgt. . at ths rate both of our planes will fly before yours. . Keep partying. . .after all, its ONLY women and Drinking. . . . .

[airborneSGT]

You guys will be ready by Friday?

[wildhare]

I won't get into an engineering debate, the requirements of the seller of an aircraft are different from those of the purchaser. I designed the plane to meet my requirements for a solid, marketable, reasonably light plane which has a high probability of success with the peole who will buy it.

It meets my requirements, once it's sold the owner is free to make all the changes he wants. We have extansively tested it "as delivered" and it worked great.

FYI the reasons all that material is in front of the firewall are several.

It reinforces the tabbed holes. If the glue joint were to break the tab/slot arrangement will keep the firewall in place for a while. With less wood in front of the tab a glue joint failure will allow the firewall to move forward and twist.

It allows triangle stock to be added without degrading the flat surface on the firewall rear which is necessary so washers and/ot blind nuts will have a solid surface to mount against.

It keeps the joint clear on the rear so that it can be inspected and reglued if necessary.

With this arrangement it is theoretically possible to start the engine and fly the plane for a short time even with no glue holding the firewall into the motorbox sides. Not recommended, but one must give some thought to how things can go wrong.

TF

[OverTemp]

Very political responseMine seems OK... I reglued all the tabs with thin and filled gaps with thick. I did have the plywood on the left side of the firewall delaminate sitting here (it may have come like that... I didn't notice and I haven't had time to mess with it 'till this week). It was delaminated back about 3 inches... back past the tab. I filled the entire area with thin CA then medium CA for any area I could get it into. I clamped all this and it seems pretty solid now.What rudder horn you using?

[airborneSGT]

I am going to use a 10-32 rudder horn. The Seiko servo is a monster. I am in the process of organizing the workshop in my house - aka the garage Its funny when I begin to do rough carpentry work and remember why I enjoy finish carpentry.

I am not going to do anything too radical to the plane for modifications. For me it does not make sense as someone else has already done the R&D and testing that has more R/C pilot skills then I can touch.

[flybye]

Hello my name is nikko and i'm an alcholic... damn wrong forum again

[KrisW]

WELL. . . .I guess that answers all THOSE questions. . . .

Okay. .build day #2

Time to fit the fuselage for full length pipes.

First order of business, remove the "equipment mounting tray". teh tray is very flimsy, not glued well at all, and so it's OUTTA THERE to make room for the pipes. It took all of 30 seconds to slice it lengthwise with a dremel cut off, then easily pry the thin plywood off the balsa stringers. (see pic)

Okay, got a wide open bottom of the plane, now we need to open up the wall under the wing tubes, so out comes the 1 1/4" hole saw to make the corner radii, and then the Dremel cutoff wheel easily slices out the rest of the "hole (see pic)

Now, we need to insulate the covering from the pipes, so we lay in some 1/16" sheet as a false bottom. It takes two pieces,glued to the stringers on the side and bottom, to make the false bottom. As you can see from the picture details, the bottom pieces are curved a little bit. this is to add just a little bit of strength between the two formers they attach to front and read, and to give a little bit of an airgap between the pipes and the balsa sheeting.

I use a two-glue method for attachment of these pieces. Where the edges of the stringers are sharp, I put a small amount of thick CA, and where the stringers are flat, I put a bead of Pro Bond. Each sheet of balsa is then laid in place, so that it gets some of the probond on it, and is then forced downwards in the middle to form a curve. ths causes the edges of the sheeting to lift up slightly, giving a slight airgap that the probone will expand to fill. In this way, the probond is on both the stringer and balsa sheet, and the CA can act as a holding glue while the probond expands as it cures and finishes the joint.

Behind this false floor, two more pieces of 1/16" balsa sheet were fitted between the stringers, but in such a way that they lay on top of the covering. Using a covering iron, I then irone the covering to the sheeting, then used a smallbead of probond on the edges, for the final adhesive. The probond will cure, expanding and making a slight fillet joint between the stringers and the balsa sheeting.

Now comes the fun part. .fitting the exhaust exits to the sheeting. Using some 1-1/4" wing tube phenolic, sliced on the bandsaw and then final shaped with a bench belt sander, I configured a small airdam on the interior of the planes floor, anchored to the 1/16" balsa sheeting, to help direct all air and exhaust toward the outside of the plane. A future mirror-image piece will be put in place on the belly of the plane, to provide a low-pressure area to help pull exhaust and air out of the fuselage.

When things get finalized, I'll add a cross brace to help reinforce these two exits and keep them from separating due to vibration.

(The stuff on the pipes is muffler tape, where they used to be mountd in another plane. The tape makes a more solid area on which to lay the pipes into a mount, without damaging them)

[KrisW]

More pics.

[KrisW]

Now for the basic fuel tank mounting installation.

I HATE having the fuel tank off the CG . .it just burns me up to see it in front of or behind the CG, because I know there will be a CG shift as the fuel level lowers.

What to do? Mount the bloody tank on top of the dual wing tube phenolics.

A simple structure of 1/4 x 3/8 spruce sticks makes a framework, and is attached to the sides of the planes framing, and to the formers in front and behind the tank location. The tube sockets will take the brunt of the carrying loads for the tanks weight, so this framework is basicaly only to keep the tank from ratting around too much, and to give a nice discrete location for the tank.

I'll be using 1/4" ny-straps to hold the fuel tank in place once everything is finished.

Now. . anyone want to see their fuel level???

A simple "window" cut into the front IP location gives a straight-shot view of the rear of the fuel tank, and allows you to see the fuel level at a glance.

[airborneSGT]

By Friday I tell yah!