wphilb

My Feedback: (10)

Aren't you worried about all that weight that far aft?

speedbrake

I reworked the aft servos and decided to place them forward of the CG. The servos are (3) 4.5 oz. total. All the other items, screws, mount plate, control rods, etc. would bring it to a total of 7 or 8 oz 42 inches behind the CG. Additional ballast would be placed 21 inches in front of the CG..... so saved perhaps a pound of ballast by changing the servo location. That is a lot. I will use pull/pull wires to actuate the control surfaces. Need to make bellcranks to attach to the brass tubes. Added the plywood bearing plate to the rudder's brass tube...really stiffens the tube. The bellcrank will be attached above the bearing plate. A 4/40 rod will connect the tail wheel to the bellcrank.

Whit, you are right about the weight aft. I was concerned and already working a solution when I got your email. One of my goals is to keep this build light. Sometimes I stray a little.......

wphilb

My Feedback: (10)

We all do (stray from adding lightness).  Smart builders like yourself are aware of the ratios and the implications of a very little changes fore and aft of the CG.

speedbrake

Had some U-control bellcranks in the junk box. They seem perfect for the task. The left elevator bearing plate is done and mounted. The rudder bellcrank is a bit larger and also fits nicely on the brass tube. I didn't have silver solder so used JB Weld to adhere the wheel collar to the bellcrank.....that stuff is great. I'll finish the right elevator bearing plate and be ready to cover the elevators.

Probably use some inner nyrod to direct the pull-pull wires at the back of the fuselage. They will travel above and below the stab spars. When ready to install the flight control surfaces I'll drill a small hole in the brass tubes so the collar allen screws won't slip after being tighened. I'm pleased with the set up...seems simple and light.

Keith

speedbrake

The rudder and elevator hinge points and bellcranks are done. To install a control surface the plywood bearing plate needs to be removed. Then the control surface is placed on the hinge points on the stab and then the wire hinge is inserted. The bearing plate is installed and then the bellcrank fastened to the brass tube. The tubes will be trimmed to length when ready to install the first time. The wire hinge will be trimmed but left with 1/4 to 3/8 inch extra length so can be pushed through the tip to remove.

Next is final shaping and sanding the elevators, then cover. The rudder is going to pose a problem. As mentioned the vertical is twisted and bowed. The twist is to the left...which is OK because it can be used to counter torque. The bow causes the rudder to stick out at the top on one side. If I sand the rudder flush with the vertical, it will be too thin at the top. I might sand it a little bit and then leave as is. Or, use the foam rudder to see if that is better.

Keith

speedbrake

Photo shows the top of the rudder. I will remove the upper hinge point and move it until the rudder is centered at the top. Some sanding will be required to thin the rudder...too thick right now. Should look a lot better when done. After the rudder is covered I'll work on the nacelles.

Keith

wphilb

My Feedback: (10)

No ideas about how to remove or mitigate that twist and bow? I thought about cutting reliefs in one side, forcing it back to center and then gluing back together the now overlapping cutting, or making a frame, applying heat and then attaching frame to straighten then allowing to cool, reheating again with frame in place then allowing to cool again, a few cycles should lock in the gains?

speedbrake

Whit,
It isn't worth the effort. This isn't a scale project so problems encountered are fixed as simply as possible. What I did was move the upper hinge point over to center the top of the rudder. That caused the left side of the rudder to stick out. I sanded that down as much as I dared. I'm covering the rudder right now. I won't worry about the twist. It came out of the mold that way. I'm glad to have all the flight controls hinged and covered. Time to move on to the nacelles, which have their own problems to solve.

Keith

Edwin

My Feedback: (2)

Just me, I'd cut it off and build another. Like you, I'm not sure what the effects will be. But I've dealt with that a lot on students trainers. Mostly lived with it and and used trim.
Edwin

speedbrake

I'm satisfied with the rudder and how it fits. I'll finish the trim tabs at a later time.

Unable to unload pictures, will try again later

speedbrake

Pictures

speedbrake

Made a template of the throttle servo mount. It fits inside the cowl, but I won't make any until the cowls are installed to make sure everything fits. The mounts will be made from 1/8" phenolic sheet. This setup will make it easy to adjust the throttle servos...and won't disturb the setup if the engine needs to be removed.

The outer nacelles are next. Will fuel proof the inside of the cowl (plywood ring) and the wing notch area. Need to sand down the flange to 3/8" and feather the edges. I'll make sure a 16 oz. tank will fit into the notch. Remeasured the wing to ensure the nacelles are where they are supposed to be. The nacelles (inner and outer) are 12" apart.

TLH101

My Feedback: (90)

I would think that mounting would trasnfer an extreme amout of vibration to the servo. The firewall tends to dampen out a lot of vibration, but there will be no dampening effect with it mounted there. Plus most of the vibrations are rotational, so that servo will be traveling a lot distance in each direction, which will amplify the vibes.

All Day Dan

My Feedback: (5)

Speed, that HS 81 servo is designed for micro use. I doubt if it will survive the vibration you are going to expose it to. Send HiTec an email with those images you have posted. Ask them what they think. Dan.

speedbrake

Number one nacelle is epoxied on. The wing is sitting on the front faces of the two nacelles to keep them aligned. A clamp is being used to hold the rear portion of the nacelle to the balsa surface. A 1/8" gap exists where I sanded down the very front portion of the flange. I will glass that area from the inside of the nacelle. I'm satisfied with the overall fit of the nacelles. There is plenty of room to reach in with my hand through the front opening of the nacelle, enough that I decided not to worry about running string for the servo leads in the wing.

All Day Dan: I left a message with Hitec...waiting for a reply.

TLH101: I have plenty of time to make a final decision on the throttle servo location. I will keep it in front of the firewall though. The answer from Hitec will obviously have some bearing on mounting them on the engine. Thanks for the input. Are you ready to resume your B-17 build?

Keith

TLH101

My Feedback: (90)

No, I finished my 79" B-17, & one is enough for now. I have a couple of other projects I want to do first.

Edwin

My Feedback: (2)

Isnt that the way it always is? For me to finish everything I want to build, I'll have to live to 150!
Edwin

speedbrake

The number four nacelle is now epoxied on. The end view photo shows the amount of down thrust in the nacelle (left side is the upper surface). I'll measure it when all is dry. The nacelles conformed to the airfoil nicely. The flanges get thicker as it goes forward, so used the dremel to thin them so they would easily conform to the airfoil.

I'm running short of epoxy so will save the remaining to glue on the inner nacelles. The landing gear mount will be next. There are two pieces. The rear mount is glued to the notch in the wing and the nacelle. The forward piece is glued to the nacelle just behind the firewall mount ring.

Speedbrake

speedbrake

The nacelle down thrust is between 3 and 4 degrees. I used some scrap balsa sheet to cover the LDG jig to see what the gear footprint would be. I'll use that to make a pattern so I can cut out the holes in the bottom of the inner nacelles. Then I can make the LDG mounts.

Speedbrake

speedbrake

The rear LDG mounts are installed. The front and rear mounts are 9 3/4" apart. The rear mount is about one inch in front of the aft plywood piece in the wing cut out, that piece is epoxied to the wing spars (see page one of thread). Two standoffs were made from 3/8 sq balsa and plywood...to properly space the LDG mount from the aft cut out piece. The standoffs also tie all three cut out ply pieces to the LDG mount for strength. 1/8" wood dowel pins will tie the LDG mount to the aft cut out piece for additional strength. The front LDG mount will be accomplished after the nacelle is installed. It will be attached to the back of the firewall.

The way it is set up there will not be a need for a hatch for the retracts. There will be access through the firewall hole and the retract cut out on the bottom of the nacelle. To set up the landing gear retract angle, the wing was placed on foam blocks and leveled. A small level was used on the rear retract mount and the holes were marked. T-nuts were added. The cut out area will be fuel proofed before the nacelle is installed. Next..the inner nacelles. The plane should be sitting on its wheels by next week!!

Speedbrake

speedbrake

The retracts were installed onto the rear mounts for the first time. The alignment seems to be OK. Just hope the LDG mount is strong enough for the task. This plane should weigh 40 plus pounds when finished. Kind of satisfying to be this far into the build...everything is coming together. The actual building part will be about done by the time I pack out and leave for the states.

Speedbrake

speedbrake

The ends of the inner nacelles are (top and bottom) staggered and difficult to hold down for gluing. I don't have a clamp with long enough jaws to reach the ends. Made a clamp from pine sticks and a spring. It can reach the nacelles ends and hold them down while the glue dries. Now I can resume installing the nacelles.

Will make the wheel and strut cut outs on the bottom of the nacelles after the glue dries. Then make and install the front retract mount on the aft side of the firewall.

Unable to upload photos at this time, system too busy I guess.

Speedbrake

speedbrake

Both inner nacelles have been glued to the wing. There are some areas where the edge of the flange is sticking up a bit....maybe 1/16 inch. These areas can be fixed with filler. The compound curve and length of the bottom of the nacelles was sufficient to cause them to raise during gluing. The top side of the nacelles is better because it is shorter in length and easier to hold down. There is going to be a lot of filler needed in the LE areas of the nacelles, where I cut them out. I will glass the inside, forward edge of all the nacelles for strength.

I'll cut out the strut and wheel holes next. There should be enough room in the forward and wheel openings to mount the retracts with little problem.

Still can't upload pictures. This is the third day....not sure what is going on with RC Universe. I noticed other people complaining as well. I noticed when this happens my avatar will not display.

Speedbrake

All Day Dan

My Feedback: (5)

Speed, what did you use to glue the nacelles to the wing? Thanks, dan.

speedbrake

Hi Dan,
All the fiberglass parts were laid up with the West System Epoxy. Nothing will stick on them except epoxy resin or epoxy glue. I used a West System Epoxy from Discount Marine....4oz bottles....seems to work well.