SENZA

also by looking at blues pick i see he has a little more assembly acquired and that the one panel with the holes in them is to sure up the firewall.

it woild be nice if some one from pilot r/c or tbm would chime in

AirTech

My Feedback: (18)

I don't understand what you mean by "the proper standoffs". Even at 2" you will need to cut them down by another 1/2" to set the cowl to engine clearance to 1/4". To be honest I don't know what "standard" size standoffs DA is supposed to ship with the 50R. In any case the TOC and SD Models 30% Yaks used to be shipped with the firewall NOT installed so the builder had the option of placing it at a location to match the engine/standoff distance. By the way I prefer to have the carburetor outside the engine box rather than spilling gas all over the inside of the fuse, and that's a personal choice.

I am old school when it comes to building planes. I do enjoy building, and rather will build a kit than an ARF. The problem is there are not that many kits available anymore of good aerobatic subjects on this size model. Granted Carden makes a good Yak ARF (Hangar 9) model on this size but I don't like much of the engineering design. For example the Carden canister tunnel is not isolated from the electronics area in the fuse, and that may lead to excess heat in the inside of the fuse. One may argue that the extra ply to isolate the tunnel will add weight but this also add rigidity to the landing gear installation. And if you think moving the firewall back is a major undertaking, try to replace the angle bracing for the landing gear located inside the canister tunnel, that would be a real bear to tackle.

One issue I will try to address on my build is the fact I feel the firewall is a little light and quite thin. So I am going to spend some extra time and effort and laminate as much as the engine box I can with a triple layer of 0.2 Oz/Sq Yd carbon fiber tissue from Aerospace Composite Products. I will be posting photos shortly.

blue77

My Feedback: (178)

Airtech..........I will be watching your posts with great interest on building the engine box...Thanks WC

show871

Just move the firewall back to use the stock standoffs or your carb wont clear the firewall......And the Carbon works nicely.......871</p>

blue77

My Feedback: (178)

Using the standoffs that came with my DL55 I am measuring about 5 inches and 5 3/16 inches for the length from the firewall to the mount....does the difference of about 3/16 inches sound correct to get the correct angle for the engine offset? Thanks WC

AirTech

My Feedback: (18)

Blue,

I believe that you mean 5" and 5 3/16" [b]from former #1 to the firewall[/b] That 3/16 difference will be just right to produce the correct trust angle, and that was what I measured on mine.

I just finished placing the first layer of carbon fiber to the outside of the engine box, and as soon as it cures I will place a second layer.

blue77

My Feedback: (178)

Hey....Thanks...5" and 5 3/16" from the big flat front to the front of the firewall/mount.....Thanks again...WC

blue77

My Feedback: (178)

One easy thing I did that I'm sure everyone else has thought of is to cut the box to where you think it should be and then drill the firewall/mount and connect it to your engine and standoffs, then clamp it in and then try to fit the cowl.....you may have to do some cutting on the cowl, whichyou would have to do anyway,but you will end up with a perfect fit....WC

AirTech

My Feedback: (18)

One thing you may want to make sure when you drill the firewall mounting holes is to maintain 0 degree incidence of the engine relative to the wing and the stab. The way I do this is by drilling the center holes first, install the center holes bolts, and clamp the mount in place. Make sure the fuselage is perfectly level with a machinist level seating on top of the canopy support longerons and then set your incidence meter to zero reference at that same location. Then attach your incidence meter to the engine prop shaft. Rotate the firewall until there is zero incidence, mark the top and bottom holes and drill at that location. Your engine will end up perfectly matched to the wing and stab.

In my experience the more time you expend in setting incidence and trust angles at the shop, the least time you will expend dialing in your model at the flying field.

AirTech

My Feedback: (18)

Today I was able to add another two CF laminations to the outside of the engine box. I also decided to make the engine box top cover removable so I removed the triangle stock from the top side of the box sides, and added triangle stock to the bottom sides (see photos). I will add 1/4" square hardwood rails to the top of the sides and install blind nuts for 4-40 bolts to hold the cover in place. It's important to fasten the cover solidly because the cover adds a lot of integrity to the engine box structure.

As soon as the finishing epoxy dries I will add some CF layers to the inside bottom and the rear of the firewall.

AirTech

My Feedback: (18)

Some more photo on the progress of the CF lamination of the engine box.

blue77

My Feedback: (178)

Hello everyone.....all the info here is great....here is where I am on the fuse and engine mount...pretty straight forward once you get started...WC

AirTech

My Feedback: (18)

Looking good Blue,

I'm going at a somewhat slower pace since last two week I have been extremely busy. And every time the weather is decent and I have a break I go flying. Next week it looks like my schedule will be more open to spend more time on the build. Keep up the good work and information flowing.

AirTech

My Feedback: (18)

I am done with the engine mount and the reinforcing of the engine box. The top box cover is attached with 4-40 bolts and blind nuts, and the rear is supported by a 1/4" square rail. (See Photo)

Many will think going trough all the trouble to laminate the box in carbon graphite may be a waste of time, In my personal opinion if you have the time, the cost in materials is minimal and I am sure all the extra work will provide many more hours of useful life to this model. This a weak area that I have seen fail in a few other models from very reputable manufacturers.

In any case here is a couple of photos of the finished product.

AirTech

My Feedback: (18)

I decided to install the throttle servo inside the engine box compartment. I am using a Hitec HS-225MG micro servo for throttle control so it required that the servo mount provided needed to be modified. For that reason I took the mount apart (is glued with hot glue and very easy to disassemble) and fabricated a top plate that fits the smaller servo. I also needed to sand a bevel to fit the triangle stock reinforcement previously installed in the inside bottom corners of the engine box (see photos).

I also finished installation of the rudder. The slots cut on the vertical stab and the rudder horn were a perfect fit.

AirTech

My Feedback: (18)

Well...this puppy is starting to look like a plane. Installed the tail gear and the main gear. Beautiful carbon graphite work, thin and strong not as massive as the aftermarket units available from TNT but these no questions will do the job they are intended for. Also installed the wheel pants. All this work is very straightforward and one don't even need instruction for this.

Epoxied the ailerons horns in place and will finish installing the servos tomorrow.

AirTech

My Feedback: (18)

Completed the ailerons servos installation using the provided G-10 arms. All the hardware for the ailerons horns looks to be of very good quality and heavy duty.

Installed the engine throttle and choke linkage. Fabricated an aluminum plate to guide the choke pushrod with a nylon bushing (see photo).

devens

Did Imiss something with the motor box mod? Could you not have gone to a shorter standoff?

AirTech

My Feedback: (18)

You are correct. One can use shorter standoffs, if you don't mind having the carburetor all the way inside the engine box, which means that you need to cut a much larger hole in the firewall to accommodate for the choke and throttle arms. I think that by moving the firewall back you don't weaken the firewall that much by keeping the holes smaller, and in my opinion it looks better. As I said before I don't mind the extra work in making the engine box a much stronger structure, in fact I enjoy tinkering with ARF models a little bit. That's my personal choice.

The RC Dude

My Feedback: (3)

AirTech after moving back the firewall did the engine end up in the center of the cowling. I read in the manual that the engine cowl has the 2 degree ofset already built in.

AirTech

My Feedback: (18)

RC Dude,

Yes indeed, the engine ended up in the center of the cowl.

I have been sidelined with medical problems last two week. In the meantime I received all my electronics to finish the build. So far I have installed a Smar-tFly Power Expander Sport that will be supporting an Expektrum AR9000 receiver, and will be powered by dual 2400mAh Fromeco LiIon's packs through a Smart-Fly SuperReg. I will be using a Smart-Fly Ignition Cutoff and manual choke. I purchased three HD-DS120M HV servos from Try Built Models. These servos were tested to output 170 oz. at 7.4Vdc . I need to find out what's the maximum input the Expander can handle since the SuprReg can only go as high as 6.4 Vdc. I will use them on the elevators and the rudder so I expect that at 6.4Vdc it will be enough power for these servos, otherwise I will have to upgrade, any suggestions will be appreciated. I already installed two Hitecs HS-5645's I had lying around on the ailerons which I feel should be quite enough for that purpose.

I will post more photos as soon as I get back from the hospital next week.

blue77

My Feedback: (178)

Airtech......Great idea for the guide for the arm to the choke.....I have been using a servo on my chokes, but this way is much more simple and leaves a channel for a cutoff switch. I just got back to work on Yak and have a couple questions for anyone......I have engine and can installed, I cut out a generous opening for the DLE 55 cylinder and a opening for the exhaust from the can.....everything else fits fine.....am I going to need more airflow? Is anyone going to use the fake radial engine front? Thanks WC

Taildragger726

I would suggest to cut out the whole bottom from the 'oil cooler' on the bottom of the cowl.

AirTech

My Feedback: (18)

Blue,

Taildragger suggestion is a good one. If you are using a Pitts style muffler you can also try opening up the bottom exit hole for the canister muffler and that will add additional airflow. I am planning on trying out the dummy engine and cutt out a hole for just the cylinder area, that way it will work as very effective baffle.

I finally had a chance to install the electronics. I mounted the power expander on stand-offs to maintain airflow around the unit, and I fabricated 14awg jumpers for the regulator power supply. I have the ignition module wired through an ignition cut-off so I will not use an external switch this time. Next I need to install the elevator servos, the fuel system and the smoke pump, but I am waiting for my canister muffler to arrive.

freeair

very nice looking model and set up but, why do they still produce these large gas models with built up wings ? what about foam sheeted balsa which is still light and also alot stronger.