CARF Yak55 SP 3.3m Build

All types of aerobatic airframes, questions, builds or general info

CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 6:27 pm

So, I had planned to put up a full build thread on this bird, but I've allowed the build to run away with itself before posting anything on here.

So, I'll put up some details of the build as it stands now and then periodically update this thread as I work through the final jobs.

Specifications for the build are as follows:

Composite-ARF Yak55 SP 3.3m (the new design) in the American Flag scheme
MVVS 190 4-cylinder engine with MVVS Headers
Proflow Large Smoothpipes
Hitec 7990 servos on the rudder (x2) and Ailerons (x6)
Hitech 7955 servos on elevators (x4)
Powerbox Competition with Futaba 7008SB receivers
Lots and lots of Secraft 'bling'
White Rose Engineering tail wheel
REVOC covers

This thing is BIG :mrgreen:

Tomorrow when its daylight I'll post some images of the Yak fuselage next to one of my Krill Sukoi's. The Sukhoi is a big model, but the Yak makes it looks small. In fact it sits so tall that I can only fit it into my Mercedes GL (a big car!) with the canopy removed - - otherwise its just too tall!
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 6:34 pm

Ok, so here are some images of the engine install. Key points are:

* C-ARF seem to have provided the model with a nice thick firewall, with 6mm tick ply applied to both faces of it (inside and outside).
* I've had issues in the part with standoffs wearing wood firewalls. And, it compressing when bolted. So, I faced both sides of the firewall with heavy duty carbon Kevlar cloth. I've found through experience that this overcomes the problem.#
* I got my good friend Nick Butler to machine up a custom engine mount for this. I did consider just standoffs, but decided I wanted something more substantial
* Nick also machined up the engine baffling for me that is fitted to the cowl. In thinking about how this would work, we shaped the engine mount in CAD so that the baffling would terminate against it, to reduce the amount of baffling material we would be adding (to keep the weight down)
* We also designed the mount so that a throttle servo mounting bracket could be bolted to this, making for a very clean throttle servo mounting arrangement
Attachments
IMG_20170105_181556.jpg
IMG_20170105_181544.jpg
IMG_20170105_181222.jpg
IMG_20170104_163810.jpg
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 6:37 pm

After having a large number of Powerbox smoke pumps pack up on me I decided to try the Secraft unit.

I've got into the habit of mounting these pumps to the exterior of the motor dome on my aircraft (i.e in the cowl area) after a previous 'incident' when a pump within the fuselage decided to spring a leak and dump fluid inside the fuselage and made a total mess! (didn't help that Craig was in the process of 'hooning' the aeroplane around, which did a really good job of evenly spreading the leaked fluid....
Attachments
IMG_20170105_181255.jpg
Last edited by Billy Bunter on Thu Jan 05, 2017 7:26 pm, edited 1 time in total.
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 6:42 pm

One of the easiest jobs was fitting the spats. I took the time to reinforce them with carbon fibre, which will hopefully ensure they last a long time.

I also decided to try some inflatable KAVAN 6" wheels, which look very beefy. Currently the are mounted using A2 stainless cap head bolts. After seeing the model assembled I'm a bit concerned these might actually bend on a heavy arrival and so I decided to order up some titanium bolts to fit instead. Viciously expensive, but significantly lighter but also significantly stiffer/stronger than steel, so hopefully these will hold up problem free.
Attachments
IMG_20170105_180620.jpg
IMG_20170105_181111.jpg
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 6:48 pm

The YAK has a fairly unique UC system which I've pictured here. Basically the legs are straight carbon rods with inserts at either end for the wheels and attachment to the fuselage mounting point.

Following the path Krill seem to have taken, one of the design updates C-ARF have made to the YAK is a composite UC leg support (the red thing), which braces the legs as the pass through the fuselage skin. They have also gone the route of a composite fin former, with the rudder hinge tabs integrated into it. I'll add images of that tomorrow.

I'm pretty paranoid about carbon being weakened from heat exposure. So, I found some very nice DEI heat wrapping used on performance cars, which I've used to protect the carbon legs as they pass by the headers.

Additionally I've wrapped the fuselage wing tube socket with DEI gold heat shielding - looks rather 'gay', but should stop any significant heat getting to the carbon wing tube I plan on using (the C-ARF metal tube is quite heavy).
Attachments
IMG_20170105_181051.jpg
IMG_20170105_181043.jpg
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 7:01 pm

I decided not to order the C-ARF tank tray and instead make up my own, extending it to also mount the Powerbox and receivers.

The approach I went with was as follows:

* I first worked out the shape of the tray I wanted with depron
* I wanted the tray to be removable and so molded up some carbon around the wing tube socket, which I would used to secure the tray to the tube. Here I just wrapped the socket in polythene and gave it a polish with some Honeywax mold release agent. Then painted it with West System epoxy, laid the carbon onto it and further impregnated it with resin. 24 hours later I popped this off the polythene and trimmed it up
* I then cut out the tray from a sheet of carbon nomex, using the depron template
* For holding the tanks in place, I went with a system that SAM showed me a few years ago: Get a couple of coke bottles and polish them with mold release agent. Then paint with resin, lay on some carbon and further impregnate it with resin. Then leave to cure. 24 hours later you can pop the carbon off and trim it up. This give a beautiful arrangement for holding coke bottle tanks. It weighs almost nothing, looking fantastic and follows the exact shape of the coke bottle if you use those form fuel tanks.
* I then bonded the carbon tank frames and the wing tube socket clip to the tray. As you can see from the images its come out quite well. Its held onto the wind tube using Velcro ties. Attached to the UC mounting frame in the front of the fuselage with three heavy duty cable ties. I'm yet to make up the arrangement for securing the back of the tray to the fuselage.

Anyway, this give me a very nice looking, super light-weight system for mounting the tanks etc, which can be removed from the fuselage in just a few moments.
Attachments
IMG_20170105_181009.jpg
IMG_20170105_180914.jpg
IMG_20170105_180823.jpg
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 7:12 pm

Coming back to the cowl and baffling, with a 4-cylinder up front I was very concerned to get the best possible baffling arrangement.

Normally with 4-cylinders the baffling goes all the way around the centreline of the engine. Air is then introduced through the upper half of the cowl at the front. Louvres in the underside of the cowl then create the negative pressure/suction to drawn the air form the upper half of the cowl, through the baffling/cylinder head fins and the out of the bottom of the cowl.

Complicating the YAK, it has four louvres in the upper half of the cowl and two in the bottom half. Thus I was concerned that if I ran a baffle around the centreline of the engine, terminating against the firewall, the majority of the air entering the cowl would get sucked out the top, rather than get drawn down through the cowl, past the fins/baffle to keep my shiny engine nice and cool.

So, Nick and I came up the a box arrangement, where the incoming air is forced to go through the baffle into the underside of the cowl, but still be able to then make its way upwards to be extracted buy the louvers in the top of the cowl, as well as the bottom of the cowl.

Rather s WORDY explanation, but hopefully this all makes sense?

For cooling, I've ordered some additional YAK composite louvres from C-ARF, which will be going into the fuselage belly at the end of the pipe to help with fuselage cooling.
Attachments
IMG_20170104_163832.jpg
Top half of the cowl. Carbon and Herex baffle box in plate, machined up by Nick
IMG_20170105_181205.jpg
Bottom half of the cowl. Just a carbon blanking plate at the front.
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 7:14 pm

The YAK fuselage has a really large canopy opening, so I've decided to brace this with a carbon cross brace. Today I bonded some M3 studding into 3K carbon tubing with Hysol and bandsawed out a couple of carbon discs. Once the Hysol has cured tomorrow, I'll get on with mounting this to the fuselage and securing the bracing rods to the carbon discs.
Attachments
IMG_20170105_180707.jpg
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Thu Jan 05, 2017 7:18 pm

OK, I have a steaming headache so enough posting for today. I'll add some more images tomorrow and in the coming days as I continue to work on this.

Please do all let me know what you think though! I'm interested in any comments, input, ideas you may have for the build.

And, maybe this will help breath a little bit of life back into this forum, encouraging other to put up some build threads for other aircraft, which seems to have died a bit of a death on HA of late.

B.
User avatar
Billy Bunter
Squadron Leader
Squadron Leader
 
Posts: 644
Joined: Sat Nov 28, 2009 6:26 pm

Re: CARF Yak55 SP 3.3m Build

Postby Andrew Bird on Fri Jan 06, 2017 10:47 am

Looks good!Some nice custom work in there.
User avatar
Andrew Bird
HA Sponsor
HA Sponsor
 
Posts: 3092
Joined: Sun Nov 16, 2008 11:08 pm

Next

Return to Aerobatic Airframes

Who is online

Users browsing this forum: No registered users and 2 guests

cron