Topic: Seagull Sea Fury with Zenoah Z20 and mods to improve scale looks (build thread)

Bought a Seagull Sea Fury a 20cc Zenoah to fit in it. I decided I would also change the horrible colour scheme to a Royal Navy Korean war one. Then a mate convinced me to change the tail feathers to a more scale like outline, so in case anyone is interested I thought I would do it online.
Here goes:
The destructions say the dim from the face of the prop washer to the firewall should be 135mm. The Zenoah is 120mm, so I had 15mm to make up. I had some decent ply which was about 6.5mm so 2 thicknesses plus glue and a glass bandage should be perfect.
   I cut two disks to fit into the cowl and drilled some holes near the outer edge. Then bolted them together using 3mm cap screws and captive nuts. The plan is to use them to hold the cowl on securely without any screws showing.
I then marked up the position of the Zenoah mounting holes on the face of a disk, to place it dead central on the disk. The bolt holes were then drilled through both disks and checked for alignment. I then drilled and reamed a hole through the centre of both disks, the same size as the one in the firewall. I then used this hole to align the disks to the firewall and drilled the engine holes through from the disk holes. The holes in the firewall were then opened up to take captive nuts. I then bolted the motor to the firewall sandwiching the disks between it and FW.
 Next to check the alignment of the cowl I cut a disk of 1/8 ply the same dia as the opening in the front and drilled a hole in the centre to fit the crank. The spark plug and inlet trumpet had to be removed to allow the cowl was placed on. The ply disk was fitted to motor and the cowl pulled up to it and centralised with it. Then I marked the position of the rear edge with a felt tip.

You may notice I have been playing around with colours on the cowl.

Next I cut most of the material out of the centre of the disk that didn't have the captive nuts around the rim to just leave a thin ring with a bulge were the bolt holes were. Then I cut the middle out to the same size as the firewall and epoxied it to the firewall using the engine bolts, dipped in vasaline, as clamps. Next epoxied a piece of GF wing join bandage around the face and down each side. When set sanded high spots off the face.



Sorry about the black paint, but you should be able to make out the glass bandage (painted it before deciding to do build on line)

  Tom

The next thing was to bolt the motor and the remaining 6mm disk to the firewall and then build some ducting, from 1/64 ply,around the motor. This was epoxied to the disk using some triangular stock to support it at the disk. I then removed the motor and disk from the firewall and cot out the area on the disk behind the firewall and lightening holes around the rest of the disk.

Disk attached to fuz without the motor.

and with the motor.


   Tom

The next stage was to secure the cowl:For this I used the thin ring cut from the first disk. I needed to remove the part that would foul the ducting and then bolt this to the front of the disk. the assembly , without the motor was bolted to the fuz and the cowl placed on up to the marks previously made on the fuz. Three small pieces of glass cloth were then epoxied in to hold the ring in place. After they had set the motor was fitted and the cowl location checked. All was OK so the ring was permantly epoxied in place.

Ring in place in cowl. Now the cowl can be fitted,  from the front, using 3mm cap screws.



  Tom

You may have noticed in the last pic a strip of ply across the ducting. This is to mount a blanking disk to direct most of the airflow through the cooling duct. I used a 1/32 ply disk I had used earlier, to align the cowl, by opening up the centre hole to clear the prop driver and cutting out an opening for the cooling duct.

You can see the two retaining screws. It is not a complete seal as I want some air for combustion.

The engine has not been fully tightened up, that is why the spinner looks a little off centre.


  Tom

I don't think the two scale cutouts for the exhausts & cooling will be enough for the Zenoah so I looked at doing the extra cooling the same as the fullsize, but decided it would be too involved. On the model there are two holes right behind the outlet of my ducting. I cant figure out what they are for, unless it is to help with the cooling.

Anyhow I don't feel like filling the fuz up with hot air, straight off the engine fins, so as that part of the bulkhead dosen't take any stresses I decided to cut out that section and line it with ply to form a channel.

 


Base is 1/32 and sides 1/8



 Tom

The engine is supplied with two paxolin arms which you have to epoxy to the throttle & choke spindles. I epoxied them on and then for security I drilled through them and the shafts and fitted split pins.


The instructions suggest you use a pushing from the servo to open the throttle. The way I fitted the carb this required  a 90deg change of direction of the push rod. As there are plenty of unused tapped holes on the engine I decided to use one to mount a bell crank.( I may change this later and use a kelvar string to pull the throttle open and let the spring close it ). I joined the crank to the throttle using ball links on a short length of rod.



 For the choke I just plan to use a short rod out the bottom of the cowl.



  Tom

Final bit of engine/cowl fit(for now): To make the openings for plug/lead and exhaust I used the strip of paper method: That is attach one end of a strip of paper to the fuz behind the cowl with the loose end over the plug and ex. Remove the cowl and mark the paper at the plug/ex locations. Put the cowl back on and mark the locations through the paper onto the cowl. Then Dremel out the cowl so it can fit over the  fitted plug, lead and exhaust and can be slid onto the fuz.




Now to the improving scale looks: I plan to remove all the covering and replace with Solatex natural. Then paint it in Royal Navy Korean war colours.


[ Specified attachment is not available ]

I also plan to make a new tail plane as the one in the kit is too heavy and the wrong shape.The fin should have radius at the front from the fuz and the rudder is also the wrong shape, so I will be replacing these as well. I will post the drawings for these parts shortly.
I also intend to fully sheet the wings.

I started to assemble the model before I decided to recover: I'd fitted the wing fillets which has made it a little more difficult to remove the covering in this area and I have also joined the centre section of the wing. Not a major problem but it would have been better if I hadn't.


   Tom

Great thread mate. I have similar intentions, but I'm putting a 1.08 glow into mine (can't afford a new Zenoah)

Great thread mate. I have similar intentions, but I'm putting a 1.08 glow into mine (can't afford a new Zenoah)

I have seen them sold 2nd hand reasonably cheap i.e. complete airframe (trainer) inc servos and Zenoa 26cc for £120

Really??

A mate offered to draw me some working plans scaled up from this sheet:-



This is the result:-











I am going to try and the sheet copied. If I am successful and anyone wants a copy let me know and I will send you one. (I might not be able to get it done because the drawing is on a number of sheets taped together)

and the colour scheme drawing:-




  Tom

Only just got back from a week away to see this.

Watching with great interest here Tom. Currently I have an SC91 in mine and it flies well, however, I am toying with stripping off the covering and doing something similar but putting a 22cc Tartan in.

Keep it up.

Charlie C

Hmmm, interesting.  I'm just starting my second, having lost the first due to reasons unknown - but might have been to do with letting it get a long way away... .  Fortunately a lot of the bits are reusable, such as the stronger retracts I fitted. (the standard ones are rubbish for a plane of this weight)
 
The only thing I'm doing to improve the looks is to move the engine (ASP120 ts with pitts silencer - goes like stink) as far back as possible and shorten the cowl to give a better look at the front.  It might need the batteries in a cradle behind the engine, but based on the previous one I shouldn't have to add weight.

I'm interested in how much weight sheeting the wings adds.  That does look a little wrong, but not as bad as the too long nose.

Oh yes, has anyone else packed up the back of the retracts to reduce the tendency to nose over?

lplus
 You are quite right about the length of the nose. I haven't worked out the scale length of the nose, but if I given it any thought, when fitting the motor, I could have quite easily chopped 15mm off the cowl, instead of packing the motor mount out.
 The sheeting is not going to add a lot of weight, but the solartex and paint could.
 I will be fitting air retracts and plan to tilt them to rake them forward in the down position.
 Not done anything with her this week due to repairing my Taylorcraft (minor midair damage) and Hanger 9 P51D (hanger damage: Tripped and fell against it breaking the tailplane). Also quite busy with domestics.




  Tom

Minor mid air damage??  Not many mid airs leave just minor damage - lucky you!  I suppose the gremlins decided you got off too lightly with that and tripped you onto the P51

Just remembered the other thing I'v done with the cowl is to open up the aperture by about 10mm all round to remove the roll over.  The front of the cowl will end up about 22 mm back from the factory position and I took 30 mm off the back edge to make it end just in front of the oil radiator intakes.

ed - What spinner are you using?  The largest I can get is the 3 3/4" 4 screw ones from radioactive.

I was lucky, just lost most of my rudder. The other guy was even luckier, only lifted a bit of covering off his wing tip.

The spinner is the same one I am using. Could only get it in red, so have had to spray it Dark Sea Grey.


   Tom

Done a bit more: I cut out all the tailplane 1/2 ribs and cut two pieces of 1/2" sq for the leading edge. Also cut trailing edge from 1/2" sq. Then I assembled the lot over the plan and superglued them. Next cut another set of LE/TE's and glued them to the assy with PVA. Then glued in the rest of the 1/2 ribs. and four 1/4" x 1/2" end caps.



I then cut some 2mm sheets to fit over the frame between the T.E.,L.E. and end caps and glued them in place, on one side, with PVA.




Made a start on one of the elevators whilst glue sets.( 2 required )
 Cut 1/2" sq L.E. and placed it in position on plan. Cut and cynoed 1/2 ribs and fitted tip block. Then sheeted over 1/2 ribs. Turned assy over and glued the matching 1/2 ribs and tip block.



Set everything aside to set over night.


  Tom