Monday, 12 October 2015

Kwik Fli IV (3)

So, this mornings work involved getting the firewall fitted. With the model still in the jig I started the alignment process.
3 degrees of Right Thrust is equivalent to 7.3mm deflection at 140mm out. (I forgot to mention that I had offset the mount on the Firewall by 7mm)
Extend the engine mount using a pointer


Adjust the side thrust so that at 140mm the (inner edge) pointer intersects with the extended centre line. Check we are at the correct height and also the firewall is at 90 degrees - Vertical - no downthrust.


Then take it all apart again - add slow setting Araldite - and reassemble 

Add triangle reinforcement pieces - adjusting angles and cutting slots for a very good fit, glue and clamp in place - I use a liberal amount of PVA to attach these - making sure that the Firewall isn't disturbed in the process.

Finally, while waiting for the glue to dry, I cut and added the two parts for the fin extension on the top of the fuselage.


Not much I can do now until the Araldite dries

Once the epoxy had set hard enough to risk taking the fuselage out of the jig. A gentle sand down outside in the early evening getting the top deck to shape was a real treat and then back to work. Its slowing up a bit now..

I have added the SLEC snakes and heavy duty push rods


At the rear end, there is a small spacer to hold the outer tubes rigidly and epoxied into place. In this shot you can see the 1/8 balsa doublers. On the plan these are full width and the sides butt up to them. Much more difficult to fabricate.
With the tubes and pushrods in place, I added the lower sheeting - grain runs crosswise..


I trim these back to size when the glue has dried.
Finally tonight, the nose leg has been added and tubes fitted for the throttle and the steerable nosewheel.


The nose leg tiller is at a funny angle so that I don't have to cut a slot in the firewall. It means none linear steering but I am not worried about that. Note the tank is back is to make sure that nothing binds and it can be installed and removed with comparative ease.

Things will definitely start to slow up now, the next job is to fit the lower front sheeting and then fuel proof the tank bay and then make a cowling. I am tempted to make one out of Fibreglass using a simple pink foam plug. I'll settle for polyester resin and sand it smooth when it sets.

The hatch was quite simple. I have added 1/4 x 1/8 spruce rails to the fuselage top. Added a 3mm lite ply rear former on the fuselage and then simply assembled the hatch from strip and a 1/2" upper deck with play formers front and rear


Pretty basic stuff and mainly following the plan
The gussets have been added because the wood is rather thin at the junction between the top deck and the sides.
The slot is for the nose wheel leg mount - which is slightly offset to cater for the right thrust


Note the blood - that is to make sure it flies OK.

And onto the Cowl

I am going to try the method used by Chris Barlow in his 2015 triple mass build blog. This involves making a foam core then covering in Fibreglass tissue and then Fibreglass cloth. Chris has kindly provided me with some useful hints in a PM - thanks Chris.
Here is the cowl.. carved and sanded from pink foam






Looks OK at this stage - it can only get worse now.. 
The cowl was then wrapped in clink film then a single layer of packing tape.


This is the release agent.
Then a single layer of tissue with polyester resin.


and sanded down to get rid of excess lumps
And then, this morning - a second layer of tissue/polyester resin has been added


Its not quite as bad as it looks. I'll leave it until this evening to harden and then sand down and possible apply another layer, Eventually a top layer of 170gm cloth will be added secured with epoxy resin.


The plug was dissolved using Petrol as suggested by Chris Barlow - that was VERY effective and the cling film and packing tape have subsequently been removed. The cowl is quite useable, It has a couple of high and low spots and unfortunately one bubble but its not as rough as I expected it would be. Tomorrow, it will get a reinforcement ring of 170g and epoxy around the inside edge and then trimmed to length and the bubble filled in.

After that, its another sand down, high build primer and filler (hopefully not much) then paint and fuel proofer. That will really show up what its like and whether it ends up in the bin

The cowl has also progressed. I reinforced the inner edge at the fuselage junction with two small strips of 170g cloth and then left it harden for 48 hours. A quick sand down and first coat with high build primer left it looking like this..


Not too bad, needs a little filler in a couple of places, so this morning I filled it with P38


.. and (rough) sanded it down again.. Quite happy with that as well. It will need the length trimming back by about 5 or 6mm which will be done when I fit the engine. I'll smooth sand it then high build primer again.
It is definitely very useable though..

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