Finish Kit

Fiberglass dust isn't much fun but the cowl is coming together in more senses than one.

The plans don't make it clear but when you come to add the lower cowl you have very little freedom at the rear because the upper corners have to snuggle up under the cowl cheeks. Their position was determined by the upper cowl. I had to trim about 1 1/8th at the rear and 5/8th at the front.
The result of this is the cowl sits slightly low, wrt the bottom of the fuselage. Having said that, there appears very little room to get the exhausts in. I think the slight discontinuity will disappear once the gear leg fairings are added.

Fitting the .063 plates behind the spinner was a great help in stabilising the position of things. i should have done it sooner.

As you can see I sanded slightly too much away just above the gear leg.

It is probably obvious to everyone but me, but I was pleased when I thought up this way of trimming the edge of the cowl. By shimming the back and front so the trim point is at a common height it was quite easy to draw a level line between the too. I placed the cowl on an old sheet of glass to ensure a flat surface.

On the -4 the firewall is straight so the cowl hinge naturally sits at right angles to it. For this reason the later VANS designs have a slope in the upper firewall so it is angled at right angles to the top of the cowl. I was lucky in that I was able to borrow a shrinker and gently modify the hinge so that it slopes down . I have never seen metal respond to the shrinker so easily. If you can borrow a shrinker, I strongly recommend you do since it was remarkably easy to make the direction of the hinge match the shape of the cowl.
This picture shows nothing in particular. The upper cowl has been attached with clecos as have the cowl cheek extensions. The problem I have is the build manual says to trim the upper cowl to the scribe line. There is no trace of a line to trim to on my cowl!








A second problem I have is this. The photograph is taken from as exactly I can, in front of the aircraft. The VS tip, roll bar, and spinner are all lining up, but look at the air scoop. It is significantly offset to the left from the pilots viewpoint. Is this normal?

Postscript - another -4 builder reminded me the carb is set considerably off centre. It is much more noticeable on the -4 than the -9 I built.

A final Sikaflex posting seems appropriate. The RV4 canopy as you probably know, hinges from the RHS to shut. This gives a unique canopy sealing problem to the -4, especially in the area behind P2.

Since I had already bonded the plexi to the frame and skirts, with Sikaflex, I wondered if the seal, which also serves to stop the aluminum of the frame and fuselage abrading each other, where they touch, might be a solution. I ended up putting a half inch wide stripe of primer onto the inner face of the canopy, and then a quarter inch wide stripe of Sikaflex onto that, and then shut the canopy for 4 days.


I was naturally concerned that the Sikaflex would stick to the unprimed fuselage, but of course it had not. It had formed a very smooth tight seal however. I am delighted.

If I did it again I would put a 'wall' of soft draft excluder in as a temporary measure, to ensure a clear inner boundary for the Sikaflex to push up against, since it has left a rather poor inner edge ....but that is next time.

There is no reason why a riveted canopy should not use this approach to providing a very tight air seal.

The second picture is simply the same area of the canopy from the outside.

I did not like the safety catch that VANS has added to the kit. As others have commented, it in no way protects me from a mistake, and only serves to provide a third attachment point of the canopy to the fuselage.
I have made up this little catch which, while a bit ''lumpy", will serve me rather better, I think. It provides a taxi position for the canopy, as well as an additional independent point of attachment of the canopy to the fuse.


Here it is mounted with clecos in its working position, beside my left shoulder. It is well out of the way. You will soon work out that in fact it is an up market door bolt.
The #8 screw is limited in its fore and aft travel by a filed slot within which it can move. I will lock it in place with Loctite. I have made up a little nylon button on the front end, but I don't like it. I must find a yellow plastic button similar to the one VANS supply with the kit.

I plan to put a micro switch on the front main canopy latch to tell me if the pin is not in place. I might put a second switch to ensure this is locked also.

There is enough friction in the system to stop the latch sliding into its locked position when I am outside the aircraft. The way the slot is designed, gravity is also working against it.

This is the view from the PAX seat with the canopy partly open. The bolt slides into one of two holes in the central canopy bulkhead. The upper hole coincides with the canopy in its locked position. The lower position stops the canopy from completely closing. Its only cracked about 1/2" but in the UK that should provide enough extra air for taxiing.





The canopy is held open by a gas strut. This is the one in the 'Spruce catalogue. It is slightly fat for the gap between the role bar and the canopy bulkhead so I will swap it for a smaller dia. one with about 2/3rds the force and more damping. (Then it will not touch the role bar and I will be able to remove the red tape.)