Finish Kit

At the time of writing, IKON has just short of 50 hours.

At the start of this blog I explained that I planned to fit oversize tires. I hasten to add that I am certainly not the first to do this in the UK, since I have been credited with this as my idea. I just brazenly steal a good idea.

The reason for this posting is, that I now have about 40 hours, and rather more importantly 80 landings, under my belt in G-IKON, I am beginning to have some experience as to how they handle the dirt. Before I go further, all 80 of these landings have been on grass. G-IKON does not yet know that hard runways exist. Just under half these are at my 1020' home strip which you can see here . Its a heavy clay soil and suffers the normal amount of UK rain. Its mown with a lawn tractor until July, and after a crop of grass has been taken from the rest of the field is maintained by my mowing team until the following spring.

For those of you who dont know sheep, they tend to cover the field in shit, and this has the adhesive properties of proseal! Recent discussion on Vansairforce at this thread , caused me to use an unflyable autumn day, to take a look inside one of the spats. What I found was good news!

With prep of the fiberglass largely complete before John arrived (see Painting I below), the first major step was to heavily scuff the coat of etch primer that has covered the parts for the last 18 months or so, with 320 grit. Its tiring and dusty, but has to be done. This is fortunately followed by a coat of primer which quickly made us feel we were progressing. (The spot in the picture is something on the lens. As I said it is dusty work!)

At this point, as the -4 all became this matt 'stealth fighter gray', it looked good enough to stop right there.

John had come armed with masks for much of the design on the tail, and the overly large British registration. The design is of a flag as you will see, that has made it through the prop, but become shredded on the way. With the speed of a -4 it is rapidly disintegrating!

Here you see the rudder mask in place.

In the picture below, the whole mask is in place except the part that implements drop shadows.

By the time you get to the clearcoat you need to have the dust under control. This may require razor wire to keep the grockles away.

As the days continued the whole design began to emerge. Don't underestimate the confusion a rooky can get into, as to which masks should be in place and which removed, at any one point in time. Fortunately, to John, this is bread and butter.
The design of the nose was only completed during the time John was painting. It was a true team effort with John, my wife and myself all contributing something. I am VERY happy with the result. Here you see it in base coat. The clear coat (shiny stuff) has yet to be added. It makes the gray come alive and lightens it slightly. for the full effect you need some sunlight.



Having started on a Tuesday, after a very long week of late nights, we were finished by Sunday lunchtime. Five and a half long days for the total job. I am delighted with a superb paint job, though it will be a while before I see it all back together, since I have to do the baffles, plumbing, controls and wiring around the engine, and the instrumentation before that.

In the meantime the painted parts complete with 'shiny stuff' are quietly sleeping and hardening.

With some hand airbrushed highlights and low lights, the flag has taken on a three dimensional quality

So if you are interested in a custom paint job, swiftly executed at an economical price, in your location I would urge you to contact John. http://www.stahrdesign.com/

It was a delight to work with someone who has executed a fabulous paint job with enough artistic merit and pride to make it worth putting a signature to.

Carrying this lot, and it is not all the products we need for painting, from the car to the workshop makes me realise just how heavy paint is. Let us hope there are plenty of volatile components.

Last Tuesday was a long day of preparation, but I have apprenticed myself to John Stahr, a professional at this job (design and implementation of custom paint schemes), so what to me had been major issues faded to nothing working with him.

To see more about his business go to http://www.stahrdesign.com/

By the end of an admittedly very long day he started shooting the first coat of the epoxy over everything. It certainly made for a dramatic change!

I never read this, or have been told it before, but the guy at my local paint shop gave me a great idea. I was complaining that fixing the last few pinholes appears to go on for ever. Up until now I have been trying to squish paint some days, filler others, into the holes with a credit card.

His reply was "Easy, take a pin and some paint, dab the pin in the paint and then in the hole." It works and it is obvious once you know. The pin displaces the air in the minute cavity, but when you pull it out the paint gets sucked in. It works!

Sorry if you already know......

And for the quote of the day, George Bush talking about Tony Blair.
"I've heard he's been called Bush's Poodle. He's bigger than that."
27th June, 2007

Filling pinholes in the fiberglass components must be the most unrewarding part of building an aeroplane. You have to question the intelligence of anyone who builds the whole thing this way!



I have tried everything for filling the holes. What works best for me is to mix up a thin cream of epoxy resin with micro-balloons. They are phenolic (?) balloons, and coloured brown. This is why it looks as though it has a rash. I spread it on with a credit card.

I use a slow setting resin so once done I leave it over night.

A small detail but it worked for me on the -9a I built, so I have implemented it here. This view is taken from on top of the engine, of the underside of the cowl, and the top of the firewall. I bonded a couple of offcuts off the cowl, to make a little clip to tuck the pins that run over the top of the firewall underneath.

Lots of fiberglass work underway. Both the engine cowls and setting up the gear leg intersection fairings. It also involves a lot of scrabbling around on the floor which I gave up at about age 5.

I have had several batches of fiberglass which are reluctant to set. Raising the ambient temperature has made them harden off just fine but I have never previously run into this before.










It looks slightly suggestive to me!

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.)

I am delighted with the way the canopy is coming together. Like so many things with this project, I think I would be able to do a much better job the second time, having learned the first time. My reservations relate to cosmetic and work efficiency issues only.

First of all I have to say once you have glued your canopy on you become very confident this stuff is not going too let go. It is very strong. The only residual concern I have, is how will it hold up after perhaps 10 years? I doubt there will be a problem, but who knows? There are many advantages that I see for gluing the canopy on:
- the likelihood of cracks I see as much reduced.
- there will be no 'working' between the canopy and frame. The joint should be completely quiet.
- the joint will be 100% waterproof.


There was a Sikaflex thread sometime ago on Vansairforce which was full of posts pointing out that the force to extend a tear in the Sikaflex was quite low. What these doom mongers missed was that before the product tears it has to extend by 500%. Since the strength is 160psi it is hard for the canopy to move.
I had read the instructions from Sikaflex many times (and everything they say should overide anything I write here), but until you work with a product it is hard to fully understand it. So much of what we work with comes in two parts; epoxy paints, Proseal etc. Although you require 3 items to make a Sikaflex glue joint is is essentially a one part glue joint.

Cleaner 226
This is fairly amazing stuff. It manages to find dirt on apparently clean surfaces. It evaporates very quickly. It is unclear if it leaves any magic residue behind once it has evaporated, but it certainly leaves the surface VERY clean. The 10 minutes that you are required to leave it for are, I think, just to ensure it has completely evaporated.

Primer 209N
This is quite a watery black liquid that is brushed on. It can 'flick' off the bristles of the brush so make sure everything near by is masked. As I understand the instructions, thin is better. The purpose of this layer is to provide a bond between the 'glue' and the metal or Plexiglas. The instructions say to leave this layer for 30 minutes minimum before adding the glue. I suspect this is quite important. When you have finished priming CLEAN THE BRUSH. I put it into the same fluid that I use to clean the spray gun. It cleans quite easily. If you leave it to harden I know of no solvent to soften it again.

Sikaflex 295UV
This is the 'glue'. Before I had used it I was quite concerned as to how runny it is. Perhaps the answer to that is, slightly thicker than toothpaste. If you squirt it into a 1/4" wide joint it does not sag back out, even if gravity is working against you. It has amazing power to stick to the primer, but in fact peels off bare metal or Plexiglas quite easily.

I used about one and a half tubes for the RV4 canopy, though most of what I used has been thrown away with the masking tape, or sanded off.

Where I learned a lot was about how to make a tidy looking joint. What I wish I had really understood before I started was this:

1. Decide where you want the Sikaflex to end up.

2. Mask all the places you do NOT want it, with electrical tape. Push the edges down hard.

3. Abrade the ali/Plexiglas with Scotchbright, and wipe the dust away.

4. Clean it with the Sikaflex cleaner.

5. Once this is dry, put a layer of masking tape on top of the electrical tape. (I found that if you put the tape on before the cleaner, the paper of the tape tried to 'hold' the cleaner beyond 10 minutes.) Wait for the cleaner to dry.

6. Prime it. Remove the masking tape. You now have a nice edge to the primer. Wait the period as defined by Sikalex. My understanding is this period is a min of 30 minutes and a max of 2 hours. The max time might only be defined because Sika are concerned about dust contamination. I do not know what the true upper limit is if you can keep the primer free of dust.

7. After the necessary time for the primer to cure, add the Sika 295UV. (If you are good at grouting bathroom tiles, you will find it easy to make a tidy job. I am not!)

8. Quite quickly, you will find the Sika is setting, or at least skinning on the outside. It does this by taking water from the air.

9. Most of the time I removed the electrical tape within an hour, though I now think it is better to leave it at least 24. Have a razor blade to hand as you remove the tape.

10. If some Sika goes where it should not, don't worry, it will peel/sand off if you leave it a couple of days, as long as there is no primer.

11. Leave it a couple of days, then tidy up with razor blades and sand paper.

Because of the difficulty of working inside the RV4 canopy I am working in a 2 stage fashion. First I apply Sika to bond it on, but don't worry about the cosmetics. Then I return after 48 hours for a cosmetic coat. If you are good at grouting you may not find this necessary.

I haven't got this far yet, but I understand that after a week or so, it will sand quite nicely. I intend to complete the fairing around the front of the canopy entirely of Sika.

If you have read this far you are obviously interested in the Sikaflex approach. Go for it! You wont regret it.

With the canopy attached to the frame my time has been spent fitting the skins. Because of the space - 1/8"- between the canopy and frame and a similar space between the canopy and exterior skins I think the whole structure is slightly larger than the typical -4 canopy. Apart from the fact that there was little trimming of the skins to do at the rear, this does not seem to present a problem.

In these pictures the skins are fitted, the spacers for the glue installed. I Would like to find sacrificial spacers that can be left inside the finished article but, to date, have not been able to find anything appropriate for sale in Europe.

The fit of the canopy over the rear fuselage is crucial and if I can get it glued and stable as it currently is, I will be pretty happy.

I look forward to getting rid of all the various layers of tape, masking tape, giving it a good clean and recovering it with a new sheet of plastic. It will be a while yet.

It will finish up as a very strong structure. I would think it is several ounces heavier than the riveted equivalent, but that is a price worth paying if I avoid cracks. It will also be waterproof!

The canopy - see the previous blog entry - is now glued and the clamps removed. Pictures to follow.

What have I learned so far:

1. The -4 canopy is a very difficult shape to work with in order to get a good cosmetic finish. Perhaps my gun is to big! Having said this my confidence has already risen to the point that there is no way I would consider riveting it. I will sort the cosmetics of the bead line later.

2. The cleaner, -226, is a very efficacious liquid. It can find 'dirt' on surfaces I considered clean. Etch primer disappears with the utmost ease.

3. The primer, -209N, is slightly unusual to work with in that you can feel it grip the metal as you brush it on. Beware of one thing, it can spatter and I got one tiny blob onto a small area of Plexiglas that had escaped masking. It cleaned up easily with the cleaner but I would not want to have left it without attention.

4. The -295UV squirts out of the gun quite easily and it is NOT a material that is prone to sag. It largely goes where you put it. Where I found it quite difficult was getting a clean looking line when I finished it with a spatula. My difficulties were compounded by the fact that I perhaps removed the masking tape to get a sharp line, a little early. Removal sometimes had the effect of rippling the otherwise good surface. I can attend to all these issues once the material has cured, plus fill in the areas between the clamps and spacers.

5. Have more rubber gloves than you think you will need standing by. I have no idea but would guess I used 30 or 40 pairs in the space of two hours. They are cheap!

What I would like to know:

My outstanding question is what is the best way to fill in the voids where the clamps were, and how to add more Sikaflex on top of yesterday's Sikaflex? Should I remove old primer and put on new where the old is showing, or should I put primer on top of old primer after cleaning again? Should I put a layer of primer on old Sikaflex after cleaning, when I want to add more Sikaflex. I have not read anything about this yet, nor had a reply to my email to Sikaflex. Anyone know these answers?

Added 20 June '07. I am nearly finished with the Sikaflex now. To answer my own question, experience tells me this. For cosmetic additions, to bond Sikaflex to itself use the primer. If it is a structural bond onto metal or Plexi, remove old primer and add new.

Finally, in case you have not already found the main link to previous offenders experience start here. http://www.matronics.com/wiki/index.php?title=Gluing_Your_Canopy&redirect=no

The canopy has been trimmed with 1/8th inch spacers installed, to allow for Sikaflex in the joints. Compared with the -9A I built, there is very little excess material on the RV4 canopy. It would not be a problem if I planned to rivet it on, but since it is to be glued, I had to be very cautious in the area to the left/right of the pilots shoulders.
A final test fit on top of the fuselage seemed appropriate. In fact I have still not trimmed quite enough off at the rear of the canopy, but that is intentional. I intend to do that when the structure is glued together, in order (hopefully) to get a very tight fit between the plexi and the fuse skin.








I have made a 'gallows' to hang it on while I work. All the other RV canopies allow you to walk in at the end for gluing, but the -4, being one piece requires you to have it held quite high if you want to work on it the right way up. At this stage I am unfamiliar with the properties of the Sikaflex so in case it sags feel I will have much better control with it this way up.

NB AS you can see in this picture its a gallows with a heater! Got to keep the victim warm!

(As always, you can get larger pictures by double clicking on them.)


With a lot of encouragement to keep tweaking the front bow, and not split it, (from VANSAIRFORCE members), I have finally made the frame fit reasonably well. The latch mechanism is mostly complete, though I still have to install the UHM blocks. It becomes a lot easier once you realise there is no reason why the push rods should not be slightly bent.












The canopy frame needed a little grinding to allow it to fit over the roll bar in several places. You can see an example here.












I recently had the role bar powder coated. Needless to say I also had to cut a part of that away as you see in this picture in order to allow the canopy bulkhead to come fully down.
















I have used the spring from the RV9A release mechanism, rather than the one VANS provided for the -4. It is a similar stiffness, but the slightly greater length seemed preferable. There is so much friction in the system at the moment that it is quite incapable of closing the mechanism, though I guess its purpose is to stop it from wandering open.

Now I need to think about VANS safety latch, and how to fit a gas strut.

As you can see here, I have had to split the central bulkhead. I guess I am building an RV4-WB (Wide Body).

It was interesting to note how much residual stress was in the structure. When I cut through, the two parts sprang far apart.


The canopy bow is sitting somewhat low. I am wondering if I should also split this. It would mean (I think) matching the curve of the bow, and the instrument panel, a much easier task.


Otherwise, it is all starting to fit pretty well.

Its time to start fitting the canopy frame. In the pictures that follow I have done little work yet, but I find myself wondering If VANS sent me a frame for a Wright Flyer or Airbus 380. it does not appear to have a whole lot to do with an RV4!

This picture is of the rear right corner. Here the fit is not too bad.




This is left rear. The frame leaves a significant space. Somehow it will need bending back without changing the fit on the opposite side. The bow was too narrow but it was quite easy to pull that out an extra 3/16th or 1/4 inch.





This picture is front left. The bow as you can see is not high enough in the center and needs to be pulled back a little.




This is front right. You cant really see it in the picture but the bow is sitting so low it is blocking usable panel space. It is also too far in, so the corner has to come out, and up.







This picture shows the other problem. The whole structure is about .25" too narrow. I will have to split the central frame; the plans allow for that.

I will possibly also have to split the front bow which is more scary!
As you can see here the front part is bent in much too tightly and sits too low.














I will be pleased when this all matches up because it would be an expensive part to damage. I see a difficult week ahead.

There has been some interest in the larger than normal tyres I am using, so I thought a couple more pictures were appropriate. While my whole aim is to handle poor surfaces better than the standard tyre, there is a limit as to how much I want sticking out of the bottom. In order to control this I have used a narrower spacer between the top of the tyre and the fairing. The space is of the order of 3/4", so I will have to keep an eye on the mud build up in there.










This picture shows the tyre inside the fairing. I am far from finished but the fairing is in position wrt the tyre. It shows just how much is sticking out. From memory of building my -9A it looks less once the weight of the aircraft is on the wheel.

I will run the tyres at a lowish pressure also to increase the flotation.

My unorthodox approach to getting the spat aligned is working well. For me the difficult bit was deciding where the centre points on the spat were. Aligning them with the yellow strings you can just see them in this picture, was easy, once I had that. I know they are pointing in the correct direction, unless gravity is having an off day. Statistically unlikely. I also know the engine frame is aligned to within 0.1 deg with a digital level.

The other big advantage is that I have a much better view from underneath, to see the tyre spat junction, for working out tyre clearance. [I need to make a nice job of that so the RV6,7 and 9 drivers see a nice job as I shoot by overhead! :-) ]



This is where the day ended. The spat is on. The next job is to drill the holes between the front half of the spat and the U-810. Once these are done it will be all locked in place pretty well with clecos. Then I will cut out more clearance for the tire.

I will probably then turn to the left wheel, since I cant do much more to this one before I mix up some glass resin to build reinforcing pads inside the spats.

The shape and texture of these things makes them appear to be alive at times. They can be quite hard to hang on to. Foam rubber on the floor to cushion them each time you drop them is useful. The other learning point is don't waste your time trying to write / mark directly onto them. Stick masking tape on and write on that.

When I built my -9A, I found I spent a lot of time on the floor trying to align the wheel spats and fairings. I was never designed to work like that, and I did not find it a particularly easy task. This time I am going to try the following.

If I place the engine frame in the horizontal plane the wheel fairings need to be exactly in the vertical plane. It then seems relativly easy to define the vertical with a plumb bob, so I know how to align the wheel fairings. I have never heard of anyone doing it this way. I wonder if there are any pitfalls. I think I will ask on VANS airforce.


My task is made a bit more complicated because I am using oversize tyres. These are 380x150-5. It is 15" dia and 6" wide. I am not the first to use them in the UK. Clearly I will have a little tyre more sticking out of the bottom, and will loose a couple of MPH, but the ground contact area will be much increased enabling my -4 to handle soft ground much better. Nearly everywhere I land is grass so it will be a significant advantage.

Assembling the items on the axle seemed more complicated than the last time I did it. It ended up like this. I was pleased to have a Supercub, with Cleveland brakes, in my hanger just outside the workshop door. VANS plan leaves a little to be desired on this point. I think the second one will be easier.

At the close of play today (that is a cricket term for Colonial readers) it looked like this.
I guess I need to tidy up! Never my strong point.

Together with the 'Finish Kit', I have ordered Sikaflex products from Jamestown Distributors, since I think I will glue the canopy on. Nearer the time I might bottle out, but others have reported excellent results with this approach. If you want to see more information on this take a look at this wiki

My reason for going this route is that it always seems to me that the drilled holes are always a risk. I prefer the idea of continuous attachment and also feel it should be more waterproof. Like most RV my -9A leaked around the frame.

I ordered the Finish Kit this week. It is all standard stuff with one exception. I asked Barb at VANS to delete the tires that come with the kit. The reason for this, as I have mentioned elsewhere, is I fly of grass and it can be soft in winter. You can see the strip here. , or if you prefer, and have broad band, land on it http://www.youtube.com/bananatime2 .

A few builders in the UK have fitted a slightly larger tire into the standard wheel spat.

The tire VANS provides is a 5.00* 5 and is 13.5" dia and 5" wide. There is another tire that fits the same 5" wheel.
From Spruce you can buy a 380x150-5. It is 15" dia and 6" wide.

My local aviation tire dealer tells me the VANS tubes will fit the larger tire.

Clearly this larger tire is not going to fit so well into the spat, but I think it is worth a try. The width alone means there is 20% more contact area to spread the weight.

In two years or so I will tell you how it all works out!

Postscript 24th Oct '06

The bigger tyres weigh 5lbs 14oz and the standard VANS supplied ones 4lbs 11oz. The tubes are common to both. So the total weight penalty is a total of 2lbs 6oz. Though I dislike adding weight, this seems acceptable for the benefit of being able to roll on soft ground.