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Sky Design Engineering Wheel Spats – Part 1

So why have we chosen different wheel spats … or wheel pants as our US cousins call them?

The RV14 is designed around 5.00×5″ wheels, which is fine for tarmac and well prepared grass. But we enjoy flying into UK grass strips throughout the year, so think 6.00×6″ wheel size might be a good option.

But of course this means that larger wheel spats will be required. Well it so happens that Sky Design Engineering in the US have produced an excellent solution, offering a carbon fibre spat kit which fits the RV14 and 6″ wheels.

Since here in the UK our Light Aircraft Association (LAA) is responsible to the CAA for kit built aircraft, I had to officially apply for modifications, for both the wheels and spats. Happily they have agreed these changes, subject to flight testing, so we’ve got the green light to go ahead and install.

Of course opting for larger wheels/spats has its advantages and disadvantages …


… the main advantages being larger wheel/ground contact area for better operational robustness on softer grass strips …

… and Sky Design’s spats offer much more ground clearance both fore and aft.


The spats are larger, so maybe not as pretty as the stock Vans. But having seen this picture of a RV14 with them fitted, we reckoned they look just fine.

They’ve been designed by Ken Krueger (chief engineer at Vans during the development of the RV14), who has done a great job combining functionality with aesthetic appeal, keeping in mind aerodynamic efficiency.

But being realistic it’ll probably increase cruise fuel flow a small amount.

All aircraft design is a compromise, and we reckon this is one worth making.


Here is a picture of the Vans kit spat, and the larger Sky Design version.

I weighed both spat/lower fairing combinations and discovered that the larger Sky Design version was a few grams lighter than the Vans version … thanks to the carbon fibre.


The kit of parts is of a nice quality, and clear instructions are provided.

The aft portion of each spat is supplied in two pieces which have to be bonded together.


The kit includes milled glass fibers, microballoons, and graphite powder which is mixed with epoxy resin to bond the two halves.


The halves fitted very well, with minimal sanding/filing of the joint required.


The kit includes attachment brackets, so the Vans equivilent components are not used.

After priming/painting I attached the nutplates.

The four circular components are standoffs … used on the inboard bracket to provide clearance around the brake calliper.

The inboard bracket is orientated rearwards, different from the Vans U-01418 INBD Wheel Fairing Brackets which face forwards.


There is a cutout guide for the wheels, but until I’ve received the 6″ wheels back from Beringer I’ve just removed a small portion.

I did this because it’s easier to gently flex the FWD/AFT spat components when fitting them together.


The FWD/AFT spat joint is adjusted by sanding to provide a consistent paint gap.


The screw holes and countersinks are folded into the carbon fibre … a neat touch : )


It’s a quick job to rivet on the attachment nutplates …


… since the spats arrive with the rivet holes already in place. They just needed a small trim with the countersink bit to ensure the rivets were completely flush.

As can be seen in this picture, the flange to which the nutplates are riveted is not carbon fibre. Aluminum corrodes readily when in contact with carbon, so wherever an aluminum part is mated to carbon, a layer of glass fabric is used to isolate the aluminum from the galvanically dissimilar carbon.

Also the cadmium plating that is typical of carbon steel screws is extremely prone to galvanic corrosion when placed in contact with carbon, and for this reason stainless steel screws are used exclusively.

They are also #8 size, making them more durable when removing/inserting with the #2 Philips bit.

All in all, nice attention to detail.


The Lower Intersection Fairings require a small trim.

Because of the shape, these have the textured layup cloth on their outside surface, which needs more work with sandpaper to smooth.


I added a small area of microballoons to fill an undulation in the moldings.


Filler in the joints and other blemishes.


The carbon fibre on one edge hadn’t formed correctly, so this was filled with harder microballoons.


The surface of carbon fibre is covered with pinholes … I need to discuss with my painter how best to fill these.


I shall have to wait until the wheels arrive before fitting the Lower Intersection Fairings to the spats.

So this is about as far as I can go with the spats whilst waiting for the Beringer 6″ wheels, which I’m hoping will be delivered mid December.

I had purchased Beringer 5″ wheels/brakes, but they’ve been very helpful and have agreed to swap them for the 6″ versions.

They are also making slightly longer axles which will satisfy the Sky Design bracket geometry.

See Part 2 here …


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