RV-14 bottom cowl misalignment with air filter frame cover

Hi Guys
Our RV-14A bottom cowl has a misalignment with air filter frame cover and the bottom cowl air intake scoop is too low, this is causing issues with fitting the rubber seals. I have linked a photo of our issue and the other side not in the photo is the same (ie its symmetrical and not twisted).
Our cowls have been fitted as per the plans and the gap around the spinner is perfect.


It looks like a few other builds has this issue from photo's on their blogs but I have not seen a description of how they remade this area with a mix of cotton flox with epoxy resin. Anyone also have this issue and please share a few photo's of your repair?

It is hard to tell since only a small amount of the spinner back plate/cowl interface is visible in your photo, but it looks to me like your cowl is a little lower than nominal.
This might be because the top cowl is not installed (this often lifts the lower cowl a bit)

As designed, following the plans exactly will result in a finished installation that has the cowl a tiny bit (maybe an 1/8") high relative to the inlet ramps. This misalignment disappears after the engine settles in and sags in engine mount vibration isolators.

rvbuilder2002 said:

As designed, following the plans exactly will result in a finished installation that has the cowl a tiny bit (maybe an 1/8") high relative to the inlet ramps. This misalignment disappears after the engine settles in and sags in engine mount vibration isolators.

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Scott, I'm FAR from this point of construction but I want to try to clarify what you're saying. It seems that you're saying the cowl will start around 1/8" high but that the difference will go away as the engine settles on the mounts. If the first part of your statement is correct, the problem would get worse.

SabreFlyr said:

Scott, I'm FAR from this point of construction but I want to try to clarify what you're saying. It seems that you're saying the cowl will start around 1/8" high but that the difference will go away as the engine settles on the mounts. If the first part of your statement is correct, the problem would get worse.

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No, I said it looked like his cowl was a little low (I meant in the context of even more than intended).... and that would equate to the spinner being high.
If the instructions are followed, it will result in the cowl being purposefully mounted with the spinner about 1/8" high.
It looked to me like the one in the photo is probably closer to double that, but I could be totally wrong since not much of the spinner is shown in the photo....

I have been working on the cowling this week. With the top cowling on my lower inlet matches the baffle quite well. The plans call for the use of two washers under a piece of angle that is cleoced to the top of the cowling. The angle rests on the spinner back plate and establishes the height of the cowling relative to the engine/prop.
Over many years and numerous aircraft I have not experienced a lot of engine sag with my rockets. I use the same isolators as the four cylinder engines and one would expect a bit more sag with a heavier six cylinder engine. After about 600 hundred hours on my current rocket I did raise the spinner by adding a large washer under the bottom engine mounts on both sides.
On the ground the engine is hanging from the engine mount. In the air the situation changes as the engine is now pulling forward. This raises the spinner and I do not like to see the spinner above the cowling in flight. We can set the spinner so that everything lines up properly on the ground and looks pretty but if we really want the alignment to be correct in the air then have the spinner a smidgen low on the ground relative to the cowling.
Keep in mind that I am always going for ultimate speed/efficiency rather then appearance. It takes a lot of time and money to get both!
Remember at the beginning I mentioned that the plans called for two washers to be used for vertical alignment of the cowl vs spinner; well I used one washer as I wanted the cowling to be a bit higher. The difference is only 0.063 and would not explain the alignment issues of the original poster.
My advice would be to follow the plans meticulously if this is your first aircraft. The plans are beautifully done and my firewall forward time has been dramatically cut with the excellent firewall forward package. The baffles are easily the best I have ever worked on and time was measured in hours rather then days.

If working to that level of detail Tom you should be concentrating on shimming to the right.
From my experience P-factor pull causes a lot more lateral displacement than vertical.

To the original poster. Following the plans has you eventually making an inlet change in the lower corners of the bottom cowling either side of your picture. There is a bit of measurement involved, a template provided, filling, sanding etc. In your case I would just cut back the bottom inlet an inch or so and pour a new one that perfectly matches the baffle surface and the corners at the same time. It will not be a lot more work then changing the corners.

rvbuilder2002 said:

If working to that level of detail Tom you should be concentrating on shimming to the right.
From my experience P-factor pull causes a lot more lateral displacement than vertical.

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Scott, wouldn't P-factor be most pronounced during climb. In S&L flight P-factor would be very small, if any at all, affecting engine/airframe alignment?

jeffw@sc47 said:

Scott, wouldn't P-factor be most pronounced during climb. In S&L flight P-factor would be very small, if any at all, affecting engine/airframe alignment?

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I was joking.... note the

A hard climb does produce a significant amount of lateral movement, but you are correct. P factor is not a factor in high speed level flight.

Front cowl mod

While helping Alan fit his cowls to his new RV14A ,we also experienced the low cowl /high engine problem.

No amount of jigging would allow the front cowl seal to transition to the front baffle assembly.

Our solution was to fab a thin piece of .063 to the shape of the lower cowl inlet and use 5 x #6 screws to secure it to the lower cowl.
Nutplates had to be fitted to the lower cowl and Micro was used to make the transition smooth. The rubber is attached to the .063 with Sika.

The cowl rubber now sits flat and firm against the front baffle.A nice benefit of this mod is that once removed ,lowering the cowl straight down for removal is a lot easier.

We followed the plans exactly,so I am not sure what we could of done differently.
I will say that the RV14 cowl/baffle install is substantially easier than the RV-10 and credit due to the Vans engineering team for making such a comprehensive kit.

Our repair for this issue.

Thanks for the feedback and questions, hopefully the following makes sense.
I agree its great kit and I'm not complaining.

Here's a photo showing our layout, it was as per the plans with the piece of aluminium angle fitted on top of the spinner with a washer to allow for future engine drop due to mounts settling.


And here is our new repair done this weekend, we built up the inner surface with flox and epoxy then sanded the fiberglass back on the inside.
Note the pink area is the original fiberglass height and the white area is the extra flox mix we added and shaped to match the original contour.


I am not sure if this reduction in the intake will affect the flow of air for the engine, any thoughts on this?

And finally here is a photo of the raised area with rubber inserted to check, looking good now.


The Vans plans call for using a flox and epoxy mixture to fix the sides so we used the same technique and mix to raise the cowl scoops, I believe using fiberglass is not good as the edges of the glass may show through the paint (but I've not seen this problem).

The plans method of matching the lower inlet corners have you taking measurements and then using an aluminum strip clecoed to the bottom cowling the right distance away from the curves. The gaps are filled with flox and this will give you the curve you need to align the baffle seal. The excess original glass is then filed off.



I took a different approach and removed the lower outboard corner. A piece of waxed baffle seal material was clamped where I want the final piece to go. Then I did a glass/flox lay up over that to get the shape I wanted. The cowling will be removed and the inside of the layup will be sanded and then glassed over to make a good bond.



Personally I felt that this was a bit easier to do on this particular cowling then what the plans call for. The inside bottom corners are pretty good and I will do a modified version of Van's method for them.
The main reason that I used this approach is that I did not like the inlet shape. The outboard inlet is converging, meaning that it is pointing inward, which is not desirable on an inlet. I can now have the inlet pointing directly aft in line with the airflow. When I finally get the bottom corners the way I want them I will remove the upper corners and glass them to match the lower corners.
It sounds like a lot of work but really it is an hour a day for three or four days to get these inlets the shape I want that also puts the baffle seal in the correct position.