Jur's RV7 Aircraft Factory
4267 hours and counting

All right... the edges are masked with double 3M electrical tape, the canopy slider received 3 to 4 coats of wax and some additional PMA liquid plastic so it won't stick to the front. (would be embarrasing not being able to get back into the cockpit wouldn't it ?) The additional buildup up flox on the sides worked well. The fillets in the front are ready, gently sanded and dusted off and degreased. The slider, windscreen and skins are well protected and masked. A centerline is drawn do indicate the initial placement of the first narrow pieces.
I think I'm fully ready for laying up some fibreglass cloth... No kiddin... 

I got some good tips from an friend who used to work in epoxy repair shops. He told me to layup the dry cloth directly on the plane and wet it out on the spot instead of wetting it on a plastic on the workbench and transferring it wet to the plane. Both work but the wet transferring method makes a mess of your hands. Everything starts sticking right away. Wetting on the plane allows you to keep your hands much cleaner for a longer time. Once the cloth is wetted out by applying it with a brush or roll, use a heatgun  from a distance to warmp up the glue. Don't heat it !, just apply some warm temperature at a distance and the resin will start spreading itself much more easibly into the fibreglass cloth. You can also easily spot excess epoxy in this way which I then roll off with a roller.

The image below shows positioning the cloth on the front of the windscreen I had first wetted out the surface and then positioned the dry cloth. Once it's in the right place, start using a brush and dip additional epoxy resin on the new piece. Make sure when laying down pieces that you don't have overlaps (this will create bulges when dried) But layers up as precise as possible..

With the part wetted out, Alain held the heatgun at 120degress C high up and moved over the pieces. This generates a nice warm but not hot flow of air over the piece. As I see it saturating the cloth, I use a epoxy roller door press is on (to avoid trapped air bubbles) and pick up the excess epoxy resin.

As it's a sticky job, I didn't take a lot of pictures during the proces. We layed up 4 layers, each time going 3/16 wider on either side. Be carefull to keep centering the higher pieces over the lover ones so you create a nice smooth transition by the staggered layers to end up with 1 layer  on the sides.
When 4th layer was on, I cut peel ply and covered the hole thing with it. The peel ply has a triple purpose. 1. it sucks up some of the excess epoxy from the top layer. 2. When hardened and pulling the peel ply off, it creates a rough surface on which you can immediatly start laying up the next layers without need of additional sanding. and 3. very important, it keeps the wet layers in the desired shap. You will see that the parts that curve a lot - especially around the top rollbar - tend to pull up de edges of the cloth and it's hard to keep them down. Once the epoxy becomes more sticky, it's easier to push it down again with a brush. Once it's down, put peel ply over if and wet the peelply so it sticks well to it's surroundings. This ensures that the cloth will not curve up again and stay nicely in place.

 Next day, I removed the peel ply. I'm satiesfied with the result so far. This is ready to receive 4 more layers of fibreglass cloth.

The world these days is full of Artificial Intelligence LLMs (large language models) and AI tools that have become available to the everyday user. Knowledge that used to be hidden in libraries and dusty books has now become available and is easily accesible to the average person, which is certainly a positive thing. Most people's knowledge of AI is limitted to the usual chat prompts.

Lately, I have been experimenting with more advanced usage, and I wanted to share my experience and knowledge with other builders as I think it could also benefit their information research.

A word of caution, which is valid for my method as well as for simple prompting using any AI chat engine: Always cross-check the response you receive from the AI model by visiting the referenced websites or sources before actually using the information in the response on your project.

LLM AI tools do "hallucinate". Hallucination is a technical term to indicate that if AI doesn't find a definite answer to your question, it may sometimes invent information based on other - probably non-relevant - sources it identifies. This causes the user to read and rely on false information. Always double-check the responses you receive, certainly if you use them for your aircraft project.

I have been playing with different AI models to see how AI can help me look up information from the web and guide me through the list of manuals that keeps getting longer and longer as I progress in the building process.

For a few months, I had been looking up information through ChatGPT with prompts like, for example: "What is the torque value for an AN924 jam nut on an AN833-6D fitting for 6D fuel lines on my RV7?" It usually comes up with a good answer as it can find the relevant information in torque tables online. It gets more difficult if the information is not publicly available, like with information in proprietary Van's builder plans and manuals.

It would have been useful if AI could actually search my Van's PDF documents and DWG plans as well as other technical install manuals all at once. I discovered the use of "projects" in Google Gemini but soon hit the boundary of how many files you can upload with the free plan of Gemini. Then I discovered Google's Antigravity app. Antigravity is very similar to Gemini, but it is more oriented toward projects and coding assistance and it also uses projects and skills. The main difference seems to be that Antigravity can also work on local folders and the information that resides in them when it searches for information. And the amount of files in the folder does not seem to be limited.

Last days, I have been busy figuring out how to cut the epoxy cloth in such a way that it fits as good as possible in order to avoid a lot of sanding once it's cured. As mentioned in the previous post, I have decided to lay up the glass permanently on the airplane such as it is described in the Vans manual. There are other methods where the windscreen is removed  after laying up, sanding and finalizing it off the airplane and then using sikaflex to attach it such as described in a kitplanes article (Easy slider: part 2) by Larry Larson.
If you go for the Vans method, the layup will have to be more accurate as all sanding can only be done on the airplane, very close to that beautifull PMMA windscreen. 

I decided to make templates just like a tailor would do when making clothes. The Vans method describes starting at 1/2" in the center and gradually increasing the width up to 8 layers by cutting each layer of cloth 1/4 inch wider than the previous. That would bring you to 2 1/2" wide. My masked 3M lines are more or less 3.2" appart. The plans state a distance between 2.5" and 3.5"is fine.
So I have increased the step a bit. Increasing by 13/32" for the first 4 layers, then by 3/8 on the last 4 layers. This will increase the width on each layer by 3/16 on each side, creating a nice step up to 3.2".

The final layer is the most critical one as that one will have to fit as good as possible between your electrical tape masking lines.
The best way I could find was to use plastic sheet which I taped to the windscreen and then used a red sharpie to draw the contours of the tape to the plastic sheet. In the image below, you can see the sheet over the side of the windscreen and upper top fuselage skin.

Below another shot of a plastic sheet to create a template by tracing the exact location of the windscreen fairing

Then I cut out the shape from the plastic and layed it on thick paper and transferred the shape on to the paper. Here you can see the two corner pieces and two curved front pieces.
Then cut out the paper shapes.

Now that all pieces are cut for the final layer. I copied the paper shapes 8 times full size.
Put layer 8 on the side and start sizing down the other paper copies per layer, stepping down 3/8 on each template. Pay attention on which side you need to transition down in width. (eg: on the top of the fariring over the roll bar, you need to transition down to the front but can remain full thickness over the rear as this part will be trimmed down later. You'll have to think about this when trimming down the paper templates. It's a job that requires patience.

All templates are finally done, 72 unique paper templates ready to be transferred to epoxy cloth.

Next day took it all back to the garage and started cutting out the templates from a roll of epoxy weave.

A circular cutting knife works best here. The direction in which you cut the cloth is not important for the windscreen but you'll have learned by now that cutting the cloth at different angles causes different degrees of stability in the cloth and can cause the fibreglass cloth to fray.
I cut out 4 layers and next step will be the actual lay up work.

Milestone day ! 
This is one of those days that you know mark the timeline of building your airplane. The moment you hang the engine in the engine mount.
After many days of thinking about missing any things on the firewall, I came to the conclusion that this is the right moment to hang the engine and move on to the firewall forward work. There are some more things I need to do on the firewall, but it's not possible to be sure about the exact location to drill large holes in the firewall until I can actually evaluate the position with the engine in place. i'm thinking of the mixture and throttle cable and alternate air cable. Other than those, I'm pretty sure everything on the firewall is in place.

The same thinking goes for the rear of the engine case. Make sure the 45° restrictor fitting for the oil pressure is mounted in the engine case prior to hanging the engine. It's almost impossible to install this once the engine is on the engine mount. Mine was already installed by PMM during engine assembly. While you are at it, also install the other oil cooler fittings in the engine case (in and out). These can also be done later but it's easier now.

First step was to remove the safety straps that held the engine to the wood pallet that was used for transport. I want to keep track of how this was done as this engine is a brand new engine that has not yet been on the test bench. When all is ready, I will need to unhook the engine and bring it to PMM Wingservice to have it running on the test bench for a first time. This has the disadvantage of extra work on removing the engine and all connections again and having to do it again after it has been run. On the other hand, the major advantage is that I do not have to worry about corrosion and idle time of the engine as it has not yet been running. The cylinders are as if they would be in a stock location on a bench waiting for an engine. There has been no movement of the cylinder heads on the cylinder walls and everything has an oil film on it as delivered from Superior Air Parts. Whether building takes me another 3 years or just 1, it won't matter. I'm gladly willing to take that extra work knowing there is no pressure.

The engine was protected well on the front and rear crankcase and supported in the front under the front with some wood block supports. I'll have to keep all this in stock so that I can re use it in the same way when I bring the engine back to PMM.

Using the engine hoist, we pulled it up, removed the pallet and moved it over to the front of the airplane. Alain helped me on this task to keep the engine in position. It's best having some extra hands around when you do this as the engine is heavy and the bolts are not always willing to go in as easy as you think it would. 

The last part of the moving is the most critical as you don't want your magneto's or fuel pump to bump into the engine mount. Having one person moving and another one guiding the engine is no luxury.

Also notice I leveled the airplane in flight mode. This is much easier to position the engine than if it would be sitting on all tyres which would require you to position the engine at an angle. This leveled way makes it much easier.

I found some documentation online from someone who did this before and described the process. I studied this carefully and upfront, had a close look at the barry mounts and dyna bolt set. You can read it following this link https://www.myrv14.com/buildlog/20150917/Engine_Hanging.pdf. Vans Aircraft also has some drawings available which are not part of the standard plan set that you receive with the kit. 

Study the plans carefully, the barry mounts have to be positioned so that the engine rests on the compression side in the bottom and the compression side in the back on the top mounts. The compression barry mounts are the ones that have a step in the rubber. The non compression ones don't have the ribble on it and look like plain rubber. If I remember well, the non compression ones also are a little larger. Also take care that the washers are in the correct locations. The barry mounts come with one big washer in the box. It's good to assemble the order of all this before starting to move the engine and have thing prepared well. I colored the position of the large washer red in the picture above.

There are 2 lengths in the dyna bolt kit. 2 x AN7-43A and 2 x AN7-44A. The longer ones go on the bottom side, the shorter ones go on the top. The difference is not much more than the length of one of the washers.

Start with the 2 top bolts. The first one is very easy... tighten the bolt but don't torque it yet, you'll probably have to loosen them again working on the bottom bolts.
You do need to tighten the first so that the barry mounts compress allowing the other hole to come in line with the engine case. Remember this is a dynafocal mount, the bolts point inwards. If the bolt is not tightened enough on one side, it's impossible to insert the second one. As you tighten the bolts, the barry mounts compress and also position themselves in the engine mount. That's important.

What I found very annoying is that you can't put a socket on the bolt head as the engine mount is in the way.  I used an extension on the wrench but that didn't make it easier.

The engine sometimes needs a bit of persuasion to get it in position :) Although I don't think this did much. Found out later it's more important to tigthen the other side and use the engine hoist to lower or lift the engine a bit in order to get a bolt in.

The large washer goes between the compression mount and the crankcase as a spacer for the bottom mounts. On the top mounts, I have put that washer on the compression mounts under the bolt head as you can see in the image below. The image has both top bolts in place and tightened.

From there on, things went less smooth and it took about an hour or 2 before I got the last bolt in so I did not take any more pictures until it was done.

I'll try to describe the further process I took.

As both top bolts were tightened, I lifted the engine a bit using the engine hoist. This allowed me to slip the barry mounts between the case and the engine mount. Don't forget the large washer between the barry cookie and the engine case. Don't forget the compression side of the barry mounts is against the engine for the bottom mounts. Then I lowered the engine again and after some wiggling I was able to put the 3rd bolt in. I did have to loosen the top bolts a bit though. 

The fourth bolt is the most difficult one. Looking with a mirror through the hole there was no way the bolt would go in. After a lot of moving up and down, I finally discovered my problem : the washer between the barry mount and the engine case was not aligned and the pressure on it is high enough that it makes it hard to move it. After lifting the engine a bit and tapping on it, I could get it more or less into place. 
A second trick I used was to take an old bolt which was smaller in size and grind down into a guide pin. Once I could slide that smaller bolt in, I was able to wiggle it around in order to get that washer and the engine hole into alignment. I put some grease on the final bolt shank and finally was able to put it in with only very light tapping of a rubber hammer.

I was feeling relieved as I bolted the final nut on that fourth bolt.

As final step, I torqued the bolts. These are AN7 which take 450 - 500 inch/lbs. I used the middle value of 480 inch/lbs. The engine will still need to come off as mentioned earlier but the position of the engine is very important when installing the cowling so I torqued it to the final value.

Took some pictures of the plane with the engine in place. This surely is a big milestone and is a "feel good" moment during the build.

Happy camper...

As I had some time left, I took out the fuel throttle body. This comes with a plastic spacer.

The orientation of the throttle body was a bit of a mystery at first but soon figured out what side was the throttle lever and which side the mixture. 
In the image below I installed it on the forward horizontal induction air intake at the cold sump of the engine. In the image below, the throttle lever is the gold colored arm.

Finally I covered the intake with some paper and masking tape in order not to get foreign objects entering the engine.

End of a productive day was off course celebrated with Alain with a good strong Belgian HQ beer.