Twisted: Week 203 - Plenums cont.

Hours to date: 1888.5

Good progress this week.

I'm now taking a day off during the week (when I can) and this seems to help with moving forward. Honestly I've been pretty frustrated with the slow speed of progress over the build of this kit but the end is in sight now and I'm redoubling my efforts to finish it by early next year. Hopefully it will be ready for paint by April/May. Then final fettling and test flying in June/July is the plan.

Onto the plenums.

After sanding the micro I still had to add a little body filler to fill in the pin holes and gaps in the micro. Once that was done I used duct tape as a release.

Then followed a tricky layup which seemed to take forever. 5 layers of carbon were used and laid up on plastic then cut out to a neat shape. My big mistake was not allowing for the fittings close to the edges - which stop the carbon from laying flat against the sides. If I were to do this job again I would remove anything close to the top edge. But it was too late as I didn't have access to the inside of the baffles as the foam plug was there. My mistake for not thinking far enough ahead again.

I find things stick better when you apply a coat of neat resin to the plug early on in the layup - then by the time you are ready to put the carbon on the resin has cured a tiny bit and become quite sticky.

As it turns out things worked out pretty good anyway and only the back area is not great - although it will still seal air tight with a good application of RTV.

The duct tape release worked well and with a couple of plastic wedges I was able to remove the plenum tops with no trouble.

Slow steady pressure is the idea here - don't force things too much.

As you can see below the plugs came out in one piece from the baffles - so if anyone wants to borrow these to layup their own plenum tops then give me a shout. They will save you at least a days work.

All that was left to do was trim the plenum tops out and then fit them with 4mm nut plates all round. I used 14 on the Starboard one and 13 on the Port one. The odd spacing is due to obstructions on the inside and or access from the outside to drill. There will be quite a lot of air pressure inside here at VNE so it's best to make sure it is properly secured. I read a forum in the USA about building a plenum for an RV8 and the forces measured were very high for the plenum. If I remember it right it was over 200 lbs at 200knots. Just think what it does to the top of your cowl if you only have baffles - no wonder they are so inefficient.

The 5 layers of carbon is just right - very strong but with just a little flexibility so the nut plates pull the edges in tight.

Next job is installing the top instrument panel and finishing all the wiring.