Sunday, 28 February 2016

Week 237 - Cowling Part 12 + seatbelt extensions

Hours to date: 2274.25

A challenging few days this last week.

First off my attempt at PVA release on the molds came out really bad on the first go, I was too greedy with trying to put down too much in one pass and ended up with runs of PVA. 

So I waited for it to dry and peeled it off - start again!

The second time I was also more careful with making sure the mold was absolutely clean and free of fingerprints or any other contaminate as another problem I found out the first time was any kind of contaminate will make the PVA not stick properly, one fingerprint can ruin the whole thing.

It turned out good the second time so it was time to cut out some carbon and get laying up.

I had a bit of a nightmare here with the layups. Not exactly sure what I'm doing wrong but maybe I should have put each layer of fabric in the mold and wet them out one at a time. As it was I did my usual method of wetting out every layer on a plastic sheet template first then cutting that out to shape and putting the whole thing in the mold in one go.

Doing this I found the carbon as one complete 4 layer piece did not want to conform to the shape of the mold very well - certainly this was the case in the front area where there are a lot of tight curves to go around.

Using a roller and some more resin I was able to finally get it to conform and stick to the mold.

The next day I noticed that a few air bubbles had appeared - too late to do anything about that now - I will have to fix it up later by filling in the low points with micro. Not ideal but as I've invested £300 worth of carbon and 2 days of work into the parts it will have to do.

As you can see the two halves are laid up separately - then trimmed down to the edge and finally I will bolt the two molds together and then reinforce the join from the inside - more about that next week.

The other little job I got done was building up the seatbelt blocks underneath the cell - as you may remember I found my seat belt did not tighten up quite enough - so I've extended the blocks underneath by about 40mm so this should be more than enough to take out the slack.

I found the lap belt to be much too long to be honest - I don't know why it is supplied that long - it could be easily 50mm shorter and still accommodate all pilots no matter how fat!

Two molds bolted together

PVA release done - second time lucky - and a centre piece being laid up for the front of the cowl.

Wetting out using a paint roller for the resin - much easier and faster than a brush.

Top half done - what a nightmare!

Onto the bottom half now.

PVA release has shrunk to a nice smooth finish here.

Lower half done - even more of a nightmare - had to cut it an overlap in several places.

Top half trimmed out and peel ply removed - a few air bubbles here and there - not good.

Seat belt block extended with carbon - just needs finishing with a thick layer of resin now to make it smooth.

Friday, 19 February 2016

Week 236 - Cowling Part 11

Hours to date: 2239.25

What a great day yesterday.

The Tangerine Dream took one step closer to becoming The Tangarine Reality.

All went well - the molds released really easily. The PVA really does a good job.

I only had to separate the parting planes on both sides and then the bottom part (top half of the cowl mold) fell off onto the floor all by itself. The other half required a bit more effort but released easily once it was started from the edges.

After a bit of sanding of the sharp edges and a little Dremel work to get rid of the gelcoat that had spilled out here and there it was time to give them a clean. I just used a hose with low pressure and then a sponge with warm water. Lucky it was a nice day yesterday and I was able to leave them in the sun to dry out.

They just need waxing and PVA release and they will be good to make a part from.

Then came the messy job of getting the plug off the engine. I was very pleased to see that there were no leaks at all of the expanding foam onto the engine area.


A little job I have been meaning to do for some time came to fruition yesterday too. Making up an ID plate out of stainless steel. This is another UK CAA requirement (for identification purposes in the event of a crash and fire). It will be bonded in the cockpit area somewhere - I haven't decided where yet.

Hopefully this weekend I can start to make a cowling...

Molds all done - but will they release?

Bottom (top) half comes off easily.

PVA release peels off like a skin.

After a wash - drying in the sun

Tangarine - yeah baby!

Now to get the plug off the engine.

The red lines show the 'Natural nozzle' created by the tapering fuse and my straight edge cowl design. This should accelerate the hot air out the back a little and regain some of the lost energy of the cooling drag.

After removing the plug - no foam leaks which was good to see.

Stainless Steel ID plate - a UK CAA requirement.

Wednesday, 17 February 2016

Oil cooler flow - from the Aniquem project

Just a taster of the good info available from the 'Making of' book.

It goes to show what a difference good ducting makes.

Note the Trumpet shape near the radiator on the duct that works better and it's smooth flow lines. I hope mine will work as well.

Original shape - straight lines and turbulent

Modified shape, curves and laminar flow.

Text from the book

Inspiration from the highest level

I've just finished reading the book below.

It is available for download from Blurb - I had many problems getting it to work BTW but converted it into a PDF in the end and put it on my iPad.

It is 531 pages! But mostly lots of photos and small bits of text - almost like a blog (but less wordy than mine!).

Very interesting to see a modern way to build a composite aircraft. Much less work and mess by using CNC machines to make molds.

The whole airframe - minus the engine - weighs about 150kg but has a VNE of 400 knots! It shows what is possible with carbon fibre structures.

Very inspiring project, what is possible with hard work and vision.

Download link below.

http://www.blurb.co.uk/b/6674510-the-making-of-anequim


Tuesday, 16 February 2016

Week 236 - Cowling Part 10

Hours to date: 2230.25

Minus 1 degrees in the garage this morning... brrrrrr - I have two heaters which take the chill off, lucky we had some sun today which helped too.

Cracking on with the lower mold half.

Just got some cross bracing of plywood to do and it will be done.

I'm quite pleased with the way it's turned out (so far) I think I made a better job than of the top mold.

As you can see I put some bolts through the parting plate areas - these are to hold the alignment exact when I come to lay up a part inside later.

Soon this stinky messy Polyester resin and chopped strand mat work will end! And not a moment too soon, some days I look like I've been tarred and feathered.

I did a little test at the back part of the mold and it seems like it will release okay from the plug - fingers crossed it does so. 

Next post will be the big reveal - how the inside of the mold looks - stay tuned!

All waxed up and ready for PVA release - the yellow stuff is filleting wax to stop any mold being built behind the exhaust as if it was it would not be able to be released from the plug.

10 coats of PVA release again. I'm getting better at this!

Gelcoat and 3 layers done. 3 more to do.

All done. Note the bolts in the parting planes for alignment later on.

After trimming and removal of the filleting wax.

You can see the thickness of the mold here.

Plywood stiffeners bonded on - just the cross braces to go and we are done.

Friday, 12 February 2016

Week 235 - Long Range Fuel tank and cowling Part 9

Hours to date: 2204.25

Well my big news is that I have given up my day job. 

So I am now working full time on the Twister.

This should mean that I will stick to my earlier timings of - ready for paint by May and ready for flight by July.

So as you will see below things are moving on quite well.

I've probably overbuilt the long range tank a bit - I think it could take a 50 cal bullet and still stay intact :). There will be no need for the internal baffle as it is plenty rigid enough and being on the center line of the aircraft any sloshing of the fuel will not affect stability anyway. I used 4 layers of 450 gsm carbon but I think 3 layers would have been enough - especially with the overlap in the corners. I found the 450 gsm carbon to really need a lot of resin to wet it out properly - I've only used 200 gsm carbon previously.

It was a real pain to get the tank to release - it took me hours with the plastic wedges and a rubber hammer. Finally got it released and realised that it does not come out of the space very easily so a few tweaks to the shape at the back will be in order. I should have built out from the sides of the baggage area at the back to allow for easier installation and removal. I may redo this area as a fix.


I've flipped the plane over and am now working on the lower half of the mold. I had to do a few repairs to the plug as there was a bit of damage caused by the wooden struts and hot glue (these were used to hold the parting boards in place). I just used filler and sanded down using progressively finer grades of sandpaper and then gave it a wax - it feels smooth and uniform enough. So much for the wax stopping the hot glue from sticking - maybe I was a bit rough getting the parting boards off?

Hopefully the lower mold will be finished and we can start laying up a part in it by the end of next week.

Baggage area all taped up with duct tape before laying up the long range tank

I made patterns for each side to make things easier

I did the back and bottom first then each side at a time.

On it's side for the long range tank layup of the right hand side panel

While on this angle I fixed these holes in the plug which were caused by the hot glue and wooden struts used to support the parting boards.

Long Range fuel tank finally out of its layup.

2x 20 litre Jerry Cans show that the capacity calculations I did seem about right - approx 35 litres.

This shows how 'form fitted' the front of the tank is.

On it's back and ready for PVA mold release for the lower cowl mold.


Tuesday, 9 February 2016

Thursday, 4 February 2016

Week 234 - Cowling Part 8

Hours to date: 2178.75


Good news is that the top cowl mold is done - a minor trim job on the rear of it and cleaning off a bit of the parting panel is needed but I will do these later.

I have a new found respect for Matthias and Thomas who built a whole plane from scratch - it really is a lot of work once you start making plugs and molds.

The wooden supports have made the mold very rigid. They were just glued and reinforced in place using resin and chopped strand mat. This is one of the benefits of Polyester resin - that you can add things afterwards to the layout without having to do any prep work of the surface - just brush on fresh resin and it eats into the previous layer and bonds. Unlike epoxy resin which needs a clean and abraded surface to bond to.

Next up will be making the long range fuel tank.

See below for a sketch of the design for it. I will make most of it while I have the fuselage bottom panel off as I need access from the hole through the rear of the baggage area to do this layup. Afterwards I can make the internal baffle and fix the rear and top panels to it. This can come much later when the plane is finished but I need to do the back, bottom and sides now.

More about that next week.

Top Mold all done with wooden supports in place.

Mold won't win any beauty contests but it is strong and rigid.

Long range tank design and location.