Cowl mod...

 I had to extensively modify the cowl for the UL520T.  After all the slicing and dicing, I had to rebuild 95% of the goggle between the top and bottom halves.  On the starboard side, I guess I over-trimmed the flange.

Luckily I had some of the strips that I laid up previously, and bonded a then piece behind the existing flange to extend it up slightly.

Hopefully this will work.

I am going to prime the entire inside of the cowl at this stage.  I want something behind the skybolt fasteners when they go on and not just bare fiberglass.  I did the port flange yesterday, then just figured I should just go do it all.  It looks so much better than the hodge podge of colours it is right now.

Then I can put all the fasteners in the cowl.  That will be exciting...

UL Regulator Cooling

Ul recommends that the regulator be cooled with some fresh air.  Apparently in the past there have been issues with hot regulators.  The one UL520T that is flying does not have any blast tube, and has been fine for years.  But, might as well do it as I have the space and its easier to do it now.

Simple C shaped bracket that picks up the regulator mounting holes.  The large holes on the front sides are for screwdriver access.

Bit of a pain to line up and mount, but doable.  Just needs finishing and its done.  Will do with the next batch of parts.

Battery box cooling

I am running 2x EarthX ETX900's located on the firewall.  With the amount of air that will be circulating under the cowl I do not expect excess heat... and the batteries are as far away from the turbo as I can make it.  However I am still planning on cooling the batteries.  I have put a 1" flange on the port side cylinder plenum, and a 1" on the battery box.

The battery box was last installed before the engine mount went on... and oh boy it was a challenge to get out.  Not impossible, but not as easy as I had planned.

Took everything apart, and riveted the flange in.  Flush on the inside of the box.  There is a 1/2" gap between the batteries.

Need to take the box off again as I have to mount the cowl fasteners on that side and it will be far easier to do that with the battery box out.

This is probably overkill, but easier to do now than later.

You can see the corresponding flange on the rear plenum below.

I am not going to route the SCAT tubes until I know where the plug wires are going to run...

Exhaust

 The UL engines comes with exhaust, muffler, etc.  Its all stainless, and very nicely welded.

There are two pipes... one off the turbo, and one off the wastegate.  Both are on V bands.

The OD of the pipe coming off the waste gate is ~2.38" (60 mm) and the turbo is 2.75" (70 mm).

The rough plan is to come off the pipes at a 45 heading towards the center.  Then another 45 to head out the bottom.

Note:  The waste gate can be rotate.  Mine was hitting the outlet pipe until I rotated that.  Once I rotated the waste gate now I can have the exhaust pointing straight down.

Going to mock everything up in place, tack everything, and then take it apart and get it finish welded - at least that was plan A.

Talked to the US UL Distributor, and asked what is the size of the pipes.  The response is "METRIC".  So where on earth can you find metric exhaust parts in North America?  I have found some, but they are not plentiful.

Ray (UL US Distributor) thinks that the factory can make exhaust with the correct tubing.  That would be good, but then the question is cost and shipping cost.  Regardless, I still have to mock everything up.

I bought a bunch of bends and fittings from the Aviation department of Amazon.  Here is what I discovered.

• 2.75" tubing matches up really well with the 70mm exhaust.
• 2.5" tubing slips over the 60mm wastegate end.

I have not cut anything yet.  Just wanted to get an idea where to go next.  I think this is going to work.

After staring (and cursing) this for weeks, I am giving up.  Going to find a shop that can just weld this up and I pay the bill.  Stupid god damn metric pipe.  I cannot find a good source for metric 316 stainless.

Contacted Hilder Rosales today at Hard Industries in Arlington.  Going to Arlington Skyfest next week, and will take him the stubs and see what he can do. I have had enough for searching for parts... I WANT AN EASY BUTTON.

Also, I contacted and heard back from UL Power.  They can source me 60mm and 70mm pipe and bends - just need to know how long.  Shipping is going to be expensive...  There is a new distributor in Canada and he is going to bring them over with his next shipment.

So fast forward 5 weeks (now early october), and I still dont have my exhaust bends.  The new Canadian distributor says that DHL is not reporting location, and they should arrive any day now.

Fast forward to January 2024.  Still no progress.

I was lamenting to some friends that I have no experience here.  So we had a building day... and I now have a TIG in the shop (on loan).

This should not be very hard... it really shouldnt.

So as I step 1... we put the lower cowl on, and mapped out using a piece of welding rod where the exit is.

Next... I need to fix the tips in place off the bottom of the fuselage and start working my way forward to the engine. 

February 2024.  PROGRESS

So I made a bracket using the air deflector fasteners as the holding point.  Then I bought some hole saws that match the tip diameter.  Voila..

So after cutting and grinding and fitting, I have one pipe.

It is not tacked yet.  I used tongue depressors and hose clamps at the joints (thanks to Bob for that trick).  Need to start on the 2nd one after I get home from the next business trip.

2nd pipe in place and close...

So after a bunch of fits and starts (long story...), I have exhaust.

Next is to build the mounts... and send the pipes for ceramic coating...

Oil Cooler

The UL power engine needs lots of oil cooling.  The US distributor does not recommend the UL cooler, and nudges people towards a standard aero classics 13 row cooler.  So that is what I bought.

To get lots of oil cooling, it is recommended to put the cooler under the prop attached to the engine.  UL makes brackets to this location, so I bought it from their US distributor (Wicks).  For the price it wasnt worth building.

There is also an oil cooler adapter that mounts up front under the oil filter.

The bracket is quite large.  Not sure if I will use this or make a new one.  Proceeding with mock up anyway to learn what i dont know (yet).

Used a pieced of 1.25 x 1.25 aluminum angle to bridge the gap and to tie in the shock mounts.  Needed to shorten the port side 'leg' that attaches to the front of the engine.

With the bracket all the way 'up', and on the angle that the bracket specifies, the cooler is still touching the cowl, but much less than it was when I started.

Used a double exposure method that I have really wanted to try since I heard about it.

Cooler mounted to engine, no cowl

With cowl and 1" tape grid around roughly the correct area.

Overlaid the two pictures in MS Powerpoint, and made them both 60% transparent.

This should get me very close on initial cuts.  Finessing will be required.

Tip(s):

- I bought the 'silent block' mounts as recommended by UL, as well as the M8 lock nuts.  They really are lock nuts... so during mock up I went down to home depot and bought M8 non lock nuts.  Much better for mockup.

After staring at this for several months, I am going to build a new engine bracket.  The UL bracket is way to big and unnecessarily heavy for my cooler.  I have a large chunk of aluminum angle that will do nicely.

Need to build the struts next.  I have the UL struts, and am just planning on using them as is.

Because I built the new bracket out of thicker aluminum, I doubt I will be able to bend it to get the ~12 degree angle that the UL bracket has.  I did flip the bracket on the cooler around to push it farther back.  But it appears to have less room than it did before.

Need to cut out the cowl pretty soon and make the inlet.

Inlet cut.  Its on a slight angle, but I am OK with that.  I dont think it needs to be straight up and down.

I had been pondering the mounts for months (well, it seemed like months).  I recently ordered all the fittings and figured it is time to go for it.

Fitting notes:

• All of the hose fittings on the cooler adapter are -10AN
• The fittings on the aero classics oil cooler are 3/8" NPT (not 1/2" NPT as I was told)
• 3/8" NPT to -10an is readily available in multiple configurations

My goal / hope is to keep the fittings at the top of the cooler.  This will make the lines shorter and lighter.  Flipping the cooler upside down meant trimming the bracket holds the assembly to the front of the engine.  As a starting point, I decided to use the UL rear brackets.  I am not sure if they are going to work, or even if I want them to work.  They are simply about 1/8" think stainless with holes it in, and you bend it to your configuration.  Gotta start somewhere.

Made a bracket at the bottom to capture the 3 holes on the bottom cooler bracket.

The fittings all look good for a first pass, except the pilot side fitting is going to change from an elbow to a straight fitting.  Also probably changing the oil cooler adapter fitting from a 90 degree elbow, to a 180.  Will try it and see if it fits.

Now that the cooler is fixed in place I need to do the fiberglass work for the inlet on the cowl.  My original plan was to make the mold out of MDF.  However, after rebuilding the inlets using foam I am starting to see the benefits.  Super fast and easy to work, and you can just sand it away when you are done.  So I think that is the method I am going to use.  Where it is captured between two pieces of fiberglass, I may just leave it.  Its definitely light.  Also going to build it in place.  Hopefully this is not a bad idea.

Quick test.  Put a piece of packing tape on the cowl... and then stuck a piece of foam to the tape with hot glue.  Seemed to hold well enough.  So that is the plan.  Tape up the sides, cut foam to fit and build the mold on the cowl installed on the airplane and see what happens.  Going to tape up the oil cooler so nothing gets on it.

Well version 1 completely sucks.  Need to start somewhere, but this needs significant work.

The below is a cowl off a Rans S19.  I need to make it look something like this.

 

Built the foam up significantly (x3).  Now its shaping / sculpting time.  I dont think this is my forte...

So I took a stab at it.  The foam is super easy to shape.  But, I am realizing I didnt build it up enough forward.  Going to extend it an inch.  I need to fix the inboard section first, sand it flat, and then more foam.

It needs to flow into the rest of the cowl.  I have a feeling I will be at this for quite a while.  I want it to look 'organic' (can't think of a better term currently).

Built it up more and started shaping again...

This is starting to go in the right direction.  Nowhere near done, but starting to not look like a minecraft character.

I spent a couple hours fine tuning the shape, and it doesnt look bad (for what it is).  Unfortunately its big, and I need lots of air through it.  I figure I am going to have to redo it completely, so I might as well learn everything there is to learn, so go ahead and glass it.  If it doesn't work out, I have learned something.

I am planning on 2 layers of glass, but I have really bad luck trying to do multiple layers at once and I will do the 2nd layer after.  I applied peel ply to much of it in small pieces.  No way I can cover it in one piece with all the curves.

Packing tape was applied almost everywhere (not the bottom corners).  So hopefully this will pop off easily.  If not, I will have to remove the foam - but will see.  It is not going to be perfect - lots of filling and sanding will be required - but gotta start somewhere and learn.  This is completely new to me.

Success!  After applying a 2nd layer of glass and letting it cure overnight, I started the process of removing it from the cowl - but first I drilled 6 holes for registration (2 on each side and 2 on the bottom).  The packing tape worked... so after some gentle pulling in multiple directions it all popped off.  Then I dug all the foam out using different size chisels.  Because the foam was multiple layers, it broke apart fairly easily.

I rough trimmed off all the excess fabric.

Next is to trim down all the flanges and clean it up a bit, then I need to open up the hole in the cowl to the inside edge of the inlet.  The plan will be to bond it on after trimming and sanding the cowl using cabo and resin, then a layer of glass from the inside of the cowl to the inside of the inlet. Then a layer on the flange, then fairing compound to make it all blend in.

I started cutting the cowl, and THOUGHT I left myself an easy quarter inch to spare so I could inch in on the inlet.  Well, its pretty much right on for the sides, but the bottom needs to come back a fair bit more.

What it looks like on the plane...

Its not horrible, but I am not in love with it.  It should be very functional, which is the most important.

I temporarily installed the oil cooler to fit the inlet.  I figured now is the time to do this as the inlet is removable.

I trimmed a bit too much on the starboard side.  Plus the bottom needs some fixing.

Its starting to look not too shabby.  Its growing on me I think.  Either that, or I dont want to start over!

I've opened up the hole in the cowl significantly to line up with the outer edge of the inlet.    Its not all the way there yet... will do the final trimming once the inlet is bonded in place so I can glass the inlet from the back and the front.

I also added 2 layers of glass on the bottom forward lip and the inboard sides.  I over trimmed in some areas, so had to build it back up.  Still more to do, but its closer.  Its easier to do all this now with the inlet removable so I don't have to constantly take the cowl on and off.  The part is significantly stronger now, and I have extra material so I can clean up some off my gaffs.

Now its time to bond it on.  The plan:

• Initial bond with resin / cabo.  Smooth the edges as best as possible, let cure.
• Fill the edge between the inlet and cowl with resin / cabo again, and taper it
• 2 layers of glass on the inside and outside
• Putty wipe the outside
• Sand

First step was to sand off the gel coat / primer around the outside.

Fit the inlet, and sand down the inside to meet the inlet.

Resin / cabo, and clecod it in place.

Test fit

So many months later... I have never been happy with the UL aft cooler mounts.  

After talking with a buddy, he offered a solution of a triangular aluminum mount.  So off I went...

Way more stable, and actually lighter.

The CAD model (Cardboard Aided Design) was perfect first time amazingly.

Cowl fits really well - thankfully.

The aft of the bracket is wobbly, and needs a bracket to tie the two of them together.  That should be easy.

Now its all about finishing on these brackets, and reinstalling.

Done.  All finished and installed...  Just need to pressure test the oil lines, put on the fire sleeve.