Fuel System

Time to start securing the pumps to the sump wall area. The on/off vlave is connected to the pumps now so its just those that need securing.

I placed the bottom click bonds and with plenty of release tape made sure they were in the right place by using a stick to force the pumps right up against the sump wall while the epoxy set. Pic 1.

This worked really well. After cure I did the clean up and then some BID disks carefully over the click bonds and the result you see in pic 3.

Using a ‘stick clamp’

BID foil circles

Clickbonds in place

Here you cam see I’ve glassed the inside of the filter indent and peel plied it. I did a cure cycle of micro first so I had a good surface to glass to.

Pic three and you can see all this coming together. I have been hacking into the pipe exits and entries and all sorts of little thing to make this work. Pic 2 shows where I’ve opened up the left bottom of the sump wall to give better pipe access.

I’m using a number of ‘Speedflow’ racing automotive fittings. You can see them as the red and blue items in some of the pictures. These are top quality and in a wider range of items than the standard AN aircraft fittings.

Glass and peel ply

Cleaned up

Another test fit

This is really fuel system and Chapter 21 although I have the pics in the heater folder. Oh well.

I’m doing high pressure fuel injection as you know. My plan of placing the on/off valve, dual pumps and then post pump filter is coming together. It ahs been challenging to make the best use of the little space I have in this plane.

I want these items as near to the common sump wall as possible to maximise the GIB leg room.

The item that was the most prominent turned out to be the mounting of the post filter. The solution has been to inlay an area in the sump wall for mounting its adel clamp. These pics are really how I laid it all out. You can see I’ve done some work in the foam.

Indent for the fuel filter

In place

Test fitting

The last bit for these fuel pipes for now was to fit them in with the arm rests. As usual it took a while. I also made a gradient in the sump lid for the seat belt exits while I was at it.

I may transition these pipes with some micro later although I think I’ll hold off in case in the edges becomes a good place for things like sight gauge lighting wires.

Arm rests and pipes

Left fit

Right fit

Yesterday was another ply of glass after the usual clean up. You don’t need any pics, it looks the same as ply 3. All up there were 2 plies, then I cut and cleaned the pipes and taped them at the rejoin. Then another two plies one top. The plys are a bit thicker than usual as I overlapped 1-2″ where I could. That said, after three ply they didn’t feel strong enough. This morning with the 4, I had really rigid pipes, what I was going for.

All up they weigh in at 15.5 ounces. Ouch, but this is a safety item I did not want to compromise. Pic 2 and after spending the day fitting both pipes and prepping, I floxed them in tonight. A lot of flox and a bit of peel ply at the transitions too. They should make the sides more rigid if anything.
Good to tick this one off the list.

Finally done

Floxed in place

Exit strake bottom, I hope

Just another ply on the pipes today. Now they are hollow I made really solid holding blocks so I can lock the pipes at any angle. You see this in pic 1. Just in the shot are the large pieces of glass I’m using.

Rather than trying to get an exact size sorted I’m wetting out the pipes and draping a big piece of bid over the top. Then I’m free to get it to conform just using this one piece without pleating several times. It should be stronger this way even if I waste a little glass.

Pic 2 and I have them carefully covered in peel ply and pic 3 is my rough heat box. That gas heater is on 100% and its pretty toasty in there. It cures the glass in a few hours and I’ll be fine for sanding the pieces tomorrow for the next step.

New holders

Another ply done

In the hot box

The job was now to remove all the blue foam for a nice clean finish to the insides of the pipes. That took quite a few hours. Most of the foam separated well after the wax and hairspray but quite a lot also stuck to the bottom and needed VERY careful work to get it to the pic 1 stage.

Next up was to epoxy the two halves together and add a 1″ tape to the outside. This was pretty tricky for the first one which I did yesterday and fast cured in front of the heater.

For the second one I floxed the two halves together and then gently held it in line with blue electricians tape. Again the heater was on full bore for a few hours. Tonight I taped them with BID. This time with .8″ tapes and then peel ply.

Pic 3 shows the usual setup of tapes done on foil. Its working out really nicely.

Tomorrow I’ll do the clean up and then look at another ply of BID on each pipe. It may need two more plies in fact. I’ll see how it feels. That would be 2 before the cut, a BID tape and two after. That might be strong enough.

Insides cleaned

Flox join

Taped with BID

After the plies cured I sanded them down ready for the next step. I needed to get the foam out of the pipes now!

Using a very fine hobby saw I hot glued a ruler to the long part of the pipe and cut through. (pic2) I did both sides and then a free hand cut from the end to the openings.

As you see in pic 3 it then opened like an oyster.

Sanded but full of foam

Careful splitting

Inner revealed

After a good hot cure yesterday the pipes were up for another prep session. It took a while to sand away shinny spots between the peel ply but it was done.

I mixed some EZ epoxy and coated the pipes after remounting them on the spindle. While I had some wet EZ I put a ply over the top of the two clickbonds in the sump that I had previously installed. Pic 2. Peel ply over the top and a 10 mt job all done.

Pic three was after 3 hours of coaxing the BID to form around the pipes. Not the easiest layup for sure. Its curing in front of the heater now and will get a couple of checks as it slowly hardens up.

Prepped and sanded

Hydramat clickbonds

Another coat curing

The pipes ended up with three lots of micro and sanding in between. Then I got the clay out and filled a few spots. Then a coat of release wax and finally several coats of hair spray. Pic 1 is good to go.

Pic 2 and I grabbed some stands I’d made to hold the spar and removed a few bits then added threaded rod and secured the ‘tools’ or plugs to the rod. It works well enough to be able to rotate the piece and hold it in position.

Pic 3 and I’ve glassed both pipes with one ply of BID and added some peel ply two. The plan was two ply at this stage but I’m beat after around 7 hours straight. I think it will be a better job too if I prep this ply carefully and then do another. It will add a days work. I am concerned and I want to ensure there are no bubbles, it is a very challenging shape to cover with fiberglass.

Pipes prepped

Re-purposed holders

1 ply of BID

Here are my blue foam pipes being made. This took a while and had a few itterations. I had to route the foam to my 1″ thickness and glue bits together using pins to hold them. I had to get the access holes right too so I could install and remove the foam block shapes.

Pic 2 and it has happened. I have my pipe ‘molds’. There was a lot of sanding and adding little bits here and there.They fit and they are removable for now.

The next part of the plan is to coat the blue foam in several layers of micro using West systems, only because I have a fast hardener for this. You can see the first coat in Pic 3.

I’ll do a few more of these until I get a smooth finish I’m happy with. This will be the shape of the inside of the pipes. Once thats all done I’ll wax the outside as you do for a mold release. Then I’ll glass them with two plys of the fuel resistant epoxy. When that is really cured, I’m going to slit the two thinnest sides and get the tool or mold out. Then I’ll tape the halves back together. Next will be two more plies for the pipes and finally I’ll glass and flox them in place so they cannot move. Ever.

Yes it will infringe on the armrests and the GIB. I’m happier with this approach rather than hiding them in the fuselage sides which would look nice buy further weaken the structure.

OK wish me luck.

Building foam shapes

Fitted pipe in foam

First coat of micro

However you look at it, not having the pipes from strake tanks to the sump installed was getting in the way of finalising many positions in the fuel and vent lines. I was going to leave this until after the strakes were built so I could get an exact entry point in the strakes level wise. This needs to be at the lowest point so all the fuel in the wings can be used.

Too bad for me, now is the time. I’ve remeasured the strake positions to within 2mm each side and thats near enough. I can make ramps or whatever is needed as a final adjustment post strake build, pre putting on the top.

Wow it would have been awkward to make these later. I was going to do clay modelling for the pipes but decided on foam instead. Meanwhile the first job was to make the access holes. It took a bit of courage to make holes in my beautiful fuselage sides. I must have hesitated for 2 or 3 seconds. hahaha Some things have to be done.

Pic 1 shows I have a 3″ by 1″ holes in each side just above where the bottom of the strakes will be. Pic 2 shows lines drawn for where the pipes will run down the side to the common sump. Pic 3 is the hole I had to make in the sump. Yes it would have been easier to do this before that lip was built. I hear you.

Pipe to strake access

Pip runs marked

Challenging access