Marty d's CH-701 build log

[Blueadventures]

Looking good.

[Marty_d]

I took a deep breath and cut the ring today to separate the top and bottom cowls.  All went well apart from a couple of little nicks where the Dremel blade went through to the outside, nothing that a bit of bog won't fix.

 

Below is a photo of the cut, the cross section shows how much the green polystyrene deformed when polyester resin went on it.

I've now sanded back and applied a coat of epoxy to both sides of the cut, will rough it up and then put a couple of layers of carbon fibre all over the new section.  Last day of holiday tomorrow so hopefully will get that done.  Actually, before I put on the carbon I might put it back on the plane to make sure there's been no change in clearance with the prop drive plate.

 

 

 

[Marty_d]

Unfortunately it was a bit damp and cool today so no fibreglassing (and the forecast for the rest of the week isn't much better.)

 

However I did fit it back on the plane and happy to report that the ring is still in the right position.

 

 

[Marty_d]

What I've learned about fibreglassing is:  Lay, sand, fill, sand, fill, sand, fill, sand, repeat.

 

Laid some carbon fibre over the filled bits, and because it's "rough side out" (ie not coming out of an internal mould), used microballoons to fill over.

Still, it's come up pretty well.  I reckon one more fairly thin mix over the whole thing and a final sand with 240 grit and it should be good to go.

 

Now - DZUS.  Anyone got any experience of fitting them?  Hints, tips, tricks?  Is the wire bit riveted straight to the inside fibreglass or do you use an aluminium doubler?  Etc.

 

The second picture is of a mould I'm making for a couple of blisters to go on the real cowl - the throttles are binding so need a bit of space above them.  I'm hoping to use the same mould for both blisters, I think the curvature of the cowl is similar enough on both sides.

 

Third picture is of my project for son Harry - a Mandalorian helmet.  We made it from cardboard pieces, then papier-mache, then I've been adding filler every time I do some fibreglassing on the cowl.  Will coat it with about 5 layers of thin fibreglass cloth, fill and sand again, then paint.

 

 

[IBob]

Nice work, Marty...and I love the helmet!

 

Dzus:

I swapped out the aluminium copies supplied, which bind, for steel ones that don't but I guess you'll be working with steel right off.

On my cowls, the wire bit is riveted straight to the back of the lower cowl fibreglass, no doubler,  countersink pop rivets BUT I found it necessary to 'adjust' many of them, which were either too tight or too loose. This would be due to variations in FG thickness.
I made the adjustments one Dzus at a time, by drilling out the rivets, then either adjusting the shape of the wire a bit, reforming it to make it a bit deeper or more shallow

or

in a couple of cases I used packers cut from thin aluminium strap (2.5mm?), with longer rivets, to pack the wire bit away from the rear face.

 

It wasn't difficult and I now get a snug cowl fastening that is easy to remove and reattach, no drama.

 

PS the hugely experienced pilot who test flew SVA for me walked to the front, grabbed the cowl by the air holes and tried to wiggle it up and down. I now do the same, after checking the prop, as part of my pre-start.

Edited January 19, 2022 by IBob

[Kyle Communications]

Mandalorian helmet?

 

[Marty_d]

10 hours ago, Kyle Communications said:

Mandalorian helmet?

 

 

It's a Star Wars thing Mark.

[onetrack]

Marty - Is this the 21st Century equivalent of test pilot protective gear? 

[Marty_d]

3 hours ago, onetrack said:

Marty - Is this the 21st Century equivalent of test pilot protective gear? 

It is for Mando - he wears a jet pack occasionally!

[Marty_d]

Tulip or not tulip - that is the question.

 

Last night I cut out bits from the underside of my cowl to ensure the muffler has enough clearance.  This is the first time both the muffler and cowl have been on the plane at the same time!

 

So as you can see there's a fair chunk out of the starboard side where the exhaust pipe runs and a smaller hole for the other end of the muffler at the port side.  I reckon the guy who made this cowl mould must have had a smaller muffler which fit inside the central channel.

 

Obviously I need to run a thin strip of fibreglass or carbon around the edges after they're sanded.  At that point, I was thinking about putting a formed lip around the holes, and at the rear opening, to encourage the venturi effect and suck the hot air out of the engine bay.

 

What do you think - are they needed?  Or just leave it open as is?

 

Cheers, Marty

 

 

 

Edited February 1, 2022 by Marty_d

[rgmwa]

FWIW I’d put a blister over the protruding muffler so it was fully enclosed and reduce the gap around the exhaust. 

[planedriver]

On 20/01/2022 at 7:47 AM, Marty_d said:

 

It's a Star Wars thing Mark.

No worries Marty, we'd recognise you anywhere.😀 You're the one on the right!

[Marty_d]

3 minutes ago, planedriver said:

No worries Marty, we'd recognise you anywhere.😀 You're the one on the right!

50 years old, bugger-all hair, big ears and still a baby... actually you may not be far off the mark Planey!

[Marty_d]

I've bitten the bullet and spent the money - on order are 3x Carlisle Turf Glide tyres & tubes, and a 70" Bolly 3 blade prop.  

[Marty_d]

The tyres and the prop have turned up!  Haven't even opened the box containing the prop - it's tempting - but it is my 50th birthday present so I'm prepared to wait 6 weeks or so.

 

Tyres are a different matter - after talking to @Kyle Communications about how difficult it is to get Savannah rims apart, I took the easy way out and subcontracted the job to a local mechanic/machinery business.  Very happy that the Carlisles are substantially bigger than the original tyres.

 

I was a bit worried about the main wheels as the new tyres are also a lot fatter than the originals, which means the brake disc is now hidden by the tyre bulge when looking from front or back.  I thought that I may have trouble clearing the spring.  Fortunately that's not the case, I put the starboard wheel on tonight and there's sufficient clearance from the spring.

 

 

[Marty_d]

Did a couple of things today - made a mount for the capacitor and wired it in.  Also made a new earth wire between the relay and engine block, as @nomadpete pointed out, the old one was a bit short when you factor in engine vibration.

 

As per the picture below, while my "new" fork is big enough for the new donuts, it's also a fair bit wider than the previous one - axle and central shaft shown.  The old shaft seems to be 5/16" threaded both ends with locknuts.

The new one will have to have a non-threaded length of 220mm plus enough for the nuts either end, so probably 250mm all up.  Probably the best way to use the existing axle will be to buy a couple of pieces of round aluminium extrusion (an offcut would do, they would only be around 40mm each), drill the 5/16" hole through the centre, then at one end of each, drill out to 16mm to sleeve it over the axle.  Thanks @Kyle Communications for the idea.

 

Question is - where do you buy high tensile rod, zinc plated?  Assuming I'd have to tap the ends myself - I only have a metric tap set so could probably do 8mm and bore out the axle if necessary.  Any ideas most welcome!

 

 

[Kyle Communications]

You can get high tensile bolts pretty long...I would try that first

 

[onetrack]

You won't be able to find a 5/16" bolt that is around 10" in length, the longest you might find is about 6".

You will have little choice but to put threads on some high tensile round bar stock, and that's best done with a lathe.

 

Miniature Bearings Australia keep stocks of all sort of useful hobby engineering items, from small bearings through to knobs through to steel aluminium and brass pieces of all types of cross-section.

They currently have in stock a couple of lengths of 316 stainless round bar in 5/16" diameter (7.94mm), which are 12" long. However, they want $30.26 for each piece, which is a bit expensive in my view.

Then there's postage on top of that, so maybe another $15-20.

 

https://www.smallparts.com.au/store/item/0r00790914ss316/?v=5050

 

Alternatively, I can have a hunt through my steel stocks tomorrow, I might have some 8mm hardened and ground round bar, which is fairly high tensile, and used for the likes of machining guides.

I know I've got quite a quantity of 10, 20, 30 and 40mm bar in this stuff, but I'm not sure that I've got any smaller diameter bar.

 

[Thruster88]

I would just get a wider axle made in steel, safety first. Make sure the through bolt threads end outside the fork, use a few washers each side.

[nomadpete]

You are wasting your time on this. Fitting fat tyres and shiny alloys won't make it go any faster. That only works on old commodores.

[Marty_d]

14 hours ago, nomadpete said:

You are wasting your time on this. Fitting fat tyres and shiny alloys won't make it go any faster. That only works on old commodores.

It's a 701, Peter.  The only thing that'll make it go faster is a tailwind.

[onetrack]

Marty, I'm sorry, I can't help with any round bar steel. I checked my steel stocks today, and the smallest I have in the high tensile hardened and ground round bar, is 10mm diameter.

[Marty_d]

Thanks for checking OT!

[eightyknots]

On 03/02/2022 at 1:41 PM, Marty_d said:

I've bitten the bullet and spent the money - on order are 3x Carlisle Turf Glide tyres & tubes, and a 70" Bolly 3 blade prop.  

No e-props propeller?

[nomadpete]

All the world's a critic. Don't listem to 'im Marty