By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Design & Build Sport Twin

Sport Aerobat for 2 x 40s

All Topics | Latest Posts

Search for:  in Thread Title in  
Nigel R23/05/2019 10:27:54
avatar
4082 forum posts
694 photos

Right, now that's dry, time to cut the wing saddle out. Template is stuck down in the appropriate place (LE above TE by 1/16" to give a half degree of positive incidence):

20190522_221852.jpg

The shape is marked with a pin and a lot of holes.

Cutout is roughed out with a dremel sanding drum, then a curved sanding block.

After I did one side, I re-used the pegs (previously used to keep doublers and sides aligned) and transferred the wing section to the second side, separated them, rough cut the second side, put them back together and finished off the sanding.

20190522_224735.jpg

The saddle is now a good copy of the wing seciton. I cut it oversize by 3/32" or thereabouts, to allow for the wing joining bandage. Any gaps will end up filled by silicone sealant, after covering.

I have a bit more prep left to go with the sides - longerons, doublers around the tailplane saddle, a few uprights.

Nigel R01/06/2019 11:58:13
avatar
4082 forum posts
694 photos

The last week has seen a bit more progress.

The most nerve wracking operation of the whole build:

20190531_214349.jpg

Nigel R01/06/2019 12:00:40
avatar
4082 forum posts
694 photos

Hacking a hole in something that just took 35 hours to put together was enough danger for one week.

So I cut some parts for the nacelles. Sides first, just like the main fuselage these are 1/8 with ply doublers

20190527_220208.jpg

Nigel R01/06/2019 12:01:40
avatar
4082 forum posts
694 photos

And some formers. These have gone through a test fit to get the size just right:

20190531_215032.jpg

Nigel R01/06/2019 12:02:31
avatar
4082 forum posts
694 photos

And I made the main formers for the fuselage and did a test fit in the jig:

20190601_080539.jpg

 

at this point I've also added the longerons and some uprights, and some 3/8 square to reinforce the tailplane saddle. 

Edited By Nigel R on 01/06/2019 12:10:54

Nigel R01/06/2019 12:04:33
avatar
4082 forum posts
694 photos

I now need to get the nacelle firewalls set up for the engine mounts and plumbing - but as I've run out of m4 hardware that will have to wait for the postman to bring another packet of tee nuts and machine screws.

Nigel R03/06/2019 09:31:27
avatar
4082 forum posts
694 photos

Well instead of twiddling my thumbs waiting on the postman I got on with glueing up the fuselage:

20190602_225416.jpg

 

A jig is one of the best workshop tools you can buy or make, I think.

Yes, the longerons are meant to be stickup up past the top of the sides. They do that in order to give something for the rear decking sheet to land on.

Annoyingly, the 1/8 ply former at the front of the wing has warped. The top half has gone wonky. Never mind. Hopefully no one will notice! The bottom 1" of that former has been reinforced with a strip of 1/16 ply to beef up the dowel hole, and that bit at least is nice and square.

The rear of the fuselage is like most of my builds, which means it gets a few crossmembers, cut and fit from 3/16 or 1/4 scrap, while it is sat in the jig. I don't know if they really add much strength by the time it is all finished with decking and sheeting and all that, but they certainly help hold things in place during the build process (i.e. keeping the fuselage sides upright and parallel and so forth).

While I was in and around the tail end, I put in the tailpost block, a lump of 3/8 soft sheet sanded down to size and stuck with aliphatic (like the main formers).

20190602_225426.jpg

All good so far (apart from that warped former). Lots to do yet but happy with the last weeks progress through the job list.

Edited By Nigel R on 03/06/2019 09:44:25

Nigel R07/06/2019 14:16:02
avatar
4082 forum posts
694 photos

20190606_232518.jpg

20190607_133615.jpg

Got the decking on. Took a while to get the shape matched up to the canopy I am gong to use but otherwise went well. I soaked the sheet and it seemed happy enough to go around the curves.

Nigel R09/06/2019 05:38:31
avatar
4082 forum posts
694 photos

I am using three pieces of 3/8 to make the front deck. I got the first two into place:

20190608_222900.jpg

20190608_224043.jpg

20190608_231646.jpg

Nigel R09/06/2019 05:41:25
avatar
4082 forum posts
694 photos

Next step is to flatten the top of the two pieces I just fitted, then add the top piece (more 3/8). Then a bit of carving.

Nigel R12/06/2019 06:26:49
avatar
4082 forum posts
694 photos

I added the top slab to the front decking.

20190610_222612.jpg

Nigel R12/06/2019 06:27:58
avatar
4082 forum posts
694 photos

I also added a slab underneath the nose area:

20190611_225805.jpg

Nigel R12/06/2019 06:29:42
avatar
4082 forum posts
694 photos

A fair amount if this timber will be sanded away. Right now the nose is looking quite chunky!

20190611_225842.jpg

Nigel R12/06/2019 06:30:42
avatar
4082 forum posts
694 photos

Also had a bit of a think about the tank install in the nacelles:

20190611_225752.jpg

Nigel R12/06/2019 06:35:06
avatar
4082 forum posts
694 photos

I think I am going to end up with the neck of the tank in line with, and the fuel lines coming through, the centre of the mount. Nothing particularly unusual. With the engine upright it is a bit lower than optimal however there isn't much I can do about that. The nacelles are not very tall!

Nigel R18/06/2019 06:29:57
avatar
4082 forum posts
694 photos

I've been doing some engine install jobs this week. First, getting the mounts on the firewall:

20190614_212420.jpg

The small ply discs are only there to make the firewall thicker so the tee nuts do not poke through to the other side. I turned then up on a drill.

Yes, the holes are meant to be in different places on the two firewalls... The starboard engine has right thrust.

I also drilled the fuel line holes. I'm intending on using standard tanks with a two line setup. Some other jobs were done too, drilling the engine mount and soldering a threaded extension on to a couple of lengths of wire cable ready for setting up the throttle run.

I also got the nacelles together:

20190617_222956.jpg

It is going to be quite cramped in there. If I'm honest I wish I'd made then a bit longer. If it comes to it the First dodge will be to get a pair of slec square tasks or sullivan slant tasks. If I still can't fit everything in satisfactorily I can always make more, I guess.

Nigel R18/06/2019 23:09:32
avatar
4082 forum posts
694 photos

Bit more on the nacelles - getting the servo mount sorted out:

20190618_225003.jpg

Tight. One to remember for next time, more space for the servo.

And a quick fit check now the nacelles are glued:

20190618_230010.jpg

Getting there!

Denis Watkins19/06/2019 07:42:15
4631 forum posts
129 photos

Wow Nigel

You have been ahead of the game from the start of this project, and there is the result

Don't skimp on the horizontal stabiliser

There is no need for a weight saving surface on this one

The horizontal stabiliser is subjected to huge forces, so build it rough and tough

Nigel R19/06/2019 13:30:45
avatar
4082 forum posts
694 photos

Thank you Denis smiley

I believe the tailplane will be strong enough. It's a fully sheeted structure, with several 'spar' members; solid sheet elevator. You are right it is not the place for a flyweight structure, the model will not be short of power when done.

There is a long way to go yet! I reckon I am about half done. Although at this point the whole thing is really starting to take shape.

Nigel R24/06/2019 09:29:33
avatar
4082 forum posts
694 photos

Some slow but useful progress this week.

I have mainly been working the throttle links. The bowden cables are cut to length and made up with a threaded adaptor soldered on, the outer sheath is in place, appropriately supported with a few balsa blocks near the servo and both installs have been tested for full and free movement. I've gone with ball joints at the engine end of things and those screw on type links at the servo end. smiley

I decided at this point that I wasn't going to rebuild the nacelles, but didn't like how the bottle tanks were fitting, so I bought my way out of the problem with two 6oz SLEC maxi tanks, which result in enough clearance for the servos to operate freely, and. allow me to completely surround the tanks with a layer of foam - which is a much better deal than I would have got using the standard bottle tanks. Lesson learned, don't skimp on the space for the gear to be installed in (should have known better, if I'm honest sad). Another couple of inches in length would have made for plenty of space.

The second whoops of the week was the discovery that the starboard nacelle, with offset for right thrust, would not have clearance between the silencer and the side of the nacelle. I would have to cut into the corner of the firewall to clear the silencer. sad I guess I could have gone the woodwork route, but this was another credit card solution - Just Engines came up with the goods here (and very quickly - always good service from them yes) in the shape of a pair of 3/4" extensions, which gets me a reasonable clearance without hacking the woodwork about.

Not sure how I could have easily avoided this (I suppose the engines could have gone in sidewinder, but I wanted them upright for ease of starting - and anyway but the time I'd noticed I'd already done the firewalls).

After spending my out of those problems, the last bit of the week's workshop time was spent on more straightforward matters - getting the main part of the 3/8 sheet top on the nacelles and stuffing in a load of tri stock reinforcement. Just like the fuselage, these will soon be in for a dose of razor plane and sanding block...

20190622_213105.jpg

The tail end of the nacelles will also get some 3/8 sheet. Inside, tri stock everywhere:

20190623_225323.jpg

Next job - two cowlings to come up with. It'll be thick sheet and tri stock again - nothing unusual planned there.

I just hope I've bought enough thick sheet...frown

All Topics | Latest Posts

Please login to post a reply.

Latest Forum Posts
Support Our Partners
electricwingman 2017
Sussex Model Centre
Slec
CML
Advertise With Us
Sarik
Latest "For Sale" Ads
NEW POLL - has the pandemic altered your event safety perceptions?
Q: Has the covid pandemic deterred you from attending shows and events in 2021?

 No, I'll be attending just as many as I usually do
 No, but I'll choose my event with greater care
 Yes, I'll attend fewer events going forward
 Yes, I wont attend any where previously I have

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E!