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

C No Ohmen

Build blog for my attempt at the Ohmen

All Topics | Latest Posts

Search for:  in Thread Title in  
Chris North 306/05/2019 02:19:51
avatar
279 forum posts
459 photos

First pass with 3mm scrap

20190505_120927.jpg

2nd pass with reduced thickness scrap

20190505_121121.jpg

Final pass

20190505_120649.jpg

and the end result...

20190505_120700.jpg

Chris North 306/05/2019 05:33:22
avatar
279 forum posts
459 photos

With the spars cut I then went on to strip the T.E sheeting ready to to set-up the first wing panel.

20190505_123424.jpg

Piers Bowlan06/05/2019 06:50:50
avatar
1823 forum posts
44 photos

Great stuff Chris. yes

Personally I incorporate the spar slots into the ply blank and use a Swan Morton knife with a no. 11 blade to cut them out before I remove the blank from the piece of balsa. I find it doesn't really take any longer to produce a set of ribs this way and avoids the extra process of sanding the spar slots, but each to their own. I also make the blank from 1mm or even 1/32 (.4mm) ply, which I find adequate and easier than a thicker piece of ply to cut around.

Edited By Piers Bowlan on 06/05/2019 06:51:51

Percy Verance06/05/2019 07:09:31
avatar
8109 forum posts
155 photos

Chris

The Permagrit sanders intentionally do not have the grit right up to edge. This is so that they can be used as you're using them, to edge sand, and the block does not catch or scratch the building board surface, and so slides easier. It's all part of the Permagrit grand plan Chris!

I'm with Piers here. I'll cut spar slots etc into the 1/16 ply blank - which I hold in place with a couple of drawing pins - which I press my finger and thumb on - when I'm cutting round it. Cutting the spar slots out of balsa blanks separately could lead to inaccuracies creeping in Chris.....

And forgive me for mentioning this, but that sheet balsa you cut the wing spars from doesn't look hard enough for the job. Hard to tell from the photo, but it does appear to look a bit on the light side colour-wise...... They need to be quite stiff for wing spars Chris. Those bits of 3mm you cut ought to be fine for rib cap strips though......

Cutting thicker sheet with a balsa stipper like yours gets more difficult the thicker the sheet is. And as you pointed out, sometimes the grain of the balsa can pull you out of line. I actually gave up on those little stripper things eventually Chris and went the whole hog.

I got this.....

proxxon-saw.jpg

 

Will cut 1/4 ply with ease, so thick balsa is no problem at all..... Sure, it's expensive, but it's one of those "why did I struggle so much before" tools, and it'll last for years too. 100% accurate cutting 100% of the time.

 

 

 

 

 

 

 

Edited By Percy Verance on 06/05/2019 07:36:38

Peter Miller06/05/2019 08:27:44
avatar
10064 forum posts
1192 photos
10 articles

You certainly produce parts to a far finer tolerance than I do!!!

I like the way you have found for stripping hard thick sheet. I could have used that a few days ago when trying to strip 3/16" sq.from 3/16"sheet.

Chris North 306/05/2019 09:30:54
avatar
279 forum posts
459 photos
Posted by Peter Miller on 06/05/2019 08:27:44:

You certainly produce parts to a far finer tolerance than I do!!!

Thanks Peter - its the combination of the Engineer in me and knowing that my Dad would have built it better. Its a curse, but if it says 6mm then 5.5mm just won't do - hence my previous comments regarding metric vs imperial !

Anyway I have found on previous builds that that that importance I place on accuracy is inversely proportional to the amount if time I have spent building it. embarrassed

Chris

Chris North 306/05/2019 09:33:34
avatar
279 forum posts
459 photos
Posted by Piers Bowlan on 06/05/2019 06:50:50:

I also make the blank from 1mm or even 1/32 (.4mm) ply, which I find adequate and easier than a thicker piece of ply to cut around.

Edited By Piers Bowlan on 06/05/2019 06:51:51

Piers,

Thanks for the feedback - I would have used a thinner piece of ply but the 3mm was to hand plus I am still tinkering with the idea of making separate wing panels and so the 3mm blank may yet be used as a root rib - but we will see.

Chris North 306/05/2019 09:37:44
avatar
279 forum posts
459 photos
Posted by Percy Verance on 06/05/2019 07:09:31:

And forgive me for mentioning this, but that sheet balsa you cut the wing spars from doesn't look hard enough for the job. Hard to tell from the photo, but it does appear to look a bit on the light side colour-wise...... They need to be quite stiff for wing spars

Will cut 1/4 ply with ease, so thick balsa is no problem at all..... Sure, it's expensive, but it's one of those "why did I struggle so much before" tools, and it'll last for years too. 100% accurate cutting 100% of the time.

Edited By Percy Verance on 06/05/2019 07:36:38

Percy - a nice piece of cutting kit but I don't build often enough at this point to warrant such an item - maybe one day.

As for the wing spars I note your concern and so will double check whether i have any harder sheet stock - these can always be used for the false trailing edge and fuselage spars if need be.

Chris

Percy Verance06/05/2019 12:55:41
avatar
8109 forum posts
155 photos

Hi again Chris

Having the small circular saw has turned out to be an advantage in that I happily buy the harder sheets of balsa left by others whom consider them to hard/heavy for normal usage. They are too hard for most uses Chris, but they're just the thing for sawing up into wing spars or fuselage longerons........

Chris North 313/05/2019 01:34:18
avatar
279 forum posts
459 photos

Well after a bit of thinking i decided better safe than sorry so put the wing on hold for a few days until I had the chance to head to the LMS for some harder spars. Not a great selection but luckily they had had some 1/4" hard spars and i also managed to pick up a couple of sheets of hard 6.5mm balsa.

Before cracking on with the wing I decided that I would make a few modifications to allow a split wing if I wanted. The wing on the Dancing Wings hobby Space Walker has a neat aligning and joining set-up that holds the wing firmly and allows alignment of the joining wing spar. Unfortunately I had to leave this model in Thailand but luckily Uncle Google was able to find a copy of the build manual and so a similar set-up was devised.

The root and first two ribs were replaced with ply while a locating lug was incorporated into the front of the root ribs which will later align with F3 former. While I could have doubled up the dowels as Peter's design, the fun in building from scratch is that you can make changes.

Chris North 313/05/2019 01:38:22
avatar
279 forum posts
459 photos

So not really a lot to show for a good few hours work at the weekend but there was a lot of cutting, sanding and re-working to make things fit.

So first up a few new ply ribs

20190511_130724.jpg

Then it was on to wing layout..

Chris North 313/05/2019 01:49:34
avatar
279 forum posts
459 photos

Quick confession to make here because I had actually started to layout the first wing section last week before deciding to replace the spars with harder wood.

Now I made life hard for myself by not only pinning down the lower LE sheet and TE sheet but also the lower center wing sheeting. I though this would make life easier later but it only really made harder at this stage. Anyway - more on that later.

So with all the ribs finished and modified I made a start with the rib installation. First up was a dry installation to check that all the ribs fitted where they were supposed to then, starting from the wing tip I lined up each rib with the plan and checked that it was vertical using a square. Note that I don't have 2 squares but I do have a bunch of old membership cards which are also ideal. Once straight and vertical the rib was tacked in place with a small spot of cyano on the spar and TE sheet. Once all in position, each rib was then fully glued using super phatic.

20190512_092339.jpg

20190512_092249.jpg

And once that was all none a metal ruler was placed over the TE and a sheet of balsa over the ribs and weight applied.

Chris North 313/05/2019 01:50:10
avatar
279 forum posts
459 photos

oops - forgot the photo..

weight applied

20190512_101616.jpg

Chris North 313/05/2019 01:58:22
avatar
279 forum posts
459 photos

While that was drying i decided to make a start on the second wing panel. This time I though it would be easier to pin down only the LE & TE sheet and to then install the center sheeting later once the panel is removed from the board.

With the sheeting pinned down, the remaining ribs were dry fitted at which point a glass of while called thus curtailing building activities for the weekend.

20190512_211256.jpg

I forgot to take some specific photos of the root mods but you can just about see in this photo the extended root rib and the alignment holes for the wing joiner / brace. You will also notice that the upper spar has also been added to the first panel and glued in place using superphatic.

Yes I know there are not many (any) pins holding the ribs up but they are all square and vertical, - honest, I measured them twice!

Peter Miller13/05/2019 08:19:01
avatar
10064 forum posts
1192 photos
10 articles

Yes,the sequence does not need or want the centre section sheet pinned down.

If you are going ot make a two piece wing what are you doing to join them? I do not see any provision for tubes and rods.Only the tube for the servo leads.

Chris North 314/05/2019 02:01:37
avatar
279 forum posts
459 photos

Peter, I have followed the spacewalker design which uses a ply wing brace which passes through the first ribs of each wing panned. It is glued one side and slides into the spars on the other. The wing is then held is place and together by lugs on the root ribs that fit into the fire wall and by a screw through each wing panel at the trailing edge. If this is not sufficient then I can simply glue the wing and the dihedral brace into one one piece. What would be your recommendation for how far a wing joiner has to go into the wing for a model of this type?

Trevor Crook14/05/2019 06:57:45
835 forum posts
65 photos

Chris, I've just remembered a minor mod I made to Peter's design. I wanted to retain the battery hatch with magnets at the back and a dowel at the front, so I angled the rear face of the hatch backwards slightly so it would drop down once the front dowel was engaged. This of course means re-profiling the rear former on the hatch and the corresponding top part of the fuselage. It works well, but was just my personal preference.

Peter Miller14/05/2019 08:11:54
avatar
10064 forum posts
1192 photos
10 articles

Hi Chris.

I should take the joiner out as far as the end of the centre section sheet.

Peter Miller14/05/2019 08:13:44
avatar
10064 forum posts
1192 photos
10 articles

Trevor's idiea is right.

I used a dowel at teh rear and a latch at the front. I angled the front former by adding some sheet to the rear face of ghe front former and shaping that to the angle.

Chris North 314/05/2019 08:43:20
avatar
279 forum posts
459 photos

Peter / Trevor - Thanks for the info. I shall have a look at that when I get to the fuselage. As for the wing joiner I will look again but if its too hard then I'll just join the wing so no big deal.

Unfortunately I have to travel for work for the next couple of weeks and so there will not be much progress until I get back - somebody mentioned time should be spent this week helping with the packing...!!

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

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

Find RCM&E! 

Latest Forum Posts
Support Our Partners
CML
Cambridge Gliding Club
Wings & Wheels 2019
Slec
Gliders Distribution
Pepe Aircraft
electricwingman 2017
Addlestone Models
Sarik
Advertise With Us
Latest "For Sale" Ads
New Poll - Sticky situations...
Q: How often - when using superglue - do you end up with it on your fingers?

 Every time
 Occasionally
 Sometimes
 Rarely
 Never
 Wear rubber gloves

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us