Chris Foss Centi Phase - RC Groups
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May 26, 2009, 12:50 PM
Late for work again!
Gary Binnie's Avatar
Build Log

Chris Foss Centi Phase

Hi folks,

I mentioned near the end of the Multi Phase thread that I had a Centi Phase on the way courtesy of eBay, a friend collected it for me and I am now the new proud owner of one slightly used 100S glider of 1979 vintage!

I was given one of these about 20 years ago and it sadly ended up going home in a bin bag when I attempted a bottom of slope landing when the lift died.

I've started this thread as a build log, it would be possible to fly it as it is but I believe that it needs some TLC first (well quite a bit!).

I apologise to the former owner if he reads this, did not meet him and I don't know if he was the original builder.

I've spent a few minutes in the garden surveying the glider, it has some 'interesting features'!

Question is do I put it in the loft with my other retired models, fly it as it is, set fire to it or spend thousands of manhours and pounds sterling to turn it into a thing of beauty?!! As the advert said 'your chance to own a piece of heritage' I suppose it will have to be the last option!

Anyway, some photos with captions will describe it best, feel free to chime in with anything Centi Phase related, I might need some help with plans/instructions/dimensions if anyone has them.

29.99 BTW, cheap as chips!


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May 26, 2009, 12:58 PM
Late for work again!
Gary Binnie's Avatar


I weighed everything before starting whatever it is that I'm going to do, I was intrigued by the weight of the wing panels as they are more than my 12 foot Multi Phase!

Right wing - 400g

Left wing - 460g (60g difference?!)

Tailplanes - 66g

Fuselage and rudder - 810g

Total - 1736g or 3lb 12 oz without radio.

Might be some lead hiding in the nose, haven't looked yet.

This will be a fairly slow, tinkering type project. I've got a kit on the way (Flair Baronette triplane) and a few unfinished projects in the loft.

May 26, 2009, 01:34 PM
Late for work again!
Gary Binnie's Avatar

Radio Modeller review

Posting a Radio Modeller review of the original kit, the only documentation that I have.

A clear canopy can be seen, the fuselage does not have fillets.

Wing panel weights given as 140g, total weight 1136g (2lb 8oz).

I have found some lead in the nose, looks like it's been poured in or glued, has some drill holes in it, assume it must have been too much.
Last edited by Gary Binnie; May 30, 2009 at 06:32 PM. Reason: Half a pound is 8 oz dumby!
May 26, 2009, 02:53 PM
Late for work again!
Gary Binnie's Avatar

Further investigation

I decided to sand the wing root area to have a look at what is underneath. I think that some car body filler has been used, the joiners look ok and the veneer seems good. The paint is very thick but is coming off easily with 80 grit so I might be able to salvage the wing panels.

The rudder is glassed with a fairly coarse weave cloth and weighed 52g which would explain the lead in the nose, easy enough to make a new one.

All good fun!

May 26, 2009, 05:15 PM
Late for work again!
Gary Binnie's Avatar

Further further investigation!

Thought I'd finish the evening off with a bit more investigative sanding!

What I can see now is extra reinforcing hardwood strip on the spar joiners, presumably full depth. Does not look like a repair but added at the build stage, overkill and weighs a ton, that's one mystery solved! These wings could be used for slope soaring I suppose.

I checked the dihedral angle that the joiner tubes have been laid in at and they're both different, quelle surprise!

Also discovered that the tailplanes are glassed the same heavy way as the rudder, looked like they were tissue covered at first glance.

The wing fillets are another mystery, from photos of other Centi-Phases none of them have fillets, they look nice but have been built at different incidence angles so I suspect that they will be getting cut off. Not quite sure what the fuselage will be like underneath though, might be opening a can of worms there. Not much to lose really!

Mrs B said that I would be better buying a new one, 'yes dear....!'

Hey ho

May 26, 2009, 05:32 PM
SB-28 UK Display Pilot
GeeW's Avatar
Now Mrs B has told you to, you had better go and buy a new doesn't HAVE to be the same type though. So long as its Black and Yellow when it's finished who's to know?

Just a thought...

May 26, 2009, 05:54 PM
Late for work again!
Gary Binnie's Avatar

To live dangerously or not?!

My life would be shortened considerably if I bought a shiny starship, anyway it's no fun assembling brand new pieces all straight and correct like!

Thought I would do this one yellow and black instead of black and yellow! The metallic purple looks like the colour of the hatchbacks that the local 'chavs' drive round in!

Aware that I am picking holes in another builder's model but we all have different standards, plenty of builders would laugh at my efforts probably.

Can't complain at the price and I might end up with a nice model of a long unobtainable type, my logic was that the fuselage was worth the money even if the rest of it was no good. I've primed 'Mr Foamwings' for some more business.

Hope to fly the Tiger back this Thursday all being well, just ground runs and paperwork to do.
May 27, 2009, 11:04 AM
Late for work again!
Gary Binnie's Avatar

Some sums!

It's a dreary damp day in England, just right for drawing and doing calculations!

I drew out the wing planform on some old wallpaper and marked the dimensions. I also drew round the rudder and tailplanes ready for new ones to be made.

Wing panels - It looks like the trailing edge is used for the wing datum with the joiner rods and spars running parallel to it, sweepback on the leading edge only with no sweepforward on the trailing edge, this makes life easier. The reason for the step at the fuselage root is that there is a 10mm difference in the chords of the fillet and wing, the wing section is also a lot thicker than the fillet (28mm and 21.5mm). It seems then that these wings did not originally belong to this fuselage (if they did something went wrong!)

Fuselage twist - Looking at the fuselage again closely I think that it is the fin that is twisted off to the right by a couple of degrees. With a steel rod through the joiner hole and levelled the root fillets are fairly similar incidence and the cockpit sides are level as well. I would like to keep the fillets as they are quite nicely done (although probably not the original design) so it looks like I will have to try and correct the rear end twist.

I have read about RC Groupers finding twisted fuselages in their new CM Pro Discus/Ventus kits and the advice that seemed to work was to twist them straight with a heat gun, does this sound reasonable?

Sailplane calc - Gives 700 sq in wing area and a wing loading of 9.8 oz sq ft based on a 3lb model. This seems a little short compared to the Flair Albatross 100S wing area of 794 sq in?

It's all helping to understand the design.


May 28, 2009, 05:17 PM
Late for work again!
Gary Binnie's Avatar

Two good things!

1. I have straightened the fuselage with a hair dryer and gentle pressure, much better now.

2. Flew the Tiger Moth home safely tonight so hopefully I can get on with some modelling!

Last edited by Gary Binnie; May 29, 2009 at 03:14 PM. Reason: Spelling mistook
May 29, 2009, 03:51 PM
Late for work again!
Gary Binnie's Avatar

Purple haze

Decided to start scraping the purple paint off of the fuselage.

Using 240 grit wet is probably not abrasive enough, might try 120 for a faster result.

A surprising number of different coloured layers, either one owner got bored or its had a few owners, can't be helping the weight.

In chronological order:

Red - Seems to be the original gel coat colour, 1979, Grease/ABBA

Blue - 1987, Madonna.

Light grey - Presumably primer for the next colour

Metallic light green -1995, U2.

Metallic purple - 2003, Christina Aguilera

Like 'Time Team' this!

It would be nice to use the original red colour but I am going to struggle to get all the remnants of the other colours off, will see.

Can't be sure but there could be a block of lead glassed in to the centre section, might be a hardwood block for mounting the hook but it seems a bit too far back.

Still got to get the lead out of the nose.

May 29, 2009, 08:04 PM
Master of the Wind
G Norsworthy's Avatar
I got one of these from a friend, Nelson Montgomery, about 20 years ago. The wing rod was a little floppy. After flying it for a while I cut out the wing roots, shortened the span, and made it a bolt-on wing. Flew it for a while longer and ultimately folded it on a winch. The fuse was orange gelcoat, decent quality, and the wings were covered in clear plastic.
May 30, 2009, 03:35 AM
Registered User
prodjx's Avatar
I'd paint over that nose with clear coat, people have actually tried to get that effect diliberatly.
May 30, 2009, 02:36 PM
Late for work again!
Gary Binnie's Avatar
Yep, the single 8 gauge joiner rod does not look up to the job, will try to improve that.

Never thought of leaving the paint as it is, does look quite racy!!

May 30, 2009, 04:16 PM
Registered User
The wing profile is definately an interesting feature .
May 30, 2009, 06:25 PM
Late for work again!
Gary Binnie's Avatar
Yes, they were on the thick side! Have dumped those wings in the garage with the motorbikes. The fuselage fillet section is much thinner and is close to a 10% Eppler 205 section.

I can't imagine that it flew very well at all, would have struggled to climb in lift.

Just reweighed the fuselage with the rudder and have 750g now instead of 810g so I have removed 60g of paint so far, that's over two ounces in old money!

Using 120 grit now to speed the process up, there was a sediment of thick purple sludge in my water bucket when I changed it tonight. 'Rattle cans' are not the best way to go and this fuselage has obviously had a few applied over the years. I will get the boys at work to paint it eventually.

I'm quite determined now to put this dear old machine back to how it was meant to be in 1979, might drop Chris another letter, he will think that I am mad!

Still got to get the lead out of the nose, is it possible folks that this was poured in hot? It looks like that is what happened but surely that would melt the fibre glass resin and there is no sign of any damage?


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