Chris Foss Hi-Phase - RC Groups
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Jun 15, 2010, 08:44 AM
Late for work again!
Gary Binnie's Avatar
Build Log

Chris Foss Hi-Phase

Wot? Another one?!!!

My new shed is in a condition where I can work in it now so I returned to the dilemna of what to build next.

For those who missed my other thrilling Chris Foss glider threads I should summarise the situation:

I had a Centi-Phase 100S RES given to me years ago and broke it on the slope.

I bought another one off eBay cheap last year, the wings were scrap but the fibre-glass fuselage was very useable and I stripped many layers of paint off it in a restoration project and then pondered what to do with it for a bit.

I scratch built a Multi-Phase 142" RES just before that, very nice but had an accident recently breaking one tip panel, surprisingly it did not get broken using an F3J winch but on a gusty approach. Chris (who was at the competition) said 'Didn't you see the note on the plan - no winch launching!' There is no note but I knew what he was saying! Can be fixed without too much trouble.

Then there was the Phase 6 sloper kit build, goes well and is getting a battering up the hills.

Earlier this year I bought another cheap unidentified glider off of eBay, the pictures seemed to show that it was a Phase Lift (which it was), a flaperonned 127" (or 151" with extended tip panels) span monster. Could fly again but it has some problems.

I also bought some very old RC soaring books which showed yet another one, the Hi-Phase.

So.... I rang Chris, had a chat and ended up with plans for the Phase Lift, Hi-Phase and a plan for an all-wooden Centi-Phase (I already had the plans for the fibreglass fuselage version).

This left me with a choice of what to build next which I have only just decided, a Hi-Phase.

Will describe the Hi-Phase and some early building in the next post.


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Jun 15, 2010, 09:17 AM
Late for work again!
Gary Binnie's Avatar

Wot's a Hi-Phase then?

A Hi-Phase is a 140" span RES glider with a four-panel, sweptback, polyhedral built up wing and a 'T' tail. I assume that the 'Hi' either comes from the high tail or that it can get very high in a thermal! The plan is dated at 1980 (or 30 years old by my maths!).

My version of the plan has a pencil drawn extension to the height of the fin and rudder which brings it above the all-moving tailplane, I guess that it was slightly short of rudder authority originally.

Also shown on the plan is a foam wing version that Chris used to supply. The chord of the foam wings is 1" more than the built-up ones, I asked Chris why this was and the answer was to increase the wing area to compensate for the extra weight of the foam wings (he kindly left off 'stupid' at the end!!).

To build a Hi-Phase originally you needed the plans, some wood and a ready-made fibreglass Centi-Phase fuselage. I have all of these and my CP fuse strangely has the wing joiner tubes for the Hi-Phase (three tubes) fitted instead of the CP system of one rod and tube. The hook reinforcing block is also in the HP position which is further rear because of the sweptback wing C of G.

I'm sure that you could build a Hi-Phase from scratch using the wooden fuse CP plan.

A 'heart in the mouth' moment for me will be chopping the fin off for the Hi-Phase tail, terminal surgery but I do have the wooden CP plan and intend to build one down the line.

Couple of pictures to explain.

Last edited by Gary Binnie; Jun 25, 2010 at 06:45 PM. Reason: Correct wing span
Jun 15, 2010, 10:18 AM
Late for work again!
Gary Binnie's Avatar

On to some woodwork.

Like the guy building the tunnel in 'War of the Worlds' I have made a start!

The woodwork part of the build is just the wings and fin structure. The tailplane and rudder are made from sheet.

I say 'just the wings', the construction is fairly involved but not impossible. Should also clarify that although it has four-panels they are joined so that there are only two five foot wings.

First step is to make some plywood rib templates for 'sandwich' pack rib production, I've just about got to the end of making the first set for one inboard panel. The lower leading edge 'D' box uses stepped 1/8th and 1/16th balsa sheet, I am using some scrap pieces to check that it will all fit nicely on the building board.

The trailing edge triangle stock has to be notched for the ribs to sit in, need to make a little tool for that job. Hope to lay a panel down on the board later today.

Jun 15, 2010, 10:25 AM
Late for work again!
Gary Binnie's Avatar
I am writing build notes in a Word document if anyone needs them, the wing structure is quite complicated and I wrote them by looking at the plan before starting as I could see some potentially tricky areas. Won't be sure if they are right until I've got a couple of panels built.

Jun 15, 2010, 01:27 PM
Registered User
prodjx's Avatar
Go Gary Go. I think it's true what they say about old glider's, they look way better than old A/C.
Jun 15, 2010, 01:31 PM
Late for work again!
Gary Binnie's Avatar
It is another nice looker, the sweep back is unusual for a Foss machine, I assume that it allows less dihedral to be used.

Toiling away in the shed, more piccies later.

Jun 15, 2010, 08:02 PM
Late for work again!
Gary Binnie's Avatar

Spare ribs (almost!)

Time to give up for today as I almost made a mistake (see lower down).

I undid the rib pack and laid them on the plan, another rib (Rib 21 - inner panel tip end) has to be made using the template directly, easy peasy.

I also numbered them to avoid embarrassment, writing the numbers in the 'D' box area where they won't be seen through any transparent covering.

Would be nice to start gluing at this stage but the ribs need quite a lot more work yet. Six of the ribs need 1/16" trimming off the rear (top and bottom) to allow for sheeting. See photos for how I did this (ace builders would do it freehand!). Two more ribs need partial trimming for diagonal sheeting over the rear drag spar, not done yet.

The trailing edge also needed slotting to take the rib tails (but not all of them, watchout!). Was wondering how to do this a couple of weeks ago when I read a great idea in an old model magazine in the loft. You basically make a slotter from glued together snapped junior hacksaw blades and a handle and 'Bob's your uncle'!! Looks like something that prisoners make though. The slots are meant to be exactly 1/8" deep, another problem to solve. I just clamped a length of scrap hardwood to the trailing edge and used it as depth stop, what I ended up with looked like it came out of a kit, very impressed!!

Next the first nine ribs need a notch or hole at the lower front for the spoiler cable guide tube, sandwiched again and done with a file. I know that I could use wing mounted servos for the spoilers but I am trying to keep it original and I think it would add weight and complication, I have no problem with the same system on the Multi-Phase (apart from trying to take the wings off with the cables still connected!!).

The last job that I looked at today was cutting the spoiler recess and spoiler sub-spar slot. I have copies of the plan to cut up and I used spray photomount adhesive to stick the section onto a stack of the ribs that need the cutout. This was where I nearly slipped up, I added all the ribs under the spoiler to the stack but luckily realised that I had included the end ribs (which only have the sub-spar cut out) before I cut anything. Phew, a close one, could have copied the ribs to make new ones but was glad to avoid doing that. Still not quite sure how to cut that bit out exactly, razor saw cuts and a scalpel probably.

Other jobs to do are facing one rib with ply and cutting the joiner tube holes.

I've been thinking about how to cover this for a while, was wondering about tissue over Mylar. Not done it before but I have plenty of unfinished wings to practise on, I think Chris might have used Nylon or heavyweight tissue originally.

Covering is a way off in the distance at the moment but it doesn't hurt to plan ahead!

Jun 15, 2010, 11:50 PM
Low altitude flyboy
MajorMal's Avatar
Nice work shed
Jun 16, 2010, 03:39 AM
Late for work again!
Gary Binnie's Avatar
Thanks, I blogged the shed build here:

No electrical power at the moment but you don't need a lot for building a model like this (unless it is winter, then you need the heater on!!).

Jun 17, 2010, 12:18 PM
Late for work again!
Gary Binnie's Avatar

Tu be or not tu be!!

Well I dithered a bit yesterday, got to drilling holes in the root ribs for the joiner tubes but stopped as I was wondering what type and diameter of tube I should use.

The plan says '1/4" tubes' but not what they should be made from (aluminium or brass), they do have to be 6 SWG internal diameter for the existing fuselage tubes (which is the designed joiner rod size). Feeling the weight of brass tube against aluminium I think 'ally' would be a better choice, if anything is going to bend it would be the rods at the wing root/fuselage joint. I don't have the right size ally tube at the moment so I am carrying on with other stuff.

I cut three pieces of sheet to form the leading edge, all tapered!

Joined the two lower forward sheets using tape on the back, opened the joint up (forming a 'V') and glued with aliphatic resin. It all wanted to curl up so my old motorbike batteries came in handy for weights.

The next little job was to make the small spruce pieces for the tapered root spar. After sanding my fingers away a couple of times making the small wedge that fills the gap I realised that the best way to do it was sand the end of a whole strip then cut it off.

That lot should be dry now (it's 31 degrees in the shed!) and I might be able to start adding ribs that don't need any more work doing to them.

Last edited by Gary Binnie; Jun 29, 2010 at 08:48 PM. Reason: Typo
Jun 17, 2010, 02:53 PM
Late for work again!
Gary Binnie's Avatar
I couldn't see any reason not to add all the lower sheeting at this stage, so I did!

There is a note on the plan saying pack the rear of the root ribs up 1/16th to allow for sheeting, I'm assuming that CF intended builders to lift the panel from the plan then sheet it. I will be leaving the upper inboard sheeting off of both inner panels because I will surely need to 'adjust' the joiner tube holes.

Have glued the lower main spar down now, more battery fun!

I will only describe the building of one panel so as not to bore you all to death, might show pictures of the other three if you are lucky!

Jun 17, 2010, 05:26 PM
Late for work again!
Gary Binnie's Avatar
Time to call it quits for today, good progress though.

Have dry fitted most of the ribs and it's starting to look like a wing.

Brought the plan indoors to have another look at it (look twice, glue once!).

Can't wait to do the spar webbing, not!!!!!!

Jun 18, 2010, 05:24 PM
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Gary Binnie's Avatar

Plodding on.

Well I did spot something not so obvious on the plan, the middle joiner rod (of three) is longer than the others, the detail was slightly hidden under the shading for the spar. Aluminium tubes are on order as well as a pair of 'Z' bend pliers. I've never had any of these, should save me from soldering clevises on both ends of a rod!!

Have now glued in all the ribs that don't need any more work and started on the spar webbing. I think this is the first glider spar that I've built with the webbing between the spars rather than glued to the back or front (or both). The only accurate way (or easy way!) to do this is glue them to the lower spar before adding the upper one, only 50 or so more to do. T'is very therapeutic making spar webs!!

The webbing starts at 3/8th thick at the root for six bays, then 1/4 for four, then 1/8th out to the end of the panel (the outer panel has the spars webbed 2/3 the way out to the tip). Looks light and strong (might be handy if I have to use an F3J winch again!).

The rib tails are slightly too short which is leaving a tiny hole where they slot into the trailing edge, will leave them overlength for the next sandwich pack.

Got bored with webbing and had a look at the spoiler box. For some reason the sub spar is slightly too close to the main spar so the full width 1" x 1/4 trailing edge stock spoiler would not drop in (also needs some allowance for covering material). Could trim the spoiler but then it would not be full width so I'm tweaking the sub-spar slots to move it back a little.

One thing I noticed on the plan is that it doesn't mention to angle the polyhedral break ribs (it does for the root rib and a template is drawn). I used an online angle calculator with the known tip panel span and the dihedral height and it came out with 8.2 degrees for the outer dihedral so if I angle both ribs at 4 degrees it should be about right. I suppose if you forgot to angle these ribs you could make a balsa filler wedge (or start again)!

All good fun, have to go to work for three days now where I will ponder colour schemes in the slack moments no doubt (maybe black and yellow this time for a change, dunno yet).


Jun 23, 2010, 09:06 PM
Late for work again!
Gary Binnie's Avatar

Bored already!

Not really, just bored with spar webbing!

Still a lot more work to do on the first wing panel, the more it progresses the more costly a mistake would be.

Had another look at the fuselage as some holes needed filling and I knew that there were some alignment problems with the wing joiner tubes.

Filled all the holes including an FM aerial lead out (this one will be on 2.4), multiple towhook positions (?!!) and the original Centi-Phase low mounted tailplane hinge and slot. I backed these with 0.25 mm carbon sheet to stop the filler falling through.

I fought for most of the day with the wing joiner tubes, just not right. I used a pair of ply wing root template ribs to look at the alignment, the middle hole had not been used (seems to go through a fibreglass rod?) and it was too high. The front and rear tubes were misaligned looking from the nose so the easiest option was to drill out the front tube and fit a new one in the right position. I think the rear tube was originally fitted 'on the skew' as the fin has a slight lean, not much that I can do about it though.

I was still not happy messing about with ply templates so I enhanced my fuselage jig with some soft pine plates screwed to the base board. A small 'eureka' moment!!

So with a rat tail file, a drill and some fiddling I should end up with three joiner tubes that will accurately fit the wings.

Here's a question; Chris Foss makes a point of recommending to use only polyester resin as an adhesive (not epoxy) as that was what the fuselage was made with originally, I have read this in other books as well.

You might wonder why I am taking so much trouble and care to restore an old model (instead of buying a new shiny one), well, it is a rare machine nowadays and I have a personal goal to build my next model better than the one before and I have to admit to enjoying building more than flying (the fear of crashing I think!!).


Jun 24, 2010, 03:03 AM
Registered User
prodjx's Avatar
Looking good.

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