Here is a list of all the postings Steve McLaren has made in our forums. Click on a thread name to jump to the thread.
|Thread: Another PSS Jet Provost Build Blog|
A couple of weeks seem to have gone by and I've done nothing. But today I found a bit of time to carry on with the covering.
I thought I'd concentrate on the fiddly bits around the tailplane. The parts are all loose but I put them all together again to see how it was looking.
Since it's supposed to rain tomorrow, I should be able to find time to start on the fuselage itself.
During the week I painted the cockpit area and glued the canopy in place. I sealed the balsa inside the canopy with a coat of acrylic varnish and then applied a single coat of acrylic matt black ( with a bit of grey for the seat cushions - not sure if that's accurate, but it all looked a bit dull in one colour!)
I used a thin slice of the instrument panel graphic supplied by Phil Cooke, and printed on my inkjet printer, pasted on with PVA. The traplet canopies have a bit of a texture so nobody's going to be able to see it too well. Anyway it gives the general impression of an instrument panel, which will do for me.
I used 'canopy glue' to attach the canopy. I've used in on quite few models recently and it seems to work very well. My plan is to cover with solarfilm up to the edge of the edge of the canopy, and then use solartrim for the canopy lines and edges, and to cover the join.
Then I've been re-shaping my air intakes. I took a fair bit off the bottom edge, and had to narrow the under-wing fairing by about 1/4 inch each side. The result looks a lot closer to what's shown on the plan:-
So then I'm onto the covering. I've been playing around with iron temperatures a bit, before I started on the model itself. So I'm now using a cooler iron than might otherwise have done.
I have now started on some of the simple little pieces - the elevators using the grey (which is supershrink polyester). I've tried to set the iron at 100degC for the actual covering phase, but it varies a fair bit as the thermostat switches. But initial results look OK, and I would say the covering is easier with the slightly cooler iron. But will it avoid the wrinkling in the sun problem? Maybe I'll find on the 1st June?
Thanks Guys.It's not that neat really. I just choose my camera angles carefully and use an old 3MP camera so you can't see any detail!
And I don't usually build this quickly, but I want to have this flying by the 12th April. For that reason, and because I think my build is already carrying a few extra grams, I'm not going to bother with the rear wing fairings, nice though they certainly look Andy.
To answer Andy's question, it's 556g or 1lb 3.6oz, at this stage. But that's without any aileron servos or linkages, and without covering. My 2 servos will be another 30g or 1oz. And then the battery - In your flying notes you mention that the original used a 600MAh Nicad so that sounds like 4 x AAA size, or 54g (1.9oz). That would make it 640g or 22.5 oz +covering + however much balance mass I need.
I really don't have a feel for the weight of the covering, but it looks like it will be heavier than your original. But I'm still hoping for decent light wind performance!
On the covering topic - well for me it has to be the red, white and grey. That's how I remember them from when I was a kid, and that's what attracted me to this build in the first place. I'll see if I can find a reg number that isn't too common.
So yes, the ironing task is looming and I'm getting a bit nervous about that. It's all a bit more critical on a scale model., A lot of my other solarfilm covered models exhibit the wrinkling-in-the-sun problem, which Andy tells me is because I use the iron too hot. So I've got myself an iron thermometer ( the instructions which came with it also confirm the wrinkling due to iron being too hot theory) and I'm going to do a bit of research/practice before I start on the real thing. I ordered all the film a few weeks ago, but now I'm starting to doubt whether I've got the right shade of red!
Whilst thinking about the covering, I thought of another question for you Andy. You mention in the write-up that the matt black anti-dazzle panel was painted with enamel paint. Was that on top of the solarfilm, with a primer like Prymol? or did you fit the solarfilm around the black painted area?
|Thread: Just Possible Jet Provost by Steve|
I hadn't used laser cut parts before either and I too was surprised by how much carbon came off the burnt edges. But I wouldn't worry about it. - Nobody's going to see the inside and there's so much sanding to do on the outside that any fingerprints will be a distant memory!
|Thread: Another PSS Jet Provost Build Blog|
This weekend I've been working on the under-wing fairing - more sculpture! And there's not much on the plan to work from and not many useful photos on the internet either. After going through this phase:-
This is what I've ended up with:-
But it sounds like I'm not finished yet. My intakes are a bit fat at the bottom (based on expert advice) so there's a bit of re-modelling to be done.
Anyway I thought it was time I put the whole thing together again. It helps to keep me going (despite the balsa dust induced cough) when I can see what I'm aiming for!
So this is how the air intakes are currently looking.
I did a bit better this weekend. I carved and sanded my ailerons to shape. I used the technique recommended by Andy - tack bonded them in place at 4 points, put a bit of masking tape on the surrounding wing surface, and then set about them with razor plane, knife, sanding block, etc until they seemed pretty much the right shape. I seemed to manage without scratching the wing skins too much, but I took off the final few microns after I'd removed them from the wing.
You will see above that I've also started on the air intakes. This build is starting to feel more like sculpture than aeromodelling! Again it's difficult from the plan to get a good idea of what shape you are aiming for so I've been studying Andy's photos and all those on the internet to get a few different angles on these intakes. I think I've just about finished them off this evening, but it's too dark to get a decent picture, so I'll have to post that later.
I have also fitted the cockpit sheeting.
I also sanded the ejector seats to fit, and check the fit of the pilots in the canopy, but I don't have a photo of that.
Unfortunately I've had broadband failure all week, so I wasn't able to report my massive progress from last weekend. This is it:-
I changed the elevator clevis to a metal one!
Actually I also drilled a few extra holes in my tip tanks, and managed to get them down to the target weight of 1oz for the pair!
I'm hoping for better progress this weekend, but I think we might be approaching that time of year when I'm going to have start mowing the lawn and tidying up the garden!
Andy, Yes that's a good point about serviceability. And I suppose you're also right about the weight thing. OK, I bow to your advice again. I'll go root around in my boxes for a metal clevis!
Well it feels like I have been sanding all weekend! But I like this bit where the real shape starts to emerge from all those rectangular blocks of balsa. So this is my fuselage now, after sanding the rear end:-
And the jet pipe from underneath:-
But my fuselage is weighing in at 9.2oz compared to Andy's target weight of 8oz. There's still a little bit more to remove at the front, and the cockpit to cut out, but I don't think I'm going to get to 8oz.
I've also added the captive nut for the wing bolt, and added the F14 doublers to reinforce the bolt plate/wing seat area. I had been thinking of leaving them out as I couldn't see that they would do very much, but after sanding the rear fuselage to shape I can now see why they are there.
I've also done some work on my elevator control horn. Andy B had expressed some concern that it looked a bit thin! Since I had made it by squashing an off-cut of the same aluminium tube I used for the aileron torque rods, it was indeed a bit thin. Also, since I planned to use a nylon clevis to minimise the weight at the rear, I was worried that the aluminium might cut through the clevis pin on a heavy landing.
I was about to re-make the whole thing using the recommended brass tube instead, but then I had an idea to reinforce it. I epoxied a small piece of 1/16th fibreglass sheet over the blade and another piece to link it back to the body. The result is show below:
I think that should be alright now. The bearing area is about 3 times what it was. What do you think Andy?
So I'm going to stick with the nylon clevis now.
I have also added the wing bolt reinforcing doublers and applied the fibreglass tape to join the wings:-
Also done my pilots. These are the same ones recommended by Phil Cooke on his blog, and supplied by the very helpful Steve at Vortex Vacforms (after I had initially ordered the wrong ones!).
Not much progress during the week as I had to go away with work. But I did do a bit more investigation into what went wrong with my port wing, and I came to this conclusion:-
I created a template on tracing paper to help with marking out the wing lower skins. I pricked through the template with a pin and joined up all the dots in the 1/16th sheet to mark out the wing shape and the rib positions. I did the right wing first, and then launched into the assembly operations. I marked out the left wing about 3 days later. And I think this is where I made my mistake. If you look at my template in this photo you can see that it uses the edge of the paper as the wing centreline datum, and it has a line marked for the outside edge of rib 1. So I think that, in marking out the 2nd wing, I have used the black line as the wing centreline datum.
After re-measuring carefully I found that the port wing is pretty much exactly 1/8th inch short. So with the extra 1/8th packer on the inboard face of rib 1, I didn't need to do any sanding to get a good fit.
All a bit embarassing really. The trouble with these build bloggs, is that you have to admit your own stupidity!
Anyway, with the extra packer in place, I have now joined the wings. The dihedral templates supplied in hte woodpack seemed to work very well ( after fitting the stabilising feet as suggested in one of the other build blogs.
I joined the root ribs with with epoxy, and then fitted the shortened dihedral brace through the slots in the lower skin.
This weekend I've also sanded the tailplane and elevators, and made the elevator joiner / control horn. I used one of the off-cuts of the same aluminium tube which I used for the aileron torque rods ( just because it was convenient).
I also joined the fin, rudder and strake together. ( I have made my decision to leave out the rudder).
And then I sanded the fuselage nose to shape and added the rear decking. So now I can do my first full view of the whole assembly.
I started to work on fitting the elevator control snake and shaping the fuselage tail. But I am taking it very slowly, That tail end is a bit complicated and delicate. I want to remove as much wood as possible, to keep the tail end light, but leave enough to keep it durable. It's not easy to figure out from the plan, so I have to keep referring to the photos in the write-up. Will post some photos, when I get a bit further.
Fitting the top skins to the wings was, for me, the most nerve wracking part of this build. It seems to me that you have just one chance to get it right. If you get it wrong, I'm not sure that you would be able to rescue much from the carnage. So I put a bit of time into the preparation
Despite my reservations, I did find that it was indeed possible to cut an 18 inch long tapered wedge from 0.8mm (or thereabouts) to zero. Actually mine faded away at about 15 inches, but I figured that was good enough. So I taped it to the bottom of one wing under the aileron spar and running towards the root, and pinned the wing down firmly. I used PVA adhesive, to give myself as much working time as possible, and set off with a few weights and lots of pins.
When I removed it from the board a few hours later I was initially really pleased with the result, until I spotted a spanwise crack of about 5 inches long in the upper skin near the aileron spar. If you look on the photo you can just about see it was there when I'd finished the pinning, but I didn't notice it until later. (It runs inboard from the 4th to last pin on the aileron spar).
There's not much curvature in that region, so I decided that it must have been a flaw in the original sheet , and I was just unlucky. Anyway I squirted a bit more PVA in it and weighted it down with a steel ruler. That seems to have fixed it, I' don't see any reason why it shouldn't be just as strong as the other skin joints in the wing.
The 2nd wing skin went on without any such problems.
Having fitted the leading and trailing edges, and sanded to shape. The wings look like this.
At this point I thought it was all going so well. Then I decided I'd better check the two wings back to back against each other - check the washout angles etc. When I did this I found the washout angles looked great, but I found that my wings were slightly different lengths! How could this be? I had initially marked them out on the bottom skins from the same tracing paper template, so I couldn't understand this. After carefully checking against the plan, I found that my left wing is more than 1/16th inch shorter than it should be, and the error is all at the root end.. Looking back on it, I think I just wasn't careful enough with the positioning of the root rib. I marked out all the ribs on the skin, except the root rib, which I just positioned against the cut edge of the skin. I still don't really understand it!
Anyway , to fix this I have glued a hard 1/8th balsa packer to the inboard end of the left wing. My plan is then to sand it down to the correct thickness before I join the wings together. Since I planned to do a fibreglass skin joint at the centre anyway, I'm hoping this mistake won't have too adverse an effect on the overall strength of the wing, and it will be hidden below all those under-wing fairings anyway.
So, back to the fuselage. I thought that once I'd got the sides joined together I was making good progress. But there's a lot of work in this fuselage!
I've put in some hours this weekend on planking the upper fuselage and cutting all those 1/2 inch blocks to shape to fit between all the formers at the front end. I also added a few 1/16th strips on the inside of the triangular sections, since mine had gone a bit crumbly after being over-zealous with the saw cuts. I'm hoping these will hold everything togehter better when it comes to shaping the fuselage later.
So this the planking.
And this is the block work finished at the nose end. I tried to make these as 'hollow ' as I could, but it's difficult to judge where the outer profile is going to end up, so I erred on the safe side.
I also added a scrap former half way back inside the planked section, as suggested by Andy.
So, maybe some shaping in the next few days?
So to the wings.
I built them pretty much exactly as the plan up to this stage (even got the spar webbing the right way round!),
I did deviate from the plan a little on the aileron torque rods. I decided not to bother with the carbon fibre reinforcement. My logic was that, being 'torque rods', they shouldn't really need the bending stiffness. And the construction was a bit simpler without the carbon. I just wrapped a bit of glass cloth and resin around the wire ends to bring them up to the inner diameter of the aluminium tube. I'm hoping that might have saved me a couple of extra grams!
Before applying the top skins, I needed to think about the wing joining. Again I decided to deviate slightly from the plan here. I decided that since most of the load in these wings is carried in the skins, it would be a good idea to go with Andy's suggestion and reinforce the skin joints top and bottom with glass cloth. Once you decide to do this, I'm not sure that the wing joiner ply brace is really going to add much. But I couldn't bring myself to leave it out altogether, so I'm going with a shortened version which just spans the inner bay of each wing, and adds a bit of shear strength to the joint. To make this easier to fit after wing joining, I pre-cut the slot in the bottom skin and cut halfway down through the ribs from the top surface. Hopefully this will preserve the stiffness of the structure for the skinning operation, but make it easier to fit the brace from the bottom later.
So this is my fuselage today, joined together. There's not much to say about joining the rear section, except that I drilled a few extra holes in F6 and F7, and sanded the inside face of the triangular sections a little concave between F6 and F7 in an attempt to save a few grams at the back end.
I've also been thinking about whether to bother with the rudder. From what I read, it sounds like most people are going to go for the rudder option. But I'm very tempted to leave it fixed (as originally designed). My logic is that, being a relatively in-experienced, casual sort of sport flyer, I'm not convinced I will make much use of the rudder, and I think I would benefit more from a lighter model which works in the lightest possible wind conditions. That way it is likely to get flown a lot more often.
I shall keep thinking about it, but I will have to decide quite soon.
|Thread: Phil's PSS Jet Provost - Build Blog|
Thanks Phil for the info on where to find some lightweight pilots. I didn't fancy the 'Pete's Pilots' version as they sounded a bit heavy, and I'm trying to build as light as I possibly can. I was messing about trying to create something from a polystyrene ball and a few bits of foam sheet, but it wasn't going well! I'll probably just end up adding nose weight anyway so it's probably a waste of time, but worth a try.
Were these the PTS 4 pilots? I hope so cos that's what I just ordered!
|Thread: Another PSS Jet Provost Build Blog|
Thanks RedBaron for the lead on clamps. I shall go check them out in B&Q today. No matter how many clamps I have, I never seem to have one that's quite right for the job.
On the Ivinghoe PSS day, I don't much much about it myself. I'm a relatively new member and until now I've not had a PSS model, so I've never been to it. I'm not sure whether it's a closed-to-club event or whether visitors are welcome, so I'd better check with the committee before I go publicising it on here (Oh it's a bit late for that!).
Right, after a bit of research on 'albums' I think I can attach some photos:-
No 1. Too many saw-cuts in too soft a bit of balsa.
No 2: Bending the fuselage sides with a workmate
That's enough for today. I'll write some more about the wings tomorrow.
I guess there are going to be lots of these blogs, so in order not to be too repetitive, and since I'm running a bit behind some others with this build, I'm going to concentrate on things which I have either done differently, things which have gone wrong, and things which I think might be of interest to other builders.
This is my first build blog. It's also my first PSS model. I've built a few models of conventional balsa construction in recent years, but always from 'full' kits. This is my first experience of a Traplet 'wood pack', and my first build from a plan since I used to make control-line combat wings in the late 70s! So it should be interesting.
I started construction a couple of weeks ago - I wasn't initially aware of the 'official' start date, but also I'm working to a shorter schedule - hoping to be ready for the Ivinghoe PSS day in mid April.
So, I'll start with the fuselage.
Mistake No 1: I didn't check that I understood what all the parts in the wood pack were before I started building. So having joined the fuselage sides together I have found that there are 2 small parts of the upper fuselage sides which I haven't used. I just assumed that the guys at Traplet had decided that this bit of the fuselage side would all be sanded away, so they must have decided it wasn't necessary. Anyway, it seems to have worked OK without these bits. It was a bit more difficult to position the forward triangular sections without a clear reference, but I managed.
Mistake No 2: I had read the info about the error in F1, but then I forgot to do anything about it until after I had built it into the battery box assembly! - but that was easily fixed.
Mistake No 3.: I was a bit over-zealous with the saw cuts in the triangular sections. I couldn't get triangular section stock from my local model shop, so I made my own from 2 strips of 1/2 inch and 2 strips of 3/8 inch, and then razor planed them to a triangular section. I selected the lightest wood I could find ,as advised by Andy. I started trying to make saw cuts at about 3/16 inch spacing with a junior hacksaw, but this just seemed to rip big chunks out of my carefully prepared triangles. If I can figure out how to use this forum software, I'll add a picture!
So I've got a bit of repair work to do there. I discovered later that you don't need that many saw cuts. because it's not that difficult to bend the fuselage sides. It requires a fair bit of force, but I discovered it was relatively easy to do if you've got a 'Black and Decker Workmate' or similar. This works very well as a controlled parallel clamp, for pulling the fuselage sides together onto F2. Then If you've got a a big spring clamp, you can use this to pull the 2 thin strips at the nose onto F1. (I was going to add a picture here too but I can't see how to do it!) Can anyone advise?
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