Nick Cripps

And don't forget to keep the engine running at all times while waiting outside the school...

Fair enough. A decent quality studlock compound is unlikely to work loose though, so you could then drill through and tap both ends for 10mm or so which would be sufficient. You could also dispense with the flats and drill through the diameter to take a tommy bar which would be much easier to produce. By the way, I'm impressed with the build and rate of progress so far, should look great in the air.

The standoffs look to be more work than necessary. Why not cut some lengths of ally bar, drill a clearance hole through and then use 6mm studding?

When setting up the throttle cut function, you need to set the servo throw percentage which can be positive or negative. Adjust that setting to get the servo to the position you require. See page 27 of the manual here.

Looking good. What's the balance like?

I'm normally more of a night owl than an early bird but I wanted to do a quick update on Smoke Trail before going off-grid again for a few days. In between doping the fuselage, I've covered the tailplane and made a start on the wing. The Litespan was stuck onto the tailplane lower surface using the cheap PVA (used wet) and, once dry, trimmed along the edges. I had to apply some extra PVA where I wrapped them around the edges and found that it did in fact adhere quite well with the use of the covering iron on the dried glue. My earlier tests with this method weren't successful and I suspect this was due to having doped the framework first (as recommended by George Stringwell). More PVA was brushed onto the upper framework and the Litespan laid on top, leaving the tips unglued at this time. The leading and trailing edges were trimmed once dry and more PVA was applied to stick the tip covering down. This was a bit tricky using the one piece and resulted in some wrinkling. Thinking laterally I tried brushing on some shrinking dope which has reduced the wrinkles a bit but I think I'm going to have to cut the tip covering away and do it again using separate pieces of Litespan. With that experience, and despite having previously baulked at the price of Cover Grip, I decided to bite the bullet and order a bottle as I wanted to be sure that the wing covering was as secure as possible. I have to say that it has worked well so far on the one panel I have covered using it. And here's a view from the other side: Back in a few days to finish off the wing covering.

That's a good philosophy to follow. Unfortunately I strive for perfection but rarely achieve it and end up with neither! I use a Dave Smith Models fuselage jig which consists of MDF brackets bolted to a piece of white contiboard. I have marked a centreline and a perpendicular line at one end but still sometimes struggle to get my fuselages correctly aligned. The square grid on the SLEC jig looks like it would be a big help so I will pick one up at a show this year. The "to do" list is coming along nicely, Steve.

That building jig is really good, it shows when things aren't square ?

I've had a bit of a break from Smoke Trail to do other things, including actually going flying for the first time in about 4 weeks! And, to be honest, the cancellation of the Nats at Barkston has knocked the wind out of my sails a bit as well so little progress was made last week. Anyway, back to it now, and tissue covering the fuselage was the next job on the agenda. I'm using some tissue which I obtained from a friend who was giving up the hobby and it came in a roll along with about 20 or so other assorted colours. I suspect it is intended more for gift wrapping as its wet strength is low and the dye comes out when you brush thinners through it but it went on reasonably well with just the odd wrinkle - fewer than I've got! You can see some of the dye on the wing seat which I've left uncovered. There's more on my fingertips from rolling the tissue round the edges. The tissue is also quite thick and will probably take quite a few coats of dope to seal.

Chuck Cunningham's article that was published in RCM is a good source of information too: Float Flying

Doh! ?‍♂️ The step should be 1/2-3/4 inch behind the CG.

Good spot, Frank, I missed that! The step should be 1/2-3/4 inch behind the step to allow the model to rotate correctly for take-off. And, yes, the Wot 4 makes a great waterplane:

Alastair Sutherland published some guidelines on the design of floats in his column in RCMW some years ago. His rule of thumb was to make the volume of each float in cubic inches equal to four times the weight of the model in ounces. You could roughly measure the dimensions of the float and work out the weight of model from that. Another rule of thumb is that the length of the float should be around 75-80% of the fuselage length but the position of the step and having a couple of inches of float protruding ahead of the prop are more important. There's also some good information on the Windermere Model Waterplane Flyers site WMWF.

That tailwheel retract is a work of art! The air pressure holding the retract down should provide some basic springing as well - clever design.

Dubro used to make a control horn that had a captive ball to which you attached a normal clevis and was available in various lengths. It appears to be discontinued now but they still offer this heavy duty version for large models: Heavy Duty Dual Control Horn

Yep, I'd do the same, Steve. It's also worth putting the wing in place and checking that the tailplane aligns when viewed from the front/rear.

You've not missed anything, Pat, no updates for a few days as I've been working on a different model and only putting the odd coat of dope onto Smoke Trail when I get chance. PM sent.

You're just not trying hard enough ?

Hi Pat, I've looked at the Tomboy plan today and realised it is much bigger than Smoke Trail and, with a built-up fuselage as well, would probably need at least 3m (possibly a bit more to allow for wastage). If you have that quantity available, please let me know the cost including postage and the easiest way to pay you. Regards, Nick

That's a very kind offer, Pat, thank you. I'm going to use the Litespan on this model but there's a set of parts for a Tomboy somewhere in a cupboard which I may build later in the year and could try it out on that. I'll measure it up tomorrow and send you a PM. Thanks also for the links to your threads, I'll have a good read of them.

After letting the test panels dry for a few hours, I moved onto the next stage: heat-shrinking to tighten the covering. Using a heat gun on the clingfilm and gently warming it as described in the video above, I found that the edges pulled away rather easily and clearly weren't really stuck down at all well. I decided that method wasn't for me so looked at the Litespan panel instead. I shrunk that with a covering iron turned up to about 125 deg C and this seemed to work well, with the covering still appearing to be attached firmly to the framework - success! I'd only covered one side of the panel and, holding it up to the light, the covering appeared to show some pinholes. Gently blowing through the surface confirmed it was not completely airtight, despite the instructions claiming so. I've now given it a coat of 50:50 non-shrink dope to seal the surface and, I hope, help to ensure the covering stays firmly stuck to the framework. I'll give it another coat tomorrow and see what it's like. With luck, the dope will not only seal the surface but also make it look even more like the tissue finish on the fuselage. A shame I won't get to try out the tissue over mylar method on this model. I'll give it a go another time but, for now, I need to get Smoke Trail finished so I can get back to the other model I've been working on, ready for the summer season.

I've put a couple of test pieces onto my scrap framework, both with the Poundland PVA used wet (no tissue paste). I have not thinned the PVA as it already has a very watery consistency straight from the bottle, much thinner than you would typically get in diy shop PVA. One panel is covered in Litespan and the other is covered with clingfilm, with the tissue to be added later. With both panels, I'm going to let the PVA dry before the next stage. Apparently, clingfilm is made from PVC or polyethylene and is typically around 10 micron thick and therefore thicker than the mylar I was planning to use (although still acceptable). The particular brand I have is stated as "non-PVC" so will be polyethylene which, as you know, stretches very easily - it will be interesting to see how it behaves with the tissue over it.

Thanks EB and Andy for your suggestions. I'll have to experiment with clingfilm but my initial thoughts are that it is thicker (hence heavier) than mylar and I'm not convinced that it has the same puncture resistance. I'll give it a try and see how it goes, it may be ok in conjunction with doped tissue. I didn't think 5-star/Starloc adhesives were still in business, Andy? Good thought, though, I think I may have some tissue paste somewhere. If I'm going to stick the covering down with wet paste then PVA should be just as good?

With the smell of cellulose dope pervading the workshop, I got my selection of lightweight tissue out to decide what colours to use. I'm going for the traditional coloured wings with black fuselage but I now have something of a dilemma over the wing covering itself. What I thought was a roll of thin mylar bought from SAMs some years ago turned out to be something else, a lot thicker and slightly opaque in colour. It looks similar to laminating pouch material (ie, adhesive-coated) but tests on a scrap framework showed it had little resistance to temperature and wrinkled easily, while still staying opaque. Not having anything else suitable as a base to tissue over, I now have to either order some mylar from Mike Woodhouse or change to a one-shot covering such as Solarfilm Litespan (which I already have in stock). Either way, I will need to find a suitable adhesive to stick the covering down as my jar of Balsaloc is just a solid lump! The obvious alternative is Deluxe Materials Cover Grip but have you seen the price? ? Some research shows that thinned PVA can be used (but my experiments so far with Poundland glue have been unsuccessful) or contact adhesive thinned with cellulose thinners. I will give that a try but if anyone has any other suggestions/experience, please let me know. So, back to the workshop, and some thinking to be done while I get high on dope fumes ?

All the woodwork has been completed with the fitting of the cabin roof and shaping of the nose. Also another small milestone has been achieved: first fitting of the engine. I knew that 8BA box spanner I bought 40-odd years ago would come in handy again: We're now ready for the first coats of dope to be applied...