Andy Sephton 1 Posted October 15, 2018 Share Posted October 15, 2018 I've decided to rescind my earlier comments on balsa spars. I've just stripped the hardest 1/8" balsa I have in stock (15lb/cu ft) and weighed a 36" length. the result was 4.0gm. Stripping a similar length of spruce came up with 8.8gm. Substituting the spars with spruce would increase the overall weight by about 60gm, or just over 2 oz. More importantly, destructive testing of the balsa spars showed them to be quite weak, so I shall be using spruce for my spars. Balsa does exist in harder grades, which would be proportionately stronger...but it would also be heavier, reducing the penalty for using spruce. Quote Link to comment Share on other sites More sharing options...
2W Posted October 15, 2018 Share Posted October 15, 2018 I was wondering if laminating 1/32 balsa to make the spars would be worthwhile? They would certainly be stronger, but probably difficult to produce. William Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 15, 2018 Share Posted October 15, 2018 Interesting research Andy, thanks for that. Ernie, I would like to do oleos, and I cannot see why not, but I haven't checked diameters etc yet Adding carbon is a good idea. I have been musing what to use to harden/sharpen the trailing edges, carbon would be my preferred choice but the .5mm rod is quite expensive. We will have to see Carbon tissue between two 32nd laminations could be an option also William. So many choices nowadays. My fear is that adding strength may just move the failure elsewhere. So I am still musing that one as well. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted October 15, 2018 Share Posted October 15, 2018 Shaping the leading edge first and adding carbon fibre tows would be easier to add strength and keep shape.Edited By Fats Flyer on 15/10/2018 13:05:31 Quote Link to comment Share on other sites More sharing options...
Richard Mallam. Posted October 15, 2018 Share Posted October 15, 2018 In response to Andy's post on using spruce rather than hard balsa for the spars. What thoughts on maybe applying webbing to the upper and lower hard balsa spars? Richard Quote Link to comment Share on other sites More sharing options...
Andy Sephton 1 Posted October 15, 2018 Share Posted October 15, 2018 I considered webbing Richard, but decided against it as it stiffens the structure. A bendy structure can often be less likely to break than a stiff one. Most of my modelling has been in free flight. In this case we would probably make the wing with two central spruce spars of around 1/4" x 3/8" and live rigging. I want to keep the model as near to the plan as I can, hence the choice of four spruce spars the same size and position as the hard balsa versions. In the end, I don't think there is a right or wrong answer. You've got to go with what your experience tells you should work. Quote Link to comment Share on other sites More sharing options...
Stuart Rusby Posted October 15, 2018 Share Posted October 15, 2018 I have pinned 1/8th balsa strips between each rib position on the plan to raise the lower wing spars so that the wing lies flat and so the ribs don't touch the plan. I have also introduced 1.5mm dia carbon rod into the trailing edge to try and reduce any warping - I am not sure if this will achieve anything! I'm impressed with the quality and accuracy of the Sarik wood components. Quote Link to comment Share on other sites More sharing options...
Andy Sephton 1 Posted October 16, 2018 Share Posted October 16, 2018 I've been looking a bit more closely at the fuselage formers. I reported above that F5 and F6 were cut too wide. In fact, the outer edge of both of them is good, it's just the inner edge where they fit over the fuselage that's too big. Quote Link to comment Share on other sites More sharing options...
Ernie Posted October 16, 2018 Share Posted October 16, 2018 I really do like to include' cockpit detail in my models. It's a bit difficult because of the sheet balsa inner box that Andys pix show. This means that the cockpit will be narrower than on the original, and the walls will not be curved. Any ideas ernie. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 16, 2018 Share Posted October 16, 2018 Hi Ernie, yes I agree. I am having to live with an elevator pushrod through my cockpit as well. I am not sure what to suggest, may have to just live with what we have? Cheers Danny Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted October 16, 2018 Share Posted October 16, 2018 well i am adding cockpit detail where i can. instrument panel is almost sorted. i have had to cut to slots in the balsa sides to get it to sit low enough. i will have to see what else i can squese in there. Tony B Quote Link to comment Share on other sites More sharing options...
Ernie Posted October 16, 2018 Share Posted October 16, 2018 Hi all, that instrument panel is truly a thing of beauty, there seem to be several variants, depending on what version we are modelling. The sheet sides make it almost impossible to get the silver fascia to sit properly in place Could the structure be modified around the cockpit, without compromising the structure, and altering the spirit of the build? ernie Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted October 16, 2018 Share Posted October 16, 2018 this is my attempt at the instrument panel. i have had to cut some slots and remove some of the balsa along the top of the cockpit sides. Tony B Quote Link to comment Share on other sites More sharing options...
Richard Mallam. Posted October 16, 2018 Share Posted October 16, 2018 Regarding strengthening the main wing trailing edge - how about applying some some 25 gsm glass cloth? Quote Link to comment Share on other sites More sharing options...
Stuart Rusby Posted October 20, 2018 Share Posted October 20, 2018 Danny, whats a good way to attach the capstrips to the wing ribs, re bending, glueing and securing? Thanks, Stuart Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 20, 2018 Share Posted October 20, 2018 Hi Stuart, i am always imparient when building and often use thin ca to speed things along. One trick that I saw the workers at Seagull do is to use your favourite slow glue, titebond, etc but then tack with CA. Amazingly the two glues dont seem to interact CheersDanny Quote Link to comment Share on other sites More sharing options...
Gordon Whitehead 1 Posted October 20, 2018 Share Posted October 20, 2018 Hi Stuart. Re bending, cap strips are best pre-bent to match the curve of the rib. To do this, lay the cap strip on your bench, lightly press down on it with a pen barrel or some other smooth rod about 3/8in to 1/2in diameter, and pull the cap strip through, lifting the pulled end at the same time. Repeat as necessary until the curve matches the aerofoil shape. Practice on a spare length of strip until you can do it without breaking the strip. The pre-curved strip will usually attach OK with PVA and a pin at each end. Cheers Gordon Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 20, 2018 Share Posted October 20, 2018 Hi Gordon, good thinking, i had completely misunderstood Stuart's question. Laminating 32nd balsa over the rib is perhaps another way.CheersDanny Quote Link to comment Share on other sites More sharing options...
Stuart Rusby Posted October 21, 2018 Share Posted October 21, 2018 Many thanks Gordon and Danny. I will get my old pen into action! Quote Link to comment Share on other sites More sharing options...
Stuart Rusby Posted October 22, 2018 Share Posted October 22, 2018 Capstrip bending worked a treat Gordon. Used a 1/2in dowel. Many thanks, Stuart Quote Link to comment Share on other sites More sharing options...
Jose L. G. Posted October 22, 2018 Share Posted October 22, 2018 Good morning Sir, Anyone has info about the size of the tailwheel of the K5674 of HAC? Thanks. José Luis Edited By Jose L. G. on 22/10/2018 10:35:48 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2018 Share Posted October 23, 2018 I will try and get some pics and wheel/tyre dims for you José Luis Cheers Danny Quote Link to comment Share on other sites More sharing options...
Jose L. G. Posted October 24, 2018 Share Posted October 24, 2018 Posted by Danny Fenton on 23/10/2018 22:30:31: I will try and get some pics and wheel/tyre dims for you José Luis Cheers Danny Thanks a lot Danny. J.L. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 24, 2018 Share Posted October 24, 2018 Andy S, Tony B, Martyn K and of course yours truly managed to get behind the wire Thank you Mr Black for giving us the okay Martyn counting rivets.......... Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 24, 2018 Share Posted October 24, 2018 My reputation is shattered :D Quote Link to comment Share on other sites More sharing options...
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