Former Member Posted September 26, 2014 Share Posted September 26, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted September 26, 2014 Share Posted September 26, 2014 In ship building and full size aircraft a scarf joint has to be at least 1:8 - so a 1/4 square should really cover 2" unless a Keyed Hook scarf is being used then I think the permissible length allowed by Lloyds of London shrinks to 1:6 Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 26, 2014 Author Share Posted September 26, 2014 Who is this Lloyd geezer ??? I ain't seen none of 'is posts !! Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted September 26, 2014 Share Posted September 26, 2014 As if you didnt know him and his mate Fred Plimsoll...... Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 26, 2014 Author Share Posted September 26, 2014 AAhhh, me old mucker Pump, those were the days Quote Link to comment Share on other sites More sharing options...
Jamie sawyer Posted September 26, 2014 Share Posted September 26, 2014 Its coming together CB,.....keep up the good work . Im following it to Jamie Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Posted by Percy Verance on 26/09/2014 20:08:44: And I'm sure you knew it Peter, but it might be worth mentioning that to obtain maximum strength from a scarf joint, the joint ought to be at least four times the thickness of the section being joined ie: a scarf joint in 1/4 square should be at least an inch........ Edited By Percy Verance on 26/09/2014 20:09:33 Yes, they taught us that on my Airframe Mechanics course in the RAF, even though I never worked on wooden aircaft. Can't remember the actual ratio but I don't think it was eight to one. Quote Link to comment Share on other sites More sharing options...
Dai Fledermaus Posted September 27, 2014 Share Posted September 27, 2014 "It's been a long night !! Couldn't sleep after a couple of days in bed so I decided to have a go at the bit wot the pilot sits in. It all looked fairly simple until I found that the 1/4 x 1/4 that comes with the kit isn't long enough to go from bow to stern front to back. Didn't see any reason why it couldn't be joined so I doubled it up on a straight section that has little stress in it" Avarst me hearty!!! It baint be "bow to stern" and it baint be "front to back". It be nose to tail. I rather suspect you're better at this Balsa bashing than you're letting on Edited By Colin Ashman on 27/09/2014 08:42:00 Edited By Colin Ashman on 27/09/2014 08:43:06 Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 Up early and ready to go ! At least I was until I started to check everything for square. It appears ( Nay !! Actually DOES ) that the nose section has a slight lean to the port side and will have to be corrected. Probably going to be easier to cut it off completely and rebuild it more carefully. A bit of epoxy and a few blocks should keep it firmly in place. I know what the cause was ( apart from bad technique ) the balsa appears to be slightly softer one side and has bent differently when drawing the sides together. This time I shall construct it with spruce and adjust the alignment. In fact it is not too much of a disaster as I think that with a bit of tweaking I can get my batteries in the nose, underneath the motor, pushing more weight up towards the nose. I can see me having fun making the hatch but I do love a challenge. Mike Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 OK all, I need some advice. I am considering covering the model with 1/32 hard balsa sheet or even 1/64 birch ply.. The reason being that I am a bit heavy handed at times and it would make it fairly strong. I can cover it with film or paint it to suit later. The parts that I have built, together with the box of bits to complete ( including electrickery bits ) come to just about 1300 grms and the plans give an AUW of 2200 grms using an ancient heavy petrol engine. If I use balsa it would add roughly 200 grms to total weight whereas ply would add nearer 325 grms. Either would still keep me well below the plans AUW Would it fundamentally change the dynamics of the model if I was to go down this path and would balance be a problem due to more weight being added towards the tail than the nose ?? Quote Link to comment Share on other sites More sharing options...
Dai Fledermaus Posted September 27, 2014 Share Posted September 27, 2014 I'm no expert, but I would not even contemplate covering the model in balsa or ply which I think would add much more weight that you might imagine. Keep as light as possible is a general rule with model aircraft. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Covering the cabin and nose with sheet would be OK. Don't cpver th e rear, it will make it tail heavy. 1/32 Balsa would not add a lot of strength. I once built a similar fuselage and added triangles of 1/64" ply over each of the joints on the rear of the fuselage. IT was almost indestructable. The most common practice at the front of the fuselage was to infill between the structural members with 1/8" balsa sheet. Stronger than the 1/32 balsa shet by a long shot. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 I should add that the 1/8" sheet does not need to be hard sheet, it can be quite soft and light Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 It is not for strength of the airframe that I am looking at this. It is to prevent puncturing of any fabric covering that will inevitably occur during transporting it around. The weight has been checked very carefully based on the density of balsa and ply currently available and the total volume of sheet required to cover the plane. What would you suggest as a strong covering that would be suitable for use by someone with no covering experience whatsoever. Keeping in mind that the wings are undercambered. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Well, you can punch a hole through thin sheet as easily or even more easily than film covering. I personally use Solarfilm Super Shrink Polyester film. Easy to cover, not as easy to burn a hole in while covering as other materials. You won't punch a hole in it under normal circumstances but a sharp object will punch a hole in anything. My models live in a crowded workshop, they are chucked in the back of the car and flown over stubble fields etc. They don't get holes in them normally. Anyway, patching a hole with film is dead easy and almost invisible. Edited By Peter Miller on 27/09/2014 11:11:19 Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Covering under cambered wing is ALWAYS a problem. Balsaloc on the ribs will help. being very gentle with the heat helps. IT can be done but not easy. Dope and Tissue was easier but the act of covering was much harder and very smelly. Tissue will puncture if you look at it too hard. Silk or Nylon? Don't even think about it . The learning curve is very very steep and you will wich you had tried on something stronger. Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 Peter, that sounds like good advice but for me there is just one problem. All the covering films that I have see only seem to come in what I can only describe as garish colours and I was hoping for a more subdued look to my model. Fluorescent colours was not what I had in mind. Quote Link to comment Share on other sites More sharing options...
Ernie Posted September 27, 2014 Share Posted September 27, 2014 Hi CB, I have used a material called diacov. It is a fabric bases heat shrink, It only comes in one colour, a neutral off white. You can spray it. Failing that, why not use solartex Antique, or white. Finally, don't even consider balsa covering. For ultimate strength, you can't beat silk, shrunk on, and finished with clear dope, and oh that smell. ernie Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 Ernie, I think I am very close to being converted to a fabric covering but I am very concerned that, when shrinking the covering, a warp may be caused. Can yo suggest a reliable way to avoid this ?? Apart from being an experienced expert of course, coz I ain't !! Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Solar film comes in a huge range of colours. Even transparent colour. Go to their website. If you send them four first class stamps you will get a complete set of samples of everything they do. Send them another four 1st class stamps and you can have a "how to cover" DVD Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 Peter, does it sound too stupid to use 1/64 ply on the underside of the wing ? It would only weigh 130 grms Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Please, forget about 1/64" ply. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted September 27, 2014 Share Posted September 27, 2014 If you want a fabric look, that is quite puncture resistant you could think about Solartex, a polyester woven "fabric" eith a heat activated glue on one side (you will need a "covering iron" - as you will for any other film covering type), doesn't shrink a great deal but I have found it much easier to get nice results with as compared with plastic film, Solartex seems to be much better at working round complex curves that film (at least when I use it it is!) - it will also add a lot of strength to your model, though it is heavier than films. And it comes in nice subdued tones too. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 27, 2014 Share Posted September 27, 2014 Solartex is a Solarfilm product Quote Link to comment Share on other sites More sharing options...
Countryboy Posted September 27, 2014 Author Share Posted September 27, 2014 Hmmmmmm. This covering bit seems like a bit of a mine field. I'm not sure that I have the skills to go for heat shrinking yet it is the method suggested by everyone. Something to ponder methinks. I was right about boats being easier ! Edited By Countryboy on 27/09/2014 11:46:54 Quote Link to comment Share on other sites More sharing options...
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