Jack Banner Posted June 12, 2014 Share Posted June 12, 2014 As mentioned in another thread, I am completing a model started by my late father. This is a low wing tailless sports model for OS .25fp called 'Amy'. **LINK** I am currently flying another of Dereck's tailless designs, Bigger Bit, and it is great fun. Amy is meant to be a bit more precise and suitable for aerobatics. I hope to have her ready, and well flown, before the NCMAC show in August. This build log is retrospective up to this point but I will update it from here on in as I intend to work on this every day from today. My pictures are pretty intermittent so I I will post what I have, ask my question and then go from there. Ok. Here comes the question Given that the cowl is built from balsa, fairly complex in shape, has lots of cut outs and is in two parts, am I better off sealing and painting it or trying to cover it in film? I think I can cover it in film but am concerned that the film will be burnt by the engine. Would sealing it, painting with solarlac and then sealing with fuel proofer (I have some Aerokote) be good? This is by far my most complicated build to date and any advice is greatly appreciated. Jack Quote Link to comment Share on other sites More sharing options...
Andy Green Posted June 12, 2014 Share Posted June 12, 2014 Very nice. I'm building a Bubbles for the same event. Andy Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 12, 2014 Share Posted June 12, 2014 First off, nicely done. I've got the Little Bit now converted to electric, which is also a great (and long lived) little model. My preference would be to cover it with tissue and dope or glass and resin then Solarlac, glass and resin would give it most strength, and being first point of contact in single point landings, ding-resistance would be a Good Thing. It shouldn't really need proofing as Solarlac is pretty good once it's cured a while though a coat of clear gloss over the top will give a glassy finish. I use Solarlac Clearcoat. Film would work ok on the outside and be quicker but you will still need to proof the inside anyway. The film is unlikely to be burnt by the engine unless there's direct contact, it's at least as heat-proof as paint, if not more so. A couple of mm clearance is enough to save it. Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 12, 2014 Author Share Posted June 12, 2014 Thanks guys, I am very pleased with it so far. I think I may have a go at glassing it. I like the idea of adding some strength to it. I nearly built an electric little bit myself and might do still. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 12, 2014 Share Posted June 12, 2014 I agree with Bob, nice job and go with the paint finish, no matter how good a job you do of film it will eventually get lifted by fuel. John Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 26, 2014 Author Share Posted June 26, 2014 Hi again, I have another question if someone would be so kind. I want to paint some of the trickier areas with Solarlac to match the solarfilm. I have the solarlac but am a little confused by the instructions **LINK** They refer to use of a 'finisher' between the initial coat of clearcoat and the final coats of solarlac. Is this just a primer or is it something specific to solarfilm? Also, could I use a varnish or even Deluxe materials Aerokote (which I have) instead of the initial clearcoat? Sorry if these seem like dumb questions but this is my first time painting. cheers Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 26, 2014 Author Share Posted June 26, 2014 oh and here is a picture of the wing complete with hinged ailerons. Looks pretty big! Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 26, 2014 Share Posted June 26, 2014 I think 'surfacer' refers to filler/primer - eg hi-build primer - to fill the grain and get an even base colour before applying the colour coats. I have to admit to not having read those instructions. I start with Poly-C and glass, then Halfords hi-build primer in a colour to suit the topcoat, then the Solarlac followed by a well thinned spray of Clearcoat, though the last is just to get a bit more depth and shine and isn't needed really. note - not forgetting the rubbing down with wet'n'dry used wet between each coat! Edited By Bob Cotsford on 26/06/2014 11:31:02 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 26, 2014 Share Posted June 26, 2014 Acrylics + cellulose can sometimes react against each other Jack, may just be I didn't leave enough drying time between coats. Now I stick to one type just in case. John Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 26, 2014 Author Share Posted June 26, 2014 OK, thanks guys. Think I have a handle on it now. I can stop prevaricating and get on with it! Quote Link to comment Share on other sites More sharing options...
kc Posted June 27, 2014 Share Posted June 27, 2014 The entire cowl and just the edges of the fuselage could be coated with Clearcoat, when dry then the Solarfilm ironed on. (Or you could use Solarlac instead of Clearcoat ) The Solarfilm sticks well to the Clearcoat which is fuel proof. Overlaps Solarfilm to Solarfilm can be treated with Prymol (etch primer) which is left to dry before ironing down. (Prymol dries in about 10 minutes) Finally Clearcoat over the overlaps for the best fuelproof finish. . Prymol also works well to repair lifted overlaps on Solarfilm-- use meths to get the film clean of oil first. Did you sand the diagonal aileron ribs to shape AFTER gluing in place? Edited By kc on 27/06/2014 11:56:50 Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 27, 2014 Author Share Posted June 27, 2014 Thanks KC, I will pick up some Clearcoat at wings n wheels tomorrow I think and get this covered next week. I did sand the diagonal Aileron ribs after gluing in place. The third picture I posted shows them sat on a board that has a medium grit sandpaper stuck to it. They were sanded on this to keep them even. I fine sanded them using a long block after that. I did consider sanding them to shape before gluing but decided sanding them in place would make it easier to get an even profile. Edited By Jack Banner on 27/06/2014 12:24:36 Quote Link to comment Share on other sites More sharing options...
kc Posted June 27, 2014 Share Posted June 27, 2014 The diagonal ribs seem better technically but much more work than simple ribs. I was surprised the aileron had the ribs exposed - i expected them to be skinned on top too. Clearcoat might be difficult to find and take some searching out! Solarlac is the same stuff I think but coloured. Best to use it outdoors due to the stuff in it and the smell. If they still use the same jars for Clearcoat then you will probably need one of those kitchen gadgets that have serated circular grips in multinple sizes to open or reopen! Good stuff though . Prymol is also difficult to find but worth using on the film overlaps or to paint onto Solarfilm. Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted June 27, 2014 Author Share Posted June 27, 2014 The Ailerons were a reasonable amount of work but are very light and stiff and look a treat, now covered. Clearcoat, well, i can only have a hunt I use Prymol when covering with film, you are right that it does help immensely for overlaps. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 27, 2014 Share Posted June 27, 2014 Nexus used to have Solarlac and Clearcoat on their stand, and they all come in tins these days except balsaloc KC. I used to sit the jars upside down in an inch of hot water for a couple of minutes to loosen the lids. Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted July 21, 2014 Author Share Posted July 21, 2014 Just a quick update on this for anyone who is wondering. Managed to get some good time in over the last few days so progress has been made! Just a few bits to do now so should be good for a maiden next time I go. Gulp. Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted July 21, 2014 Share Posted July 21, 2014 looks smashing sir. maiden will be a dodle Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted July 21, 2014 Author Share Posted July 21, 2014 Thanks Tony, I appreciate the confidence boost! I will report back once aviation has been committed. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted July 21, 2014 Share Posted July 21, 2014 It looks well Jack, very sporty John Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 22, 2014 Share Posted July 22, 2014 Looks great Jack - colour scheme is almost exactly the mirror image of mine - which has a tendency to blend in with cloud so yours should be nice and visible. Make sure the C of G is as per plan (or a little forward) and keep the speed up on landing and you shouldn't have any dramas on the maiden! Quote Link to comment Share on other sites More sharing options...
fly boy3 Posted July 22, 2014 Share Posted July 22, 2014 "Amy" a lovely looking and very well built model. Hope all goes well on maiden. One question, and I do not wish to hijack the thread, but looking at the picture of the front of the model, the thrust line is near the bottom of the balsa cowl. Wonder how the designer worked out where the thrust line goes, or is the design spec. above us normal fliers. Cheers Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted July 22, 2014 Author Share Posted July 22, 2014 Thanks Flyboy3. Regarding your question I am not sure, not having much of a clue when it comes to designing. I do know that this design followed very similar high wing (Bigger Bit) and mid wing (Bubbles) versions by the same fella. I seem to remember reading that Bubbles suffered from some sever coupling in knife edge and the Bigger Bit certainly does. I think Dereck intended this design to be more aerobatic and neutral in knife edge and having the thrust line low, in front of the wing, might well be linked to that. If it survives the maiden I will let you know! Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted July 22, 2014 Share Posted July 22, 2014 Hi , I remember building an own design back in the eighties which was similar to Amy and i remember it needed a lot of down thrust in it . It did fly very well . I never got around to it but one of my party tricks , i had planed for my this model was to tape a dummy tail plane on the back which would come detached mid flight just to see the look on spectators faces as the tail plane floats down to the ground . Good luck with the maiden Steve , Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted July 23, 2014 Share Posted July 23, 2014 Looks great Jack. Got to ask, any funnies from your mates like " Yer forgot the tail " etc...etc Roger Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted July 23, 2014 Author Share Posted July 23, 2014 Hah, not really they are all used to my odd planes as a bigger bit is my main hack. I did have one guy ask me where I bought it though, which made me chuckle.I bottled it on the maiden today. The wind was in the wrong direction and very gusty. I was simultaneously impressed by my own good sense and disgusted with my cowardice. Quote Link to comment Share on other sites More sharing options...
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