Fuse

[david miles 7]

Thanks for that Bob. You guys are really important to a "know nothing" person like me. I made what I thought were quite reasonable assumptions about things like auto- rudder and thermals, but I couldn't have been more wrong. I'm glad I asked the question.

David.

[Richard. W.]

No problems, David.. Asking questions is always good and I for one am happy to help where I can......The only thing which is annoying are those people who ask questions but really only want you to agree with their already formed opinion, so ignore any advice given which doesn't agree with them.

To give you some idea of what people here are saying, many years ago now I lost a model O.O.S. (out of sight) at Old Warden....It was fitted with a fuse dethermaliser which went off but the model still shot upwards........The model wasn't a high performance, duration type, it was a little "Cherub" (Vic Smeed plan I believe, of about 30" span) powered with a 0.5cc D.C. Dart.......I'd only fitted the dethermaliser for a bit of fun as the model should never have needed one really but the one time it did, the damn thermal was so strong it made no difference.

[Piers Bowlan]

Here is the KK Caprice, 51in span free flight glider and the plan is available as a free download from Outerzone here. I rather like the free flight Amethyst from West Wings. Rather nice video of it here. 

I don't know why you would prefer to build a free flight model David when radio control has never been so inexpensive and reliable and also avoids losing the model in a flyaway. Even the smallest free flight model can be converted to radio control so easily without adding excess weight, you just put the battery in the nose instead of lead.

 

 

Edited By Piers Bowlan on 25/03/2019 15:22:40

[Richard. W.]

I tend to agree with you, Piers.

Free Flight was fun and very enjoyable to me for many years. There's definitely a nostalgia value and it teaches the art or skill of trimming a model to fly.

That said, there are the downsides previously mentioned, regarding space, more restricted flying days and frequent long walks... As you rightly say, even the cost isn't a factor as it was a few years ago.......A flyaway is certainly less likely although not impossible as one of our club members lost a model last summer. I wasn't there to see it but apparently it was at altitude and he suffered a total loss of signal, along with catching a large thermal... Away it went and hasn't been seen since.

[Bob Cotsford]

Sam35 looks to be the place for olde-worlde models and freeflight, iirc there is a growing trend towards 'radio assist' which just allows RC control of a small rudder for emergency use just to keep the model within bounds, otherwise the models are trimmed and flown as pure freeflight.

[david miles 7]

Thanks for everyones help and advice. Funnily enough, after looking at what seems to be hundreds of glider plans on "google images" I finally decided a "plank" type model was best to start, and had already decided that the "Caprice" looked a good one to start with. I do feel the slight pressure to start with a R/C model, but I feel that I would like to get the hang of basic making and flying first

I must say that you guys are really useful to get a beginner started - Thanks.

David.

[PatMc]

David, if you have decided on the Caprice you can get a set of laser cut ribs from here, saves a fair bit of hassle.
I've got a rib set for a Graupner Amigo glider which were excellent quality.

[Don Fry]

Posted by PatMc on 25/03/2019 17:26:48:

David, if you have decided on the Caprice you can get a set of laser cut ribs from here, saves a fair bit of hassle.
I've got a rib set for a Graupner Amigo glider which were excellent quality.

For fair, read a lot. A plane flys on its wing. And cutting ribs is a knack.

[david miles 7]

Thanks Don. As the ribs don't have a flat base, I think I will probably will get some.

David.

[Piers Bowlan]

Under-cambered ribs can be a little challenging to cover David but don't let that put you off, some Balsaloc applied to the underside of the ribs can help. Provided you can still get it of course. If not, some PVA would probably work too.

[david miles 7]

Hello Piers. Thanks for your post. I had intended to buy a full size plan. I checked your link to the free plan download, but it was A4 size. Is it possible to get a full size copy free? Am I missing something - Am I able to "scale up" the A4 version somehow ?

David.

[Richard. W.]

I don't know whether you can get a full size building plan of Caprice, David but if you can't it is certainly possible to scale up an A4 drawing. Any plan can be scaled up or down to whatever size you wish but of course it involves more work and it isn't for everyone.

When you feel ready to try cutting your own wing ribs, whether it's free flight, radio or control line, the method I prefer if there are several ribs of the same size is to cut one rib from 1/16" ply. Take care with this one and sand it so it's just a fraction smaller than you need....Just a fraction, the thickness of your craft knife blade.... Make two pin holes in the rib and superglue two pins in so the points poke through about 1/32". These are just to prick into the balsa and stop the template from sliding......Now simply use the template and a sharp scalpel type knife to produce as many ribs as you wish.. Keep the template so that if/when damage occurs, it's easy to make some new ribs.

The main thing though, David is to enjoy yourself and have fun with the hobby.. Don't feel under pressure to build a certain model or to fit radio. Yes, the models mentioned in the replies above are all sensible choices for a beginner but it's going to be YOUR model so you have to have a feel for it or the build will become a chore.......Just don't decide to build a Spitfire as your first model.

[david miles 7]

Piers. About under-cambered wings. The Caprice plan instructions mention covering wings in tissue. I can't find anything ( youtube and google  explaining how to get tissue to sit tightly on under cambered wings. Can you point me to anything, or is there a way that all modelers know about?

I did see a mention about ironing the under cambered wing covering, but I assumed that it couldn't possibly be for me - how could you use a clothes iron on a concave surface !

David.

[Richard. W.]

**LINK** This is the type of iron used for covering models, David but small free flight models are covered in tissue as the iron on coverings are much too heavy for them.

The best way to get tissue to stay fixed to an undercambered wing is to dilute some waterproof, white PVA glue and paint it onto the bottom of the ribs and stick the tissue to it. Let this dry completely before misting with water to shrink the tissue..........There are other ways. Some people can do it by just using dope as an adhesive but I always found the glue method easiest.

Hope that helps.

[PatMc]

David, in practice it's not as difficult as it seems. Adhering the cover material to the underside spar helps hold the it in place. It was quite common for schoolboys in the 1940's & '50's to build models with tissue covered undercambered wings.

[John A H]

One last option to suggest. The West Wings Swallow kit can be built as free flight or as Radio Control with a rudder and elevator and it has flat bottomed wing ribs so a bit easier to build. I don't think West Wings are trading at the moment but some model shops may still have them in stock. If you buy a kit you could make copies of the fuselage parts incase you wanted to make an RC version after the Free flight one.

If you struggle covering with tissue you can use light weight iron on films on these models - Litespan or SolarLite from the Solarfilm company work well. They still have some available on their website. Litespan looks like tissue so still gives you a retro look (you need to use Balsaloc, also from Solarfilm company, to stick it to the airframe using an hot iron which is also used to tighten the material).

[Piers Bowlan]

Posted by david miles 7 on 25/03/2019 22:14:55:

Hello Piers. Thanks for your post. I had intended to buy a full size plan. I checked your link to the free plan download, but it was A4 size. Is it possible to get a full size copy free? Am I missing something - Am I able to "scale up" the A4 version somehow ?

Outerzone. David, if you click on 'download' and again on the 'download plan' and the other files (ribs etc) on the next page. It will open in PDF and, on my Mac at least, it shows 25.5% so it fits on my screen. Click on 100% and print it off in tile format, so just tape the A4 sheets together and voila, you have a full size plan for free! Alternatively take an A4 plan to any commercial copy shop for enlargement like this one near me for instance. Even easier is to download the files to a memory stick and get the printers to print them off for you. Should cost about £2.50 for an A0 sheet (you can email them the PDF as another alternative). While you are at it you can get any plan enlarged or reduced at no extra cost. Also mirror images are useful for when you only have a left or right wing shown on the plan.

Ribs. The Caprice kit from Ripmax is probably the easiest way to build the model but if if you prefer to cut your own parts there are several different approaches but I usually do as Richard suggested earlier, cutting a rib from thin ply. I find 1/32 is adequate, fixing it to the wood with Fast Tack or similar and cutting round it with a Swan Morton knife/No.11 blade. For tapered ribs you can tape the rib plan over the wood and prick through the outline of each rib onto the wood. I find it more accurate than tracing and is much quicker than you might think. Then just cut out the rib with a model knife.

Covering. Some people still like to use tissue and dope on lightweight models. It may be traditional but the problem is that it is brittle and punctures easily. The major drawback is that that warps can occur as the dope dries and the tissue shrinks. I built a rubber powered AJAX for my son about 25 years ago and used Solarfilm Litespan/Balsaloc for covering. I recently threw the model away during a house move but the covering was still intact! If you do get a dent in the covering it can be ironed out and a warp can be removed with the application of heat to re-shrink the covering. The Ajax has under cambered ribs incidentally like most models of the period.

 

Edited By Piers Bowlan on 26/03/2019 11:49:36

[Plummet]

Posted by david miles 7 on 21/03/2019 15:00:12:

Hello Everyone.

This is my first post.

I have just downloaded the plans for a Frog Diana 36 inch wingspan glider. I notice that there is a "string fuse" at the end of the fin. Can anyone tell me what it is for? This is my first attempt at building a model glider!

Thanks for any help.

David Miles.

Just for completeness, the original question asked what is a "string fuse". I have skimmed through the answers and I don't think (I could be wrong - if so, sorry) that anyone has answered this question.

The string fuse is a piece of string that will smoulder, without going out, and that will burn at a fairly predictable rate. For a dethermaliser the tailplane is held down with a rubber band. The string fuse is lodged in between the strands of the rubber band and it is lit before the flight.

It smoulders, and when the burning part reaches the rubber band it breaks the band, and another rubber band pulls the tailplane up to an angle where the glider stalls and decends quickly.

When I was a kid I used to make string fuse by dissolving some saltpetre (potassium nitrate) in water, and then soaking cotton string in the solution. Take out the string and let it dry.

When you light the string it may burn, but if you blow out the flame it will continue to smoulder.

(The saltpetre reacts to the heat from the burning string by breaking down and releasing oxygen. This helps to prevent the smouldering going out. Saltpetre is used in gunpowder for the same purpose, so you may get funny looks if you try to buy it nowadays.)

The string should burn at a steady rate. Test a piece of it to calibrate how long a piece you need.

Plummet

[david miles 7]

Hello Plummet. thanks for your words. I did get some useful "fuse" answers that allowed me to work out what it all meant.

On the subject of fuses though. I was thinking about them as I feel asleep last night. I have an interest in electronics and it occurred to me that it might be possible to make an electronic de thermaliser that is triggered by ones car fob ( I haven't seen how far away from ones car that these fobs work yet ) So you would be able to bring down your model when you decided rather than when the timer ran out. Do you/anyone know if D/T's like this exist?

David.

[PatMc]

David, I don't think a car fob would have the range necessary. There already are radio DT systems being used for free flight. Since they are mainly meant for competition use they tend to be pricey for what they are.
There's a fairly detailed article about RDT's starting from page 7 of this vintage model newsletter. The link is to the PDF file of the newsletter so will probably result in a warning asking if you trust the source.
It might be as cheap & more useful in the long run to consider using a cheap normal TX with matching lightweight Rx & servo.

BTW here's another good, simple FF glider plan - the Tri-star - downloadable from Outerzone. This one has constant chord wings & uses flat bottom ribs, making it easier to produce the ribs using a single pattern & removing the complication of covering undercambered wings. The original magazine intro article is also downloadable via the same link.
I helped my son make one about 35 years ago & can vouch for it being easy to build & a good flyer.

[Martin Dilly 1]

A couple of points here. The fuse norrmally used for dethermalisers is cotton lampwick, which usually has a red spiral thread running round it, which makes setting the time you need simple. However, it must be used with the non-burning end in a snuffer tube attached to the model. This both helps to locate the fuse so it doesn't wave about and act as a random trim tab, but also ensures that it can't drop off and also extinguishes it after it's burnt rhough the rubber band holding the stab in the flying position. I think Flitehook has DT fuse, and he also carries a lot of specialist free flight materials and other items that you won't find in the few surviving high street model shops, some of which have no idea there's any other sort of model flying than RC.

An auto-rudder is a device that holds the rudder of a glider straight for towing, but goes to the glide setting after the towline drops off the towhook. A free flight model will be trimmed to circle in order to keep it in the thermal that, hopefully, you have released it into, since the object in contest flying is duration.

[Pete Collins]

Hi David - reading through this thread I felt a few words on covering were in order. When you check out old plans they will usually recommend tissue covering as this was used almost exclusively on small models 'back in the day'. This involves covering the framework with tissue paper, shrinking it with water, and then proofing it with a varnish-like material called dope. It's a fairly skilled technique that we all had to learn back then because there was no sensible alternative. Nowadays there are lots of alternatives ie Iron-on plastic films or polyester tissues. you really need to do some research to find the way you want to go. If you are interested in using the old methods of tissue covering then you should check out some of the vintage model aircraft forums. I can recommend 'Stick n tissue' although I think it is now a closed forum so you won't be able to post on it, I don't think that will stop you from viewing. (but I could be wrong!)

[Plummet]

Another thought comes to my mind ...

It is a good idea to make sure that a burning fuse does not make contact with tissue and dope covering.

One of the constituents of dope is nitro-celulose, which is chemically the same as guncotton or the flashpaper magicians use.

Otherwise the results might be spectacular.

Plummet

[david miles 7]

Thanks to everyone's help/ideas about fuses and tissue covering.

Thanks to PatMc's recommending the Tri-Star. Each time a member suggests a design,, I look and say to myself " YES,- this is the one!" Tri-Star now looks the best/easiest.

About my wireless D/T idea. I tried to google wireless de-thermalisers to find out their range, but I couldn't get one hit on the subject ( perhaps I used the wrong search words ) So this evening I walked my dog to the end of my street - 400 feet and my car key fob unlocked my car doors - it may just have worked even further. Anyone know the range of these "expensive" competition D/T's?

David.

[Plummet]

Look at the indoor electric models. They are ultra light, but they have full house radio control. All you want is a single channel that activates the dethermaliser. Their receivers are ultra light, as are their servos.. Is this the way to go?

Plummet