Tissue vs Film - Weight

[Nigel Heather]

Is there much difference in weight between a tissue and dope and heat shrink film?

 

Considering building a fun fighter, want to go electric so looking a ways to keep the weight down and even lighten it.

 

One thought was to use tissue and dope rather than film - two reasons, I presume  tissue and dope is lighter, but is it!  and I presume that tissue and dope will be cheaper.  As I will have to paint the covering either way the finish isn’t that important.

 

And what about strength - the fun fighters are foam wings, light ply and balsa sheet - no open structures - so would there be much of a strength difference between the two covering options.

Edited June 17, 2023 by Nigel Heather

[Cuban8]

Tissue V heatshrink covering is an old subject with a variety or arguments both pro and con depending on model size, type of construction and intended finish. My advice to you when building a foam wing, ply and balsa fun fighter would be to make all of your weight savings during construction, gear choice and installation. If you can get away without ballast, or at least reduce it to a minimum to get the CG correct then so much the better.

Go for a heat shrink finish for simplicity- any difference between that and tissue, dope and paint is not going to be an issue IMHO. BTW, a painted tissue finish can very quickly gain unnecessary weight if not carried out correctly.

As you suggest, without lightweight open structures that will need the strength and stiffening that shrunk tissue and dope provides, your funfighter will be fine without it.

Edited June 17, 2023 by Cuban8

[Nigel Heather]

36 minutes ago, Cuban8 said:

Tissue V heatshrink covering is an old subject with a variety or arguments both pro and con depending on model size, type of construction and intended finish. My advice to you when building a foam wing, ply and balsa fun fighter would be to make all of your weight savings during construction, gear choice and installation. If you can get away without ballast, or at least reduce it to a minimum to get the CG correct then so much the better.

Go for a heat shrink finish for simplicity- any difference between that and tissue, dope and paint is not going to be an issue IMHO. BTW, a painted tissue finish can very quickly gain unnecessary weight if not carried out correctly.

As you suggest, without lightweight open structures that will need the strength and stiffening that shrunk tissue and dope provides, your funfighter will be fine without it.

Thanks, definitely would reduce weight during the build.

 

For example lighten the tail, elevator, fin and rudder - I see that as a double win, reducing weight immediately but also eliminating/reducing the need for ballast up front to balance.

 

I’ve heard the plane has ply doublers that can be replaced with balsa.

 

Also cutting holes in formers.

 

This is an idea in my head - appreciate to hear whether it is sensible.  I believe the tail feathers are balsa sheet.  Thing of cutting sections of those and filling them in with ribs and thin sheet. It’s only going to be a few grams but I figure a small reduction back there has a big effect up front.

[John Lee]

There are lots of variables but ballpark:

 

Tissue & dope 2grams/sq ft

 

Solarfilm 6 grams/sq ft

 

so for say,  3 square feet in a fun fighter weighing about a kilo, the difference will be a rounding error 

[Nigel Heather]

6 hours ago, John Lee said:

There are lots of variables but ballpark:

 

Tissue & dope 2grams/sq ft

 

Solarfilm 6 grams/sq ft

 

so for say,  3 square feet in a fun fighter weighing about a kilo, the difference will be a rounding error 

 

Thanks, that really puts it into perspective - 12g in 1500g

[Engine Doctor]

If you can find any try using Airspan and dope. Airspan is a polyester covering that is porous so needs dope yo seal and fix .

Having said that the first funfighter i built gor my son was covered on doped tissue looked and flew great. First landing and it hit a stone tgst took a huge lump out of the botom of the wing. Repaired it and glassed tge botyom of the wing  . No noticable difference in flight  with heavier covering.

[Cuban8]

On 17/06/2023 at 09:59, Nigel Heather said:

Thanks, definitely would reduce weight during the build.

 

For example lighten the tail, elevator, fin and rudder - I see that as a double win, reducing weight immediately but also eliminating/reducing the need for ballast up front to balance.

 

I’ve heard the plane has ply doublers that can be replaced with balsa.

 

Also cutting holes in formers.

 

This is an idea in my head - appreciate to hear whether it is sensible.  I believe the tail feathers are balsa sheet.  Thing of cutting sections of those and filling them in with ribs and thin sheet. It’s only going to be a few grams but I figure a small reduction back there has a big effect up front.

Be careful about replacing the ply doublers with balsa - the designer felt they were required and fun fighters do get knocked around a bit. The back end is the real problem and any point aft of the CG position.......an area I must admit to sometimes falling into the trap of overbuilding, including tails and fins despite knowing the pitfalls. It's never really noticable as work proceeds, but takes you by surprise when setting the CG.  My Brian Taylor Spit is probably carrying a pound of nose ballast too much because I took my eye off the ball during the build.

If the wood in the kit seems more suitable for floorboards, then change it out, annoying but neccessary. I'd not bother building another tail from ribs etc, but maybe some sensible lightening holes could be cut without compromising the strength or stiffness of the component. Even a few grammes of saving will make a worthwhile reduction in nose weight.

Edited June 18, 2023 by Cuban8

[Nigel R]

On 17/06/2023 at 08:58, Nigel Heather said:

Considering building a fun fighter, want to go electric

 

My own take;

 

Cut some big holes in the ply doublers, electric needs not the structure of an IC.

 

I'd consider:

1 replacing the tail end with a built up and sheeted structure

2 using the existing fuselage sides as templates and cutting from light timber

3 seeing what the decking was like and taking a similar approach, i.e. if it is heavy then replace it.

 

Sure, funfighters may get knocked around, but build it to fly well as a priority.

 

I'd not tissue/dope if you have an open structure wing. If it is foam veneer then do whatever you want for covering.

 

 

[Cuban8]

19 minutes ago, Nigel R said:

 

 

Sure, funfighters may get knocked around, but build it to fly well as a priority.

 

 

 

 

Excellent advice - no such thing as 'crash proofing' in the real world.

[Engine Doctor]

3 hours ago, Cuban8 said:

Excellent advice - no such thing as 'crash proofing' in the real world.

Exactly build to fly not crash! But too light makes for a not very durable model. A decent balance works for me.

[leccyflyer]

All of my funfighters are covered in tissue and dope and then painted with Humbrol enamels. It's a nice robust finish that weathers well/ I know that some funfighters are finished in garish, non-scale, film finishes, but to me that entirely loses the essence of what the models were originally designed for., I'm also not convinced that remaking the sturdy sheet balsa tail surfaces, which survive the rough and tumble of funfighter life well, is a worthwhile exercise. They have short noses and long tail moments, but it's just a fact of life that you'll have to make the best use of the available battery weight if you are going electric, compared to a relatively heavy glow engine up front.

[David Davis]

A little off topic perhaps but I was intrigued by this video by Mark Robinson in which he covers a vintage model in tissue over doculam. Apparently the finished weight is 120 grammes per square metre (gsm.) As the tissue is only 15 gsm and the doculam is 34gsm then the weight of the dope and varnish must accout for the rest.

 

https://www.youtube.com/watch?v=oSi81sbQQK4

 

Solartex weighs between 85 and 98 gsm depending upon colour.

[J D 8]

  Don't know if any still around but Litespan is a strong light weight covering 28-30 gsm.

   The tail of my now 50 year old Matador was recovered with silver litespan a few years ago 32-35 gsm, just a clear lacquer spray to fuel proof. Wing is still original tissue [ well some of it ] with many patches. Rather brittle and needs to be handled with care these days.

[Cuban8]

Some excellent advice than one can pick and choose between as circumstances dictate. On the subject of Litespan, I see that it's still available from Solarfilm and their website is fully up to date and apparently, well stocked. I thought they'd gone out of business.

[Engine Doctor]

1 hour ago, J D 8 said:

  Don't know if any still around but Litespan is a strong light weight covering 28-30 gsm.

   The tail of my now 50 year old Matador was recovered with silver litespan a few years ago 32-35 gsm, just a clear lacquer spray to fuel proof. Wing is still original tissue [ well some of it ] with many patches. Rather brittle and needs to be handled with care these days.

 

Hi JD8  litespan is already fuel proof as it comes. If clearcoat is used as an adhesive and a thin film along overlaps/ edges it is very fuel proof as opposed to fuel resistant. My Frog 45 is 15 plus years old, is diesel powered and gets covered in fuel when filling and burnt fuel / oil and the only part that was fuel proofed using clearcoat was the inside of the engine bay / cowling and  wing seat . No sign of fuel soaking . Brilliant covering sadly not readily available any longer.

[Tom Gaskin 1]

Goerge Stringwell used to advocate tissue over mylar for open structures which has the strength of film and the rigidity of tissue. I used this method on a 2M glider wing and the gain in strength and 'handleability' is quite amazing. I got both mylar and tissue from freeflightsupplies.co.uk.

 

For a fun fighter tissue, dope and paint is the most practical as Leccy says.

[J D 8]

            Hi ED, Looking at my Matador recon I probably just sealed the edges. As you say a great covering done about ten years ago and resisting the effects of PAW exhaust. Lucky I am to still have a number of Litespan sheets as when doing an order I put an extra number 1 in the quantity box 😄 All are silver though.

  Engine bay was fuel proofed with car filler as it was all I had all those years ago. Still good as pic shows after a recent re plum of fuel tank and clean up show.