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Ribs

Willow fuselage (re)assembly

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Ribs

Hello all,

 

I was wondering if someone might give me a little help.

 

I am rebuilding a Willow fuselage nose after noticing the parts were coming loose. The movement was sufficient to have an effect on the v-tail rods, so I thought this must be an issue that should be sorted.

 

After some pulling about, I notice a couple of things

 

1. The inner nose was 'bonded' to the rear fus molding, with some kind of spongy packing. 

2. The cratch did not appear to be epoxied to the fuselage rear of the above packing.

 

I've made a little drawing of how things go together - see attached. Can someone give me some pointers/tips on how to make this a solid fit? As it stands, it looks like there is no way the crutch/servo tray could ever have reached out to the fuselage sides to be bonded to it. To achieve this, I may well have to make another crutch.

 

Perhaps I am misreading the guidelines (linked from the Willow site) and this is 'as designed'. Also does anyone know what this spongy packing is - it looks a little like a weird double sided tape and has a little give - Grommit saw it on Friday and thought it was normal. This seems to generate a nose arrangement with quite a bit of compliance - good for crash survival maybe, but not very stiff/secure.

 

Any help, much appreciated.

 

cheers,

Ribs

fuselage.pdf

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mtreble

Hello all,

The movement was sufficient to have an effect on the v-tail rods, so I thought this must be an issue that should be sorted.

 

I agree. I would make a new crutch that fits, and glue the whole lot together with plenty of epoxy so that it is solid!

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g0ggg

Hi Ribs

This is the recommended assembly, I found this after I assembled mine

 

 

http://willowracing.blogspot.co.uk/p/some-build-notes.html

 

 

Normally there a wide rubber ring that fills the gap not double sided tape this is designed to absorb force on hard landings.

 

I found this technique after I built mine, so I changed the ply former so that the ballast tube forced the former against the fuselage sides, which is stronger than cutting the nose slots..

 

I'm close to Whitesheet in wilts if you need help or would like to see my construction.pm me

 

Yes as Mark suggests loads of epoxy is definitely the order of day,

A tip  my mistake was to epoxy and align everything up, then check the nosecone fitted ok.  Removing the nosecone moved everything so I  had re-align everything again in a hurry before glue set.

 

Hope this help I'm frequently at whitesheet also

 

Neil

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Ribs

Thanks Guys,

 

I'll have another look at the crutch in the workshop and make some internal measurements of the nose - the instructions on the website do seem to indicate that the crutch should be bonded to the fuselage sides:

 

A 10ml syringe from Tesco and using the off cut from a snake outer makes the perfect tool for applying epoxy to the servo tray, both inside the mmain fuselage and in the inner nose.

 

 

any ideas about replacing the rubber sleeve? I have scrapped the original in the disassembly process. I wonder if a piece of bicycle inner-tube would serve the purpose well. A question that pops into my head though - if the crutch is bonded by epoxy to the fuselage inner - this would make a flexural element at the inner fus/outer fus joint seem strange - wouldn't the flex produced increase the likelihood of the crutch/fuse epoxy bond cracking.

 

I'm sure it will all go back together rock solid anyhoo.

 

cheers,

Ribs 

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mtreble

I'm sure Ian (willowf3f at yahoo.co.uk) could provide you with a new rubber sleeve.

An alternative would be to fill the void with carbon tows or sock for a rigid assembly.

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Woodstock

I would tend towards the other side of the spectrum and use glue with some "give", namely Goop (or it's equivalents).  I am using Goop more and more and more:  it's incredibly strong, but retains some flexibility, so cracking from when the airframe flexes is not an issue.  I use it most particularly for servo trays.  We all know that composite airframes flex:  in my opinion trying to make it "solid" with brittle epoxies is OK in the short term, but I don't believe it's an optimum long-term approach...

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Ribs

Thanks for the advice guys.

 

I've made a survey of the fus internal shape today, and there is definitely a 3mm or so gap, both sides, between the original crutch and the main fuselage molding. Just no way the two parts could have been bonded together. This is further backed up by the dry appearance on the edges of the crutch behind the area where the rubber ring was. Fair enough, I guess this is a hard place to get glue in to, but I'm not going to rebuild it like that - packing it out or a new crutch/servo tray will be the order of the day.

 

Still pondering on flexible vs stiff glue.... will look up this goop stuff.

 

cheers,

Ribs

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Ribs

It looks similar to Evo-stick contact adhesive, that you used to get (think you still can) in red tubes and tins. Sort of rubbery glue with a lovely smell....

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Skip

Goop (urethane glue) is incredibly messy. As is silicone. It depends on whether or not the fuselage needs any additional stiffness where the crutch mounts as the flexibility of goop or silicone would offer less than an epoxy/glass/carbon solution.

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oipigface

It looks similar to Evo-stick contact adhesive, that you used to get (think you still can) in red tubes and tins. Sort of rubbery glue with a lovely smell....

I don't think you can get it any more. The smell was too much of an attraction for some people!

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Woodstock

Goop isn't polyurethane glue (that's known as Gorilla glue amoung others), and used in small quantities it's not messy at all (it doesn't stain your fingers like Gorilla).  It dries to a glossy clear finish - very neat and attractive.  It is available from a local crowd (Tom Satinbed knows the name), or you can use "Shoe-goo" as a near identical alternative.  Because these adhesives are capable of gluing shoes together this gives an idea of how strong + flexy they are (I have for instance Gooped new rubber soles onto a pair of Crocs and they are holding out a few years on..

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isoaritfirst

Personally I like my fuslages to be effectively one piece. Any shock is then spead down the fuselage length evenly any taken in the natural flex of the gas cloth. Adding in points that are different in strength will focus all the problems into one spot and the model be significantly weaker for it.

 

To achieve it first you need the inner nose to be a nice fit into the outer nose cone. This might ttake some reworking of the willow and possibly shortening the outer nose cone. Not all cones will allow this but if the last few mm are not tapered then cutting it back to suit shouldn't be  a problem and is well worth considering. Adding a microballon mix into the inside of the nose cone to achieve a snug fit is also worth while, but don't add to much or you will end up with a heavy cone that will be harder to tape on. 

 

I would then make the fit between the inner nose and the fuselage rear section a good fit by wrapping a collar of wetted out glass cloth around the inner to build up its diameter, and sand back to a decent fit. Glue it in place with a slow setting epoxy and if needed a few microballoons to thicken the mix. The crutch fix to the inside of the rear fuselage adds little, except perhaps a resistance to the fuselage being crushed by the wings. But you have to decide if crushing the fuselage and saving the wing boxes is a worthwhile sacrifice. So adding strength to prevent the fuselage sides being crushed is something that each model needs assessing on. My FS4 suffers here as the wings are long and heavy and the standard fuselage has no extra support behind the nose cone, so I chose to make the servo plate run back some way to even out the strengths. But it was a considered addition and wasn't built as a bullet proof construction. Just getting the balance right to avoid unnecassary silly cracks and problems but to still break if needed is key. With the WIllow i think the fuselage at this point is pretty strong but if you wished to add some extra level of anti-crush a plate pushed in to the fuselage via the wing jopiner hole and then glued to span between the front incidence pins would be easy to achieve. Or alternatively glue a carbon rod straight through the fuselage front incidence holes and use this as the pins as well.

 

I think the rubber ring idea is simply a cost effective way of making a stock inner nose work within the rear fuselage. Nothing wrong with that The Willow knows its market. But personally I would take the trouble to rework.

 

Once done Always tape on your outer nose with a decent wrap of insulation tape. This will add significantly to the overall strength by ensuring the whole fuselage is seen as a single item in any arrival.

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Skip

That'd be why my attempt at using goop was a spectacular failure!

I was referring to urethane glue not polyurethane, but even still it was the wrong shizzle manizzle.

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stewartg

I am using PU glue more and more it sticks anything to anything, literally, and foams up as it sets filling any voids to make an incredibly strong joint which is not brittle. Ideal for bonding materials of different flexibility like wood and composite. It's also very good for bonding EPP as the foaming drives it into the pores of the foam making the join much stronger than the foam either side. Drawbacks? It needs a bit of practice to master the foaming action dependent on moisture and the thickness of the glue layer and it's only available in beige.

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Bobbyr

I had this same Dilemma couple of years ago ,

                           After I dug the Willow out of a  "mickeys"  welsh hill :blink: ,

                                                 The rubbery stuff got removed , and I used micro balloons in a 30 min resin mix to realign the nose section to the fuse . but I used a jig to keep it straight   :drool: as was suggested back then.

                                  It makes for a solid fuse , but if it was to nose dive in . the area around the micro balloon mix would give before its V tailed arsenal passed through its nose  :thumbsup: if you get my drift .

                            Don't think its really a big deal to have the nose more solidly fixed in my opinion .

 

 

                                                   Bob

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isoaritfirst

PU is great for working with epp, or wood. Like cyano it likes the moisture to activate it. More moisture equals more foaming, but more foaming may equal a weaker joint. The foam itself has no great strength, goop is great where you may want a flexible joint, like a shoe sole or somewhere that needs a former adding to secure servos etc but requires no added stress points that a more solidly fixed former may add. 

 

As in my previous post IMO failures and stress points need to be considered, in some cases a solid fix completes a one piece assembly and transfers stresses throughout in other cases adding in a solid fix may simply add a stress point where fails will become concentrated .

 

But then there is also the agument for convenience, if there is little to choose between different fix methods then convenience or availability has a part o play as well. By example I use hot glue for some jobs purely because its a convenient and cyano just because its easy.  The one thing that I enjoy breaking is the rules....  Building should be fun and often I do things using different techniques just to keep it interesting..

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Ribs

Things only men can have long discussions on: "So, Are you a Urethene glue user? Do you brace your fus or do you let it crush to save your box? What's that? Your leaving.... so soon! But wait, let's talk more, have I told you the one about the Hoerner tips....?"

 

:)

 

Anyway, loads of interesting input here, thanks fellas. I have a fus jig that needs an excuse to be used again. Got down and dirty with the moldings last night and they've cleaned up well and are ready for a new servo tray if I go that way. The V-tail servo screws weren't biting on much in their apperture, so I've kind of convinced myself to just remake and rebuild it all nice and tight. I have some carbon cloth to wrap the inner nose in and the crutch will be built wider to meet the fus sides below the wing - probably using 30min epoxy throughout.

 

Well that's the plan - I'll just have to man up and get out in the cold garage!

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isoaritfirst

Things only men can have long discussions on: "So, Are you a Urethene glue user? Do you brace your fus or do you let it crush to save your box? What's that? Your leaving.... so soon! But wait, let's talk more, have I told you the one about the Hoerner tips....?"

 

:)

 

 

 

 

 

That's it then - I'm off,

 

 

---     to another thread to have a deep and meanigfull discussion about life.

 

or is that LiFe.

:)

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