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severngoose

Beefing up polyester fuselages.

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severngoose

I find that 2 part epoxy with carbon or cloth  does not bond particularly well, any suggestions?

 

Tim C.

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thermaldoctor

Try polyester resin

Regards

Neil

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pete beadle

Hi Severngoose

I've always found that epoxy resin pressed through the carbon cloth or tows with a sponge  works well

If you start in the middle of a wing surface or along the centre line of a fuselage, you can load up the sponge with epoxy skinning resin, push the resin through the cloth or tows with the (well filled) sponge full of resin, and work outwards, going over each application twice, to spread out the resin and leave the minimum resin in place which has been pressed strongly onto the surface(s) you are covering, produces the best combination

Regards

Pete

BARCS1702

 

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severngoose

Thanks Pete & Neil, I have followed Peters method but hot with total success.

On the other hand polyester resin  gives off very nasty fumes which are no good for me.

The search goes on !

 

Tim C.

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satinet

Wetting out the cloth properly should always be done. The whole point of laying up cloth is to wet the entirety of the fibres or you might as well not bother.

The problem is that epoxy doesn't stick well to polyester.  Although i thought it was the other way round. Maybe it just needs a lot of keying.

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severngoose

I  entirely agree, in the future I am going to make a better job of keying the polyester using a coarse paper .

On balance even if 100% adhesion is not possible what ever you can achieve will stiffen up the fuselage.

Tim C.

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pete beadle

Hi severngoose and TomS

I think the problems with applying polyester to epoxy items (or vice versa) is that they are two very different chemical compositions.  A fuselage moulded in epoxy has a "soapy" feel to it's surface, while the hard polyester skin does not, there's a good reason for that......

As Tom says, on polyester items, "keying" them through their surface/skin is essential to produce an area that is  helping to strengthen the bond 

The most important thing NOT to do, IMO, is not to trowel loads of either "stiffener" onto either surface, thereby raising the overall weight which will, in turn, increase the effect of the impact:(

Good luck

Regards

Pete

BARCS1702

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satinet

What's stiffner ?

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pete beadle
1 hour ago, satinet said:

What's stiffner ?

 

4 hours ago, severngoose said:

On balance even if 100% adhesion is not possible what ever you can achieve will stiffen up the fuselage.

Hi Tom

Correctly spelled stiffener:yes::thumbsup:

Regards

Pete

BARCS1702

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MikeDaBike
4 hours ago, pete beadle said:

 

Hi Tom

Correctly spelled stiffener:yes::thumbsup:

Regards

Pete

BARCS1702

I think it's an alias for pedant, Tom ... 😎

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satinet
5 hours ago, pete beadle said:

 

Hi Tom

Correctly spelled stiffener:yes::thumbsup:

Regards

Pete

BARCS1702

Pete

It's a genuine question about what you mean by stiffener.

T

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pete beadle

Hi Tom

Please see MikedaBike's post above........apparently he thinks saying this is justified.....do you? I find it offensive, was that the intention do you think? I do

Regards

Pete

BARCS 1702

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satinet

I just wanted to know what you meant by stiffener.  

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pete beadle

Hi Tom

I was trying to reply to severngoose's commen as follows:-

12 hours ago, severngoose said:

On balance even if 100% adhesion is not possible what ever you can achieve will stiffen up the fuselage.

To me Severngoose is saying that, whatever bond he achieves, will "stiffen up the fuselage" - what stiffens up something is, for me anyway, a stiffener

Sorry but that's as clear an explanation as I can provide.......adhesive users I know often describe the curing process as "stiffening up" referring to the change in viscosity of the two-part mix curing.......is that better?.....believe me I wasn't trying to be a sm*rt*ss, I was just commenting in what I thought of as a jocular manner......sorry if I offended anyone by trying to joke about this:)

Regards

Pete

BARCS1702

 

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MikeDaBike
19 hours ago, pete beadle said:

Hi Tom

Please see MikedaBike's post above........apparently he thinks saying this is justified.....do you? I find it offensive, was that the intention do you think? I do

Regards

Pete

BARCS 1702

Apologies if I've offended. No offence meant to either. I was under the impression that "stiffner" vs "stiffener" was being debated. Back under my rock  I crawl ....

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Andy_B

I think what Tom was referring to was 'troweling (stiffener-stiffner)'  onto anything , Pete as an ex glue salesman  surely there is no stiffness in the glue and the stiffening comes from what ever it is you are bonding with the glue to .

 

 

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Brett82
On 05/03/2020 at 09:13, severngoose said:

On balance even if 100% adhesion is not possible what ever you can achieve will stiffen up the fuselage.

I dont think he is referring to the curing process or stiffening up of the mix. I think its a little more simple than that. 

If you read the posts before I think he is simply saying if you lay some cloth down with epoxy or polyester resin, then even if the adhesion is not 100% to the existing layer, the fact there is an extra layer will make the fuselage more stiff/more rigid/less flex.

Although if you want more strength you need a good bond to the existing layer. A quick google search will show Epoxy over a Polyester layer will never give a good bond (although keying will help). 

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pete beadle

Hi Andy B

Absolutely correct sir, however as Severngoose said:-

17 hours ago, pete beadle said:

On balance even if 100% adhesion is not possible what ever you can achieve will stiffen up the fuselage.

....the addition of glass-cloth impregnated with either epoxy or polyester will"stiffen " the surface to which it is applied:yes:.....may not strengthen it but, especially if he uses polyester, will stiffen it......

Exactly what Brett82 said while I was typing s-l-o-w-l-y

Regards

Pete

BARCS1702

PS Had enough of this subject yet?

 

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isoaritfirst

Personally I think you are wasting your time with trying to lay anything onto the inner surface of the fuselage. 

The two material will not bond together well, and I suspect that all you will add is weight. Building epoxy/carbon or epoxy/glass fuselages requires much more than cloth and epoxy. They need to cure correctly and the materials need to be layered in appropriate directions and thicknesses. 

Curing requires pressure and heat. I don't see how you would apply any pressure. Just layering it in will be a weak and heavy finished item.

You would do better using the existing fuselage as a plug and then making a mold, to allow a correctly made epoxy fuselage.

But that is a lot of work. 

Alternatively - I suggest that you go back to my original suggestion of adding formers down inside the fuselage. You could make these from EPP and jam them in place, or tack them with silicon. Making several that are linked together with longerons may be a workable technique. Anything that will hold them in place to help stop the fuselage deforming during a crash. 

Anyone else getting a stiffy?

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oipigface

Mike’s written my reply for me. 

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