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Old Sep 18, 2012, 07:20 AM
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There are many ways to get fibreglass (or any other reinforcement you want) into / onto wings, here are 3 :

1) Glass straight on top of a traditional veneered foam wing. Filled with a light coat of bulked-up resin to create smooth surface. Primered then sprayed.

2) Glass underneath veneer of foam wing - can be messy as its a lot of ducks to get in a row, but is easy to finish then with solarfilm etc.

3) Vacuum-bagged foam. Produces glass-like surface that can be painted before the lay up is started to impart colouring onto / into a thin gel-coat

They are probably the most popular. Yours should work fine, just might be a fair bit heavier than they needed to be. You could have gotten away with submersing a spruce spar in the top and bottom surface, then brown-papering over that. To be honest, even that's probably overkill - Chris Goulds gets away with a lot less in his designs that use brown paper and PVA.

If you're not sure on the soldering, don't bother changing them out, but the ESC will probably appreciate at least a little air over it. Maybe a small duct and vent?

As for the tailplane - for that size I'd have used a flat balsa plate and maybe cut some lightening holes in it. Jobs done.

Edited to add : I'm not bashing your design at all, kudos to you for getting it done I keep trying to save up for an APM 2.5, but other projects or house stuff get in the way
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Old Sep 19, 2012, 04:36 AM
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Quote:
Originally Posted by awmeade View Post
There are many ways to get fibreglass (or any other reinforcement you want) into / onto wings, here are 3 :

1) Glass straight on top of a traditional veneered foam wing. Filled with a light coat of bulked-up resin to create smooth surface. Primered then sprayed.

2) Glass underneath veneer of foam wing - can be messy as its a lot of ducks to get in a row, but is easy to finish then with solarfilm etc.

3) Vacuum-bagged foam. Produces glass-like surface that can be painted before the lay up is started to impart colouring onto / into a thin gel-coat

They are probably the most popular. Yours should work fine, just might be a fair bit heavier than they needed to be. You could have gotten away with submersing a spruce spar in the top and bottom surface, then brown-papering over that. To be honest, even that's probably overkill - Chris Goulds gets away with a lot less in his designs that use brown paper and PVA.

If you're not sure on the soldering, don't bother changing them out, but the ESC will probably appreciate at least a little air over it. Maybe a small duct and vent?

As for the tailplane - for that size I'd have used a flat balsa plate and maybe cut some lightening holes in it. Jobs done.

Edited to add : I'm not bashing your design at all, kudos to you for getting it done I keep trying to save up for an APM 2.5, but other projects or house stuff get in the way
Cheers for the info, I think i'll go with PVA/WBPU Varnish and Brown paper to remove the twist in the wings (hopefully it will stick to Polyfilla, but i don't think it will).

I have another set of foam cores for an identical plane to this one, however i'd like to make it at least 1kg lighter, I may go with a single thick CF Tube in the wings with a smaller tube inserted for the join. Then Straight Fibreglass over the surface of the foam,

In option 1 you mention veneered foam wing, what is the purpose of veneering prior to fibreglassing? Will the fibreglass not be strong enough on its own with a single spa? I guess the covering will act like webbing as well, or should i still put a full depth spa in the wing?

I'll create a little scoop for the ESC and put it in the rear part of the plane, Just need to figure out how to ensure water doesn't get into the esc area via the scoop, is there a way to let air in, but not water?

As for the tail, My LHS doesnt sell thick balsa to make the tail out of, so thought foam and fibreglas would be a strong alternative, I think I am overestimating the strength fibreglass can add to a structure, I could use the 175gm fibreglass matt, as opposed to the 25gm matt,

Hmmm, decisions decisions...

Thanks again all for your help, it is helping a lot
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Old Sep 20, 2012, 02:58 AM
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The glassfibre over veneer method is quite popular, but trying to answer your questions made me think why! I guess once the foam core is cut, its very easy to veneer the foam by using the female blanks to form a press and hold the veneer on. This of course gives you great rigidity in the skin of the wing where it matters, and also protects the airfoil shape.

Glassing over this is just to create an even stronger finish that resists dings well, and can be finished nicely with sprays etc. If the builder had access to vacuum bagging, I expect that the veneer would be mostly be dropped.

Have you still got the full depth spar I saw in the early pictures? That will make this wing very strong, but it will still have a tendency to twist, which a strong skin will stop.
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Old Sep 20, 2012, 03:08 PM
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Wing construction

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Originally Posted by awmeade View Post
The glassfibre over veneer method is quite popular, but trying to answer your questions made me think why! I guess once the foam core is cut, its very easy to veneer the foam by using the female blanks to form a press and hold the veneer on. This of course gives you great rigidity in the skin of the wing where it matters, and also protects the airfoil shape.

Glassing over this is just to create an even stronger finish that resists dings well, and can be finished nicely with sprays etc. If the builder had access to vacuum bagging, I expect that the veneer would be mostly be dropped.

Have you still got the full depth spar I saw in the early pictures? That will make this wing very strong, but it will still have a tendency to twist, which a strong skin will stop.
A ha, cheers for the information, I was under the wrongful impression that foam and a fibreglass skin was enough to strengthen a wing. The wing does still have a full depth spruce spa through the thickest section of the wing. As I think these wings are heavy enough, I have gone with the Water based Polyurethane varnish and brown paper method (even though the paper is white!).

I will be cutting the Polystyrene foam cores tomorrow, and i was going to simply fibreglass over the foam to form the Cathedral tail. Do you think that the tail sections will need extra reinforcement?

Is 175gm fibreglass skin going to add considerable strength do you think?
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Old Sep 21, 2012, 02:41 AM
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Glass over foam is very strong - its just the manufacturing method to get it on there well (i.e. vacuum bagging) has a steep learning curve and requires some out of the ordinary equipment.

Be careful with white paper - I think it is sealed somehow to stop ink running (and so might not bond as well), whereas brown paper is more porous. I think.

Looking good so far tho
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Old Sep 21, 2012, 01:24 PM
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Help with tail design and reinforcement, & White paper, not a good idea!!

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Originally Posted by awmeade View Post
Glass over foam is very strong - its just the manufacturing method to get it on there well (i.e. vacuum bagging) has a steep learning curve and requires some out of the ordinary equipment.

Be careful with white paper - I think it is sealed somehow to stop ink running (and so might not bond as well), whereas brown paper is more porous. I think.

Looking good so far tho
I have cut the tail sections out, and now need to think about how to reinforce them prior to covering in fiberglass/brown paper and water based polyurethane varnish.

Here are my thoughts, cut Ailerons out, and then cut 45 degree angles in each half so they meet nicely at the top, then stick together, and cover with a layer of 175gm fibreglass, no spas or other reinforcements.

Option 2, insert a full depth spa at the thickest part of the wing, then cover in brown paper and water based polyurethane varnish. I am not sure how to get strength where the two halves meet though.

Any suggestions?

RE: The main wings,
Someone suggested i use white instead of brown, I believe i used the wrong sort of white paper, it does not look like it has absorbed the varnish, and has begun to peel of the wing in some areas. I'l definitely use brown next time. The wings are quite heavy now, but I have learnt a lot in making them, the next ones will be twice as light!

R
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Old Sep 25, 2012, 02:45 PM
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Any thoughts on tail design?
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Old Sep 26, 2012, 04:17 AM
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New hotwire looks great, nice job. As for the ailerons, I'd try and face them with balsa before glassing. Only reason is that they are (usually) long and thin, and tend to twist easily when you are working with them. It will be the devil's own job to get them to stay flat and square as you glass them, so a nice hard leading edge will stiffen things up for you, and also provide some anchorage for hingeing, depending on which way you go there.

Not sure on the tail design, didn't someone mention swept area earlier in the thread? I'm a big fan of Andy Lennon's book on model aircraft design if you find a copy.
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Old Sep 28, 2012, 03:07 AM
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Quote:
Originally Posted by awmeade View Post
New hotwire looks great, nice job. As for the ailerons, I'd try and face them with balsa before glassing. Only reason is that they are (usually) long and thin, and tend to twist easily when you are working with them. It will be the devil's own job to get them to stay flat and square as you glass them, so a nice hard leading edge will stiffen things up for you, and also provide some anchorage for hingeing, depending on which way you go there.

Not sure on the tail design, didn't someone mention swept area earlier in the thread? I'm a big fan of Andy Lennon's book on model aircraft design if you find a copy.
The Ailerons were just basic polystyrene on the last 2.5 metre plane i built, it was a slow flyer though, I have considerably strengthened up the Ailerons with Brown paper and WBPU Varnish. However the finish is pretty poor. After my first positive experience with fibreglassing a few nights ago, I think i will straight fibreglass over polystyrene for my next build,

Picture below of my test piece covered in one layer of 175gm fibreglass, Finish isnt perfectly smooth, but better than standard foam finish!

I may also look at something called 'vacuum bagging'. It apparently gives a smoother finish.

I Am thinking of building the tail section out of standard polystyrene, then just fibreglassing over the join and other parts to make it strong,

Any input in the meantime would be great!
Rich
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Old Oct 02, 2012, 08:02 AM
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Cathedral tail construction has begun...

Tail halves cut and joined, ruddervators cut off and ready to cut channels for servos and servo holes prior to covering with a layer of 170gm/sqm fibreglass and epoxy resin.
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Old Oct 02, 2012, 05:24 PM
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Does anyone know how to install the servos for this type of tail, mirroring each other like standard aileron servo placement, or the same was as eachother?
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Old Oct 03, 2012, 04:19 AM
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One servo per tail surface, and program the transmitter as a vee tail, or "ruddervator". I know how to do it on a Futaba 9C, but I'm sure its fairly simple on most radios.
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Old Oct 03, 2012, 05:29 AM
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One servo per tail surface, and program the transmitter as a vee tail, or "ruddervator". I know how to do it on a Futaba 9C, but I'm sure its fairly simple on most radios.
Cheers, I am aware that I need to install 1 servo per tail surface, my question is, what orientation do I install the servos?

for clarification, I have drawn a picture with 2 options, option A, and option B...

I also have a futaba 9c! image below...
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Old Oct 03, 2012, 02:55 PM
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Shouldnt matter - you can reverse the movement in your TX settings when first setting up
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Old Oct 07, 2012, 10:05 AM
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Build update - 07-10-2012

The plane is coming along nicely, the tail fits perfectly on the booms, But is a little heavy, I may use lighter glass for the surface of the tail next time, and use the heavy stuff for the critical strength areas. 25gm fibreglass should be enough to remove twist in the wing/tail.

The ruddervators are glassed and drying, as soon as they are ready I am going to add the hinges, add them onto the tail along with the ailerons, and do a test glide down a local hill.

Pics...
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