6 Turning 4 Burning

[Don Fry]

In fairness, Erf, it will balance about the wing. That is where the weight is. The rest is a bit of material in front of, and behind the wing.

A bit of a concern, one of the videos showed a slightly twitching flyer, and a horizontal nodding behaviour, what looked like Dutch Roll. And that is a symptom of marginal vertical stabiliser/rudder area.

[Erfolg]

Don, I agree with what you saw, I saw the same.

I know the rudder area is massive, I would be surprised if it was or is the issue. The wing is pretty much flat, there being no dihedral.

Although under certain circumstances my canard, does a sudo dutch roll in turns if going slow. Fast no issue.

I think you may be mistaken with the motors and fuel tanks relative to the CG, they are on the wrong side, together with the tail assembly, they need something up front to balance the moments. Assuming that the model is IC, there is only the Rx, a battery and perhaps some fancy electronics, may be a couple of servos?

I am really interested how the issues will be manged and resolved, without lead.

In my mind it could be a big glider, other than the Power Plants and their fuel to mess simplicity up.

[Don Fry]

Not sure about a massive rudder.

I see a reasonable rudder, a short moment to the CG, and a load of nose in front. But something was causing the bloodhound on a track nod.

and Erf, if it was simple, this builder wouldn't bother. I reckon I'm being clever sticking crow brakes onto an Avicraft Panic. Different league.

[Erfolg]

Don

The moment arms are about 50/50. There is a lot of structure in the Rudder/fin and tailplane.

If you look at a drawing of the rudder/fin it is large. Compared to the wing area, probably something like I would expect, for a sailplane. The B17 had its rudder/fin enlarged due to poor tracking, which was also large.

In essence, it does not matter what I think. although i expect i will learn something form others struggles.

[Trevor Crook]

I'm not sure I'd agree with the "fly in any weather" design aim, but that's down to personal preference. I like scale models to look scale, on the ground and in the air. As the B36 is so huge, even a large model is going to have a large scale ratio - even a 1:10 scale model would have a 23' wingspan. To look right, this would have to cruise at 30-40 mph and take-off and land at about 10-12 mph. In order to do that, it needs to have a low wing loading, and will therefore be impacted by strong winds. Assuming it's not going to enter competitions and have to fly in all weathers, it could be restricted to sub-10 mph wind days, when it would look very nice.

However, it's not my project, and I could never imagine building such a thing, let alone getting the weight down enough, so I'll just keep watching progress with interest and admiration.

[Erfolg]

Trevor

You are spot on, what I, or others think, does not really matter. Although the exchange of views has to be interesting.

Coming from a model glider and competition background, it is not unusual to fly them in all weathers. My largest, @144" wingspan has flown in 20 mph winds, my Ridge Rover, +100" span (now stacked away), even my 3m Algebra has also flown in very similar winds. Are they relevant, they are in as much the spans are large with modest bodies, similar to the B36. The plus side they could be landed quite slowly even in dead calm weather. As for scale type speeds, probably pushing it a little near to the stall to be continuously flown as such.

I was thinking about what SR is about to do. I must admit I think he has both wrong footed me, and about to show me a technique I have not used.

In the past I have made my own plugs and moulds, then pulling my own fuzs. Below is a selection I have lying about in a bucket. A pile of tail booms (fishing rod blanks) are in the background.

At first I thought he was about to make a female mould from a plug he has started, for the nose and tail.

Still having some PVC pipe of the same size SR has shown us, I thought OMG, that is heavy. I then thought it must be a whole fuz.

My experience of making moulds, is that it is very hard work, time consuming, on this scale expensive. For one body, hmmm. He must have another idea.

I am now guessing, could it be a variation on the lost former method. Which I must confess I have never tried. Mainly as I saw my gliders as consumables, although the Earth would scream in agony when impaled by a model. Even then there would often be minimal damage to the model. So how would you do it? lay up on top of a prepared plug, well waxed. The cut longitudinaly. Given the contours it is probable that the shells would pop of, without an incredible amount of effort.

I have however rubbed down GF mouldings to smooth them out, in a bath of water with soap. Both time consuming, and ruins your hands, even with your marigolds on.

At the size indicated, as a slope soarer, a lot of the CG issues disappear, As for landing, the real one used barn doors for flaps.

Go on, give us a clue SR 77!

[SR 71]

Done a little more, started to shape the MDF, very dusty in my new hanger, way to cold outside

[Erfolg]

Come on, give us a clue.

I guess you are not using the dust bag, I hope you are using a breathing mask. Even using a belt sander, it must take some time?

Are you using templates? As I cannot see them?

Edited By Erfolg on 24/01/2020 21:35:33

[SR 71]

Hi Erfolg there is nothing special about the build, straight forward plug, mould and cast the finished fuselage in an effort to keep it light at the rear end, i hope as i have little experience

im doing it by eye and a centre line along the top of the fuselage, i like to think things out as i go along,look on the internet at all the pictures and films i can find, its not a competition class model, i not good enough for that, i just like building something different to run of the mill, and these things have stuck in my mind for 70 years so i thought it was about time to have a go at one, Before its to late, not my type of flying model i must say as you can only go round and round with it, but i will enjoy the challenge of build

Tony

[Erfolg]

I did spot the centre line.

I am about to start a small lay up myself, a couple of cowls. What has surprised me, is how much I have forgotten. Another aspect is the small roller tool I used for consolidation was thrown away, on the basis, I will never do any layups again.

I am now busy saving paper cups for my mixes, looking for alternatives to lolly pop sticks for stirring. When making canoes, I could buy big ones from Strand Glass, later i pinched my little girls (who are now middle aged) lolly sticks.

After a lot of thought i have decided on Polyester Resin, as I notice that all my moulds were polyester, and my experience is predominantly with that Resin.

I have made my patterns for cutting the glass. Now I find I only have woven rovings or cloth, which although draping well, do not pick up detail like surface tissue did.

So many niggly issues. In the past I was just a member of a small amateur team, with a guy from Piranha mouldings, a member of the Manchester Canoe Club (as I was) and a Scout Master, whose hut we used (making some canoes for the scouts). I had my Trylon book, plus all the pamphlets from Strand Glass and their technical support. Now I know nothing.

Yet, big moulding jobs like yours need a lot of preparation and so on.

For me the wrong time of year for my moulding as I must do it in the garage and it is probably border line on temperature, and the atmosphere far to damp.

I will keep watching with interest.

[SR 71]

I have done a little more on the plug, its all about the right shape, some filling sanding, filling sanding to do, also the radome on the bottom of the fuselage plusone at the tail

[SR 71]

I find this forum difficult posting pictures in the correct order,

[SR 71]

The plug is ready for glassing, i have cut the 4oz cloth for two layers, just waiting for the order for the resin to arrive

[SR 71]

Well a disaster, got the resin kit and i have laid the two layets of cloth on the plug, but its not gone off, so on contacting the suppliets it appears that they have sent the wrong stuff, three small bottles of hardener and not resin but a large bottle of hardener, being the first time iv bought resin from them i did not know what it should be like, they are full of apologies and have sent me a new kit and some clothes and things to clean the plug, have spent a few hours on it but the hardener is to well soaked into the MDF to come out, the plastic pipe has come relatively clean , BUT

[Dickw]

Is it worth trying to paint a thin coat of 'resin only' on to the MDF to see if it will react with the soaked in hardener and form a thin crust you can work on top of?

I know it's a desperate measure, but if all else fails what have you to lose.

Dick

[SR 71]

Yes thats an idea Dick, but if i give it a coat of resin mixed as it should be then all the extra hardener soaked into the MDF should only make it go of quicker, ????? maybe LOL

[Jon H]

Posted by Dickw on 02/02/2020 23:03:29:

Is it worth trying to paint a thin coat of 'resin only' on to the MDF to see if it will react with the soaked in hardener and form a thin crust you can work on top of?

I know it's a desperate measure, but if all else fails what have you to lose.

Dick

You could also mix the resin (assuming its epoxy) with some epoxy thinner or meths to thin it down. Its then more likely to mix with the hardener already soaked into the material. A quick blast with a hair dryer or heat gun will evaporate the thinner leaving you, in theory, with nicely mixed epoxy

[Don Fry]

West Systems recommend heat, and acetone/thinners to remove the material. I would not use epoxy on top of hardner. You will end up with uncured epoxy on the surface, then a layer of various thicknesses of resin in different cures, over the sealed in hardner.

Try heat, and acetone, then a normal mix, thinned, to seal the hardener in.

Life, and this hobby in particular is a bitch.

[Erfolg]

I must admit straight away, I do not know with certainty what you are doing.

Are you laying the cloth on the plug, as a means of creating a plug, from which you will be making a female mould?

At first I thought you would be laying up on the mould to produce a shell, which would be cut from the plug.

Now I have come to the conclusion, that is not the intention, as with the materials you have used you would need to form a barrier, be it a sealed surface, waxing and possibly anther release agent, be it PVA (the moulding type) and waxing. So that approach appears to be a non starter.

So I await further developments.

As per the difficulties, they will be overcome, as in essence all of the suggestions, can be made to work. Dependent on your technique for the body actually is, one may be slightly better than another, luck as well as judgment etc., all play their part.

[SR 71]

The acetone would not shift the gunk, so i have laid 4oz cloth on and brushed the new resin and hardener, in that they sent me, ill see what happens

[Andy Stephenson]

Acetone is a good solvent but it's ineffective on epoxy, cellulose thinners is what you need.

A.

[SR 71]

Tried that first Andy it did not work either

[PatMc]

Isn't isopropyl alcohol (IPA) the correct solvent to use for uncured epoxy resin ? I assume it would also dissolve the hardener.
IIRC methylated spirits can also be used for cleaning up but not quite as effective as IPA

[SR 71]

Last Monday i glassed it again having scraped as much of the gunk off as i could, just mixed a normal mixing of resin and applied with 4oz cloth, pleased to say it has gone hard, had it in the house all week

So today ill take it back out to the hanger and start sanding, iv also ordered a stack of ply and balsa from Slec so when that comes i can start that side of the build, been looking for engines / motors for it, surprised how little HK have got, one glow engine and all the electric motors that will do the job are out of stock

[Erfolg]

Well done, there is always a way. Sometimes not as perfect or as straight forward as you want, yet as much as an achievement as something routine. Once again, WELL DONE!