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smcouch77
Guest
It will make a great addition to an already awesome plane! How do you load the bombs?
Steve
Steve
SE5a CONSTRUCTION BEGINNING TO . . .
- Thread starter Greyhead
- Start date
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alan2525
Guest
This old SE5a is getting more and more technical by the minute! Lovely workmanship on that bomb rack mechanism! I'm really impressed by how fast you manage to put all these little scratch built bits together - the devil is in the detail! I always find working on painstaiking parts to be really irritating and normally have a box full of failed attempts after a couple of days graft!
Great Work as always!
Great Work as always!
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- Grahame
I mounted the bomb rack on some scrap balsa whilst I adjusted the bomb cradles. This adjustment turned out to be quite critical; a balance between having the bombs loose and able to swing about or too tight to allow the release bar to move under the spring tension.
In fact it was so critical that I have had to number the bombs to ensure they are fitted in the same positions, the slight variations in the diameters of the bombs where the cradles support them was enough to cause problems.
The bombs are held in position by different length pins that pass through loops on the bombs, which themselves pass through slots in the base of the bomb rack. This photo was taken before any adjustments were made; the bombs are now equally spaced!
Steve
The bombs are loaded in the reverse of the order that they are released. With all the bombs released the release bar projects 20mm from the end of the bomb rack, I don’t think this will be too obvious “in flight” but if it is I’ll shorten the release bar and extend it with a length of piano wire. The first bomb is held in position and the release bar pushed in to engage the release pin through the bomb’s loop, the slot in the release cam is such that the previous indexing pin can pass back through it when the release bar is pushed in. The cam is then moved (at the moment by hand but once on the model by flicking the retract switch on the transmitter) to the other position. The release bar can then be allowed to spring back against the cam whilst the next bomb is put into position and the process repeated until all 4 bombs are in position.
In fact it was so critical that I have had to number the bombs to ensure they are fitted in the same positions, the slight variations in the diameters of the bombs where the cradles support them was enough to cause problems.
The bombs are held in position by different length pins that pass through loops on the bombs, which themselves pass through slots in the base of the bomb rack. This photo was taken before any adjustments were made; the bombs are now equally spaced!
Steve
The bombs are loaded in the reverse of the order that they are released. With all the bombs released the release bar projects 20mm from the end of the bomb rack, I don’t think this will be too obvious “in flight” but if it is I’ll shorten the release bar and extend it with a length of piano wire. The first bomb is held in position and the release bar pushed in to engage the release pin through the bomb’s loop, the slot in the release cam is such that the previous indexing pin can pass back through it when the release bar is pushed in. The cam is then moved (at the moment by hand but once on the model by flicking the retract switch on the transmitter) to the other position. The release bar can then be allowed to spring back against the cam whilst the next bomb is put into position and the process repeated until all 4 bombs are in position.
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The bomb rack is bolted to 4 small brackets fitted between the undercarriage legs; the release arm has a ball-joint soldered to it just inside the fuselage bottom and the control rod passes forwards between the undercarriage cross members and the fuselage bottom.
A mini servo to operate the bomb release is located in the engine compartment attached to the firewall by an “L” shaped servo mount.
Commercial “L” servo mounts seem to me to be very expensive for what they are so I make my own from “L” shaped plastic extrusion from B&Q; I bought a 6ft length for a couple of quid years ago and I’ve still got half of it left!
A mini servo to operate the bomb release is located in the engine compartment attached to the firewall by an “L” shaped servo mount.
Commercial “L” servo mounts seem to me to be very expensive for what they are so I make my own from “L” shaped plastic extrusion from B&Q; I bought a 6ft length for a couple of quid years ago and I’ve still got half of it left!
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tigertc
Guest
Words fail me when i try to say how good this is looking Grahame.
Cant wait for her to fly. Are sure about all the weight you are adding? I am no proffesional in these matters, but you do tend to keep adding things.
*Wates for kitchen sink to be added
Cant wait for her to fly. Are sure about all the weight you are adding? I am no proffesional in these matters, but you do tend to keep adding things.
*Wates for kitchen sink to be added
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Terry
Weight is always a consideration with scale models; because it isn’t a property with a “tipping point” it’s tempting to say, “it can handle another few grams.” The trouble is all these few grams add up and can end up as a few kilograms!
Of course given enough power anything will fly but as the weight increases for a given wing the flying speed has to increase to generate the extra lift required and it can get to the point where the model can no longer be flown in a scale manner, which really defeats the object of the exercise.
One advantage of these early biplanes is that because they didn’t have powerful engines available at the time, they were designed lightly loaded with lots of wing area, unfortunately the aerofoil sections are not as efficient as more modern ones but in practice weight isn’t usually too much of a problem, drag is what really saps the power.
Personally I don’t over concern myself with the weight, I just build as light as I can, allowing for sufficient strength, certain details have to be added to be scale and there’s nothing that can be done about it. The bomb rack on the other hand isn’t essential so if needs be it can be easily removed with 4 bolts, but I hope it’s OK as I think it will be a real “talking point” and increase the appeal of the model.
Grahame
Weight is always a consideration with scale models; because it isn’t a property with a “tipping point” it’s tempting to say, “it can handle another few grams.” The trouble is all these few grams add up and can end up as a few kilograms!
Of course given enough power anything will fly but as the weight increases for a given wing the flying speed has to increase to generate the extra lift required and it can get to the point where the model can no longer be flown in a scale manner, which really defeats the object of the exercise.
One advantage of these early biplanes is that because they didn’t have powerful engines available at the time, they were designed lightly loaded with lots of wing area, unfortunately the aerofoil sections are not as efficient as more modern ones but in practice weight isn’t usually too much of a problem, drag is what really saps the power.
Personally I don’t over concern myself with the weight, I just build as light as I can, allowing for sufficient strength, certain details have to be added to be scale and there’s nothing that can be done about it. The bomb rack on the other hand isn’t essential so if needs be it can be easily removed with 4 bolts, but I hope it’s OK as I think it will be a real “talking point” and increase the appeal of the model.
Grahame
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alan2525
Guest
Those pics of the Bombrack clamped to the shelf in your workshop gave me a big smile! Looks absolutely superb and certainly worth the extra bit of weight that they add to the model! Certainly looks very purposeful!
I wish I had a little bomb rack like that in my workshop for those times when the part just doesn't turn out quite how you wanted it!
When she's airworthy - I'd love a chance to see her in flight and a close up look! Any plans of a Scale Models meet?
:bravo:
I wish I had a little bomb rack like that in my workshop for those times when the part just doesn't turn out quite how you wanted it!
When she's airworthy - I'd love a chance to see her in flight and a close up look! Any plans of a Scale Models meet?
:bravo:
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tigertc
Guest
Something bad happens when we try to organise a meet...we need to call it something else.
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Bunkerbarge
Guest
A 'Gathering', or is that a bit too Stephen King!!?
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Alan
I’m not into competitions so the only place I’ll be showing the SE5a is the TMFC “Bring a Model Night” where we take our winter projects for other members to peruse and I’ll fly her from our field at Redmarshall.
It’s a long way from County Durham to Essex but if you’re every up this way drop me a PM and you’re more than welcome to come and have a look, you might even get a cup of tea if you’re lucky!
Grahame
I’m not into competitions so the only place I’ll be showing the SE5a is the TMFC “Bring a Model Night” where we take our winter projects for other members to peruse and I’ll fly her from our field at Redmarshall.
It’s a long way from County Durham to Essex but if you’re every up this way drop me a PM and you’re more than welcome to come and have a look, you might even get a cup of tea if you’re lucky!
Grahame
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alan2525
Guest
How about a Jolly? Sounds less Stephen King than a Gathering - plus Jolly suggests the consumption of Alcoholic Beverages* too!
* Beer
:gathering
:beer2:
* Beer
:gathering
:beer2:
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Something I’ve never done before is to make a “static” prop, after all the object is to end up with a flying model not a static display, but as I’ve got time on my hands I thought I might as well give it a go. An added incentive is the fact that I’ll be using a 13" or 14" prop for flying whereas the scale diameter is 18¼" so the flying prop does look very small.
As I said I’ve never done this before so it’ll be a case of trail and error and hope for the best; to make things easier I decided to go for a 2 bladed prop. I thought of making it laminated but it would be quite costly to buy the wood and as I’m not certain of the outcome I decided against it. From a front view photo I produced a template, glued it to a piece of knot-free pine and cut it out with a jigsaw.
I was very surprised that it only took about an hours work with a plane and a rasp to produce a reasonable looking prop, and a large pile of wood shaving!
As I said I’ve never done this before so it’ll be a case of trail and error and hope for the best; to make things easier I decided to go for a 2 bladed prop. I thought of making it laminated but it would be quite costly to buy the wood and as I’m not certain of the outcome I decided against it. From a front view photo I produced a template, glued it to a piece of knot-free pine and cut it out with a jigsaw.
I was very surprised that it only took about an hours work with a plane and a rasp to produce a reasonable looking prop, and a large pile of wood shaving!
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Bunkerbarge
Guest
That's quite an achievement Grahame. It looks very good and I know that propellers are one of the most difficult things to make. Especially carved from solid like that.
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A working prop is in a completely different league from the one I’m making; a static prop just has to look right, it doesn’t have to produce thrust or withstand any of the forces that implies. I certainly wouldn’t want to trust my prop to fly the SE5a!
The prop blades have been thinned down considerably, initially using the Dremmel but finishing off by hand. One coat of stain has been applied, several more to go.
The props had various things done to them and as I have no evidence as to what, if anything, was done to the prop of E5808 I can choose the variant I like best.
The choices I know about are:
1. Metal reinforced leading edges.
2. Metal reinforced tips.
3. Both of the above.
4. Outer half of blades fabric covered.
5. Blades bound with several turns of cord about mid point.
6. Plain stained wood with no additions.
At the moment my preferences are 1 or 5, I’ll probably try litho plate for reinforced leading edges first, if that doesn’t work I’ll go for the binding.
The prop blades have been thinned down considerably, initially using the Dremmel but finishing off by hand. One coat of stain has been applied, several more to go.
The props had various things done to them and as I have no evidence as to what, if anything, was done to the prop of E5808 I can choose the variant I like best.
The choices I know about are:
1. Metal reinforced leading edges.
2. Metal reinforced tips.
3. Both of the above.
4. Outer half of blades fabric covered.
5. Blades bound with several turns of cord about mid point.
6. Plain stained wood with no additions.
At the moment my preferences are 1 or 5, I’ll probably try litho plate for reinforced leading edges first, if that doesn’t work I’ll go for the binding.
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I’ve got the easy bits out of the way first; it certainly looks better than the “standard” Laser prop nut.
For flying I normally use a 13" prop with a 6" pitch, but having seen how much better the model looks with a bigger prop I’ve been thinking, if the pitch was reduced to 4" then the diameter could be increased to 15" or 16". This has the advantage of increased static thrust, which is useful for overcoming drag, also the model will fly slower for any given revs so the engine can be tuned for maximum power without having to fly like a pylon racer.
Searching through the catalogues I found that APC do make a 16" x 4", the downside being that it is about 3 times the price of a 13" x 6"; do the looks really matter that much?
For flying I normally use a 13" prop with a 6" pitch, but having seen how much better the model looks with a bigger prop I’ve been thinking, if the pitch was reduced to 4" then the diameter could be increased to 15" or 16". This has the advantage of increased static thrust, which is useful for overcoming drag, also the model will fly slower for any given revs so the engine can be tuned for maximum power without having to fly like a pylon racer.
Searching through the catalogues I found that APC do make a 16" x 4", the downside being that it is about 3 times the price of a 13" x 6"; do the looks really matter that much?
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Bunkerbarge
Guest
Like everything else on this model Grahame it just simply looks superb.
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I thought that getting the litho plate to bend around the prop blade following the curved leading edge would be a problem; one reason why I got the hub etc. done first! As it turned out it was no problem at all, the most awkward thing to do was embossing the rivets as this had to be done last of all and it was quite tight to get the embossing wheel in. To make the job easier I “opened out” the litho plate somewhat then carefully refitted it to the prop blades using just my fingers and a cloth to ensure none of the rivets got flattened.
Of course it all looks very shiny and ex-works at the moment, a bit of weathering will soon change that.
I have to say that I’ve thoroughly enjoyed the last few days making the static prop; obviously it won’t improve the model as a flying model but all in all I think it’s been worth it, hope you agree.
Of course it all looks very shiny and ex-works at the moment, a bit of weathering will soon change that.
I have to say that I’ve thoroughly enjoyed the last few days making the static prop; obviously it won’t improve the model as a flying model but all in all I think it’s been worth it, hope you agree.
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tigertc
Guest
Beautiful!!
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Well I think now is the time to change the title of this thread by substituting “END” for the last 3 dots. I still have to fit the fuel tank and the radio gear, but I don’t think this really constitutes “CONSTRUCTION”. There are still some small bits of detailing to do but nothing significant, I’ll post photos if I think they’ll be of interest.
I moved the settee and took a few photos against a plain wall, which hopefully shows up the detailing more clearly; when the better weather arrives I’ll take some “al fresco” for a more realistic effect before I risk the first flight!
I’d like to thank everyone who took the trouble to post a reply, be it either help, suggestions or just words of encouragement; with special thanks to Giles for the research material, Christian for the photos and Steve for the inspiration and help with the Cooper bomb rack!
I moved the settee and took a few photos against a plain wall, which hopefully shows up the detailing more clearly; when the better weather arrives I’ll take some “al fresco” for a more realistic effect before I risk the first flight!
I’d like to thank everyone who took the trouble to post a reply, be it either help, suggestions or just words of encouragement; with special thanks to Giles for the research material, Christian for the photos and Steve for the inspiration and help with the Cooper bomb rack!
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tigertc
Guest
And may i be the first to say well done and congratulations on a truly inspiring build.
A stunning model.
A stunning model.