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Old May 10, 2012, 06:16 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
Build Log
Peter Rake’s 58” Sopwith Swallow

Hello everyone.

Just starting on the Sopwith Swallow.

Specs:
  • Wingspan: 58”
  • Length: 36”
  • Weight: ~60




I didn’t turn up a lot of information on the Swallow. Most of the information about the plane can be found on Wikipedia, but in a nutshell, the Swallow was an attempt started in Oct 1918 to convert a Camel F1 from biplane to monoplane.

The prototype’s performance was not as good as the Camel’s so the design was abandoned. The Swallow was sold and converted to civilian use. It was later scraped in 1927.





Manzano Laser provided the laser cut parts. Here is the list of wire/wood I purchased. I'll try to keep this updated if there are any changes:

36" Balsa Sticks:
2 - 1/8 x 3/8
1 - 1/8 x 1/4
2 - 1/8 x 3/16
2 - 1/4 x 3/8
2 - 3/16 x 3/8
10 - 3/16 x 3/16
1 - 3/16 x 1/2
6 - 1/16 x 3/16

36" Balsa Sheets
2 - 1/16 x 4

24" Bass Sticks
3* - 3/16 x 3/8
3* - 3/16 x 1/2
9 - 1/16 x 3/16

*Only 2 required if you can get lengths of 30"

Ply Sheets
2 - 1/32 x 6 x 12

Wire
30" of 16 ga - 1.3mm
30" of 14 ga - 1.6mm
30" of 12 ga - 2mm
46" of 10 ga - 2.5mm

Electronics - Subject to Change at this Point
  • 4 - Hextronik MG16 Servos
  • 60amp ESC -
  • 480 Motor
  • 2 cell 2600 this will probably change depending on balancing - may go with 2 packs if I need more weight up front.
  • 13 x 6.5 prop
  • 7 Channel Receiver with Satellite

************************************************** ************************************************** *********************************
Power and Weight Specs

************************************************** ************************************************** *********************************

2 Cell:
Batt: 2 x 2200
Weight: 59oz
Watts: 217
Amps: 29
Watts/lbs: 43

3 Cell:
Batt: 2 x 2200
Weight: 63oz
Watts: 492
Amps: 44
Watts/lbs: 94

Flying on 2 cells goes fairly well. Cruising speed is pretty good but a long take-off is required and if you have to abort a landing, be very careful - let the plane build up speed before pulling up too quickly.

Flying on 3 cells doesn't leave you much throttle to play with in the scale speed range.

If you can work out a combination that gives you 60 watts/lbs, I think you'll be dialed in very nicely.

I've played around with a few different motors and props I've had but haven't come up with a combination that gives me anything much different yet.
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Old May 10, 2012, 06:24 PM
Balsa builder and balsa basher
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Nice looking Plane I'll have to return later for the build pics.
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Old May 10, 2012, 07:35 PM
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Norfolk, England
Joined Sep 2001
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Charles,
Okay mate, just so we all understand your reasoning, I'll play Devil's Advocate.

I'm surprised by your weight estimate, I would have thought much closer to 3 1/2 pounds (56 ounces) as top end. Even my old, and very heavy FS .40 powered one only weighed about 5 lbs and that was Solartex covered, used full size servos and carried the standard 600 mAh receiver pack.

When I design a model I usually envisage a 2s pack and a model that doesn't have the thrust to go OOS vertical, so is there a particular reason you intend WW2 warbird type power levels for the model? I would have expected to see about 65 -70% of the watt/lb levels you are talking about - around 50 watts/lb. Although the motor specs actually indicate over 100 watts/lb on 3S and 13x6.5 prop - along with around 85 ouces of thrust.

I can't help feeling there might be a slight surplus of power here.

Pete
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Old May 10, 2012, 11:46 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
Hi Pete.

I think I'm going to be pretty close on the weight estimate after weighing the wood and other parts. That did include two batteries though. I have found some lighter ones though that will save 4oz on the estimated weight - hadn't updated my spreadsheet before I copied the data over so I'll update my post.

I'll be trying to keep this as light as I can and update the weight as I go along. Hopefully it will come in closer to 56oz.

Is there a site that you go to calculate the power measurements?

Thanks.
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Old May 11, 2012, 05:05 AM
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Norfolk, England
Joined Sep 2001
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Charles,
I was just basing the figures on the specs in your link. I aim for about 50 watts/lb on this type of model, which normally puts them into 2S territory.

Pete
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Old May 11, 2012, 10:24 AM
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Joined Sep 2003
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For comparison, the 54" SPAD is 5lb. It was built VERY heavy. It flies well on 350W. 3s4000 or 3s5000.

The 58" Pietenpol is light at about 3lb. It flies on around 150W (2s).

The 60" YMF is even heavier. Designed and built so I could fly with a glow engine (diesel in my case). 8lb. It also flies on electric with ~700W.

All are under 100W/lb and closer to 50 or 75W/lb. I usually start with too much power and keep cutting back until I am happy with it. For example. The YMF started with 1000W (6s5000). I cut back to 5s and now fly it on 4s.

charlie
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Old May 11, 2012, 01:39 PM
Slip the surly bonds...
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Christchurch,England
Joined Aug 2004
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Hi Pete,

It's been a long time since we were on the same thread!

The Swallow and Scooter were different aircraft to very similar specs: you only have the "green/natural linen/RAF markings" option for the Swallow, but the Scooter had a number of colour and marking schemes, which I could track down given time.

The big advantage of 2 cells is that you will be able to drive a much bigger prop than a similar 3-cell set up. I agree with Pete that 50 watts/lb is enough to give better-than-scale performance for this type of aircraft, and no Sopwith could ever climb vertically, so why do you need more power?

Best of luck with this project,

Mike
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Old May 11, 2012, 01:51 PM
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Norfolk, England
Joined Sep 2001
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To put a little context to that, I've been playing about overlaying ther Piet on the Swallow plan. The Swallow has a little more bulk, but constructionally they are both very similar (no great surprise there). So, my 56 ounce estimate doesn't look too far off the mark, depending on pack weight.

Just playing with Charlie's figures, 150 watts on 2s means his motor is pulling in the region of 21 Amps. Which means a single 3000 mAh pack should give flight times in the region of 9-10 minutes at relatively high throttle settings. Possibly 12- 15 minutes with throttle management.

Charles, don't take too much inference from any of this, I'm just expanding on my own thoughts for all to see.

Pete
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Old May 11, 2012, 02:38 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
No worries Pete.

Glad to have everyone's input before I go out and actually purchase the gear.

I have a couple of motors that might do the job. I'll set them up and get some numbers off the watt meter.

That will shed some more weight as well - we'll get to 55oz yet.
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Old May 11, 2012, 04:07 PM
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Norfolk, England
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Hi Mike,
I must have been writing at the time you posted and missed you.
I agree wholeheartedly, two different aircraft. IIRC, the Scooter was slightly less span and the wing sat a bit lower. They raised it slightly on the Swallow to give clearance for the gun. This one is definitely a Swallow, not an enlarged version of the Scooter, which ended up finished as a Swallow. The odds are that at least one of these will get a Scooter colour scheme - probably the red (?) fuselage job.
On which subject, I have no preference for finish on this model, not enough people will know the difference for it to matter, so Charles has a pretty free hand in that department. The armed, PC10 finished job does look good though, just not as pretty as the red Scooter.

This one, a rubbish shot but all I have, is a 1/4 scale Scooter built for a Laser .90 (that actually turned out to be a Laser .60. It flew like a powered glider. 84" is a lot of model for a .60 FS.

Pete
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Old May 11, 2012, 08:32 PM
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Quote:
Originally Posted by PETERRAKE View Post
To put a little context to that, I've been playing about overlaying ther Piet on the Swallow plan. The Swallow has a little more bulk, but constructionally they are both very similar (no great surprise there). So, my 56 ounce estimate doesn't look too far off the mark, depending on pack weight.

Just playing with Charlie's figures, 150 watts on 2s means his motor is pulling in the region of 21 Amps. Which means a single 3000 mAh pack should give flight times in the region of 9-10 minutes at relatively high throttle settings. Possibly 12- 15 minutes with throttle management.

Charles, don't take too much inference from any of this, I'm just expanding on my own thoughts for all to see.

Pete
Pete,

Almost nailed it. On the Piet I get about 15 min flight times. And those are continuous touch and goes. A lot of the time I don't use full power for climb. Just touch wheels, add a few notches of power and back in the air again. Do the circuit at about 50ft altitude.

charlie
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Old May 20, 2012, 04:11 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
Progress Report

I've got a fair bit done at this point - started wings, h stab, v stab, fuse.

I'll start of with the wings and then post pics of the other parts as they get further along.

Construction of the wings is pretty straight forward. The wing is built in 2 sections then joined together at the center using some pre-cut balsa and ply parts. Since the wings are swept back, using a long spars to join the wings isn't practical.

Fig 1 shows the right wing built up to the point were all of the straight pieces have been connected. R8 - a 1/8th ply rib used to hold the servo - has not been glued in at this point. Leave that out so you have room to place the servos. I've also left out the servo arm exit plate which goes in the bottom of the wing. This will be positioned after R8 has been glued in.

Fig 1


Figures 2, 3 & 4 are close-ups of the wing root and wing tip. Ply plates are glued in between R3 and R4.

Fig 2

Fig 3

Fig 4


The wing tips are 1/8th bass parts that need to be bent to form an arc that follows the arc of the ribs. To get the arc, I traced out the WT1 (long front section) out on cardboard and used that to get an arc that looked right. I used a marker to draw a line on the rib, then traced that onto paper to make a template I could use to create a form. I cut up some scrap wood on the band saw, soaked the bass for a few minutes, then clamped it down on the form. I let that dry overnight and then used the same form to the other wing tip piece.

WT2 is longer than the distance between the spars if laid flat but after it is curved, it may not be long enough, depending on how much curve you use. I had to add a 1/8th piece of balsa to fill the gap.

What hasn't been added yet, is a balsa gusset underneath WT1 for a little more support. If I was going to doe this again, I would have extended the front bass spar out about 1.5 cm and used that for the gusset because where I placed WT1 would have only required me to shave a little off of the top of the spar to allow WT1 to site where I finally placed it.

WT2 (small section in the aileron) didn't need to be curved. You will need to bevel the edges resting against the trailing edge and the main aileron spar to get that piece to sit correctly.

Figures 5, 6 and 7 different views of the wingtip - sans gusset.

Fig 5

Fig 6

Fig 7


Next step is to join the wings.

There are pre-cut triangular pieces of balsa that are laminated together to form the from section of the joiner pieces. Behind the triangular pieces, short play spars are inserted. These ply spars (DB1 and DB2) have holes along what should be the top edge. Make sure the holes are on the top-side as you will need them later when joining the legs of the top pylon to the wings.

Test fit everything before gluing. The ply spars and wing ribs are a tight fit so ease those parts together.

Pete - The notches are cut for the front joiner in R1 and R2 are 3/32's to wide. Not a big deal, I just added some 3/32 strips in between DG and DB1. You see in Fig 8 that there are a couple of strips in-between those two pieces.


Fig 8

Fig 9

Fig 10


I've glued the two halves together now and will set up the servos and wiring next.

I'll hold off on the sanding until I get ready to cover the plane.
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Old May 20, 2012, 04:16 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
Power System

I've bench tested a 480 size motor on 2c and a 13x8 prop. Got 29 amps and 217 watts.

Looks like a good combo. Gives me extra power if I need it, or a little flexibility with the weight.. I'll probably go with a 13x6.5 so that should bring the w/lbs down to somewhere in the high 50's
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Old May 21, 2012, 03:58 AM
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Norfolk, England
Joined Sep 2001
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Thanks Charles. I can see what happened, I measured to include the brace and then added the brace thickness. I've altered those parts on both plan and cut file. I've also made the WT1 parts 1/8 longer.

Pete
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Old Jun 02, 2012, 05:16 PM
Charles Sherman
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Victoria BC
Joined Sep 2009
277 Posts
Progress Update

HStab and VStab started. Both need to be sanded then cut away into the separate sections.

Nothing tricky here. Just built over the plans. Laminated 4 pieces of 1/16 x 3/16 for the VStab. Ran out of 1/16 x 3/16 so I used 3 pieces of 3/32 x 3/16 for the tips of the HStab.

The shaded section on the hstab will be cut away so the elevators are separated. I'll fill in the gaps in the vstab lamination - couldn't get that last bend done without cracking the wood. Shouldn't be an issue when covered.




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