Sopwith Dove for CO2

[Squirrelnet]

I've added the side formers to the nose to give the circular shape and i think I'll face the front in 1/64 ply to glue the engine mount onto.

I've also made up a tail and fin using the laminated outlines a did last week. I've gone for a very simple structure following scale lines out of 3/32" sq, so flat plate tail . The control surfaces are built in as well so no moving surfaces for trimming

[Squirrelnet]

Couldn't resist a quick lash up of the bits so far 

[Jmk89]

Very nice

[Squirrelnet]

Fitted the engine today so I can build the rest of the fuselage around it.

The front former has been faced with some 1/32 ply, not too worried about weight upfront on such a short nosed design.  The engine sits on 1/16 ply mounting box which I drew up from Mike's 50" IC plan settings of 8 deg down and 3 deg right.

Like the other Co2 Sopwiths I've done I've left the top of the mounting box open so I have easy access to the mounting nuts so I can get the motor out for servicing etc and fine tuning thrust adjustments can be made with shims between the engine backplate and the mount   

To make sure the engine still exits the cowling, which I have not yet made, in the right central location I made up a guide from a circle of card with a central hole so I could make sure lining it by eye. Obviously any future thrust line changes during trimming will effect this but good to try to start off in the right place at least.

Once happy with position I marked it up and the ply engine mount was epoxied to the bulkhead

[Squirrelnet]

The tank is built into the model and is located as far forward as I can on the rear of the bulkhead. I did consider fitting even further forward inside the cowling but it looks tight so decided against it.

The tank is held in with a 3/32 former and will boxed in on the left side with another 3/32" panel. The filler is underneath which should be ok with the undercarriage on. Ultimately the tank will sit a tad lower and there'll be a v shape cut into the front former as per the original which will allow some warming air over the bottom of the CO2 tank and supply pipework

Needless to say with the engine fitted CG is WELL forward but once everything else is built I'm pretty confident it won't be

[Flygrimm]

Squirrelnet

I haven't seen mentioned which CO2 motor that is.  I have a GM-160 that I got a while ago but am not sure which size model it can handle.

Stuart

[Squirrelnet]

Hi Stuart

This is from George's CO2 Motor List he complied for a CO motors FB group

GM160 - Wingspan 650-800 / 26"-31"  suggested model weight  60-100g


The GM300 is quite large for the 24" span Dove but the motors do work well throttled back if you can afford the extra weight up front . With these rotary engine types the answer is usually yes. Staying comfortably under the max weight is the way to go with CO2 motors IMHO

[Flygrimm]

Thanks S

The GM160 should do me well then for a medium size model.  Maybe I could get it in my Guillows Thomas Morse Scout.  Only 24" but being a bipe it might work or it could be too heavy.

That GM300 sure looks big.  I'm guessing about twice the size of mine. 

Stuart

[Squirrelnet]

A bit of revision this afternoon.

George very kindly pointed out that that is a lot of downthrust on my previous shots so I thought I'd measure it ...er.. 10 degs  . It does line up with the drawing which says 8 degs but it's clearly too much so I gently removed the engine mount and re adjusted it to less downthrust. I've actually gone with about 7 degs which has worked well on 3 previous short nosed models with CO2 power and there is scope to easily add more with packing if needed. I spent the rest of the time pondering how to do the undercarriage. I was thinking of just using bass wood but feeling the weight with the gm300 it may need some wire in it to withstand flying outside

[Squirrelnet]

I decided to go with a wire frame for the undercarriage which was formed from some 18swg.

The front leg will attached to the main engine firewall but the rear is attached to a strip of hard balsa that has been covered on 3 sides with some Proskin. This is preformed glassfibre and epoxy sheet . It takes superglue very well and can be lamianted with balsa to form something as strong as Ply but for a fraction of the weight

The rear leg mount has not been glued in yet while I consider the rest of the super structure. The cabanes are next ...

[gravitywell]

I just love the way you did the coaming around the cockpit openings.  Must have been very fiddly.

[Squirrelnet]

Thanks Glen

 It really isn't that fiddly to do, once the top section is stuck on it's fairly strong and easy to sand the inside to shape


 Cabane struts today.

I've used wire for the undercarriage as this will be an outdoor model so difficult landings in difficult conditions is par for the course but for the cabane taken a different approach. The plan is the lower wing will be structural part of the biplane wing set up with possibly a 1mm carbon spar joining the two wings to the fuselage. It's a technique borrowed from Bill Dennis and means the cabane structure can be much lighter in construction. Wire would no be overkill for the cabane so after talking to Mike Stuart at the last Trinity I've gone for nylon strimmer cord to join the cabane struts to the fuselage. This will provide a flexible mounting so the model will be one piece and use working thread rigging to hold everything square

First step was to make up a test strut to see how it works. The struts have a 1mm ply core with balsa either side, a 3/8" long slot is cut in the end and some 1.3mm strimmer cord cyano'd in. The nylon takes cyano well and provides a strong joint. To join the cabane to the fuselage another slotted ply plate will be attached to the inside of the fuselage

[Squirrelnet]

With the test piece looking like it will work I made up a set of 4 cabanes using the same technique


On the Dove the front ones are wooden to an airfoil section while the rear ones are round metal ones so the were cut and sanded to shape


I've made a cardboard template for the centre section so I can attache the struts to fuselage and get them in the right position. Further accurate fitting of the final centre section can be done when the nylon cord is attached to the wingspars

[Squirrelnet]

The front cabane strut mount is just a small triangle of 1mm ply with a 1/16 balsa spacer so I can glue to the bulkhead. As this mount will take any bad landing impact the top surface was given a covering of Proskin cyano'd on.

With very thing jigged up so it's at least in the right ballpark when it comes to fitting the actual top wing the mountings were cyano'd into the fuselage

[Squirrelnet]

The rear struts are fitted in the same way with ply gussets slotted for the strimmer cord

These were easier to fit as the mounting could be attached on the workbench and the strut fed through the hole in the top decking. A 1" strip of 3/32 joins the cabane to the UC mount with the strut mounting cyano'd to the rear of this