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Workshop Build-along — Douglas Skyraider Part 15 — Engine Installation

GSNadmin

Staff member
If has been a while since we updated everyone on out Skyraider build-along so here’s newest post detailing the engine mount and installation for the 85-inch version of our Ziroli Skyraider. I always liked the removable, through the firewall setup for engine attachment as it makes it so much easier to work on the power system. I used my CAD program to draw up a simply box and attachment rim for the airplane and had my buddy Pat at LaserCutUSA.com cut the parts for me. The rest is very easy and took about an afternoon to hang the engine.
2017-04-03_110100_eng1.JPG

I am using a Fuji 43cc with electronic ignition so I made the box/tank shelf long enough to accomidate the tank, throttle servo, with the idea that I would mount the ignition module in front of the firewall.

2017-04-03_110913_engine4.JPG

The engine fits nicely in the cowling area on the plans.

2017-04-03_110950_engine5.JPG

So after adjusting the prop hub position, I marked the location of the new firewall mount box.

2017-04-03_111042_eng6.JPG

I made the sides of the box from 1/4 inch ply and keyed the 1/4 inch firewall face to the sides as shown here.

2017-04-03_111208_eng7.JPG

I used lite ply for the aft bulkhead and the top and bottom of the engine box.

2017-04-03_111253_eng8.JPG

I made the firewall just wide enough for the engine attachment bolts, and you see here the blink-nuts have been ground back to clear the sides. I also doubled the firewall with a second layer of 1/4 inch plywood to seat the blind nuts and to stiffen the firewall. Zap 20 Minute Epoxy was used throughout.

2017-04-03_111359_eng9.JPG

Once the box was glued together with epoxy around the firewall and thick Zap CA in the aft section, I placed the box on the plans to mark the front of the main firewall.

2017-04-03_111525_eng10.JPG

Here are the two main parts of the engine box.

2017-04-03_111556_eng11.JPG

I also had a new F-1 Firewall cut with the required rectangle opening to clear the tank support section.

2017-04-03_111705_eng14.JPG

The new F-1 was epoxied to the front of the fuselage with slow setting epoxy and clamped into place until the glue had set.

2017-04-03_111753_eng13.JPG

I left the chin sheeting off of the fuselage so I could easily clamp the new F1 firewall to the F-1 bulkhead.

2017-04-03_111912_eng12.JPG

Here I am fitting the box through the firewall for a last check for size. it easily slides into place.

2017-04-03_112004_eng2.JPG

Here you see I also added tri-stock around the attachment rim.

2017-04-03_112858_eng17.JPG

Looking through the cockpit opening the aft attachment points will use blind nuts and bolts to anchor the box to the fuselage’s vertical side structure. The bolts can be accessed through the wing saddle.

2017-04-03_112128_eng16.JPG

Using scrap 1/4 inch ply, I set all the blink nuts so I could easily glue them into place for each of the six attachment bolts.

2017-04-03_112319_Engine17.JPG

So with a few bolts installed, the engine is attached to the firewall and the box structure is attached to the main firewall for a very solid installation. Next step is installing the throttle servo and linkage as well as the fuel tank plumbing.

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