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Midwest Extra 300

 

This page is not intended to cover the whole process of building this kit but to highlight some of the construction features along the way. 

I have decided to power this 80" Extra 300 with a Moki 2.10. Radio will be a Futaba 8 channel. I decided to build this airplane instead of the Hostetler Edge 540 at this time. The Edge 540 will come next.

Midwest has done a great job of engineering this kit along with high quality materials and great customer service. When the box arrived from Chief Aircraft via. UPS in perfect condition with a dented canopy I emailed Midwest and stated that I had the kit without any box damage but the contents must have shifted and dented the canopy. I mentioned that I was willing to purchase another canopy but they said one was on its way free of charge. A few days later it was on my doorstep. Thank you Midwest!

The new Extra 300 kit comes with a laser cut horizontal stab ribs along with laser cut parts for the vertical stab and rudder. This new stab in my opinion is stronger and looks better on this model. I am in the process of making a carbon fiber landing gear for this model and will construct a plug and mold for the cowling and wheel pants  which will be featured on this web page.

 

In order to remove extra weight from the fuselage I decided to substitute 5# balsa for the 1/32 plywood top deck and turtle deck. The 4" sheeting was edge joined prior to gluing to fuse. The drawback to the balsa sheeting is the lack of durability but the weight savings outweighed this factor. To increase the strength of the sheeting and give it some rigidity carbon fiber tow was utilized as formers. The carbon fiber formers pictured here were pre wet with epoxy and then slid under the stringer. The sheeting when formed was higher than the stringer so the carbon tow former was slid under the stringer. If the top sheeting was pressed down to the stringer in this case it would have had a significant bow or dip. The stringer was a little bowed when installed. Fiber glass cloth strips could serve well as formers also. The idea behind this method is to save weight with the balsa sheeting then regain some of the rigidity by going underneath the sheeting and adding reinforcements to add rigidity. Wood selection is very important to get the easy wrapping bends. If different wood sheeting densities are edge glued together then they will not bend evenly around the formers.

 

Carbon fiber tow was used to strengthen the attachment of the landing gear plate to the fuselage. The landing gear plate was recessed on the ends approximately 1/16" to allow the carbon fiber tow to set flush with the bottom of the plate. The carbon tow extends vertical up the two formers and wraps around the bottom of the plate thereby locking the plate into the formers. Glass cloth was also used to reinforce the corner joints of the engine box and front formers. This method of tying parts together is much stronger than using balsa gussets. A good resin such as West System should be used to wet and attach the tow in this application.

 

Extra 300 fuse with balsa sheeted front hatch and turtledeckThe fuselage has been lightened by enlarging the cutout openings and adding balsa in place of the 1/32" plywood front deck and turtledeck. The balsa will not be as durable as the plywood but I feel it will make a better flying airplane by keeping the weight down. The underside of the balsa turtledeck will have carbon fiber stringers and formers added for rigidity like the front hatch above.

 

Midwest Extra 300

This airplane is a quick build if you are used to scratch building. The fuselage goes together fast and straight with the interlocking light plywood parts. 

 

One modification I made was in the stabilizer trailing edge. The instruction book and the plans call for the horizontal stab trailing edge to be glued onto the stab halves before joining thereby giving a trailing edge with a butt seam. I decided to join the stab halves over a one piece trailing edge for increased strength without any additional weight gain. The elevator halves in the picture still need to be trimmed at the root for rudder clearance.