Okay now for the powerplant discussion. I am thinking of using the Saito 125 4-stroke. Since I am saving my pennies I will need to buy the Saito engine mount so that I can build the fuse without having the engine. Not sure how long I can build around adding the F2 fuselage bulkhead and installing the blind nuts (which is why I want to get the engine mount instead of using the included adjustable engine mount).

To save money I couldgo with thetwo stroke O.S. 120 AX (I have two .46 AX and love them both).

So whichengine will perform best mounted upside down?
Are there any tricks to cranking and priming an inverted engine?

I guess thata starter will be anecessity instead of the chicken stick thatI usefor the 4Star and my Profile.

"Are there any tricks to cranking and priming an inverted engine? "

Just be sure not to overprime, and flood the glow plug and/or hydraulically lock, and bend the crank. If all else fails, turn the airframe over, and start so that the engine is in the upright position.

Les

If I remember correctly it is the two cycles that get cranky starting in an inverted position, the 4 stroke engines with their valve systems are somewhat protected against hydraulic lock and flooded glow plugs.

I haven't had problems with inverting 4-strokes. But note, that on the SE5a I'm using the engine upright (and it still fits under the cowl).

Okay, inverted engine seems to indicate 4-stroke. I keep coming back to that same conclusion but hate to have to spend the extra money $120.00, there goes my $95 budget for full set of drawings.

On another note, it looks like lowering the top wing about 3/4 to1 inch will improve the silhouette, any lower and it is too close to the fuselage. (Maybe this "fun scale" is off in the fuselage department as well.)

Thanks for the info, now back to wing panels. I have included a picture with the mounting brackets and a picture from the manual showing how2 ribs are used to sandwich an inner rib with cutouts for the aluminum brackets. The inner rib R4-T or R4-B is the only difference in the top and bottom wing panel, nice easy design. See how fun it is to do the same 43 steps 4 times each !!!

A lot of building seems to boil down to this. You do it, then you do it again, and then again and again until eventually it's done. Very zen. If you mean $125 extra for a 4-stroke vs a 2-stroke (and a set of Replicraft plans), I'd say absolutely go with the 4-stroke! It's a fine investment in scale modeling. And really you don't need the Replicraft drawings for this build. You're already laid out some very respectable scale goals for this model.

I am very honored by my Tolstoy Zen Master's kind words (or is it Dostoyevsky Zen Master?)

BTW, I don't know anything about the size or weight of the Dynaflite model. But my 1/6 scale SE5a uses a Saito 56 4-stroke and that's plenty of power. So I'm wondering if a Saito 120-size 4-stroke is "too much" for your model. Would a 90-size 4-stroke be enough for your 1/5 scale model? What do the plans call for? You might also want to check on people who built the FunAero SE5a.

Cool, I just noticed that the specs call for 7 to 8 servos (single or dual elevator servos). So my elevator plan is actually an option rather than a modification.

I am beginning to think that thedesign of this model thatmakes it"fun scale" might be that to meet the IMAA legal 64" resulted inanincrease to wing span fromthe true 1/5 scaledimensions.

The plans are drawn with a OS .91 Surpass 4-Stroke. Since .91 is the bottom of the engine range and I am adding soooo much extra glue on the wing panels and the extra servo, I hate to be at the bottom of the engine range. I am not interested in ripping the wings off with speed but would rather have the extra power when needed. So my use of the Saito 1.25 (1.20)with a higher pitch prop is for power rather than speed.

I am not the greatest pilot and like to fly 3 mistakes high, but I got try to "pop it up" into a hover. !!!
(The RAF pilot will never do that, but Snoopy will try it.)

Would a side mounted 2 stroke work?

Based on the plan on my wall and the size of the OS .91 Surpass the answer is no, the fuse is only 5 inces wide, so the OS 1.20 AX would be a close fit at best. The main problem is getting really good airflow over the cylinder. The radiator opening is vertical and will provide better airflow for vertical (either inverted or upright). Plus invertedgets the prop coming outcloser to the center of the fuselage for a more scale look.

Not to mention that a side mount would possibly getting in the way of the modifications to the sides of the fuselage where I am going to be adding detailed valve covers and header/exhust,

Remember you need an exit for the incomming air. If it's not sufficient your engine will over heat. I ended up cutting an area behind the engine in the firewall that lets air exit out of the cockpit. Before doing that my engine was running hotter. Even when baffeled.

Great idea about the hole in the firewall. Look at the plans that I have posted. Which is best; hole up top (heat on servo) OR hole down low (heat on the fuel tank). Or is the hot air not a problem to either?

My engine is mounted upright, the airflow works essentially the same as in the diagram below. The blue line represents a balsa baffle that directs the hot air down and out (though a scale opening on the bottom). Note that the fuel tank has been moved up. The opening should be level with the carb.

File upload isn't working.

So the scale openning would be behind my firewall and in front of the basswood landing gear block with the balsa (1/4" ?) baffle. Does the actual plane have the vents on the bottom like this replica does (or that a stupid question).

One thing is that there were several engines used in the SE5a. If I remember right the non geared ones had the prop at the bottom straight to the crankshaft and the geared ones were at the top because of the gearbox. If the Dynaflite is copying is one of the geared engined ones, the inverted engine would make the head hidden.

First, yes, that replica is exactly right. Not only were there louvers on the bottom but there was also that large gaping semi-circular opening. Second, TFF is right that there were two basic versions of the SE5a produced, one with a geared engine (which often had problems) and one with a non-geared engine. I think the geared engine was called a Viper Worsley. Conveniently for us modelers we can do the geared version, which allows up to mount the engine much lower.

Have you seen this DynaFlite SE5a build?

http://www.rcgroups.com/forums/showthread.php?t=1109657

He's using a Saito 91.

Thanks for that build thread, I had not thought about the need to change the outward angle of the cabane, I was focused on the obvious angle change from bact to front. I will also need lots of coaxing through the landing gear. I am a total dumbass with at soldering iron. I learned much and once again see how sloppy my balsa fitstogether but the Iadd glue, filler and covering and it willlook okay.

So, the Saito .91 and use only2 aileronservos. Sounds like a possiblity.

We all start out that way. Go back a few years in my threads and you'll find me cussin' and swearin' at (silver) soldering. I still hate it, but I've attained a certain skill and I'm no longer afraid.

Before when you were quoting 7-8 servos that just seemed wrong on a 1/5 scale WWI fighter. On a 1/6 scale model it's usually 5 servos (throttle, aileron, aileron, rudder, elevator). With your model you could add one more for two on the elevator. If you need more power, just use more powerful servos. And the Saito 125 also sounded like overkill for this model. And the Saito 91 will be cheaper and might even fit inside the cowl. And you shouldn't allow yourself to think along the lines of: "I'll build heavy then stick in a BIG engine."

You need to stop thinking "strength" and instead just think about what would minimally do the job. Even a 1/16" sheet of balsa (maybe with a couple of 1/8 x 1/8 "stays") would do the job of directing the air down and out.

Thanks for the encouragement, I only have a $5 soldering iron and no idea what flux or silver soldering is. The electrical solder has flux in it. So is it more like doing copper pipe soldering? I guess I can Youtube it or better yet find someone to help me.

For the baffle I can do 1/8 balsa The Right bottom panel is hanging on the wall with white glue fillets drying before I put the top leading edge sheeting on. I am in the process of starting on the LAST panel (right top). Then only the top center will be left. I can't wait for my EASTER holiday, so excited to build and fly over this 4 day weekend!!!

Here is what I acomplished yesterday, building the last wing panel and the top center. Once I get both right wing panels to the same point, I will add the wing tips, then work on the aileron mounts.

Hooray, made progress on both projects today. I have now gotten the bottom skin on the top center section and now both right wing panels (top and bottom) are at the same point, ready for the top sheeting and wing tips.