da Rock

Well, I get the 12x6x3s that I run on the OS61FXs from Master Airscrew. (They recommend that one for .90-1.08. Amazing???)

The 13x8x3 I run on my OS75AX same: MA. (and they recommended that for 1.08-1.5 ????)

The 14x7x3s that run on my OS91FXs also same: MA. (and they recommended that for 1.5-1.8 ????)

Guess engine performances have increased since they published those recommendations.

I was wondering about that 14x8x3 myself, because MA only lists 7 and 9 pitch in 14" diameter 3-blades.

stallwart

I must be mistaken about the MA 14x8 3-blade; it is probably a 14x7. I know the 12" MA 3-blades are only available in 12x6 and 12x8.

When Kyosho has the 3-blade spinner available for the new 50 size BF-109 as a separate accessory, I have an 11x7 to put on my older 109 powered by a Saito 62.

mike early

Ah oops. I have the 12x8x3 right here on my work bench.

It's a shame they don't make a 14x8x3 prop. I need one.

da Rock

I've been using their 15x7x3 trimmed a bit for about a year now. When you trim a prop's diameter the pitch number loses a bit of it's "truth" (if they were ever true to begin with). It isn't used all the time, but it's a bit better summer prop than some of the untrimmed 14s.

You do need to be a "careful builder" when adjusting props. It's not a task for the slap-together-and-fly modeler. However, you do fill in some gaps the prop mfg's really don't come close to filling. Probably the most detrimental thing to the popularity of 3-bladers is the lack of selection. And with trimming you can fix that a bit.

Remember that the amount you're adjusting is going to apply to THREE blades, not just two. You will be surprised also at how effective just 1/8" removal can be.

mike early

I have a 15x7x3 that I do not use. I think I will carefully cut 1/4" or so off the blades and see what's what. Thanks for the tip.

da Rock

Make sure to balance afterward. Good thing about MasterAirscrews is their hub had slots in it. It's rather easy to balance their 3-blades by placing small lead pellets in there. Hold in temporarily (while balancing) with a bit of balled up masking tape and when the right amount is found, glue it in with something like GOO. It fills and holds, and the hub is enclosed by the drive and prop washers as well.

I usually make a template or pattern of my tip shape to insure the tips are uniform. Using a fixture clamped to the table of my band saw insures that all the blades are equal length and the first cut on each is the same shape. If the prop was balanced before shortening, using that method often results in a modified prop that is still in balance.

KLF1292

To say this thread is old is an understatement but I need assistance. I'm hoping some of those that have built this plane are still around.

I've had the plane for over a year now and I'm just now getting around to the build.

Anyway, I need to decide on an engine: the Saito 72 or the new Saito Gas FG-14B (my heart is with the FG-14)? However, is the structure of the firewall and overall build of the SQS version of the plane sufficient to handle the weight of either engine? I've reinforced the firewall with fiberglass and placed a thin sheet of balsa sheetinig on the bottom side of the horizontal stab (a known issue). Should I epoxy a reinforcing sheet of ply behind the firewall?

I've also installed a pair of LADO electric retracts and I'm planning to reinforce the retract bays with thin fibergalss.

Suggestions?

stallwart

I'd go with the Saito 72. It'll fit inside the cowl and fly the plane very well.

Here's another pic of my older version with a Saito 82a for power.

KLF1292

Stall,

The FG-14B is basically the same case as the 82a with the power of the 72 but better fuel efficiency (less fuel load per flight). Looking back, if you could have traded the 82a for the FG-14B, would you done it given how well a 72 power equivalent would be expected to pull the plane around.

Also, based on your experience with the plane, do you think the planned / installed reinforcements are overkill or necessary?

stallwart

I would probably consider the FG-14, except for the weight of an additional battery for ignition and occasional interference problems associated with gas engines. Plus, I'm heavily invested in 4-stroke glow power.

In any case, reinforce the firewall and the area where the retract bellcranks are attached. I recommend using 4-40 rods for retract control rods. I also used clear covering material on the underside of the tail feathers to cover the hinge line (applied with elevator in an up position). Also, consider sealing the covering material. Older Kyosho covering will let go fairly quickly; the newer printed covering might not be much better, based on my experience with the 50 size Spitfire.

My P-40 is a great flier, easy to taxi, takeoff and land.

KLF1292

Thanks for the info.

I hope mine turns out as nice as yours based on the pic and has a similar life span. I've installed the LADO electric retracts and Robart 650 struts. The blue covered bottom will be painted dove gray and a flat clear final. Top-side will get a flat clear coat as well. Cowl and canopy to be painted just the way you have done.

Which spinner did you use? I'm thinking about a 2.75" 3-bladed spinner from True-Turn and possibly having it powder coated red, if that's possible.

stallwart

Thanks for the compliment!

I used Tamiya acrylic paints to match covering colors as close as I could, then coated the plane with Minwax spar polyurethane satin. I now wish I'd used a lighter blue or gray for undersides (see Dallas Clinger's P-40 in an online search). But at 85 MPH and 85 ft. it looks ok.

Since I chose to use a 3 blade prop, the only suitable spinner I had on hand was the H-9 PTS P-51 2.75" plastic spinner. It's inexpensive, but being plastic, I'm wary of it.

Kostas1

Guys i have an OS 91FX...what do you think ?