Author Topic: I like the Primary Force (Read 5275 times)

Mike Griffin · « **on:** September 12, 2016, 04:52:33 PM »

I like Mike Pratt's Primary Force so much, I thought I would build 3 of them. What I have done so far.

Mike

JoeJust · « **Reply #1 on:** September 12, 2016, 05:59:33 PM »

And because I'm such a nice guy you are going to ship one of them to me, right?
Joe

Mike Griffin · « **Reply #2 on:** September 12, 2016, 06:31:05 PM »

Quote from: JoeJust on September 12, 2016, 05:59:33 PM

And because I'm such a nice guy you are going to ship one of them to me, right?
Joe

RIIIGGGHHHTTT

JoeJust · « **Reply #3 on:** September 12, 2016, 07:32:34 PM »

Thanks for the positive reply Mike, I knew you were a swell guy. Do you have my shipping address?
Joe

RknRusty · « **Reply #4 on:** September 12, 2016, 08:01:51 PM »

I think the PF is one of the coolest sport planes ever. The one in the picture was built from plans by a friend back in the early 2000s, if I recall correctly. Flies really fast with an LA.25.
Rusty

Mike Griffin · « **Reply #5 on:** September 12, 2016, 10:02:45 PM »

Hi Rusty,

One of mine will have an Enya .30 on it and the other two are going to have LA.25s on them. This model flies and handles as well as any flapped model I ever built or flew. It is a great design.

Mike

Perry Rose · « **Reply #6 on:** September 13, 2016, 05:32:24 AM »

Are they the updated version?

eric rule · « **Reply #7 on:** September 13, 2016, 09:07:23 AM »

I knew you had way too much time on your hands!!! (LOL)

Glad you are back building again.

Mike Griffin · « **Reply #8 on:** September 13, 2016, 10:39:32 AM »

Quote from: Perry Rose on September 13, 2016, 05:32:24 AM

Are they the updated version?

Hi Perry

To answer your question, yes and no..LOL. I bought a short kit from Mikey not to long ago, which by the way is a great kit, but I made a few of my own adjustments when building the wing (nothing that would affect the way the plane flies). Mikey has added a small strip of leading edge sheeting to the wing in his updated version and if you notice on the wing I covered with Polyspan and SLC, I extended the leading edge sheeting back to the spar which is further back than Mikey shows on the new plan. That was just something I wanted to do. On the other wing, I used the ribs and cut patterns from them to construct the wing with a typical "D" tube type construction rather than the I beam configuration that Mikey designed, however I did use the leading edge sheeting width that he shows on the new plan. I did that just to see if it makes any difference in the way it flies or not but I don't really think it will since the airfoil is the same.

Nothing different much on the fuselage except I am adding an inboard tripler just to cover the blind nuts for the engine bolts.

I have said it before and I will say it again, this airplane will fly the pattern as well as any flapped model I have ever flown, especially in the hands of the right pilot. It is a great design.

Mike

Dale Barry · « **Reply #9 on:** September 14, 2016, 03:56:48 PM »

I built one of these several years ago and painted it like Spiderman for my grandson, and as Mike said it flies as good as most flapped planes. the corners were incredible. I need to get the plans or another short kit since I now have two more grandsons.

Larry Renger · « **Reply #10 on:** September 14, 2016, 04:09:48 PM »

Ray Firkins has an electric one that is a delight to fly!

Shug Emery · « **Reply #11 on:** September 14, 2016, 07:15:21 PM »

Impressive in triplicate.
Wonderful flying planes for sure.
Shug

Don Chandler · « **Reply #12 on:** September 15, 2016, 11:20:09 AM »

I have 3 of them and still fly one on a regular basis. Have a short kit out in the shop. I've always flown them with LA 40's on 015 lines at 61 feet eyelet to eyelet. What line diameter and length are you using when on a .25?

I've also been using an LA 25 on a shoestring that flys reasonably well using a APC 9/5. Will that work on a PM?

Don

Dan McEntee · « **Reply #13 on:** September 15, 2016, 08:34:45 PM »

Quote from: Don Chandler on September 15, 2016, 11:20:09 AM

I have 3 of them and still fly one on a regular basis. Have a short kit out in the shop. I've always flown them with LA 40's on 015 lines at 61 feet eyelet to eyelet. What line diameter and length are you using when on a .25?

I've also been using an LA 25 on a shoestring that flys reasonably well using a APC 9/5. Will that work on a PM?

Don

I lay claim to having one of the first production ARF's flying when the kit was released. It was in January or early February of that year, and I had mine flying in time for our Ice-O-Lated stunt contests. I built mine exactly to the manual with a LA.25. Same line length and handle spacing. Put 2 flights on it in windy weather to break in the engine the week before the contest, and just did a couple of loops and inverted flight to check out the tank. Did two full patterns with it the morning of the contest to finish setting balance, and took a second place with it in Profile P-40 at the contest. In my opinion, it was just enough poop for it to fly the pattern in good air. If you had any wind at all you were in for a hard time. I replaced it with a FP.25 to get some experience with that engine, and it was just a bit better, I think. I used APC 10-4 prop on each, SIG 10% Champion, and model weighed in the 42 to 45 ounce range. if it was a solid 6 ounces lighter, which I think some guys got out of a kit built copy, that would make some difference. I have an OS.32 on mine now and I love that combination. I use a Zinger 11-4 Pro, SIG 10% Champion still, and went out 2 feet on the line length for the same lap time, between 5.1 and 5.2.
Type at you later,
Dan McEntee

Don Chandler · « **Reply #14 on:** September 16, 2016, 12:54:48 PM »

Thanks for the info. I'll put mine together this fall and focus on keeping it light.

Mike Griffin · « **Reply #15 on:** September 16, 2016, 03:59:15 PM »

Since I was building three of these at once, I decided to run a little experiment with the stab/elevator hinging. I used flat pinned hinges on one, Robart Hinges on one and Dacron cloth hinges on one. Guess which one is the most flexible?

Mike

CircuitFlyer · « **Reply #16 on:** September 16, 2016, 04:28:19 PM »

I'd guess the cloth hinge (until you get a few coats of finish on it, and they may get sluggish) I bought some Robart hinges for a project and each one had a bent hinge pin that made them too tight. I guess in production when they swage the end they inadvertently bend the pin.

Paul

Mike Griffin · « **Reply #17 on:** September 16, 2016, 08:21:25 PM »

Paul you are exactly right. The cloth hinges are by far the most flexible. I have pretty much used cloth hinges exclusively over the years. The Robart hinges are good and I did not have the problem you mentioned. My last choice of the three types are the flat pinned plastic hinges.

Mike

Mike Griffin · « **Reply #18 on:** September 19, 2016, 04:53:21 PM »

A few more pictures. The three fuselages with carbon fiber veil. Except for the one horizontal stab and elevator, the tail feathers are covered with SLC. They will be scuffed and painted. The carbon veil covered parts will be finished using Phil Granderson's method.

MikeyPratt · « **Reply #19 on:** September 20, 2016, 09:32:15 AM »

Quote from: Mike Griffin on September 19, 2016, 04:53:21 PM

A few more pictures. The three fuselages with carbon fiber veil. Except for the one horizontal stab and elevator, the tail feathers are covered with SLC. They will be scuffed and painted. The carbon veil covered parts will be finished using Phil Granderson's method.

Hi Mike,
Outstanding job on the three copies of the P/F. During the design favse of the P/F I built a number of models and kept records of the weights on all components to make sure the weights would not get out of hand. It has always been my opinion that lighter is better thus reducing the amount of balsa & plywood was a key to building light weight models. We are all so lucky that modern finishing methods, laser cut parts, modern engines, that we almost anyone can build and finish a good looking & flying models.

Hinges: There is no doubt the the cloth hinges are always the most flexible, allowing smooth control deflection through the the control range. I've had pretty good luck with most of the hinge types but still prefer the cloth hinges.

All up weight: The best weight for the P/F is in the mid thirty ounce range (36 to 38). Most of the ARF models came out at 42 + ounces with some as high as 48 ounces. These models weren't bad but lacked the snap in turns for an outstanding score in the pattern. My 1st prototype was 35 ounces with a Fox 35 (very short life from broken up line).

Engines: This is one of the benefits of modern times. As the engines have improved, it is much easier to get decent engine runs. This makes it simpler to trim your models and makes changes where they are needed in the aircraft instead of making changes to the engine for the best run.

Keep up the good work,
Mikey

sadams714441 · « **Reply #20 on:** October 13, 2016, 04:54:26 AM »

Morning Mike
What size lines are you using ?

Steve

Mike Griffin · « **Reply #21 on:** October 13, 2016, 08:05:11 AM »

Hi Steve,

I will probably use .015 x 60ft lines or 62 Ft. Primarily because that is what I have on hand. I use .18 x 65 ft on a 60 size model. I am putting an Enya .30 in one of them and .25 engines in the other two again primarily because this is what I had... I just finished covering the third wing with Ultarcote. I have not been in any big rush.

Mike