Sig Akromaster Power

LAST EDITED ON Mar-24-04 AT 06:02 PM (CDT)
 
The original questions I asked about perfect power for the Akromaster is somewhere buried way deep in forum. I did get a lot of great responses and several folks suggested the OS Max .10 which I have, but, in flight today, it barely managed the ship. Altitude is a factor here at 7300 feet average for Santa Fe.

The rest of the engines were rejected by knowledgeable folks as too much power, such as the HB .15 or ST G .15, or OS .20 FP. I do have a new in box Cox .15 Medallion that recommends in instructions a 9" prop with 3 pitch. Is this too much? Or about right for standard CL? It seemsas it might be a good fit? See any problems?

I liked 8-4's for Cox Medallion 15's, but that should be a good match to a plane the Akromaster's size. I have only a minimal amount of higher altitude model flying experience. The way I understand the usual way of dealing with it is to apply a minimal finish to keep the weight down, and to add an extra rib panel to each side. Your Akromaster isn't any heavier than about 13-14 Ounces ready to fly, is it?

I am surprised if you used an FP 10 and found it inadequate. What prop did you use on it? It needs to be turning up fairly fast to reach its best power output.

.

Kiwi

Thanks Kiwi: I might be on the heavy side. I don't have an accurate scale here. This weekend I'm going to a friends home in Denver who repairs and rebuilds pharmacy scales, and look for a digital in his stock. Will get back with you on weight.

william,
Is it an old Max .10 or a FP .10? What prop are you using for it. I would use a 8x4 to start. Play around with sizes a bit. Most of us do not live at high altitudes, as Kiwi said, so we can only guess what's best.

The Medallion should work fine. I would use an 8x4 or 8x5 prop but since I am not at high altitude I would suggest you try the 9" prop first and see how it runs.

Although my present Akromaster has a Fox baffle .15, I have started construction of another Akromaster kit I have had around for a few years. It will have a TT .10 and 8x4 prop (to start).
I am modifying the wings by NOT cutting off the end sections of the LE and TE. This will increase the 'span about 4".

I was using a 7"3pitch on the OS .10 Max FP. It is not the steel fin, but aluminum. The exhaust port is "not" completely open, but partially open, with the sleeve port pointed toward the rear, taking up approximately half of the space. On the rear case cover is (1307).

LAST EDITED ON Mar-24-04 AT 08:56 PM (CDT)
 
I was using a 7"3pitch, mainly because I had it in stock. I have some of George Aldrich's old/new stock 9" 3 and 4 wooden props and possibly some 8s that might fit the Cox though. Have to break them out. The .10 is a beautiful engine and runs like a dream. But I think altitude is against it. I bought a dremel today, and am going to look for places to hollow and lighten the ship. Also the extra wing length might help. I'll have a digital camera soon and post the finished revised/powered ship. Thanks to all

Good idea on the wingspan increase. I have a duplicate Sig kit here and will increase the next one. Love these kits. Very good wood. I do need an accurate scale though, as my materials might come through on the heavy side.

No. It wasn't too much power, but too much WEIGHT (for the powerplants you listed vs the airframe in question). Power is a GOOD thing and more is better and you can always "throttle back"; you can't go the other way around.

Jake

Sides, I thought you'd settled on the Norvel .074 which would be a good match power and weight wise.

No, Novel was never in my choice of engines, however, I have heard they are good engines.

LAST EDITED ON Mar-24-04 AT 09:20 PM (CDT)
 
Hi: I don't have a digital scale, but the instructions for the HB .15 state a weight of 0.320 (of a pound, metric?) & the Cox Medallion instructions state 4.243 oz. I have an HB .12 sitting here, and the engines look identical. I weighed on a flimsy stamp scale, an OS Max .20 fp just now, and an HB .20. Nearly the same weight. Back to the Cox. The Cox looks like a good match. Thanks for the info.

The MVVS 2cc (.12) diesel with an 8-5 is a pretty good match. Don't use a tank over 1 oz. unless you intend to fly all day . . .

LAST EDITED ON Mar-24-04 AT 08:53 PM (CDT)
 
William:

What fuel were you using? It would be normal use enhanced nitro content at that altitude as the nitro is an oxydizer that makes up for lower oxygen content at altitude. 15% for sure and I would think 20 is not out of the question for the OS FP .10

Anyone else on this?

Curt,
I concur! (I know I can't spell early in the morning)
I would have probably gone with 15% to start with, and added from there! We are about 400 FT, ASL.
Bill <><

Darn guys! That might be it. I was using up a metal can of Fox Super Fuel with the following: 29% castor, 64% methanol, 5% nitromethane, 1% detergent, 1% ignitors. I recently ran out of the Sig fuel I have been using on the older ST engines which has 15% nitromethane and a synthetic/castor mix lube. Could be a fuel problem. Thanks.

That might be a big part of the problem. I don't believe the FP needs that much oil either. Try some sig champ 15% 20% half and half.

When you do that, you will have to open the needle up quite a lot from your 5% fuel setting. THe engine will react like it is getting alot mor air--so will be very lean unless you open the needle. Consumption will go back up as well.

Let us know.