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BD-4 Builder/Owner: Steve Mahoney


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Name Steve Mahoney
Address 2476 NW Crimson Ct  
McMinnville, OR 97128, US
Airport KMMV  
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Project Status flying  
First Flight  
Pilot Done structural analyses on wings; helped designing the super tube  
Last Update 2002-02-11  
Remarks IO 360, curved windshield, vertical opening doors, short composite wings, IFR equipped (in case you wondered about the picture...)  
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Images
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At Arlington, 2003     Edit the text to this image Delete this image  
At Arlington, 2003     Edit the text to this image Delete this image  
Arlington, 2003.     Edit the text to this image Delete this image  
Engine heated pitot tube mounted on the number one cylinder. The following text is from a message to the mailing list on Wed, 10 Mar 2004:

I too had some of the same concerns about the current draw and running those big heavy wires that far out on the wing. Besides that, those heated pitot tubes are big and add drag. I too fly IFR (some) I pick my battles very carefully as the BD is a hand full for me in actual conditions and I really don;t have that much IFR time in it yet. I tend to limit my filing IFR to punching through layers or departing a fogged in fields where I know it's clear above and I won't be in the soup very long. I have picked up a little Ice a couple times.... and man! ....I have to tell you that it really hurts performance compared to the 206 I took my instrument training in ( the big 206 has so much drag you hardly notice a little Ice) . Both times in the BD I wasn't in it very long (by plan) so I never got much accumulation 1/8 inch or so. I couldn't see out of the windshield when I broke out into the sun. A good thing this was in Oregon and Scott DeGayner didn't fly up along side and radio " Hey Steve how that race we talked about!"

Roger Mellema told me once that he picked up quite a load (think it was more than an 1 inch) In Texas I believe, he was trying to punch through a front and he didn't think he would be in it that long and was very concerned ... he was able to maintain control and altitude and made a safe landing will most all the Ice still on the plane. This is one situation that I hope I never encounter.

Enough story ........and on to the details of problem solving ..... I noted some time back that when I was doing cooling tests, I installed a small pitot tube in the front right air inlet to make some pressure measurements and this location mapped almost perfectly to my airspeed indicator, even at slow speed and high angles of attack. So I made one out of brass, as this conducts heat very well and stuck it between the fins on the forward cylinder. I have a small switch so I can select the airspeed indicator source from either the heated Cylinder or the pitot tube on the wing. It works well for me as my air inlets are oversized and thus map to the airspeed indicator fairly closely. Consumes no Juice.     Edit the text to this image Delete this image  
Another shot of the pitot tube.     Edit the text to this image Delete this image  
Installation of a Nippon Densol alternator.

This text was sent to the mailing list on Wed, 10 Mar 2004:

As far as sizing the alternator, I have found for me, that the worst case is at night after I land and I turn on the taxi light.

Because of the limited visibility I tend to taxi very slowly at a very low RPM. If I am at a tower airport, I usually have everything on. Radio, Nav lights, taxi light ect. and taxing very slowly (worried about the tower controller writing me up for an runway incursion if I accidentally put one tire over that yellow line) and this is my biggest electrical load at the worst possible RPM. around 700 -800.

I had flown with an old Delco alternator I bought from a auto wreaking yard for many years (18) and over 1000 hours, with never doing a thing to it. I have to admit that it served me well!. Last month I found that it was getting a little loose in the bearings. so rather than rebuilding it I bought a rebuilt Nippon Densol off a 87 Toyota Corolla off Ebay. This is a more modern design and has an internal regulator which I really like. It's also is about 2 lbs lighter than the old Delco....(you all know how much I like that! ) It also has an internal fan (good). I rewired it so that I can turn it off in flight if necessary as I have a split master switch. I also turned a pulley to match the lycoming belt. ..see picture I will post .The smaller Nippon does very well at the lower end of the rpm range, and so far I am very pleased with it's performance. I believe that it is rated around 50 amps (at what RPM I don;t know) . but as I said earlier that it's the low speed output that I am concerned with.     Edit the text to this image Delete this image  
I too was appalled at the weight of the standard BD doors. It seemed to me that most of this was due to the upholstery. I made these out of fiberglass and with a foam core. They have door pocket to hold maps, papers etc. and a pencil holder too. Can't remember how much wt I saved. noticed that I did not add back the upholstery...just zolotone paint.

To test them I taxied faster and faster with the door partially open until I was 1ft off the ground. Turns out they don't slam against the wing like I though they might. Since then, I have flown with them open (not sure I would do this again) although it turned out ok ......... sure is windy and scary when you look down.     Edit the text to this image Delete this image  
I pulled up the carpet and shot this picture of my gear box this weekend.     Edit the text to this image Delete this image  
A secret peek into Steve Mahoneys work shop ..whats going on inside during those long rainy and dark Oregon winter months. I bet Scott DeGaynor might be a little surprised next summer if he decides to come the northwest Eaa fly Inn at Arlington this year.     Edit the text to this image Delete this image  
The blue color is a protective plastic cover which will be pealed off the sheet metal later.

These are the closed plenums type baffles that are commonly found on formula 1 racers. The advantages are that they can be sealed with very little air leaks and thus, reduce cooling drag. When I assembled the engine I installed rubber grommets on the push rod tubes. The grommets make it easer to achieve a good tight air seal. This is the same system that I used with good success on my old engine.

In the pictures attached you will also see the beginnings of the new inter cylinder baffles that wrap around the Jugs. These keep the air flow in close contact with the fins and avoid cold spots. I couldnt believe how crude the standard Lycoming inter-cylinder cooling baffle are they essentially just dam the air at the bottom of the cylinder so that most it flows thru one small area of the fins thats got to cause a cold spot and is very inefficient use of the pressurized cooling air. Although I have to admit that most aircraft with Lycoming engines use these standard inter cylinder bafflesthey must work, because you dont see that many cracked cylinders in that area .but oh, they are very inefficient.     Edit the text to this image Delete this image  
Another picture showing the assembly of the plenums. The bottom of the Slots below the grommets on the push rod tubes are enclosed with a 2nd piece of sheet metal not shown.     Edit the text to this image Delete this image  
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Articles

Flight Story: "BD-4 vs. 600 HP AT-6" How Steve's 180HP BD-4 outrun a 600HP AT-6.  
Flight Story: "Winter Flight" Flying over the cascades on a cold winter day.  
Flight Story: "Idaho Hop" (2001) Flying from Portland, OR to Idaho for the afternoon.  
A Panel Upgrade Description of an IFR panel upgrade.