Bensen Drop Keel Conversion Plans?

Cresco750

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Jan 14, 2012
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38
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NZ
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McCulloch J2
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Fixed wing: too many. Rotary wing: not enough.
My apologies if this has been discussed before, but has anyone produced plans to convert an original, already flying B8M into a drop keel design? I did a search but only found reference to new design drop keel gyros based on the Bensen.

Thanks
 

Mike484

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Houston, Texas
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RAF 2000 w/Horizontal stabilizer, KB3 w/tall tail
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Roger Farnes at [email protected], syas he has a drop keel kit. You may want to see what he offers.

Most drop keel mods are very simple and just use two cheek plates and a longer nose wheel fork.

Do you have a Bensen you want to modify or are you looking at building one?
 

SandL

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Royal Wootton Bassett... UK
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Bensen Merlin dragon wings Rotax 532
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Mine was a B8 with a bar axle and rotax 532

there was a conversion kit supplied by Gary Layzell to convert a stock bensen to centreline thrust (droped keel conversion)

basically
cut the keel a bit before the prop (to allow for a lower prop)
add suspension and do away with the axle. (thus raising the whole gyro slightly otherwise the gyro will not rock back on it's tail properly)
mount the gearbox upside down (reducing the prop centreline) hence the need to drop the keel a few inches
bolt the new keel and tail section back on under the original keel
raise the seat, make sure you can reach the pedals, (may also need a longer stick)
there were a few other bits, best communicate with Gary as he did a few I think.

I guess you are starting with a stock bensen (if there is such a thing)
best to ask Gary about it ... but he is not easy to contact , He is now residing in the south of France. but may be able to offer advice if needed.
 

Cresco750

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McCulloch J2
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Fixed wing: too many. Rotary wing: not enough.
Thanks for the leads. I don't currently own a Bensen but I have the opportunity to pick up a very tidy, basically original version with a VW motor.
From what you're saying, the drop keel conversion is really only suited to a Rotax powered version since it relies on the lower thrust line offered by the inverted gearbox, ie lowering the VW engine to obtain a lower thrust line would also have the effect of lowering the CofG and therefore offset any advantage being sought?

Does anyone have any photos of this arrangement?
 

Passin' Thru

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One example

One example

Here's an example of the Neal Carnes "Sparrow" conversion.
 

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Timchick

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A stock Bensen with a Mac engine is pretty close to CLT. If the VW engine is direct drive it could be real close also. A double hang test will tell. Maybe all it would need is a good stab.
 

Roundwing

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usa
I have not done a double hang test on my VW powered KB-2 as found it to be very stable with the horizontal stab I put on it.

I did have to put the leading edge 3 degrees down to get it to trim out for hands off flight.

I sheared it out of .125 2024 aluminum and bolted it together.
 

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Cresco750

Newbie
Joined
Jan 14, 2012
Messages
38
Location
NZ
Aircraft
McCulloch J2
Total Flight Time
Fixed wing: too many. Rotary wing: not enough.
The "Sparrow" is basically the design that I imagined when I was thinking drop keel Bensen mods. Does anyone know whether these plans / kits are being sold by anyone nowadays?
 
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