Longerons

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Medic9204

Well-Known Member
Joined
Jan 22, 2005
Messages
46
Location
Williamsport, Pennsylvania
I am looking at 15' wooden longerons for my plane (Tiger Moth). Aircraft Spruce asked if they could be cut down to make my shipping cheaper, and I realized I don't know. Anyone know of a way to splice or otherwise re-attach such parts? As it stands now I don't want to do that, but if someone has an idea I'd love to hear it.

Basically, is there a way to make a long board out of two short ones without losing strength and increasing weight too much?

Thanks!
 

cgwendling

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Joined
Jul 30, 2004
Messages
86
Location
Grenora, ND
I don't know about your plans, but on my Avenger the plans specifically told me where a splice could be made on the longerons and how long the splice should be.
I chose to to put full length ones in and order other long items, push pull tubes, struts, spar material and other things because I needed them anyway and they couldn't be spliced.
 

Craig

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Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Splicing

Medic -

Splicing a longeron isn't too difficult. You will need to make the bevel at least 16:1 - if you are splicing a 3/4" square piece, it will need to be 16 x 3/4" (12") long. Do match the grain on the wood - you want the grain running parallel to the scarf.

Also - try to cut the bevel (Scarf joint) with a very sharp tool, and try to avoid sanding - it will fill the pores of the wood, and prevent the best joint possible. If you do have to sand, get the sawdust out of the end grain - compressed air helps.

You can scarf plywood the same way - just use the 16:1 ratio. Look at the Bingelis book for more details.
 

Falco Rob

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Joined
Apr 8, 2004
Messages
185
Location
Perth, Western Australia
Medic,

Everything that Craig said, but not too sure about not sanding - I've never been able to get the angles just right without some sanding! But do ensure the joint is dust free when you glue it.

But before getting to this stage, how much extra is the freight?

I think you'll find that your labour to scarf and join the longerons, (not to mention the doubt that may creep into your mind about the integrity of the splice) will offset a few bucks more in transport costs.

Of course I guess I am just a tad grumpy on this issue - at least you guys in the US have the option of road freight to keep the costs down.

My last shipment from ACS for a small package of AN fittings and a few bolts was a cool US$79, and that was via the US Postal Service.

But the record goes to DHL / ACS who charged me US$51 to ship two turnbuckle forkends!

I figure that's about US$25 per oz.
 

spduffee

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Joined
Sep 22, 2011
Messages
567
Location
Renton, WA
This is an old thread, but relevant to my situation. I too have to make a splice in the longerons. I have seen the splice made on a vertical member and splices made in the middle of the open field (between two vertical members). Is one way stronger/better than the other? So far I have it planned on a vertical member. Any thoughts?

Thank you,

Shawn
 

FritzW

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Log Member
Joined
Jan 30, 2011
Messages
3,776
Location
Las Cruces, NM
Hi Shawn,

Sounds like your making progress on the Flea.

Strength wise it shouldn't matter but you typically put "doublers" on either side of the splice, the doubler might affect how you put the vertical in. A bigger factor would be if the longeron is curved, the splice could make a flat spot in your curve.

There are ways around that though: laminating, steam bending, etc... One of these threads has a lot of discussion on that.
 

spduffee

Well-Known Member
Joined
Sep 22, 2011
Messages
567
Location
Renton, WA
Thanks Fritz! Progress is a relative term... I am still planning, which is a good thing. "Sweat more in peace, bleed less in war" kind of thing. My splice, I see, actually is on a slight curve. I can move it forward to a flat spot.
 

wwz7777

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HBA Supporter
Joined
Aug 8, 2012
Messages
54
Location
Northfield, MN
Hello!
I, too, have the need for long longerons. I’m wondering if it matters where the splice is placed, ie near the firewall, in the tail , or just aft of the cockpit? My plans don’t show a location so I’m looking at this from a structural standpoint.
Thanks in advance!
 
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