FWIW I upped fus-26 under the doorsill to .025 and added two diagonal
stringers and it has
been fine. I can understand upping this to .032 as it is the primary
load path transferring a landing load back into the fuselage. I believe
there have been a number of reports of flexing/oil canning/ smoking
rivets in this area.
I decided not to change the triangular fus-25.
I don't doubt that the heavy firewall doubler plates reduce firewall
damage in a ground loop, hard landing, or prop strike. I do doubt
whether they are worth the weight or need to be so large or thick for
most of us. Perhaps the doubled firewall (stainless + aluminum) is a
reasonable compromise for anyone doing that. That is about all I did
although I guess I did weld up larger bathtub engine mount fittings to
get a better fit than the original old one piece parts had. Extra
weight sure adds up fast. Probably more important to upsize the corner
wraps to .025 or .032. I upped the lower ones to .025 and they have been
fine even with the heavy soob engine. The moved firewall also eases the
stresses on the corner wrap a bit. (and turned out to be almost
essential for W&B when I put the amphibs on my particular airplane)
For a rotax 912 I'd probably leave all this stuff (except fus-26) stock.
It is too easy to get carried away making upgrades that extend build
time IMO. Things that reduce maintenance or everyday wear make sense to
me but it is impossible to make it impervious to a hard landing. Most of
us can tell you what we did but only guess at the future worth of the
decision. A fair number of pilots without taildragger time have put my
aircraft to the test with nothing bent so far.
Ken
360+ hours on 119R
Curtis Langholz wrote:
I am just completing the finishing gussets for the rear carry through
and float bulkheads. After doing a lot of archive searches and
looked at a lot of the pictures it has raised a lot of questions
about what needs to be beefed.
On the Ontario mods to fus - 25 & 26. What is the reason for doubling
the skins here? Do they buckle under landing stresses or is it to
stiffen the door area? I did double the lower door sill which made
them very solid.
The fuselage is complete to the firewall, did the MAM mod to shorten
the boot cowl 3", also added the brace between the motor mount
brackets.
I have seen Wayne Oshea's firewall mods which raises another question
about the stability of the stock firewall. Why does the firewall
need such large, thick doublers? If anyone can lend a suggestion I
would appreciate it.
Thanks,
Curtis
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