Seaplane doors: bottom door frame buildup

Zzz

Zzz

Resigned and bitter
I've always really liked the gullwing-style seaplane doors on aircraft like the Highlander, and plan to build them for my Bearhawk. One problem that is inherent to all 4-place Bearhawks is the steep angle of the struts up to the wing, causing an impingement for the door swing. I'm not a fan of the mouse door, so I see two options, both involved adjusting the height of the door.

1. Build up the door frame so that the entire door is shorter (red line in photo.)
2. Build up only a short section of the door frame, building a complementary cutout in the door itself that meshes when the door is closed (blue line in photo.)

Without the luxury of have wings bolted on, my question is: How much does the lower door frame need to be raised to accommodate a door that will clear in the upswing?

If anyone has done this, it would be great to see some in-process photos. Thanks!

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You only need to raise the lower sill in the forward area, I think (from memory)... But I think it was about 3". I have some photos from someone who did it, I'll see if I can find them...

Scratch that - I already posted them on this forum, they were from Heath. He used a mouse door. It must have been someone else I remembered seeing with a raised door sill.
 
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I'm following this with interest. Glad your going down this road before me Z.

alaskabearhawk has some good pics on his kitlog site. He said he had to raise the door frame 2". I think I'm going to raise the sill like alaskabearhawk did but I'm not going to add the extra tube.
 
whee said:
I think I'm going to raise the sill like alaskabearhawk did but I'm not going to add the extra tube.
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My original plan was to just build a little box section out of 16 or 20 gauge steel, the minimum size for the door cutout, and weld it to the existing door sill. I was going to do a thin stainless flash over the door sill anyway, and it would all be covered up. I really don't want to build the entire thing up since on the AviPro quickbuild, the sill is all done and nice.
 
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To me raising the sill seems like one of those jobs that could end up being far more involved than it first seems. Could you do a mouse door on the seaplane door, with some sort of spring action to keep it out of the way on the down swing? In another week or two I could try and get a measurement of the closest distance from the window hinge line to the strut. Would you be planning to use the OEM window hinge parts as door hinge parts, or would you be beefing those up?
 
I had to raise the door sill 3", have a door frame clearance of 1/4" to door sill and a door skin overlap of door frame of 1/2" to give about 3/8" clearance to the wing strut when opened.
 

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I must have had a brain fart or something as I only raised mine two inches, not three like Gavin. I know Rob Taylor raised his two inches and it works fine. After all the work I put into mine I'm not going to do the extra inch and make it work as is. Dang it!
 
alaskabearhawk said:
I must have had a brain fart or something as I only raised mine two inches, not three like Gavin. I know Rob Taylor raised his two inches and it works fine. After all the work I put into mine I'm not going to do the extra inch and make it work as is. Dang it!
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I think it will depend on how much overlap you like between the door and the fuselage. Less door overlap will mean more strut clearance.

mswain said:
There is also the mod Colin did, yet another way to avoid the mouse door.
http://bearhawkforums.com/forum/bearhawk-4-place-plans-build/3813-flip-up-cabin-doors
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I think this is great! The more content we can share and compile into one place, the stronger and more useful / helpful and inspiring the Bearhawk forum becomes.
 
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I raised mine by 2" . I attached few photos after i was done with the wing installation and tried the door to assess clearance with the strut. The maximum radius from the hinge line to the strut is 32". I have about 1.5 " clearance between the strut and door frame. More than enough for a good door skin overlap.
Mike.
 

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Aero_tango said:
I raised mine by 2" . I attached few photos after i was done with the wing installation and tried the door to assess clearance with the strut. The maximum radius from the hinge line to the strut is 32". I have about 1.5 " clearance between the strut and door frame. More than enough for a good door skin overlap.
Mike.
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Nice, tango. What did you use for hinges?
 
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Here's the seaplane door hinges for the pacer. These are adjustable in and out. I should have used plastic washers between the door hinge plate and the door jamb hinge.
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I'm starting to build my seaplane doors. You guys that built them did you curve the front lower section of the door and does it allow the door to sit flat enough against the wing to fly with it open?

I think the door has to be curved to look good but I'm concern that it won't sit against the wing good enough to fly with it open.
 
I've considering various ideas, including seaplane doors that may curve out. While at OSH this year, I specifically inquired of a few owners of other planes that had such and how they worked out for flying while open. Each said surprisingly well and stable. All were low speed aircraft, Kitfox etc. I'm still a little pessimistic though.
 
I recently decided to build seaplane doors. I wasn't sure what the best way to build up the door sill was until I saw a post by Nev where he used wood. I found a piece of 4x4" balsa on ebay. Ripped it in half and used my brother-n-laws planer to make 1 3/4" boards. Fortunately I had taken measurements when I had the wings on so know that this gives me clearance with a 3/8 door overlap. I used some 3/16" machine screws from Ace and large washers to attach the balsa to the steel door formers. Covered with fabric and made a sill cover with 3 layers of carbon. The issue I have now is that I had an extension of the boot cowl that now is not high enough. Haven't found a solution to that, definitely do not want to redo the boot cowl. Waiting on a few more parts to start on the carbon tube frames for the doors. Composite rear passenger and baggage doors are complete except for finishing.

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That’s a great solution. Very much looking forward to seeing how your carbon tube framed doors go. I really think that’s the best way to go.
 
You could make a cosmetic cover for the door sill all the way down to the now too short boot cowl extension.
 
I will for sure make composite cargo doors after my project is flying. The front doors, I thought I would but had serious second thoughts. I calculated out the weight savings for carbon and aluminum square tube. Carbon is a bit lighter per foot, but each intersection of tubes is going to add weight as you have to reinforce the joint, and spread the load down both directions of the intersection. That is going to cut into the weight savings over welded square aluminum tube. The cost of CF square tube is pretty high. Ultimately, most of the weight of an all glass door is......the glass.

My aluminum welding is still sub par. Working on it. This morning I made 3 thin wall SS blast tubes. AL would have been slightly lighter, but my ability to weld .016 SS far exceeds my ability to weld thin aluminum.
 
After visiting Simon and chatting over his build this past weekend we were wondering if, with the changes in the B-model components, it's still necessary to raise the sills for a seaplane door to clear the strut? Can anyone confirm this?

Also agree this would be a great kit option ;)
 
Has anyone tried to open a seaplane style door in-flight ? Or had one come open by accident?

Mine have a single gas strut at the aft of each door. They're not stable enough to be opened with the engine running, so I'm adding an extra strut to the front of each door which I think will make them much more stable. I want to be able to have them open when taxying in hot weather. They don't need to be opened in-flight, but I wouldn't mind knowing what might happen if one was opened accidentally. One of those things.....if it can happen, then it probably will.
 
I raised mine 2 inches (copied Rob) and this worked well. You could probably get away with not raising the sill on the B model, but it'd be very close.
 
Someone asked me recently whether it's possible to build seaplane doors without raising the lower door sill. On mine I raised the door sill during the build by 50mm thinking it was needed to clear the strut however it appears that on the B model this is not necessary. I measured my plane and Simons, and both have the clearance needed between the lower door and the wing strut when partially open. The picture below shows 52mm (2") clearance with the overlapping door skin.

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I have seaplane doors. Single gas strut at front. I always open door(s) when it is hot for taxi. Mine did open once accidentally while flying. Surprisingly with no ill effects. I did close it quickly, and have not tried flying with it open since. It's windy out there!!
 
I built seaplane doors for my pre B model 4-place. I raised the door sill 1.75" based on measurements taken when I had the wings on. Then I worried that that wasn't enough, hearing how much others had raised the sill. When I finally got the wings back on I was relieved to find I had plenty of clearance. I would have been OK with 1.25" instead of 1.75". It works out well though as I didn't have to trim the overlapping skin. It wouldn't be possible to use a seaplane door without raising the sill on the original 4-place without making some sort of provision for strut clearance.
 
Nev. I measured our standard B model ZK-RJE yesterday. The actual opening size would just, just allow a seaplane door to open past the strut. However the flange making the door weatherproof would not fit. So some slight adjustment of the sill would be necessary to raise it say 10mm, but only at its lowest point. NZCAA could require some sort of extra restraint to fly with the door open as the seat level is above the opening. Also a deflector to stop your hair being blown out of place!
 
Good to know Richard and hopefully of use to those considering Seaplane style doors in the future. If I was to do it again I'd probably leave the door sill as it was and just make adjustments to the door itself.
 
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