Adding a Bow Deck

[minuteman62-64]

In preliminary stages of a small modification to my aluminum skiff. Planning to make a deck extending from current bow seat to stem.

Factory configuration and preliminary cardboard mock-up of deck:

 

[minuteman62-64]

Re: Adding a Bow Deck

OK, can't figure out how some of you guys make posts with text, then photos, then more text, etc. So, have to resort to multiple posts.

Anyways, decided to raise the deck 3 inches above current bow seat elevation and carry it forward to the stem on the same plane. Did a "sit-down" test at that height and it actually seemed more comfortable than current seat elevation. Also will provide a little more storage capacity. Should note that this will not be a casting deck (too unstable). Just provide a storage compartment with a place so sit and stow more gear above.

So, current seat material is 1/2 inch plywood. Probably go with 1/2 inch plywood for new deck. Made a gauge of 2 1/2 inch strips of plywood laid across seat to scribe the line where the new deck will intersect the sides of the hull (first photo).

Second photo shows existing seat removed. A bonus. If you look closely you can see a pop rivet and a solid rivet that apparently were left on top of the floatation foam back in 1982 by the manufacturer.

Preliminary plan is to rivet 3" aluminum channel to both flanges at the top of the seat compartment and run additional aluminum framing from there to bow.

 

[Woodonglass]

Re: Adding a Bow Deck

Get yourself a FREE Photobucket account and then use the IMG Code to copy and paste your pics into iBoats. Careful about getting your deck too high. the boat can get "Tippy" sometimes when you do!!!

 

[minuteman62-64]

Re: Adding a Bow Deck

Get yourself a FREE Photobucket account and then use the IMG Code to copy and paste your pics into iBoats. Careful about getting your deck too high. the boat can get "Tippy" sometimes when you do!!!

It is not going to be a casting deck or any kind of "stand-on" deck. I've already determined (by standing on the existing seat) that it will be too tippy/unstable to stand upright on. When launching I will step from the trailer spare tire on to the deck and then into the boat. Other than that, it will be a seat and another flat place to stow some gear.

I'm not going to carpet or add any other type of finish (skid strips, etc.) that will give the perception that it is to stand on.

 

[minuteman62-64]

Re: Adding a Bow Deck

I've got a CAD program that is kind of complicated (for me anyways), so I draw up a lot of my projects to keep my CAD skills up. It also allows me to kind of simulate walking through the construction stages and tweak the design as I go. So, as a result, here's my thinking on the framing (see attached diagram). I haven't quite mastered some of the trimming techniques so the ends of the angles are not quite as they will be - but you can get the idea.

My metal supply house has a 6061 aluminum angle that, in a 1 1/2"x1 1/2"x1/8" size, using a conservative loading assumption, will support the deck and associated loadings (I had to break out my old structures books for this one). They also have a 6063 3"x1"x1/8" aluminum channel that will mount to the existing seat flanges, provide the 3" increase in elevation I'm looking for, and provide the mounting for the longitudal angles. Plan is to do all fastening with 3/16" blind rivets - closed end for the ones that pierce the hull and regular for those on the interior.

For the top I'm thinking of 1/2" MDO plywood. The hatch dimensions are approximate - I haven't decided if I'll use a store bought hatch or make the hatch cover by reinforcing the plywood hatch cutout.

All of the above have implied question marks - I'm open to suggestions/critiques/etc.

 

[jigngrub]

Re: Adding a Bow Deck

I would go with .063 (1/16") gauge instead of .125 (1/8") material, it's easier to work with and will save you some weight. Once everything is riveted together and the decking is installed it'll be plenty strong enough.

I'd rivet all of the metal to metal with the closed end blind rivets and fasten down the decking with the open end blind rivets.

 

[minuteman62-64]

Re: Adding a Bow Deck

I have some .063 6061 sheet that I'll be forming into angle brackets to fasten the structural members together. There won't be any bending involved with the angle, and not that much of it, so, I'm not that worried about workability or weight.

Only reason I was thinking of open end rivets for inside was to avoid the steel remnants from the pull-pins. However, closed end do have a stronger grip strength - I'll keep that in mind. Someone did give me a source for closed end rivets with aluminum pins in another thread.

I want the decking to be easy (sort of) to remove and replace (for maintenance). So I'll be fastening it with 10-32 ss screws and nylock nuts. With the dimensions I've planned all of the nuts will be reachable via the hatch.

 

[jigngrub]

Re: Adding a Bow Deck

You can get the aluminum/aluminum CEBR here:
closed end blind rivets

 

[minuteman62-64]

Re: Adding a Bow Deck

I'm now committed. Purchased $37 in aluminum (channel and angle) today. Not yet beyond the point of no return - I can still just go ahead and re-paint the old seat and re-install it (find another use for the aluminum and tell everyone that's what I was planning to do all along). But, no reason to back off yet.

Spent some time looking at rivets (blind/pop type). Read a lot on pros and cons of ss vs. aluminum, particularly in marine environment. Impressed by about 5:1 strength advantage of ss over Al. Then looked at pricing. Hmmm. Spend $0.15/rivet for Al and maybe replace a few in 10 years, or, spend $1.15/rivet for ss and die happy knowing whoever gets my boat won't have to worry about rivet failure. I think I'll go with the aluminum. Also think I'll go with the closed end, both outside the hull and on the interior. Looks like I can do it all with one size - so I can keep it simple and just buy one size batch of closed end Al/Al mandrel rivets.

Next step: cut to size and mount the channel pieces to the existing seat flanges. Once done I will be at the point of no return.

 

[minuteman62-64]

Re: Adding a Bow Deck

Cut channel pieces to size (1/8" shy of hull on each side to avoid "hard spot" on hull). See first photo with pieces laid in place. This will raise bow deck 3" above current seat elevation. Space between existing foam and deck will be filled with old reliable pool noodles.

Second photo shows how I transferred 3/16" hole locations from existing seat flange to channel. Used a 3/16" transfer punch, from the bottom, but the aluminum sheet on the sheet flange was too thin to allow the punch to properly align. Cut some pieces of 1/8" aluminum and drilled 3/16" hole in each. Used transfer punch to line up holes and two-sided tape to fasten in place. Then clamped channel to seat flange and punched a mark for each hole.

Put the first piece of channel in place and dropped some 3/16" bolts through the holes - lines up good (one of my better experiences with transferring multiple hole locations). The 3/16" rivets I'll be using call for a #11 drill bit so I should actually have a little play when I do the final assembly.

 

[minuteman62-64]

Re: Adding a Bow Deck

I'm now committed. Fastened forward riser to seat flange using 3/16" closed end blind rivets and my new HF 1/4" air operated rivet gun (nose shown in attached photo). Five rivets, five "ka-chink's" and done. Only complaint: it comes with a plastic retainer to catch the mandrels when they pop off. I put it on, thinking I'd keep a bunch of aluminum mandrels from dropping into the bilge and rattling around later. Didn't notice the retainer had a slit in it - first mandrel caught in the retainer then dropped out the slit into the bilge I don't get the point of the slit. Put a piece of tape over the slit and finished up, catching the remainder of the mandrels.

May be over kill, but, the only failure I've had with an aluminum pop rivet was a result of corrosion in the seam between the two pieces being fastened. So, laid down a bead of 5200 between the two pieces and slathered some 5200 on each rivet before setting. I'm hoping that will keep moisture out. I'll also come back later and seal the heads with whatever sealant I have available.

 

[minuteman62-64]

Re: Adding a Bow Deck

Got slowed down by weather - couple of weeks with temperatures way down in the 60's Now back to work.

Cross members installed. As planned, used 3/16" aluminum blind rivets w/aluminum mandrels. All joints liberally lathered with 3M 5200 to (hopefully) keep moisture out. Cross member in bow is 1.5" x 1.5" x 1/8" 6061 T-6 aluminum angle. Fore/aft members will be same. Brackets against hull are fabricated from 0.09" 5200 sheet aluminum.

Next step: cut and fit two fore/aft members (see plan at top of post). Will also use the 0.09" 5200 aluminum sheet to fabricate mounting brackets for these.

 

[minuteman62-64]

Re: Adding a Bow Deck

Framing now complete. First photo shows all of the members fastened in place. The 3" rise over the old foam floatation, formed by the channels, will be filled with ole reliable pool noodles. Sitting on the foam is the workhorse of the project so far, my trusty HF rivet gun.

Second photo shows detail of fore/aft to cross member fastening. Gussets are 0.09 5052 aluminum sheet. White stuff is the 3M 5200 that was liberally smeared between pieces and on rivets. Based on difficulty removing some drops of fully cured 5200, I may actually get some un-anticipated structural benefit

Seems good and stiff. I'll simulate a load test tomorrow. I'm pretty confident on the static load capacity. Don't know how the rivets will do vibration-wise. I've aligned the rivet heads so all can easily be drilled out and replaced if necessary.

Hope I haven't created a corrosion problem. I've got a 5052 alloy hull, 5052 alloy gussets, 6061 alloy angle iron, 1100 alloy rivets and 1100 alloy channels as seat risers. I guess time will tell.

 

[jigngrub]

Re: Adding a Bow Deck

Looks good.

I'd go ahead and frame out the hatch opening too:

 

[minuteman62-64]

Re: Adding a Bow Deck

Looks good.

I'd go ahead and frame out the hatch opening too:

That was one of the options I considered. I have a drop-in bow floor piece (photo attached - may be overkill, but that's how I built it ) that provides a flat floor in the extreme "V" section of the bow. The frame, as built, is designed to provide support for the decking and still allow space the bow floor piece to be removed for bilge access/maintenance. By making the hatch framing part of the deck framing I'd lose the ability to remove the bow floor piece (without partially disassembling the deck framing). So, my plan is to put the hatch framing on the bottom of the deck. That way I remove the deck and can pull out the bow floor piece.

 

[greenbush future]

Re: Adding a Bow Deck

That's going to be one very solid bow area for sure!! Are you a engineer by chance? Your project looks real good, cant see why anyone would want to pull any of that out.

 

[minuteman62-64]

Re: Adding a Bow Deck

That's going to be one very solid bow area for sure!! Are you a engineer by chance? Your project looks real good, cant see why anyone would want to pull any of that out.

Actually, I'm a Civil Engineer by education - however, it's been 50 years, so I had to pull out my old structures books for a quick refresher .

Only reason for pulling any of the framing out would be if vibration turns out to cause problems with loose rivets or if there are rivet corrosion issues. The remedy (at least the remedy I've planned for) would be to drill out the existing 3/16" alloy 1100 rivets and replace with alloy 5200 rivets or bigger diameter rivets or maybe even SS rivets.

 

[minuteman62-64]

Re: Adding a Bow Deck

Moving on - using door-skin material to scribe and form template for deck material. Once again proving that time I spent watching the granite guys make the templates for my kitchen counter tops wasn't wasted.

I'll be cutting the 1/2" MDO decking with a bevel, approximating the slope of the hull side. So, I've learned from experience (don't ask :blue: ) that the bottom of the template has to be the top of the deck. Hence the 1/2" plywood scraps sitting on top of the frame during the scribing/fitting/forming process.

Going to buy the MDO today, cut out the deck outline, and (hopefully), drop it in place for a test fit.

 

[minuteman62-64]

Re: Adding a Bow Deck

Bought the MDO plywood this morning and, with the help of a friend, traced the template and cut out the deck piece (see photo).

Dropped it in for a test fit (see second photo). Not too bad - a few swipes with a belt sander and it will fit nicely.

Third photo shows verification of load assumptions. Good and solid. Will get even better once the deck is attached to the framing so it all acts as a unit (as long as I don't screw it up with the hatch cutout .

 

[jigngrub]

Re: Adding a Bow Deck

The hatch cut-out will weaken it some and that's why I suggested framing the hatch opening, but you can do that later if you need to.