starcraft pm160 structure question

[jondevos]

Hey everyone. I just started a restore job on a 1988? Starcraft pm160 aluminum boat. I have stripped it down and am ready to start rebuilding it. After removing the deck I found the rivets on the 2 main supports under the floor have all been popped off. It appears to me that the flotation foam may have possibly done this As Every Single Rivet Had Popped. What my question is, do I need to put in pour in foam or will I be able to use just the blue board from home depot. I understand the foam gave support to the floor but I also believe it is part of the reason the floor was so rotten. Based on the attached pictures can anyone tell me if the foam had any structural role in the boats design outside of rigidity of the floor? I figure I can replace the foam with blue board insulation and add some extra aluminum supports from side to side.

 

[jbcurt00]

It may have looked like your Topic didn't post, but it did:
starcraft pm160 structure question

If you got an error message indicating that the site admin had been notified, it's a glitch that's in process of resolution. Hang in w/ us. Pix are also a challenge to post, but if you use photobucket & copy, paste the IMG code under each pix, the pix show up IN your post rather then as attachments that must be opened:

The IMG code looks like this:
IMG]http://i1246.photobucket.com/albums/00O0O_7F1ewQJ3g61_600x450_zpse86102df.jpg[/IMG
And the pix show up like this:

I'm not familiar w/ how an SC PM160 is built, but the SC crew will be along shortly to give you all the help you'll need. And then some.

Until you get some pix up, here's some SC topics to read thru, LOTS of great tin boat building tips in here:
Starcraft Boats

Welcome to iboats dry dock, Tin division

 

[kjsAZ]

http://forums.iboats.com/forum/boat-...is-it-worth-it

In short: the foam adds strength to the construction. Whether it's needed is something only the manufacturer could tell. The disadvantage of the blue (or pink) foam is that it gets eaten by fuel and most other chemicals, burns extremely well and degrades with heat. PU foam (also in the pourable version) doesn't but can crumble under severe vibration and shock.
My guess is more that the rivets failed because the foam was compromised and didn't provide the additional strength any more. The foam isn't rigid enough to exert enough force to rip out rivets.

 

[jondevos]

Ok thanks for the help. I have fixed the post to add the pictures properly. I originally made the post from my phone and got some errors. The 2 main supports that were along the inner edges of the foam are the ones I am referring to. I believe the foam was added after the floor was installed and pushed up on the floor popping all the rivets. The supports were not able to sit down flush where they were supposed to because there was foam that had pushed underneath them.

 

[dozerII]

Every StarCraft I have taken apart has had all or some of the rivets in the stringers popped. I don't think it is from the foam! It happens in newer models with pour foam as well as the older models with sheet foam. I believe the problem is from the boat being used with a rotten floor causing the rivets in the outer edges of the floor to let go which then allows the floor to rock side to side on the stringers popping the rivets.

 

[jigngrub]

I'd like to see/know what kind of rivets were used to fasten the stringers to the ribs. Were they the cheap open end blind rivets or the much better and more expensive closed end blind rivets?

Even if the foam did lift the stringers away from the ribs and popped the rivets out, the foam replaced the rivets for securing the stringers to the hull. The foam bonded to the hull and to the stringers and held them in place. This is one of the overlooked benefits of the expanding urethane foam.

Expanding urethane foam bonds and secures itself to the hull, it doesn't vibrate, or move around, or rattle and squeak like the sheet foam... it is secure. If your boat swamps or floods with the sheet foam below deck, the only thing holding the foam in the boat is the deck to stringer and angle fasteners and the stringer to rib fasteners. If they fail under the load the decking will be ripped free of the hull and all of the foam will float on top of the water and the boat will sink to the bottom... and you've already seen how sturdy the stringer to rib fastening is.

However, if the sheet foam is secured to the hull before the decking is laid it will alleviate the afore mentioned problem. This practice is recommended in the USCG Boat Builders Handbook:
http://www.uscgboating.org/regulations/boatbuilder_s_handbook/flotation_part2_c.aspx

3) Foam blocks and other shapes must be secured so that no movement in any direction occurs that will effect the flotation's performance.

Unfortunately, I have not seen one sheet foam installation on this forum done correctly... everyone installs it loose under the decking.

Your best and strongest build will be with the expanding urethane foam, second best will be sheet foam secured to the hull, and sheet foam installed loose will be the least desirable.

 

[jondevos]

Every StarCraft I have taken apart has had all or some of the rivets in the stringers popped. I don't think it is from the foam! It happens in newer models with pour foam as well as the older models with sheet foam. I believe the problem is from the boat being used with a rotten floor causing the rivets in the outer edges of the floor to let go which then allows the floor to rock side to side on the stringers popping the rivets.

Actually that makes a lot of sense. The outer edges of the floor were anything but solid. I didn't even need to pull the rivets to remove it. As far as rivets go, they are the cheap open end rivets. I plan to replace with either closed end blind rivets (cherry max) or possibly screws. Any reason not to use stainless screws?

 

[jigngrub]

Screws would be my second choice, closed end blind rivets would be my first.

 

[Bob_VT]

The rivets pop from the pounding of the hull. I have a Starcraft 16'SS (same hull) and they do pound in a chop. The open ended rivets are softer to allow something to "give"

Examine that live well hose very carefully since it will be ba a pain to replace after the deck is in.

As far as foam replacement..... people have used blue board, pool noodles, empty plastic bottles and 2 part foam. My vote is towards the 2 part foam and the 2lb density is absolutely fine because the foam is not part of the structure strength in that hull. It is really dealer's choice....... the "older" starcrafts I had were filled with sheets of white Styrofoam from the factory.

 

[jondevos]

The rivets pop from the pounding of the hull. I have a Starcraft 16'SS (same hull) and they do pound in a chop. The open ended rivets are softer to allow something to "give" Examine that live well hose very carefully since it will be ba a pain to replace after the deck is in. As far as foam replacement..... people have used blue board, pool noodles, empty plastic bottles and 2 part foam. My vote is towards the 2 part foam and the 2lb density is absolutely fine because the foam is not part of the structure strength in that hull. It is really dealer's choice....... the "older" starcrafts I had were filled with sheets of white Styrofoam from the factory.

I looked over the hoses and they look ok. As far as access after the floor is installed, I have an access port I will be installing in the new floor just aft of the live well. I will be doing a thread for the whole restore outside of this. This post is mainly focused just on the foam question. I will be adding extra aluminum bracing tonight after I do a water leak test.

 

[REdington]

Here is the way I did mine. First laid in 1" between the ribs,








then using the table saw, cut 2" thick foam in strips with 11 degrees on the bottoms and between 3 and 4 degrees on the tops. I used a 3/8" X 2" piece of alum as a straight edge from the top of the rib to the rib on the other side. I made them just a hair high so the wood floor would compress the foam just a little.






Hope this helps you.

Rodney

http://forums.iboats.com/forum/boat...g-and-hull-repair/660850-18-84-sylvan-rebuild

 

[REdington]

Oh I forgot that I used 1" also on the stringers under the flange.

Rodney

 

[jbcurt00]

Note that Rodney painted the hull where he intended to put foam against the hull:

GOOD idea, really good idea...

 

[Watermann]

Welcome to the iboats dry dock. :welcome:

Nice resto project SC you have there Jon. :thumb: The foam didn't cause the rivet heads to pop and the foam is just for flotation. The reason the rivets get loose, break and sometimes the hull cracks is because people continue to use the boat with compromised rotten wood. The decking, side panels, cabins, consoles and splash wells all add structural integrity to these boats, not the foam.

 

[jondevos]

Thanks for the pics and info guys. I have started a thread for my restore here http://forums.iboats.com/forum/boat...-repair/8175835-1988-star-craft-pm160-restore

 

[jbcurt00]

Just ask a mod to add this Topic to your resto thread if you like

 

[jondevos]

I didn't know that was possible. Any way to make this happen mods?

 

[Watermann]

Hey where's GaB? He's normally all over this sort of Mod request.

 

[PaulyV]

Note that Rodney painted the hull where he intended to put foam against the hull:

GOOD idea, really good idea...

why is that a good idea to paint the areas?

 

[GA_Boater]

why is that a good idea to paint the areas?

Inactive thread - 7 years. Start a new one.

Closed.